Task 4 - What do we know about vaccines and therapeutics?

What is known about the effectiveness of drugs being developed to treat COVID-19 patients?

Antiviral drugs are also being widely investigated to find the effective agents against SARS - CoV - 2 . Favilavir is the first drug approved by the National Medical Products Administration of China for the treatment of COVID - 19 , following a clinical trial conducted in 70 patients in China . The early results of clinical trials using chloroquine phosphate , an old anti - malaria drug , in the patients with COVID - 19 was promising . 7 Therefore , in the cocktail protocols presently used for treating patients the usage of chloroquine phosphate , as an available drug , is recommended . Gilead will start two large phase 3 studies for evaluating the safety and efficacy of remdesivir , an RNA polymerase inhibitor 4 that was first developed for Ebola , in about 1000 adult patients diagnosed with COVID - 19 based on the positive preliminary investigations and the previous results shown on MERS - CoV . Some other drugs such as lopinavir / ritonavir and interferon beta that have indicated efficacy in animal models against MERS - CoV before , are also being tested . 4

So far , no drugs , monoclonal antibodies or vaccines have been approved to treat human infections due to coronaviruses . Several pre - existing and potential drug candidates , including chloroquine and remdesivir , have been considered [ 10 ] [ 11 ] [ 12 ] . The discovery and marketing of new compounds often require months to years . However , in the face of the global spread of COVID - 19 , effective interventions for severe cases of COVID - 19 are urgently required . Although little is known about SARS - CoV - 2 , several insights may

Data regarding antiviral therapies and other treatment strategies , as well as their potential interaction with CV medications and CV toxicities are summarized in Tables 3 - 5 Methylprednisolone is another drug under investigation that is currently being used to treat severe cases of COVID - 19 that are complicated by ARDS ( 48 ) . This steroid is known to cause fluid retention , electrolyte derangement , and hypertension as direct CV effects , and also may interact with warfarin via an undescribed mechanism . Clinicians are advised to observe for these drug interactions .

Given the lack of clarity about the effect of the ACEi Q5 and ARB on ACE2 and SARS - CoV - 2 interaction and the development of COVID - 19 , it is not currently possible to recommend using either ACEIs or ARBs with the purpose of treating COVID - 19 . If needed , short - term discontinuation or delay of initiating ACEi or ARB in patients with otherwise controllable or mild hypertension , stable heart failure , or stable chronic kidney disease is unlikely to have negative consequences . However , longer - term effects will need to become clarified with time . Currently , the authors continue to administer these drugs to patients unless they are critically ill and at high risk for hypotension and kidney injury . Thus , at present , the effect of either ACEIs or ARBs in patients with known COVID - 19 infection on the severity of illness during the virus infection remains unknown and it is unclear whether the differences between ACEI and ARB are clinically relevant in these patients .

In late December 2019 , an outbreak of an emerging disease ( COVID - 19 ) due to a novel coronavirus ( named SARS - CoV - 2 latter ) started in Wuhan , China and rapidly spread in China and outside [ 1 , 2 ] . The WHO declared the epidemic of COVID - 19 as a pandemic on March 12 th 2020 [ 3 ] . According to a recent Chinese stud , about 80 % of patients present with mild disease and the overall case - fatality rate is about 2 . 3 % but reaches 8 . 0 % in patients aged 70 to 79 years and 14 . 8 % in those aged > 80 years [ 4 ] . However , there is probably an important number of asymptomatic carriers in the population , and thus the mortality rate is probably overestimated . France is now facing the COVID - 19 wave with more than 4500 cases , as of March 14 th 2020 [ 5 ] . Thus , there is an urgent need for an effective treatment to treat symptomatic patients but also to decrease the duration of virus carriage in order to limit the transmission in the community . Among candidate drugs to treat COVID - 19 , repositioning of old drugs for use as antiviral treatment is an interesting strategy because knowledge on safety profile , side effects , posology and drug interactions are well known [ 6 , 7 ] .

What is known about the effectiveness of drugs tried to treat COVID-19 patients?

So far , no drugs , monoclonal antibodies or vaccines have been approved to treat human infections due to coronaviruses . Several pre - existing and potential drug candidates , including chloroquine and remdesivir , have been considered [ 10 ] [ 11 ] [ 12 ] . The discovery and marketing of new compounds often require months to years . However , in the face of the global spread of COVID - 19 , effective interventions for severe cases of COVID - 19 are urgently required . Although little is known about SARS - CoV - 2 , several insights may

In late December 2019 , an outbreak of an emerging disease ( COVID - 19 ) due to a novel coronavirus ( named SARS - CoV - 2 latter ) started in Wuhan , China and rapidly spread in China and outside [ 1 , 2 ] . The WHO declared the epidemic of COVID - 19 as a pandemic on March 12 th 2020 [ 3 ] . According to a recent Chinese stud , about 80 % of patients present with mild disease and the overall case - fatality rate is about 2 . 3 % but reaches 8 . 0 % in patients aged 70 to 79 years and 14 . 8 % in those aged > 80 years [ 4 ] . However , there is probably an important number of asymptomatic carriers in the population , and thus the mortality rate is probably overestimated . France is now facing the COVID - 19 wave with more than 4500 cases , as of March 14 th 2020 [ 5 ] . Thus , there is an urgent need for an effective treatment to treat symptomatic patients but also to decrease the duration of virus carriage in order to limit the transmission in the community . Among candidate drugs to treat COVID - 19 , repositioning of old drugs for use as antiviral treatment is an interesting strategy because knowledge on safety profile , side effects , posology and drug interactions are well known [ 6 , 7 ] .

In late December 2019 , an outbreak of an emerging disease ( COVID - 19 ) due to a novel coronavirus ( named SARS - CoV - 2 latter ) started in Wuhan , China and rapidly spread in China and outside [ 1 , 2 ] . The WHO declared the epidemic of COVID - 19 as a pandemic on March 12 th 2020 [ 3 ] . According to a recent Chinese stud , about 80 % of patients present with mild disease and the overall case - fatality rate is about 2 . 3 % but reaches 8 . 0 % in patients aged 70 to 79 years and 14 . 8 % in those aged > 80 years [ 4 ] . However , there is probably an important number of asymptomatic carriers in the population , and thus the mortality rate is probably overestimated . France is now facing the COVID - 19 wave with more than 4500 cases , as of March 14 th 2020 [ 5 ] . Thus , there is an urgent need for an effective treatment to treat symptomatic patients but also to decrease the duration of virus carriage in order to limit the transmission in the community . Among candidate drugs to treat COVID - 19 , repositioning of old drugs for use as antiviral treatment is an interesting strategy because knowledge on safety profile , side effects , posology and drug interactions are well known [ 6 , 7 ] .

In December 2019 , the 2019 novel coronavirus pneumonia ( NCP , officially named Coronavirus Disease 2019 ( COVID - 19 ) by the World Health Organization ) broke out in Wuhan , Hubei , and it quickly spread to the whole country and abroad . The situation was at stake . The sudden and serious COVID - 19 epidemic has brought us a lot of urgent problems . How to effectively control the spread of COVID - 19 ? When does the population infection rate rise to its peak ? What will eventually be the number of infected patients ? How to make early diagnosis ? What effective antiviral drugs are available ? How to effectively treat with existing drugs ? Can it successfully improve the survival rate of critically patients ? In response to the above questions , we put forward corresponding suggestions and reflections from the perspective of the infectious clinician .

In December 2019 , the 2019 novel coronavirus pneumonia ( NCP , officially named Coronavirus Disease 2019 ( COVID - 19 ) by the World Health Organization ) broke out in Wuhan , Hubei , and it quickly spread to the whole country and abroad . The situation was at stake . The sudden and serious COVID - 19 epidemic has brought us a lot of urgent problems . How to effectively control the spread of COVID - 19 ? When does the population infection rate rise to its peak ? What will eventually be the number of infected patients ? How to make early diagnosis ? What effective antiviral drugs are available ? How to effectively treat with existing drugs ? Can it successfully improve the survival rate of critically patients ? In response to the above questions , we put forward corresponding suggestions and reflections from the perspective of the infectious clinician .

Show results of clinical and bench trials to investigate less common viral inhibitors against COVID-19

Antiviral drugs are also being widely investigated to find the effective agents against SARS - CoV - 2 . Favilavir is the first drug approved by the National Medical Products Administration of China for the treatment of COVID - 19 , following a clinical trial conducted in 70 patients in China . The early results of clinical trials using chloroquine phosphate , an old anti - malaria drug , in the patients with COVID - 19 was promising . 7 Therefore , in the cocktail protocols presently used for treating patients the usage of chloroquine phosphate , as an available drug , is recommended . Gilead will start two large phase 3 studies for evaluating the safety and efficacy of remdesivir , an RNA polymerase inhibitor 4 that was first developed for Ebola , in about 1000 adult patients diagnosed with COVID - 19 based on the positive preliminary investigations and the previous results shown on MERS - CoV . Some other drugs such as lopinavir / ritonavir and interferon beta that have indicated efficacy in animal models against MERS - CoV before , are also being tested . 4

Nonetheless , there are hundreds of clinical trials ongoing internationally on different drugs that utilize various mechanisms of action [ 41 , 51 ] , including trials on other nucleosides inhibitors ( e . g . , ribavirin ) , protease inhibitors ( e . g . , lopinavir / ritonavir ) , and interleukin - 6 receptor inhibitors ( e . g . , sarilumab ) [ 41 , 47 ] . Another well - known candidate that is being evaluated in multiple trials against COVID - 19 is chloroquine ( or hydroxychloroquine ) , which is already approved as an antimalarial ( and for extraintestinal amebiasis ) [ 41 , 48 ] . Results of the clinical trials currently underway in the U . S . and China will provide crucial information about whether remdesivir represents a viable treatment option for COVID - 19 [ 20 , 49 ] . If the trial findings are ultimately positive , it will be imperative to ensure that the drug is produced on a commercial scale capable of meeting the demand generated by both the current pandemic and future outbreaks . Such a change in production may also allow for the added benefit of the drug becoming more available for agricultural and veterinary use for relevant indications .

In this study , an accelerated FEP - ABFE based virtual screening strategy with bioassay validation is introduced as a rapid protocol to accurately discover anti - COVID - 19 proteinase Mpro inhibitors . The Clinical trial ( ChiCTR2000030055 ) was registered . As a result , we has finished its first - round clinical trials including 31 patients with COVID - 19 and it demonstrated markedly improved clinical outcomes .

AbstractThe new coronavirus COVID - 19 , also known as SARS - CoV - 2 , has infected more than 300 , 000 patients and become a global health emergency due to the very high risk of spread and impact of COVID - 19 . There are no specific drugs or vaccines against COVID - 19 , thus effective antiviral agents are still urgently needed to combat this virus . Herein , the FEP ( free energy perturbation ) - based screening strategy is newly derived as a rapid protocol to accurately reposition potential agents against COVID - 19 by targeting viral proteinase Mpro . Restrain energy distribution ( RED ) function was derived to optimize the alchemical pathway of FEP , which greatly accelerated the calculations and first made FEP possible in the virtual screening of the FDA - approved drugs database . As a result , fifteen out of twenty - five drugs validated in vitro exhibited considerable inhibitory potencies towards Mpro . Among them , the most potent Mpro inhibitor dipyridamole potentially inhibited NF - κB signaling pathway and inflammatory responses , and has just finished the first round clinical trials . Our result demonstrated that the FEP - based screening showed remarkable advantages in prompting drug repositioning against COVID - 19 .

The current ongoing epidemic of SARS - CoV - 2 and COVID - 19 worldwide has emerged as a significant global public health threat . While urgent regulatory measures in control of the rapid spread of this virus are essential , scientists around the world have quickly engaged in this battle by studying the molecular mechanisms and searching for effective therapeutic strategies against this deadly disease . At present , while the exact role of autophagy remains debatable , there is overwhelming evidence suggesting that the endocytic pathway plays a key role in mediating viral entry for many CoVs including SARS - CoVs , MERS - CoVs and possibly SARS - CoV - 2 . As a result , several inhibitors targeting the endocytic pathway appear to have the therapeutic potential in treatment of COVID - 19 , including a lysosomotropic agent CQ and a clathrin - mediated endocytosis inhibitor chlorpromazine 43 , 63 , 65 , 68 . Since both are FDA - approved and clinically available , clinical trials either as a single therapy or in combination with other anti - viral drugs are much needed .

Show results of clinical and bench trials to investigate naproxen against COVID-19

The urgently launched clinical trials worldwide on investigational medicinal products for the current COVID - 19 outbreak should read out within weeks to months . We can anticipate the notion of drug repurposing for emerging viral diseases to be scrutinized based on these results . At a deeper level , this is a battle not only against COVID - 19 but for the very soul concept of new antimicrobials and their clinical indications : ‘ one drug , one virus versus one drug , multiple viruses or multiple drugs , one virus are the contenders ’ [ 19 , 20 ] .

This review is the first to evaluate the outcome reporting of protocols of TCM and western medicine clinical trials for treating COVID - 19 . The results showed variations in the outcome reporting . For outcome measurement instruments / outcome definitions and outcome measurement time , there is also heterogeneity . However , many primary investigators did not provide outcome measurement instruments / outcome definitions or outcome measurement time . It is difficult to predict results of clinical trials now . But it is obvious that these problems may result in the exclusion of some studies from systematic reviews / meta - analyses due to the heterogeneity of outcomes or outcome measurements . It is a waste .

Antiviral drugs are also being widely investigated to find the effective agents against SARS - CoV - 2 . Favilavir is the first drug approved by the National Medical Products Administration of China for the treatment of COVID - 19 , following a clinical trial conducted in 70 patients in China . The early results of clinical trials using chloroquine phosphate , an old anti - malaria drug , in the patients with COVID - 19 was promising . 7 Therefore , in the cocktail protocols presently used for treating patients the usage of chloroquine phosphate , as an available drug , is recommended . Gilead will start two large phase 3 studies for evaluating the safety and efficacy of remdesivir , an RNA polymerase inhibitor 4 that was first developed for Ebola , in about 1000 adult patients diagnosed with COVID - 19 based on the positive preliminary investigations and the previous results shown on MERS - CoV . Some other drugs such as lopinavir / ritonavir and interferon beta that have indicated efficacy in animal models against MERS - CoV before , are also being tested . 4

Currently , chloroquine and remdesivir are under phase 3 clinical trial and open - label trial for treatment of SARS - CoV - 2 infection respectively ( Table 2 ) 72 . Preliminary results showed that chloroquine phosphate had apparent efficacy in treatment of COVID - 19 73 . However , caution must be taken during clinical use of chloroquine as its overdose is highly fatal without known antidote 74 . Despite the lack of documented in vitro data supporting the antiviral efficacy on SARS - CoV - 2 , several antiviral chemotherapeutic agents have been registered for the clinical trials for the treatment of COVID - 19 ( Table 2 ) 72 .

All patients with COVID - 19 - infected pneumonia received antibacterial agents , 90 % received antiviral therapy , and 45 % received methylprednisolone [ 92 ] . Clinical trials are underway to investigate the efficacy of new antiviral drugs , convalescent plasma transfusion , and vaccines . Most of the trials were initiated by investigators and the study period is 1 to 11 months . Although the final results of these studies will take a long time to complete , the interim research data may provide some help for the current urgent demand for therapy [ 93 ] .

Show results of clinical and bench trials to investigate clarithromycin against COVID-19

Show results of clinical and bench trials to investigate Minocyclinethat against COVID-19

The urgently launched clinical trials worldwide on investigational medicinal products for the current COVID - 19 outbreak should read out within weeks to months . We can anticipate the notion of drug repurposing for emerging viral diseases to be scrutinized based on these results . At a deeper level , this is a battle not only against COVID - 19 but for the very soul concept of new antimicrobials and their clinical indications : ‘ one drug , one virus versus one drug , multiple viruses or multiple drugs , one virus are the contenders ’ [ 19 , 20 ] .

This review is the first to evaluate the outcome reporting of protocols of TCM and western medicine clinical trials for treating COVID - 19 . The results showed variations in the outcome reporting . For outcome measurement instruments / outcome definitions and outcome measurement time , there is also heterogeneity . However , many primary investigators did not provide outcome measurement instruments / outcome definitions or outcome measurement time . It is difficult to predict results of clinical trials now . But it is obvious that these problems may result in the exclusion of some studies from systematic reviews / meta - analyses due to the heterogeneity of outcomes or outcome measurements . It is a waste .

Antiviral drugs are also being widely investigated to find the effective agents against SARS - CoV - 2 . Favilavir is the first drug approved by the National Medical Products Administration of China for the treatment of COVID - 19 , following a clinical trial conducted in 70 patients in China . The early results of clinical trials using chloroquine phosphate , an old anti - malaria drug , in the patients with COVID - 19 was promising . 7 Therefore , in the cocktail protocols presently used for treating patients the usage of chloroquine phosphate , as an available drug , is recommended . Gilead will start two large phase 3 studies for evaluating the safety and efficacy of remdesivir , an RNA polymerase inhibitor 4 that was first developed for Ebola , in about 1000 adult patients diagnosed with COVID - 19 based on the positive preliminary investigations and the previous results shown on MERS - CoV . Some other drugs such as lopinavir / ritonavir and interferon beta that have indicated efficacy in animal models against MERS - CoV before , are also being tested . 4

That so many such studies are being conducted in parallel suggests that that the scientific community is making a huge effort to clarify this question , but this effort is probably insufficiently coordinated . In support of this observation , the Chinese authorities have recently issued a directive to regulate and coordinate clinical trials studying potential pharmacological treatments for COVID - 19 [ 11 ] . The results of these trials will be the first available on humans , since studies published to date on the characteristics and management of patients with COVID - 19 did not report data about chloroquine use [ 1 , [ 12 ] [ 13 ] [ 14 ] [ 15 ] . Of note , the WHO published a generic protocol for randomized clinical trials to investigate the clinical efficacy and safety of drugs in hospitalized patients with COVID - 19 ( i . e . a " master template " for researching drugs in this setting ) [ 16 ] .

Currently , chloroquine and remdesivir are under phase 3 clinical trial and open - label trial for treatment of SARS - CoV - 2 infection respectively ( Table 2 ) 72 . Preliminary results showed that chloroquine phosphate had apparent efficacy in treatment of COVID - 19 73 . However , caution must be taken during clinical use of chloroquine as its overdose is highly fatal without known antidote 74 . Despite the lack of documented in vitro data supporting the antiviral efficacy on SARS - CoV - 2 , several antiviral chemotherapeutic agents have been registered for the clinical trials for the treatment of COVID - 19 ( Table 2 ) 72 .

Which are the methods evaluating potential complication of Antibody-Dependent Enhancement (ADE) in vaccine recipients?

Rapid deployment of antibody - based vaccination against SARS - CoV - 2 raises a major concern in accelerating infectivity through Antibody - Dependent Enhancement ( ADE ) , the facilitation of viral entry into host cells mediated by subneutralizing antibodies ( those capable of binding viral particles , but not neutralizing them ) ( Dejnirattisai et al . , 2016 ) . ADE mechanisms have been described with other members of the Coronaviridae family ( Wan et al . , 2020 ; Wang et al . , 2016 ) , and it has already been suggested that some of the heterogeneity in COVID - 19 cases may be due to ADE from prior infection from other viruses in the coronavirus family ( Tetro , 2020 ) . We suggest that although the T cell epitopes presented here are expected to be safe in vaccination , B cell epitopes should be further evaluated for their ability to induce neutralizing antibodies as compared to their potential to induce ADE . As it has been shown that T helper ( T H ) cell responses are essential in humoral immune memory response ( Alspach et al . , 2019 ; McHeyzer - Williams , Okitsu , Wang , & McHeyzer - Williams , 2012 ) , we expect that the T cell epitopes presented here will activate a CD4 T cells and drive memory B cell formation when paired with matched B cell epitopes .

In the article " Is COVID - 19 receiving ADE from other coronaviruses ? " author has suggested the possibility of antibody dependent enhancement ( ADE ) of SARS - COV - 2 disease ( COVID - 19 ) as a potential mechanism of the increase severity of the disease [ 1 ] . Although it ' s an interesting hypothesis , we should be careful in attributing ADE to enhanced severity of the current disease . As viruses from same group share cross reactivity , it is not uncommon to have cross reactive antibody responses [ 2 ] . Outside of the dengue virus serotypes family , which has demonstrated ADE in animal models , the ADE of the viruses using sub - neutralizing antibody levels has largely been restricted to in - vitro experiments . Cell culture experiments are considered pre - requisite to moving forward to animal experiments , however , not always result is translated to in - vivo setup . There is lack of collective innate / adaptive immune response in - vitro , which is presented in - vivo and the intricate interactions drive the disease pathology . Deliberate reduction in the neutralizing antibody levels in in - vitro assays and lack of innate immune response from other cells may result in an artificial ADE in cell - culture . As COVID - 19 spread across the globe a common pattern of underlying morbid conditions such as diabetes and cardiovascular conditions is appearing . Such underlying conditions are known to present immune response dysfunction [ 3 , 4 ] . As reported by Channappanavar et . al , immune dysregulation may contribute to lethal pneumonia induction by SARS - CoV [ 5 ] . To date , vaccines are the most effective way of protecting against infectious diseases . Improper attribution of ADE in the absence of robust demonstration in animal models may hinder / scuttle the efforts to develop effective vaccines against COVID - 19 and or other viruses of human health importance .

All these vaccines face uncertainties , however , not the least of which is the lack of a reliable animal model in which to test them . Undertaking clinical trials of a SARS vaccine in a setting of vanishing perception of the potential risk of re - emergence of the disease is yet another difficulty . A final uncertainty is the possibility of immune enhancement , a phenomenon which was observed when studying vaccination of cats against the feline coronavirus , FIPV : animals vaccinated with a whole inactivated virus vaccine showed accelerated disease and death after exposure to wild type virus . The humoral response to FIPV does not seem to be protective but can in fact lead to drastically accelerated disease , presumably due to antibody - dependent enhancement of target cell infection via Fc receptor - mediated attachment of virus - antibody complexes . Control of infection and FIPV clearance are thought to primarily depend on cell - mediated immune responses [ 85 ] .

Previous studies of SARS - CoV have shown that the S protein , particularly the RBD , may induce highly potent neutralizing antibodies that protected vaccinated animals against SARS - CoV challenge [ 43 , 49 – 51 ] . It is thus expected that the S protein in MERS - CoV will also be important for the development of vaccines . Song et al . showed that vaccination with a recombinant - modified vaccinia virus Ankara ( MVA ) expressing the full - length S protein of MERS - CoV induced high levels of neutralizing antibodies in vaccinated mice [ 52 ] . However , Cao and colleagues have reported that although the MVA - based , full - length S protein - dependent SARS vaccine could induce neutralizing antibody responses in ferrets , it failed to protect the vaccinated animals from SARS - CoV challenge . Even worse , this vaccine was associated with enhanced inflammatory and immunopathological effects , resulting in serious liver damage in the vaccinated ferrets after viral challenge [ 53 ] . Therefore , caution should be taken when the full - length S protein of MERS - CoV is used as a vaccine antigen since the non - neutralizing epitopes in S protein may induce antibody - mediated disease enhancement ( ADE ) effects , as those elicited by the S protein of feline infectious peritonitis virus ( FIPV , also a CoV ) [ 54 ] .

With regard to the most severe cases of infection registered both outside and within the Hubei province , it is most likely that these individuals have been primed by one or more coronavirus exposure within a narrow time window , leading to the effects of Antibody - Dependent Enhancement ( ADE ) [ 4 ] . Such a hypothesis is in line with the previous observations dating back to the previous SARS outcome in 2003 when human coronaviruses , known to cause mild infections , were hypothesized of priming the high mortality scored in China . Here , anti - Spike protein antibodies were indicated as potentially involved in the enhancement mechanism [ 14e18 ] . In this view , it is plausible that Hubei province patients are featured by a more severe clinical picture , since more likely to be recurrently exposed to the coronavirus .

What is known about the use of best animal models and their predictive value for a human vaccine?

Capabilities to discover a therapeutic for the disease

The copyright holder for this preprint ( which was not peer - reviewed ) is the . https : / / doi . org / 10 . 1101 / 2020 . 04 . 04 . 20047886 doi : medRxiv preprint appear to have low mutation rates due to RNA proofreading capability . Drug combination 199 therapy and more aggressive dosing , including consideration of loading doses to rapidly 200 achieve therapeutic exposures , may be beneficial to maximize efficacy of these repurposed 201 antiviral agents . However , they may be relevant in pre - or post - exposure prophylaxis 202 administration to reduce viral replication and hence the risk of disease progression . 203

Since the outbreak of the novel coronavirus disease COVID - 19 , caused by the SARS - CoV - 2 virus , this disease has spread rapidly around the globe . Considering the potential threat of a pandemic , scientists and physicians have been racing to understand this new virus and the pathophysiology of this disease to uncover possible treatment regimens and discover effective therapeutic agents and vaccines . To support the current research and development , CAS has produced a special report to provide an overview of published scientific information with an emphasis on patents in the CAS content collection . It highlights antiviral strategies involving small molecules and biologics targeting complex molecular interactions involved in coronavirus infection and replication . The drug - repurposing effort documented herein focuses primarily on agents known to be effective against other RNA viruses including SARS - CoV and MERS - CoV . The patent analysis of coronavirus - related biologics includes therapeutic antibodies , cytokines , and nucleic acid - based therapies targeting virus gene expression as well as various types of vaccines . More than 500 patents disclose methodologies of these four biologics with the potential for treating and preventing coronavirus infections , which may be applicable to COVID - 19 . The information included in this report provides a strong intellectual groundwork for the ongoing development of therapeutic agents and vaccines .

Recently , the C - type lectin CD209L ( also called L - SIGN ) was discovered to be a further human cellular glycoprotein that can serve as an alternative receptor for SARS - CoV [ 82 ] . The interruption of virus - receptor interactions could be a potential target for future therapeutic strategies ( Figure 4 ) . In this respect , the receptor - binding S1 domain of the SARS - CoV S protein represents a possible target for new SARS antiviral drugs . Also , antibodies against ACE2 , but not inhibitors binding to the active site of ACE2 may be useful for the development of therapeutic strategies .

Several mAbs ( fully human or humanized ) that target both the S1 - RBD and non - RBD as well as S2 domain of CoVs have been generated and tested in cell cultures for virus - neutralizing capability as well as in animal models for prophylactic and post - exposure efficacies . 65 These antibodies could be useful tools also in the development of vaccines , therapeutic drugs , and antiviral inhibitors .

The outbreak of the novel coronavirus disease COVID - 19 , caused by the SARS - CoV - 2 virus has spread rapidly around the globe during the past 3 months . As the virus infected cases and mortality rate of this disease is increasing exponentially , scientists and researchers all over the world are relentlessly working to understand this new virus along with possible treatment regimens by discovering active therapeutic agents and vaccines . So , there is an urgent requirement of new and effective medications that can treat the disease caused by SARS - CoV - 2 . The research includes the study of drugs that are already available in the market and being used for other diseases to accelerate clinical recovery , in other words repurposing of existing drugs . The vast complexity in drug design and protocols regarding clinical trials often prohibit developing various new drug combinations for this epidemic disease in a limited time . Recently , remarkable improvements in computational power coupled with advancements in Machine Learning ( ML ) technology have been utilized to revolutionize the drug development process . Consequently , a detailed study using ML for the repurposing of therapeutic agents is urgently required . Here , we report the ML model based on the Naive Bayes algorithm , which has an accuracy of around 73 % to predict the drugs that could be used for the treatment of COVID - 19 . Our study predicts around ten FDA approved commercial drugs that can be used for repurposing . Among all , we suggest that the antiretroviral drug Saquinavir ( DrugBank ID DB01232 ) would probably be one of the most effective drugs based on the selected criterions . Our study can help clinical scientists in being more selective in identifying and testing the therapeutic agents for COVID 19 treatment . The ML based approach for drug discovery as reported here can be a futuristic smart drug designing strategy for community applications .

Clinical effectiveness studies to discover therapeutics, to include antiviral agents

In terms of therapeutics there is no known effective pharmaceutical agent . There are over 200 registered clinical trials registered in China alone . Putative agents include antivirals ; Griffithsin , a spike protein inhibitor , nucleoside analogues eg . remdesivir , ribavirin and protease inhibitors such as lopinavir / ritonavir . Immunomodulatory and other host targeted agents include interferon , chloroquine and immunoglobulins . Corticosteroids will potentially have benefit for immune mediated lung damage late in the course of disease [ 6 ] . Much of the theory stems from what we have learnt from limited trials in other corona viruses [ 7 ] .

Just like SARS - CoV and MERS - CoV [ 2 , 56 ] , there is currently no clinically proven specific antiviral agent available for SARS - CoV - 2 infection . The supportive treatment , including oxygen therapy , conservation fluid management , and the use of broad - spectrum antibiotics to cover secondary bacterial infection , remains to be the most important management strategy [ 15 ] . According to the research on molecular mechanisms of coronavirus infection [ 57 ] and the genomic organization of SARS - CoV - 2 [ 6 ] , there are several potential therapeutic targets to repurpose the existing antiviral agents or develop effective interventions against this novel coronavirus .

Due to the severe lung injury caused by SARS - CoV and MERS - CoV , patients who were infected and required invasive mechanical ventilation and extracorporeal membrane oxygenation had a very high mortality . 2 , 3 , 16 Unfortunately , no specific coronavirus antiviral agents or vaccines have been proven to be effective . In a historical control study , a combination of protease inhibitors ( lopinavir and ritonavir ) was associated with substantial clinical benefit among patients with SARS - CoV . 17 Results from in vitro cell and in vivo animal studies suggest that a combination of lopinavir / ritonavir and interferon - b1 may be effective against MERS - CoV . A placebo - controlled trial of interferon - b1 and lopinavir / ritonavir was initiated in patients with laboratory - confirmed MERS requiring hospital admission in Saudi Arabia . 18 Remdesivir , a 1 0 - cyano - substituted adenosine nucleotide analogue prodrug with broad - spectrum antiviral activity against several RNA viruses , may be evaluated . 19 The first reported patient with COVID - 19 infection in the United States was administered remdesivir . Based on worsening clinical status , IV remdesivir was given for compassionate use on hospital day 7 ( illness day 11 ) . 20 Two randomized controlled trials have been registered to evaluate the safety and efficacy of remdesivir in mild / moderate or severe patients with COVID - 19 viral pneumonia . 21 , 22 Kirchdoerfer and Ward 23 noticed that nonstructural proteins ( nsp ) 12 polymerase may be a template for the design of novel antiviral therapeutic agents to interrupt the assembly of the SARS - CoV core RNA - synthesis machinery . COVID - 19 has full - length genome sequences with > 75 % nucleotide identity with that of SARS - CoV , 7 which allows the molecular e2 Editorial structure information to be used as a model for coronavirus antiviral design . Clinical studies should assess the effectiveness and safety of monoclonal and polyclonal neutralizing antibody products and aim to discover therapeutic targets against immunopathologic host responses .

Since the outbreak of the novel coronavirus disease COVID - 19 , caused by the SARS - CoV - 2 virus , this disease has spread rapidly around the globe . Considering the potential threat of a pandemic , scientists and physicians have been racing to understand this new virus and the pathophysiology of this disease to uncover possible treatment regimens and discover effective therapeutic agents and vaccines . To support the current research and development , CAS has produced a special report to provide an overview of published scientific information with an emphasis on patents in the CAS content collection . It highlights antiviral strategies involving small molecules and biologics targeting complex molecular interactions involved in coronavirus infection and replication . The drug - repurposing effort documented herein focuses primarily on agents known to be effective against other RNA viruses including SARS - CoV and MERS - CoV . The patent analysis of coronavirus - related biologics includes therapeutic antibodies , cytokines , and nucleic acid - based therapies targeting virus gene expression as well as various types of vaccines . More than 500 patents disclose methodologies of these four biologics with the potential for treating and preventing coronavirus infections , which may be applicable to COVID - 19 . The information included in this report provides a strong intellectual groundwork for the ongoing development of therapeutic agents and vaccines .

To date , there are no SARS - CoV - 2 - specific antiviral agents . Researchers have been racing to find possible treatments to save lives and produce vaccines for future prevention . To support research and development efforts to discover effective therapeutic and preventive agents for COVID - 19 , CAS , a division of the American Chemical Society specializing in scientific information solutions , has analyzed scientific data related to the development of therapeutic agents and vaccines for human coronaviruses since 2003 . The analyses presented in this report are based on the CAS content collection , a scientist - curated data collection covering published scientific literature and patents from over 60 patent authorities worldwide . For a subset of the analyses , both CAS and MEDLINE data were collectively analyzed .

Which are the models to aid decision makers in determining how to prioritize and distribute scarce, newly proven therapeutics?

As recognized by the World Health Organization ( WHO ) , mathematical models , especially those devised in a timely fashion , can play a key role in providing health decision - and policy - makers with evidence - based information . Modeling can , indeed , better help understanding : i ) how transmissible the disease is , ii ) when the infectiousness is highest during the course of infection , iii ) how severe the infection is , and iv ) how effective interventions have been and ought to be .

Severe acute respiratory syndrome Covid - 19 ( SARS - CoV - 2 ) has been declared a worldwide emergency and a pandemic disease by the World Health Organisation ( WHO ) . It started in China in December 2019 , and it is currently rapidly spreading throughout Italy , which is now the most affected country after China . There is great attention for the diffusion and evolution of the CoVid - 19 infection which started from the north ( particularly in the Lombardia region ) and it is now rapidly affecting other Italian regions . We investigate on the impact of patients hospitalisation in Intensive Care Units ( ICUs ) at a regional and subregional granularity . We propose a model derived from well - known models in epidemic to estimate the needed number of places in intensive care units . The model will help decision - makers to plan resources in the short and medium - term in order to guarantee appropriate treatments to all patients needing it . We analyse Italian data at regional level up to March 15th aiming to : ( i ) support health and government decision - makers in gathering rapid and efficient decisions on increasing health structures capacities ( in terms of ICU slots ) and ( ii ) define a scalable geographic model to plan emergency and future CoVid - 19 patients management using reallocating them among health structures . Finally , the here proposed model can be useful in countries where CoVid - 19 is not yet strongly diffused .

COVID - 19 threatens to overwhelm hospital facilities throughout the United States . We created an interactive , quantitative model that forecasts demand for COVID - 19 related hospitalization based on county - level population characteristics , data from the literature on COVID - 19 , and data from online repositories . Using this information as well as user inputs , the model estimates a time series of demand for intensive care beds and acute care beds as well as the availability of those beds . The online model is designed to be intuitive and interactive so that local leaders with limited technical or epidemiological expertise may make decisions based on a variety of scenarios . This complements high - level models designed for public consumption and technically sophisticated models designed for use by epidemiologists . The model is actively being used by several academic medical centers and policy makers , and we believe that broader access will continue to aid community and hospital leaders in their response to COVID - 19 .

is the ( which was not peer - reviewed ) The copyright holder for this preprint . https : / / doi . org / 10 . 1101 / 2020 . 03 . 17 . 20037671 doi : medRxiv preprint worldwide ( 14 ) . In Iran , the first case of COVID - 19 was reported on Day 30 of month 12 ( Bahman ) in Iranian calendar from Qom , and we used the reported data until March 29 , 2020 ( 15 ) . As of the time of the up to date this article , March 29 , 2020 , According to the Daily Reports in Iran , 38309 COVID - 19 , 2640 deaths were reported . in recent weeks , Firstly , universities and schools , then public places and shrines were closed . People are referring to health centers and hospitals , and the public is almost alarmed by the epidemic of panic and inaccurate reporting in cyberspace . The recurring and important questions are : How is the size of the epidemic of COVID - 19 in Iran and how long and when will the epidemic go down ? We cannot answer these questions with certainty , but it can be investigated in terms of pathogenic behavior ( coronavirus ) , host conditions , behavior ( human ) and environmental factors of coronavirus transmission , daily reports of definitive COVID - 19 patients released by Iran Ministry of Health and Medical Education and the use of modeling given the assumptions and the percentage of error . Indeed , although the models are different , multiple , and changeable in nature and do not insist on the correctness of the forecasts , the decision - making conditions for health policy - makers and authorities are more transparent and helpful ( 16 ) . This study aimed to model and determine the epidemic trend and predict COVID - 19 patients in Iran using mathematical and statistical modeling .

The procedures of the interactive fuzzy approach are given as follows : ( 1 ) First , the priority level of the three objective functions f1 , f2 and f3 are determined by the decision - makers . ( 2 ) The best solution foptimal and the worst solution fnadia of the three objective functions are calculated . The foptimal is obtained by optimizing each objective function individually . The fnadia is calculated with a lexicographic method based on the given priority level of the objective functions in order to obtain non - dominated efficient solutions [ 67 ] . The range of each objective function can then be determined . ( 3 ) The satisfaction level of each objective function can be calculated by the fuzzy membership functions given in Equations ( 35 ) – ( 37 ) , which ranges from 0 to 1 . ( 35 ) μ1 ( x ) = { 1 , if f1 < f1optimal f1nadir−f1f1nadia−f1optimal , if f1optimal≤f1≤f1nadia0 , if f1 > f1nadir ( 36 ) μ2 ( x ) = { 1 , if f2 < f2optimal f2nadir−f2f2nadia−f2optimal , if f2optimal≤f2≤f2nadia0 , if f2 > f2nadir ( 37 ) μ3 ( x ) = { 1 , if f3 < f3optimal f3nadir−f3f3nadia−f3optimal , if f3optimal≤f3≤f3nadia0 , if f3 > f3nadir ( 4 ) With the given priority level of different objective functions , the multi - objective optimization problem can then be converted to a single objective model with the ε - constraint method given in Equation ( 38 ) , where εf2 and εf3 are the required satisfaction levels : ( 38 ) Maximize μ1 ( x ) Subject to : μ2 ( x ) ≥εf2μ3 ( x ) ≥εf3εf2 , εf3∈ [ 0 , 1 ] Equations ( 5 ) – ( 34 ) ( 5 ) The satisfaction levels εf2 and εf3 can be adjusted in order to generate a set of Pareto optimal solutions , from which a preferred combination can be selected by the decision - makers .

Efforts targeted at a universal coronavirus vaccine

The novel coronavirus infection ( COVID - 19 or Coronavirus disease 2019 ) that emerged from Wuhan , Hubei province of China has spread to many countries worldwide . Efforts have been made to develop vaccines against human coronavirus ( CoV ) infections such as MERS and SARS in the past decades . However , to date , no licensed antiviral treatment or vaccine exists for MERS and SARS . Most of the efforts for developing CoV vaccines and drugs target the spike glycoprotein or S protein , the major inducer of neutralizing antibodies . Although a few candidates have shown efficacy in in vitro studies , not many have progressed to randomized animal or human trials , hence may have limited use to counter COVID - 19 infection . This article highlights ongoing advances in designing vaccines and therapeutics to counter COVID - 19 while also focusing on such experiences and advances as made with earlier SARS - and MERS - CoVs , which together could enable efforts to halt this emerging virus infection .

This report provides an overview of published information on global research and development of coronavirus - related therapeutic agents and preventive vaccines based on the extensive CAS content collection , with a focus on patents . It includes an overview of coronavirus morphology , biology , and pathogenesis with a particular focus on antiviral strategies involving small molecule drugs , as well as biologics targeting complex molecular interactions involved in coronavirus infection and replication . The drug - repurposing effort summarized in this report is focused primarily on agents currently known to be effective against other RNA viruses including SARS - CoV , MERS - CoV , influenza , HCV , and Ebola as well as anti - inflammatory drugs . The potential impact of biologics for treatment of coronavirus infections is promising and includes a wide variety of options including bioengineered and vectored antibodies , cytokines , and nucleic acid - based therapies targeting virus gene expression as well as various types of vaccines .

These studies demonstrate the rapid development and immunogenicity of novel microneedle array ( MNA ) delivered recombinant coronavirus ( SARS - CoV - 2 ) vaccines . MNA delivered MERS - S1 subunit vaccines induced potent and long - lasting antigen antigen - specific immune responses . Notably , MNA delivery of these vaccines generated significantly stronger immune responses than those administered by traditional subcutaneous needle injection , indicating the improved immunogenicity by skin - targeted delivery . These efforts with MNA MERS - S1 subunit vaccines enabled the rapid design and production of MNA SARS - CoV - 2 vaccines , capable of eliciting potent virus - specific antibody responses that were evident as early as 2 weeks after immunization . Rapid design and production of MNA - embedded SARS - CoV - 2 - S1 subunit vaccines using clinically applicable MNA fabrication methods supports the development of MNA delivered recombinant coronavirus vaccines for clinical vaccine applications . Collectively , our studies support the clinical development of MNA protein subunit vaccines for COVID - 19 and other emerging infectious diseases .

The development of vaccines for human use can take years , especially when novel technologies are used that have not been extensively tested for safety or scaled up for mass production . Because no coronavirus vaccines are on the market and no large - scale manufacturing capacity for these vaccines exists as yet ( Table 1 ) , we will need to build these processes and capacities . Doing this for the first time can be tedious and time consuming ( Figure 1 ) . CEPI has awarded funds to several highly innovative players in the field , and many of them will likely succeed in eventually making a SARS - CoV - 2 vaccine . However , none of these companies and institutions have an established pipeline to bring such a vaccine to late - stage clinical trials that allow licensure by regulatory agencies , and they do not currently have the capacity to produce the number of doses needed . An mRNA - based vaccine , which expresses target antigen in vivo in the vaccinee after injection of mRNA encapsulated in lipid nanoparticles , co - developed by Moderna and the Vaccine Research Center at the National Institutes of Health , is currently the furthest along , and a phase I clinical trial recently started ( ClinicalTrials . gov : NCT04283461 ) . Curevac is working on a similar vaccine but is still in the pre - clinical phase . Additional approaches in the pre - clinical stage include recombinant - proteinbased vaccines ( focused on the S protein , e . g . , ExpresS2ion , iBio , Novavax , Baylor College of Medicine , University of Queensland , and Sichuan Clover Biopharmaceuticals ) , viral - vectorbased vaccines ( focused on the S protein , e . g . , Vaxart , Geovax , University of Oxford , and Cansino Biologics ) , DNA vaccines ( focused on the S protein , e . g . , Inovio and Applied DNA Sciences ) , live attenuated vaccines ( Codagenix with the Serum Institute of India , etc . ) , and inactivated virus vaccines ( Figure 1 ; Table 1 ) . All of these platforms have advantages and disadvantages ( Table 1 ) , and it is not possible to predict which strategy will be faster or more successful . Johnson & Johnson ( J & J ) ( Johnson & Johnson , 2020 ) and Sanofi ( 2020 ) recently joined efforts to develop SARS - CoV - 2 vaccines . However , J & J is using an experimental adenovirus vector platform that has not yet resulted in a licensed vaccine . Sanofi ' s vaccine , to be made using a process similar to the process used for their approved Flublok recombinant influenza virus vaccine ( Zhou et al . , 2006 ) , is also months , if not years , from being ready for use in the human population . Creating infectious clones for attenuated coronavirus vaccine seeds takes time because of large genome size . Safety testing will need to be extensive .

Since the outbreak of the novel coronavirus disease COVID - 19 , caused by the SARS - CoV - 2 virus , this disease has spread rapidly around the globe . Considering the potential threat of a pandemic , scientists and physicians have been racing to understand this new virus and the pathophysiology of this disease to uncover possible treatment regimens and discover effective therapeutic agents and vaccines . To support the current research and development , CAS has produced a special report to provide an overview of published scientific information with an emphasis on patents in the CAS content collection . It highlights antiviral strategies involving small molecules and biologics targeting complex molecular interactions involved in coronavirus infection and replication . The drug - repurposing effort documented herein focuses primarily on agents known to be effective against other RNA viruses including SARS - CoV and MERS - CoV . The patent analysis of coronavirus - related biologics includes therapeutic antibodies , cytokines , and nucleic acid - based therapies targeting virus gene expression as well as various types of vaccines . More than 500 patents disclose methodologies of these four biologics with the potential for treating and preventing coronavirus infections , which may be applicable to COVID - 19 . The information included in this report provides a strong intellectual groundwork for the ongoing development of therapeutic agents and vaccines .

Efforts to develop animal models and standardize challenge studies

Currently , humans infected with MERS - CoV have been reported to develop a severe acute respiratory illness with symptoms of fever , cough , shortness of breath , and often , renal failure . More than half of the reported patients have died . Some laboratory - confirmed cases reportedly experience a mild respiratory illness . The development of animal models that reflect these variations in the human population is challenging . In this study , we sought to develop an animal model that displays these symptoms . Our studies have tested mouse , ferret , and guinea pig models and found these animals are not susceptible to MERS - CoV ( unpublished data ) .

Early effort was directed in developing animal models for SARS - CoV , but the specificity of the virus to ACE2 ( receptor of SARS - CoV ) was a major hindrance to such efforts . Later , a SARS - CoV transgenic mouse model was developed by introducing hACE2 gene into the mouse genome . 51 The first animal model used for developing a MERS - CoV vaccine was rhesus macaques . Infected animals showed clinical symptoms such as increased body temperature , piloerection , cough , hunched posture , and reduced food intake . 52 Another frequently used animal model for MERS - CoV is the common marmoset , wherein the virus caused lethal pneumonia . 53 Humoral and cell - mediated immunity could be detected in both rhesus macaques and common marmoset following MERS - CoV immunization . 43 , 52 , 53 Roberts et al . established golden Syrian hamsters ( strain LVG ) as a model to assess vaccine protection to different SARS - CoV strains . 47 These hamsters are a potential model for studying CoV pathology and pathogenesis and vaccine efficacy . The attenuated NSP16 CoV vaccine was studied in mice . 54

Effective vaccines are essential for interrupting the chain of transmission from animal reservoirs and infected humans to susceptible hosts and are often complementary to antiviral treatment in the control of epidemics caused by emerging viruses . Efforts have been made to develop S protein - based vaccines to generate long - term and potent neutralizing antibodies and / or protective immunity against SARS - CoV 81 , 91 . Live - attenuated vaccines have been evaluated in animal models for SARS 92 . However , the in vivo efficacy of these vaccine candidates in elderly individuals and lethal - challenge models and their protection against zoonotic virus infection have yet to be determined before a clinical study is initiated . This is probably because SARS died down 17 years ago and no new case has been reported since .

It is necessary to further test the therapeutic and preventive effects of this truncated S - RBD in an animal model . Thus far , however , no small animal model has been established for a MERS - CoV challenge study [ 37 ] . While the lung cells of Syrian hamster express the receptor of MERS - CoV , it was reported that this animal model was not susceptible to the induction of MERS - CoV infection [ 38 ] . Rhesus macaques could generate pneumonia - like symptoms within 24 hours of MERS - CoV infection [ 39 ] ; however , the macaque system is not as widely applicable as a small animal model . Therefore , we are awaiting the establishment of a small animal model in order to carry out viral challenge studies .

A very important question for understanding SARS - CoV - 2 infection is what systems can be used for study . Early studies on SARS - CoV - 2 determined that the cellular receptor for the virus is ACE2 , similarly to SARS - CoV ( 3 ) . This knowledge helps to develop an understanding of susceptibility of certain in vitro cell lines to infection with the novel virus . The likelihood is that if cells were not permissive for growth of SARS - CoV , they probably will not support growth of SARS - CoV - 2 . As more labs around the world start researching the new virus , a better understanding of the permissive cell lines will be developed , an important step to testing therapeutic options and developing a better understanding of basic aspects of SARS - CoV - 2 virology . The more challenging aspect of lab - based research on the novel human coronavirus will be developing small - animal models . The early research on receptor usage suggests the virus is not able to infect cells expressing mouse ACE2 ( 3 ) , thus making a mouse model potentially challenging . Whether expression of human ACE2 in mouse lungs using adenovirus or mouse adaptation of SARS - CoV - 2 can develop appropriate models , as was done for SARS - CoV ( 18 ) , is a pressing question . Whether other small - animal models can be used also needs to be investigated . These models will be essential for thoroughly testing therapeutic candidates and vaccine strategies and understanding the pathology of disease .

Efforts to develop prophylaxis clinical studies and prioritize in healthcare workers

Approaches to evaluate risk for enhanced disease after vaccination

All these vaccines face uncertainties , however , not the least of which is the lack of a reliable animal model in which to test them . Undertaking clinical trials of a SARS vaccine in a setting of vanishing perception of the potential risk of re - emergence of the disease is yet another difficulty . A final uncertainty is the possibility of immune enhancement , a phenomenon which was observed when studying vaccination of cats against the feline coronavirus , FIPV : animals vaccinated with a whole inactivated virus vaccine showed accelerated disease and death after exposure to wild type virus . The humoral response to FIPV does not seem to be protective but can in fact lead to drastically accelerated disease , presumably due to antibody - dependent enhancement of target cell infection via Fc receptor - mediated attachment of virus - antibody complexes . Control of infection and FIPV clearance are thought to primarily depend on cell - mediated immune responses [ 85 ] .

Several SARS vaccine candidates elicited neutralizing antibodies and were effective in protecting young mice or hamsters from challenge [ 48 , [ 57 ] [ 58 ] [ 59 ] [ 60 ] [ 61 ] [ 62 ] [ 63 ] . However , reports of immunopathologic reactions in older mice and in nonhuman primates vaccinated with SARS - CoV vaccines that were subsequently challenged with SARS - CoV [ 57 , 59 , 62 , 64 ] have revealed two concerns about proceeding to clinical trials with SARS - CoV vaccines . First , there is a precedent for coronavirus - vaccine associated disease enhancement ; kittens immunized with a vaccinia virus vectored feline infectious peritonitis virus vaccines developed severe disease when they were subsequently infected with FIPV [ 65 ] . In these kittens , non - neutralizing or sub - neutralizing antibodies facilitated viral entry into macrophages . The concern that is extrapolated from the FIPV vaccine experience to human SARS - CoV vaccines is whether vaccine recipients will develop more severe disease if they are exposed to or infected with SARS - CoV after neutralizing antibody titers decline . The second concern is whether recipients of a SARS - CoV vaccine would be at risk of developing pulmonary immunopathology following infection with an unrelated human coronavirus , for example , 229E , OC43 , HKU1 or NL63 that usually causes mild , self limited disease . Although findings from preclinical evaluation have revealed these concerns , studies in animal models may not be able to provide data to confirm or allay these concerns .

Several SARS vaccine candidates elicited neutralizing antibodies and were effective in protecting young mice or hamsters from challenge [ 48 , [ 57 ] [ 58 ] [ 59 ] [ 60 ] [ 61 ] [ 62 ] [ 63 ] . However , reports of immunopathologic reactions in older mice and in non - human primates vaccinated with SARS - CoV vaccines that were subsequently challenged with SARS - CoV [ 57 , 59 , 62 , 64 ] have revealed two concerns about proceeding to clinical trials with SARS - CoV vaccines . First , there is a precedent for coronavirus - vaccine associated disease enhancement ; kittens immunized with a vaccinia virus vectored feline infectious peritonitis virus vaccines developed severe disease when they were subsequently infected with FIPV [ 65 ] . In these kittens , non - neutralizing or sub - neutralizing antibodies facilitated viral entry into macrophages . The concern that is extrapolated from the FIPV vaccine experience to human SARS - CoV vaccines is whether vaccine recipients will develop more severe disease if they are exposed to or infected with SARS - CoV after neutralizing antibody titers decline . The second concern is whether recipients of a SARSCoV vaccine would be at risk of developing pulmonary immunopathology following infection with an unrelated human coronavirus e . g . 229E , OC43 , HKU1 or NL63 that usually causes mild , self limited disease . Although findings from preclinical evaluation have revealed these concerns , studies in animal models may not be able to provide data to confirm or allay these concerns . Factors to consider when selecting an animal model . Animal models should be tailored to the goals of the study . If the primary goal is to elucidate pathogenesis , the model should replicate key aspects of the disease and immunological reagents should be available . The demographic background ( e . g . age for SARS ) of the animal should be taken into consideration . In contrast , animal models used in vaccine / antiviral efficacy studies must demonstrate meaningful differences between vaccinated and unvaccinated control groups . Special consideration should be given to how animals from different demographic backgrounds respond to the vaccine / antiviral under investigation . To determine the correlate of protection , it is necessary to study the immune response to the vaccine as well as the immune response elicited after challenge with the homologous coronavirus . It may be of interest to evaluate the response to challenge with other coronaviruses that the vaccinated host may encounter . Gretebeck Table 1 Coronaviruses associated with disease in humans .

not serve as a model for all coronaviruses ( Table 2 ) . The ability to elicit clinical disease , viral replication and pathology depends on the expression of the viral receptor , the species and the demographic characteristics of the animal . Infection of young mice with SARS - CoV was not ideal because there was limited histopathology and no clinical disease . However the combination of two approaches , using mouse - adapted SARS - CoV in older mice , resulted in a model of ARDS that represents a more stringent challenge for the evaluation of vaccine efficacy than either alone . Unfortunately , immune defects associated with aging are complex and can influence results of vaccine evaluations [ 55 , 56 ] .

Because infection in young mice was cleared rapidly without clinical disease , in addition to infecting older mice , two approaches were employed to enhance clinical signs of disease in young mice : the development of transgenic mice expressing the human ACE2 ( hACE2 ) receptor and the adaptation of SARS - CoV to mice by serial passage . McCray et al . demonstrated that expression of hACE2 under the control of an epithelial cell - specific promoter K18 resulted in lethal SARS - CoV infection [ 38 ] . However , SARS - CoV infection in K18 - hACE2 mice was associated with central nervous system disease , which was not a feature of SARS in humans . Tseng et al . developed two lineages of transgenic mice expressing hACE2 under the CAG promoter , a strong composite promoter consisting of the cytomegalovirus immediate early enhancer , the chicken b - actin promoter , rabbit globulin splicing and polyadenylation sites to drive high levels of gene expression in mammalian expression vectors [ 39 ] . The transgene - positive mice ( AC70 and AC63 ) showed robust viral growth , generalized illness and tissue pathology after infection with SARS - CoV [ 39 ] . The lethal lineage of mice ( AC70 ) showed a wider spectrum of clinical manifestations , including death , than the nonlethal lineage mice ( AC63 ) . Transgenic mice were used for pathogenesis studies and evaluation of vaccines and other therapeutics [ 40 , 41 ] .

Assays to evaluate vaccine immune response

Data from animal CoV vaccination suggest that systemic humoral or cell - mediated immune responses induced by parenteral administration may not be adequate to prevent respiratory tract infection . 66 Because respiratory mucosa is the initial site in CoV infection and transmission , mucosal immunization , such as using intranasal vaccine , 67 could be an effective strategy for prophylaxis by induction of mucosal and systemic immune responses . The molecular mechanisms of mucosal and systemic immunological factors are different , such that it is difficult to predict the surrogate marker for CoV efficacy . The best surrogate assays for protection as well as herd immunity toward different CoV infections warrant detailed investigations .

Limited information is currently available on which parts of the SARS - CoV - 2 sequence are recognized by human immune responses . Such knowledge is of immediate relevance and would assist vaccine design and facilitate the evaluation of vaccine candidate immunogenicity , as well as monitoring of the potential consequences of mutational events and epitope escape as the virus is transmitted through human populations .

Neutralizing antibodies ( Nabs ) play a critical role in protection against a variety of viral diseases . An accurate assessment of Nab responses in virus - infected patients is needed to determine immune correlates of protection . It is also an essential and integral part of a vaccine development process . Conventional virus - neutralization assays require the use of replication - competent , infectious viruses . Evaluating virus - neutralizing activity of a large number of antisera with these assays is undesirable due to safety concerns , especially for a biosafety level 3 ( BSL3 ) pathogen like SARS - CoV . The same safety concerns have prompted our laboratory to utilize replication - defective pseudoviruses for HIV - 1 neutralization assay ( Kim et al . , 2001 ) . In this assay , nonreplicating Moloney murine leukemia virus ( MuLV ) particles pseudotyped with HIV - 1 envelope glycoproteins are used ( Schnierle et al . , 1997 ) . These pseudoviruses encode a h - galactosidase gene , which allows detection of individual infected cells when stained with X - Gal ( 5 - bromo - 4 - chloro - 3 - indolyl - h - D - galactopyranoside ) . In this study , we report development of a SARS - CoV pseudovirus neutralization assay , which should be particularly valuable for researchers who may not have easy access to BSL3 containment facility . Additionally , we describe a high - throughput system for quantitative analyses of X - Gal stained cells . This assay system should facilitate rapid evaluation of antibody responses to vaccine candidates and / or entry inhibitors against SARS - CoV .

The copyright holder for this preprint ( which was not peer - reviewed ) is the . https : / / doi . org / 10 . 1101 / 2020 . 03 . 18 . 20038059 doi : medRxiv preprint Overall , the assays developed and validated in this study could be instrumental for patient contact tracing , serosurveillance studies , as well as vaccine evaluation studies . However , since various studies will be carried out in different labs , it is crucial to calibrate and standardize assays developed by different labs using well defined standard references as a part of diagnostic assay validation . This is not only needed to reduce interassay variability , but to also harmonize the results obtained from different labs using various assays ( 14 ) . This is crucial for better comparison and interpertaion of results from different studies as well as evaluation of vaccine trials , allowing for uniform assessment of immunogenicity , efficacy and better understanding of correlates of immune protection ( 15 ) . Thus , setting up reference panels is a vital element in our preparedness approaches to emerging viruses . All rights reserved . No reuse allowed without permission .

Most preventative vaccines are designed to elicit a humoral immune response , typically via the administration of whole protein from a pathogen . Antibody 230 vaccines typically do not produce a robust T - cell response . [ 72 ] A T - cell vaccine is meant to elicit a cellular immune response directing CD8 + cells to expand and attack cells presenting the HLA Class I restricted pathogen - derived peptide antigen .

Process development for vaccines, alongside suitable animal models

Suitable animal models for evaluating vaccines for SARS - and MERS - CoV are lacking or highly limited , making the process of vaccine development highly challenging . 42 , 43 Development of an efficient animal model that mimics the clinical disease can inform on pathogenesis as well as to develop vaccines and therapeutics against these CoVs . Several animal models have been evaluated for SARS - and MERS CoVs including mouse , guinea pigs , hamsters , ferrets , rabbits , rhesus macaques , marmosets , and cats . 42 , 44 - 50

Why does this take so long ? As mentioned earlier , there are currently no approved human coronavirus vaccines . In addition , many technologies used ( production platforms , vectors , etc . ) are new and need to be tested thoroughly for safety . The target for the vaccine , the S protein , has been identified , and vaccine candidates are being generated . This is usually followed by two important steps that are typically needed before bringing a vaccine into clinical trials . First , the vaccine is tested in appropriate animal models to see whether it is protective . However , animal models for SARS - CoV - 2 might be difficult to develop . The virus does not grow in wild - type mice and only induced mild disease in transgenic animals expressing human ACE2 ( Bao et al . , 2020 ) . Other potential animal models include ferrets and NHPs , for which pathogenicity studies are ongoing . Even in the absence of an animal model that replicates human disease , it is possible to evaluate the vaccine because serum from vaccinated animals can be tested in in vitro neutralization assays . Post - challenge safety data should also be collected in these cases to assess for complications such as the ones seen SARS - CoV - 1 and MERS - CoV vaccines . Second , vaccines need to be tested for toxicity in animals , e . g . , in rabbits . Usually , viral challenge is not part of this process , because only the safety of the vaccine will be evaluated . This testing , which has to be performed in a manner compliant with GLP ( Good Laboratory Practice ) , typically takes 3 - 6 months to complete . For some vaccine platforms , parts of the safety testing might be skipped if there is already sufficient data available for similar vaccines made in the same production process . Vaccines for human use are produced in processes that comply with current Good Manufacturing Practice ( cGMP ) to ensure constant quality and safety of vaccines . This requires dedicated facilities , trained personnel , proper documentation , and raw material that was produced to be of cGMP quality . These processes have to be designed or amended to fit SARS - CoV - 2 vaccines . For many vaccine candidates in the preclinical phase , such processes do not yet exist and have to be developed from scratch .

Based on the previous experience in developing SARS - CoV vaccines , current advancements and potential strategies in the development of MERS - CoV vaccines have been discussed in this review . Apart from inactivated and live - attenuated virus vaccines , DNA - and VLP - based vaccines , particularly subunit vaccines containing the RBD of MERS - CoV S protein , are critically important . Additionally , suitable adjuvant formulation and appropriate administration routes may need to be further considered to enhance the immunogenicity of the vaccine candidates . Furthermore , development of effective animal models for MERS - CoV infection is important for evaluating the efficacy of MERS - CoV candidate vaccines . Taken together , the strategies discussed above will have important implications for the development of effective MERS vaccines in the future .

Previous reviews on SARS have summarized the approaches for the development of effective CoV vaccines , pointed out the importance of SARS - CoV S protein as a target for vaccine and therapeutic development and outlined a roadmap for the product development of a SARS - CoV RBD protein - based subunit vaccine with manufacturing for future clinical testing [ 43 – 46 ] . In this review , we will briefly discuss current stages of MERS vaccine development , and provide potential strategies for developing MERS vaccines based on the experience from development of SARS vaccines , with the focus on subunit vaccines and how to improve the efficacy of MERS subunit vaccines . In addition , we also summarize current animal models for MERS - CoV and emphasize the importance for evaluation of efficacy of MERS vaccine candidates in effective animal models .

Despite the lack of suitable models , several groups are developing vaccines and therapeutics against MERS - CoV ( Zhang et al . , 2014a ( Zhang et al . , , 2014b Chan et al . , 2013 ; Hart et al . , 2014 ; Coleman et al . , 2014b ; de Wilde et al . , 2014 ; Dyall et al . , 2014 ; Kim et al . , 2014 ) . Vaccine candidates are being evaluated for immunogenicity and antivirals are being evaluated in vitro . Medical countermeasures have the potential to advance along the path towards regulatory approval if a susceptible small animal model can be developed and used in conjunction with the marmoset model . In concert with public health efforts , novel therapies could curb the on - going MERS - CoV epidemic and reduce the morbidity and mortality associated with MERS - CoV .