key: cord-0815319-0lgigmj2
authors: Abdel-Moneim, Ahmed S.; Abdelwhab, Elsayed M.; Memish, Ziad A.
title: Insights into SARS-CoV-2 evolution, potential antivirals, and vaccines
date: 2021-02-22
journal: Virology
DOI: 10.1016/j.virol.2021.02.007
sha: 0952988c385f9e2a5c23522d4cffbcf4120d3051
doc_id: 815319
cord_uid: 0lgigmj2

SARS-CoV-2 is a novel coronavirus, spread among humans, and to date, more than 100 million of laboratory-confirmed cases have been reported worldwide. The virus demonstrates 96% similarity to a coronavirus from a horseshoe bat and most probably emerged from a spill over from bats or wild animal(s) to humans. Currently, two variants are circulating in the UK and South Africa and spread to many countries around the world. The impact of mutations on virus replication, virulence and transmissibility should be monitored carefully. Current data suggest recurrent infection with SARS-CoV-2 correlated to the level of neutralising antibodies and with sustained memory responses following infection. Recently, remdesivir was FDA approved for treatment of COVID-19, however many potential antivirals are currently in different clinical trials. Clinical data and experimental studies indicated that licenced vaccines are helpful in controlling the disease. However, the current vaccines should be evaluated against the emerging variants of SARS-CoV-2.

nucleocapsid G204R amino acid substitutions. Meanwhile, the GH clade contains spike D614G plus NS3-Q57H amino acid substitutions. The O clade contains viral sequences that do not cope with any of above-mentioned criteria (Table 1) . Currently, G, GH, GV and GR are the major clades and account for more than 91% of all global SARS-CoV-2 sequenced genomes (GISAID sequence database).

The GISAID clades are further divided into two major lineages: A and B. A numerical value of the descendants was given to sub-lineages with a maximum of three sublevels (ex. A.1.1.1). This nomenclature is known as the Phylogenetic Assignment of Named Global Outbreak Lineages (Pangolin), which is supported by a freely-available website (https://pangolin.cog-uk.io/) (Rambaut et al., 2020a) . open source tracking introduced a new nomenclature system, in which a novel clade is introduced when the frequency of circulation reaches approximately 20% for worldwide strains (Hadfield et al., 2018) . Five clades were identified as being globally widespread: 19A (the root clade that spread in China then to the rest of Asia), 19B (the ancestor of the December 2019 Wuhan strain), and clades 20A, 20B and 20C. Clade 20A emerged due to D614G amino acid substitution in the spike glycoprotein during the European outbreak in February 2020. The latter spread globally during late February, from which clades 20B and 20C emerged in Europe and North America, respectively. All three clades (20A, 20B and 20C) belong to the GISAID G clade and harbour the D614G mutation in the spike (Korber et al., 2020) . Two variants of concern emerged. The Nextstrain classification was modified to include labels correspond to an emerging variant and the prominent spike mutation and currently new clades 20D, 20E, 20F, 20G, 20H/501Y.V2, and 20I/501Y.V1 have been added (Bedford et al., 2021) as shown in Table 2 .

The SARS-CoV-2, VUI 202012/01 variant under investigation (which has been detected in the UK) belongs to 20B, clade GR, lineage B.1.1.7. and will latterly be referred to as the Variant of Concern (VOC) . It has spread to many countries around the world, in Africa (Gambia, Mayotte and Nigeria), (T716I, S982A, D1118) (Rambaut et al., 2020b) . Another VOC also emerged in South Africa that possesses 80A, 215G, 484K, 501Y, and 701V amino acid residues in the spike protein. It spread to Africa (Botswana, Ghana, Kenya Mayotte, Mozambique) Asia, (Bangaladish, Israel, Japan, South Korea, and United Arab of Emirates), Australia ( Asutralia and New Zealand), Europe (Austria, Belgium, Denmark, Filand , France, Germany, Irland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, Turkey, and United Kingdom), North and Central America (Canada, USA, Panama). These mutations developed unexpectedly, and the possible explanations for this are as follows: i) a prolonged infection among patients with reduced immunocompetence (Choi et al., 2020; McCarthy et al., 2020) , ii) increased mutation rate as a consequence of immune pressure during reinfection, iii) adaptation of the virus in a susceptible animal then transferring infection back to humans, as was detected in mink in Denmark (deletion 69-70 and Y453F) (Laussauniere et al., 2020). Some mutations can provide a selective advantage for the virus, including increased transmissibility, increased receptor binding affinity or providing the virus with the capacity to evade the host immune responsiveness or by simply altering neutralising epitopes. An earlier D614G variant increased the viral cellular infectivity but did not alter the clinical outcome of the disease (Volz et al., 2020 ). An attenuated SARS-CoV-2 phenotype was hypothesised based on 382 nucleotide deletions in SARS-CoV-2 Singapore strains . Such deletions resulted in the removal of the transcription regulatory sequence (TRS) of the ORF8 with subsequent assumption of reduced fitness of virus replication (Muth et al., 2018) . Interestingly, a J o u r n a l P r e -p r o o f similar deletion phenotype was detected in SARS-CoV at the end of the 2003 outbreak (Chinese-SARS-Molecular-Epidemiology-Consortium, 2004) . In addition, an isolate with 81 nucleotide deletions with subsequent deletions of 27 amino acids in the ORF7a was also reported in Arizona, USA (Holland et al., 2020) ; however, such variants have since disappeared.

The D614G amino acid substitution was found in a B-cell epitope (Koyama et al., 2020) . The majority of the SARS-CoV-2 strains with D614G mutation also demonstrated P4715L and P323L amino acid substitutions in ORF1ab and RdRp, respectively. Spike D614G mutation in G, GR, and GH clades is suggested to be linked to higher viral loads (Bhattacharyya et al., 2020; Korber et al., 2020) , while rapidly-spreading strains were linked to the presence of the Nsp12 P322L (Pachetti et al., 2020) . The GR clade is more prevalent among patients with severe disease manifestations (Korber et al., 2020) . Conversely, Grubaugh et al. doubt the possibility of a clear role for the D614G mutation based on currently available data, and that extensive experimental and epidemiological studies should be conducted to determine the impact of D614G on the current epidemic (Grubaugh et al., 2020) .

Currently, there is no information on the impact of VUI 202012/01 mutations on the virus binding to the target cells, its transmissibility, disease severity, and the possible impact on virus neutralisation by antibodies from vaccinated and/or infected patients.

It is assumed that N501Y increases the binding affinity to ACE2 (Starr et al., 2020) , and it has been found to increase both virulence and infectivity in experimentally-infected mice (Gu et al., 2020) . Although each of N501Y and P681H have been detected previously in SARS-CoV-2, it is the first time these have concurrently been present in the same virus. The VUI 202012/01 virus strain possesses the ORF8 Q27stop mutation that shortens the ORF8 protein with subsequent J o u r n a l P r e -p r o o f loss of function. However, ORF8 deletion was found to have only a slight effect on virus replication (Gamage et al., 2020) .

It is well known that protection against coronaviruses depends on the development of 

Coronaviruses are subjected to high-frequency recombination events. Such recombination was responsible for virus evolution as reported in SARS-CoV (Hon et al., 2008) , MERS-CoV (Corman et al., 2014) and was also speculated to occur due to a recombination event of the RBD from Malayan pangolin coronavirus (Wong et al., 2020) . Most SARSr-CoV viruses do not use ACE2; however, there is a possibility of acquiring such ability either by cumulative mutations or natural recombination with subsequent emergence of new SARSr-CoVs able to infect humans (Fan et al., 2019) . Accordingly, experimental chimeric SARS coronaviruses were successfully synthesised. This was achieved using a bat-SCoV genome and with the SARS-CoV receptor binding domain (Becker et al., 2008) BtCoV HKU5 containing the SARS-CoV spike (S) glycoprotein (BtCoV HKU5-SE) (Agnihothram et al., 2014) in addition to a chimeric virus of murine adapted SARS-CoV backbone containing SHC014 spike bat coronavirus (Menachery et al., 2015) . The latter was found to replicate efficiently without prior adaptation in both mice and J o u r n a l P r e -p r o o f human airway cultures. Such findings confirmed the possibility of natural recombination in the emergence of potential pathogens to humans and denoted the potential risk of constructing chimeric viruses based on natural circulating betacoronavirus strains since increased virulence to humans could not be excluded (Menachery et al., 2015) .

All patients exposed to SARS-CoV-2 possess detectable IgG + RBD-specific plasma antibodies and neutralising plasma for ~3 months (Isho et al., 2020; Marklund et al., 2020; Wajnberg et al., 2020) . Seroconversion begins after 7 days in 50% of symptomatic patients and after 14 days in all patients (Lan et al., 2020; Wölfel et al., 2020a; Wölfel et al., 2020b) . However, some mildly infected patients do not show detectable IgG (Lou et al., 2020; Okba et al., 2020) . This conflicting finding was explained by how low the sensitivity of the used technique was and the difference in the targeted antigen (Long et al., 2020; Marklund et al., 2020; Wajnberg et al., 2020; Xiao et al., 2020a) . This was confirmed by the fact that all patients with undetectable IgG showed evidence of the presence of neutralising antibodies using neutralisation assay (Marklund et al., 2020) .

The COVID-19 severity is correlated to the IgG antibody titers since antibody titers were found to be higher in severe cases in comparison to mild ones Zhao et al., 2020) .

protective antiviral functions after 3 months of exposure (Rodda et al., 2020) . IgM+ memory Bcells dominated in the first 20 days followed by a gradual increase in IgG1+ memory B cells . The latter cells express CD27 and positively correlate with the T follicular helper (Tfh) cell number that suggest high robustness . In addition, memory B cells showed upregulation of CD80, CD180 and TACI that assumed activation upon re-J o u r n a l P r e -p r o o f exposure to the antigen (Berkowska et al., 2011; Berkowska et al., 2015) . It was assumed that B cell memory is durable for up to 8 months, which would probably be protective upon reinfection.

Accordingly, re-infection is proposed to be milder than the first exposure .

Increased neutralising antibodies, IgG + classical memory B cells, Tfh, CD4 + memory T-cells, and IFN-γ CD8 + T cells were detected. The IgA + against the receptor binding domain sharply declined after 3 months, which denotes that short-lived plasmablasts IgA (Rodda et al., 2020) , SARS-CoV-2-specific memory B cells, and predominant IgG+ B cells with lower frequencies of cells expressing IgM and IgA were detected (Dan et al., 2020; Hartley et al., 2020; Juno et al., 2020; Rodda et al., 2020) . Based on such findings, memory B cells are expected to respond rapidly to SARS-CoV-2 re-exposure, thus generating neutralising antibodies that will provide protection (or at least guard against a severe form of the disease).

In-vitro stimulation of CD4 + memory T cells from SARS-CoV-2 recovered individuals resulted in a rapid expression of Th1-and Th17-cytokines and upregulation of both ICOS and CD40L on CXCR5 + cells (Rodda et al., 2020) .

It has been found that the SARS-CoV-2 antibody level declines over time (Gudbjartsson et al., 2020; Ni et al., 2020) , which might reflect a retrenchment of immune responsiveness.

Meanwhile, mild COVID-19 induces an expanded population of memory B cells and CD4+ memory T cells. However, different levels of severity of COVID-19 could result in different levels of immune memory and subsequent immune protection (Rodda et al., 2020) . Rare cases of SARS-CoV-2 reinfection were detected in different countries. It is known that protection correlates with homologous reinfection and antibody titers. To date, no major change in the spike protein was detected based on the GISAID sequence database. Thus, SARS-CoV-2 re-infection was suggested to be milder (Abu-Raddad et al., 2020; . Three previously-exposed J o u r n a l P r e -p r o o f individuals with neutralising antibodies did not get sick when exposed to reinfection (Addetia et al., 2020) . Moreover, in an overnight camp, a previous seropositive attendee was not infected, while non-previously infected persons tested positive (Pray et al., 2020) . However, severe infections were also detected in some cases following re-infection (Selvaraj et al., 2020; Tillett et al., 2020; . A severe form of the disease in re-infected cases is unclear. It could be due to a huge viral load in the second attack of infection (Guallar et al., 2020) , infection by a more virulent strain, or the presence of poorly neutralising or non-neutralising antibodies being a progenitor for antibody-dependent enhancement (ADE) (Du et al., 2016; Karthik et al., 2020; Khandia et al., 2018; Wang et al., 2014) . This phenomenon was documented in both SARS-CoV and MERS-CoV (Du et al., 2016; Wang et al., 2014) , where SARS-CoV was found to be able to infect immune cells that lack the ACE-2 receptor through antibody dependent entry (Jaume et al., 2011; Wang et al., 2014) . Further, ADE was detected in the presence of diluted anti-spike protein antibodies, but not with anti-nucleoprotein antibodies (Wang et al., 2014) . Interestingly, mAbs targeting the SARS-CoV spike epitopes (other than RBD epitopes) can lead to ADE (Wang et al., 2016) . Similarly, non-neutralising antibodies against MERS-CoV led to ADE experimentally in rabbits (Houser et al., 2017) . Although ADE was recorded in related viruses of SARS-CoV-2, using an animal model for human infection does not accurately reflect immunopathogenesis in humans. To date, there is no evidence that ADE occurs or even induces a serious effect in COVID-19 patients. In addition, the pathogenesis of a model virus strain in animals does not fully reflect human infection because most viruses are highly species-specific (Arvin et al., 2020) . Plasma therapy using a passive transfer of antibodies from the recovered patients was successfully used in the treatment of COVID-19 patients and proved to increase the survival rate and reduce the disease severity as reviewed in (Alghamdi and Abdel-Moneim, 2020) , in which it J o u r n a l P r e -p r o o f was also reported with both MERS-CoV and SARS-CoV infections (Cheng et al., 2005; Ko et al., 2018; Mair-Jenkins et al., 2015) .

Remdesivir is an adenosine nucleoside analogue that inhibits viral replication probably by binding to RdRp (Eweas et al., 2021; Wu et al., 2020), M and nsp14 (Eweas et al., 2021) . It is of interest that M and S as well as M and N interactions are critical for the assembly of viral proteins (Siu et al., 2008) . Remdesivir also possesses a high affinity to TMPRSS2 and An initial dose of 200 mg followed by a daily dose of 100 mg for 4 days is the current recommended regimen for treatment of children (> 12 years old and ≥40 kg). A single dose of 5 mg/kg in the first day, followed by daily dose of 2.5 mg/kg is the recommended regimen for treatment of children (≥3.5 kg to <40kg). The drug is given by intravenous infusion for a period of between 30 and 120 min. This treatment could be extended for an additional 5 days if there is no improvement in the treated patients. Liver injury, nausea, rash, and allergic hypersensitive reactions are among the detected side effects of Veklury (FDA, 2020b). An NIH-sponsored clinical trial revealed that remdesivir shortened the time of recovery , J o u r n a l P r e -p r o o f however, a WHO SOLIDARITY trial showed that remdesivir showed neither a significant reduction in the duration of hospitalization or mortality (Pan et al., 2021) .

On 16 th February, 2020, favipiravir (T-705), a viral RNA polymerase inhibitor, was approved for marketing in Zhejiang Province, China (National-Health-Commission-of-the-People's-Republicof-China, 2020). To date, SARS-CoV-2 has been tested against five FDA-approved drugs: chloroquine phosphate (an old antimalarial drug), ribavirin, penciclovir, nitazoxanide and nafamostat, in addition to two viral RNA polymerase inhibitors: remdesivir (GS-5734) and

favipiravir. Both remdesivir and chloroquine were found to be more effective than the other drugs following in vitro evaluation .

Ivermectin, an antiparasitic drug, was found to possess antiviral activity against dengue virus and was also found to possess potent in-vitro anti-viral activity against SARS-CoV-2 (Caly et al., 2020) . It is assumed to play a role in preventing viral entry since it interacts with both the SARS-CoV-2 S protein and the human ACE-2 receptor (Eweas et al., 2021; Lehrer and Rheinstein, 2020) as well as TMPRSS2 (Eweas et al., 2021; Glowacka et al., 2011) . It also binds efficiently to SARS-CoV-2 nsp14, N and M proteins with a potential role in alleviating the efficiency of virus replication and assembly (Eweas et al., 2021) and N nuclear import that is mediated by IMPα/β1 (Caly et al., 2020; Rowland et al., 2005; Tay et al., 2013; Timani et al., 2005; Wagstaff et al., 2012; Yang et al., 2020) . It is likely that it binds to SARS-CoV-2 Mpro and PLpro with subsequent inhibition of post-translational cleavage of viral polyproteins (Eweas et al., 2021) .

Chloroquine and hydroxychloroquine interfere with virus entry (by blocking the terminal glycosylation of ACE-2), and inhibit the post-entry mechanism through alkalinisation of the endosome pH (Vincent et al., 2005) . They also inhibit the biosynthesis of sialic acid (Vincent et prophylaxis (Barnabas et al., 2020; Boulware et al., 2020; Rajasingham et al., 2020) . In addition, many retrospective observational studies deny its value in COVID-19 treatment (Geleris et al., 2020; Magagnoli et al., 2020; Rosenberg et al., 2020) and also in some prospective clinical trials (Cavalcanti et al., 2020; Horby et al., 2020) . However, more than 100 clinical trials conducted on the efficacy of chloroquine and hydroxychloroquine are still ongoing ; thus, it may be too early to determine conclusively the value of such drugs.

Camostat mesylate (a serine protease inhibitor) inhibits TMPRSS2 and may be a candidate drug for treating SARS-CoV-2 since it was proved to inhibit SARS-CoV in BALB/c mice (Zhou et al., 2015) . In a ddition, bromhexine hydrochloride (a mucolytic cough suppressant) is an inhibitor of TMPRSS2 and could also be used for treatment, since it was found to be effective for both influenza viruses and coronaviruses (Lucas et al., 2014; Shen et al., 2017) . More recently, a severe COVID-19 patient recovered following treatment with a soluble recombinant human ACE-2. After treatment, the virus disappeared from the patient and there was a significant decline of different cytokines (Zoufaly et al., 2020) . EIDD-2801 is a ribonucleoside analogue 

On 21 st November 2020, the FDA provided an EUA for using a combination of casirivimab and imdevimab, which are monoclonal antibody therapies (MABs) against the SARS-CoV-2 S protein. It is administered by intravenous infusion for mild-to-moderate (but not severe) COVID-19 cases (12 years of age or ≥ 40kg) and to patients at risk of developing severe COVID-19, including patients ≥65 years old or those suffering from chronic diseases. It was proven that the combined MAB therapy improved the clinical outcomes within 28 days post-treatment. It is not recommended for COVID-19 patients who are hospitalised and in need of high-flow oxygen or mechanical ventilation. Treatment among such patients might be accompanied by deterioration of the disease conditions for those patients (FDA, 2020a).

To date, five vaccines have been licenced, as follows: i) two RNA vaccines: BNT162b2 (Pfizer and BioNTech) and mRNA-1273 (Moderna); ii) two inactivated vaccines (SinoPharm and Bharat Biotech); and iii) a non-replicating adenovirus vector vaccine (AstraZenca). The BNT162b2 from Pfizer and BioNTech was the first authorised candidate vaccine (mRNA in lipid nanoparticles) with 95% efficacy (Polack et al., 2020) , then the SinoPharm inactivated vaccine, followed by Moderna (mRNA-1273) that demonstrated 94.1% vaccine efficacy , and more recently the AstraZenca adenovirus vaccine that demonstrated 90% vaccine efficiency together with the COVAXIN from Bharat Biotech (the first indigenous vaccine). The The COVID-19 mRNA vaccine is encapcidated into a lipid nanoparticle (LNP) (Mulligan et al., 2020; Walsh et al., 2020) . The mRNA-1273 was developed by Moderna/NIAID and BNT162b1 and BNT162b2 were developed by BioNTech/Fosun Pharma/Pfizer and are among the potential RNA vaccines . Another effective vaccine is the subunit vaccine containing recombinant purified spike protein of the SARS-CoV-2 coformulated with Matrix-M1 adjuvant (Novavax) (VAC-LSTM, 2020). In terms of immunogenicity, adjuvanted, protein-based vaccines are followed by mRNA vaccines then J o u r n a l P r e -p r o o f ChAdOx1-based vaccines, and AdV5-based vaccines then the inactivated seem to rank the lowest. Post-vaccine side effects are highest for vectored vaccines and lowest for inactivated and protein-based vaccines and mRNA vaccines (Krammer, 2020).

A live attenuated vaccine is considered among the best for human viruses with many successful models including for poliovirus, measles, rubella, mumps, and yellow fever. The fact that it simulates natural infection without causing the disease causes it to induce mucosal, humoral and cell-mediated immune responsiveness against the virus. However, this type of vaccine requires a long time for development and to ensure vaccine efficacy and safety. Currently, three SARS-CoV-2 live attenuated vaccines (two from India and one from Turkey) currently exist. Two are in pre-clinical testing while Codagenix/Serum institute of India is in clinical phase I (VAC-LSTM, 2020).

Due to the urgent need for a potent vaccine against COVID-19, an acceleration in advancing vaccine development exists. However, the adoption of novel human vaccines without previous licensed models may lead to uncertainties regarding long-term safety issues. Meanwhile, most vaccine trials have not been conducted on the most vulnerable subjects, which includes the elderly, pregnant women, and children. The role of different vaccines on the autoinflammatory responses such as paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) has not been examined (Koirala et al., 2020) .

Like ADE, vaccine-associated enhanced disease (VAED) has been detected in preclinical trials of SARS-CoV and MERS-CoV vaccines when associated with low neutralising antibodies (Graham, 2020; Haynes et al., 2020) . However, this was not detected with the SARS-CoV-2 and mRNA-1273 vaccine , although, monitoring of the possible VAED risk J o u r n a l P r e -p r o o f needs to be carefully monitored. However, an important pending issue is the longevity of the neutralising antibodies and protective memory immune responsiveness. It is apt to mention that neutralising antibodies persisted for 3 months after the second booster dose of vaccine . The World Health Organization (WHO) estimates that 2 billion doses of an effective vaccine will be available by end of 2021; however, since the world population is 7.7 billion, there will not be enough vaccines to accommodate the world's entire population. A priority list of populations who are at highest risk of infection/spread and high fatality in need of vaccination has been developed by the WHO, and healthcare workers, the elderly population above 60 years of age and people younger than 60 years who have comorbidities have been given the highest priority in early vaccination campaigns.

Lessons from the SARS-CoV outbreak in 2002-2003 were not heeded, the most important being to never allow free will to challenge nature. Although, there is no report of foodborne transmission of SARS-CoV/SARS-CoV-2, transmission is assumed to be introduced by close animal-to-human contact or by the virus being inoculated through skin injuries that probably occur during butchering of such animals for food consumption. It is speculated that consumption Whether the immune pressure in the absence of sufficient herd immunity will increase the mutation rate or evolution of immune-escape variants is not known. The successful and rapid development of mRNA based vaccines against SARS-CoV-2 will be helpful to control other viruses (e.g. Ebola, Dengue).

Although nobody can predict the future course of the SARS-CoV-2, nonetheless, some facts about this emerging virus are now clear. In the spirit of strong implementation of the One Health concept, the restriction and even the ban of both live wild animal markets and experimental induction of recombination studies on SARSr-CoV are highly recommended. Although remdesivir is the current FDA approved antiviral drug for treatment COVID-19, however, a doubt raised about its significance in reducing the duration of hospitalization or mortality rate. This finding, although requires more confirmation, highlights the need of developing potential antivirals against the SARS-CoV-2.

A second wave of the disease has now been recorded worldwide, with a tremendous increase in the number of COVID-19 patients over recent months, which reflects the long-term battle with J o u r n a l P r e -p r o o f COVID-19. Upregulation of both memory B cells and T follicular helper (Tfh) cells upon reexposure to the SARS-CoV-2 were recorded. Accordingly, re-infection is proposed to be milder than the first exposure. Meanwhile, the sharp decline of IgA + after 3 months might be responsible for the re-infection in previously infected patients and probably vaccinees. Such Duan, K., Liu, B., Li, C., Zhang, H., Yu, T., Qu, J., Zhou, M., Chen, L., Meng, S., Hu, Y., Peng, C., Yuan, M., Huang, J., Wang, Z., Yu, J., Gao, X., Wang, D., Yu, X., Li, L., Zhang, J., Wu, X., Li, B., Xu, Y., Chen, W., Peng, Y., Hu, Y., Lin, L., Liu, X., Huang, S., Zhou, Z., Zhang, L., Wang, Y., Zhang, Z., Deng, K., Xia, Z., Gong, Q., Zhang, W., Zheng, X., Liu, Y., Yang, H., Zhou, D., Yu, D., Hou, J., Shi, Z., Chen, S., Chen, Z., Zhang, X., Yang, X., 2020. Effectiveness of convalescent plasma therapy in severe COVID-19 patients. Proc Natl Acad Sci U S A 117 9490-9496. FDA, 2020b. https://www.fda.gov/media/137566/download, Fact sheet for healthcare providers emergency use authorization (EUA) of veklury® ( remdesivir) for hospitalized pediatric patients weighing 3.5 kg to less than 40 kgorhospitalized pediatric patients less than 12 years of age weighing at least 3.5 kg. FDA, USA. 

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Nuclear/nucleolar localization properties of C-terminal nucleocapsid protein of SARS coronavirus

COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing

Hydroxycytidine Is a Potent Anti-alphavirus Compound That Induces a High Level of Mutations in the Viral Genome

COVID-19 vaccine development pipeline. Vaccine Centre at the London School of Hygiene & Tropical Medicine

Chloroquine is a potent inhibitor of SARS coronavirus infection and spread

Evaluating the effects of SARS-CoV-2 spike mutation D614G on transmissibility and pathogenicity

Ivermectin is a specific inhibitor of importin α/β-mediated nuclear import able to inhibit replication of HIV-1 and dengue virus

Robust neutralizing antibodies to SARS-CoV-2 infection persist for months

Safety and immunogenicity of two RNA-based Covid-19 vaccine candidates

Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro

Immunodominant SARS Coronavirus Epitopes in Humans Elicited both Enhancing and Neutralizing Effects on Infection in Non-human Primates

Antibody-dependent SARS coronavirus infection is mediated by antibodies against spike proteins

Durability of responses after SARS-CoV-2 mRNA-1273 vaccination

Virological assessment of hospitalized patients with COVID-2019

Virological assessment of hospitalized cases of coronavirus disease

Evidence of recombination in coronaviruses implicating pangolin origins of nCoV-2019

Analysis of therapeutic targets for SARS-CoV-2 and discovery of potential drugs by computational methods

Profile of specific antibodies to SARS-CoV-2: The first report

Isolation of SARS-CoV-2-related coronavirus from Malayan pangolins

The broad spectrum antiviral ivermectin targets the host nuclear transport importin α/β1 heterodimer

Treatment with convalescent plasma for COVID-19 patients in Wuhan

Orally Efficacious Broad-Spectrum Ribonucleoside Analog Inhibitor of Influenza and Respiratory Syncytial Viruses

Antibody Responses to SARS-CoV-2 in Patients With Novel Coronavirus Disease

A novel bat coronavirus reveals natural insertions at the S1/S2 cleavage site of the spike protein and a possible recombinant origin of HCoV-19

Protease inhibitors targeting coronavirus and filovirus entry

Safety, tolerability, and immunogenicity of a recombinant adenovirus type-5 vectored COVID-19 vaccine: a dose-escalation, open-label, non-randomised

Immunogenicity and safety of a recombinant adenovirus type-5-vectored COVID-19 vaccine in healthy adults aged 18 years or older: a randomised

China Novel Coronavirus, I., Research, T., 2020c. A novel coronavirus from patients with pneumonia in China

Human recombinant soluble ACE2 in severe COVID-19