Biology subjects

Silvas, J.

Publications and source records attributed to Silvas, J..

3 recordsLinked to original sources

bioRxiv2021

A bifluorescent-based assay for the identification of neutralizing antibodies against SARS-CoV-2 variants of concern in vitro and in vivo

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged at the end of 2019 and has been responsible for the still ongoing coronavirus disease 2019 (COVID-19) pandemic. Prophylactic vaccines have been authorized by the United States (US) Food and Drug Administration (FDA) for the prevention of COVID-19. Identification of SARS-CoV-2 neutralizing antibodies (NAbs) is important to assess vaccine protection efficacy, including their ability to protect against emerging SARS- CoV-2 variants of concern (VoC). Here we report the generation and use of a recombinant (r)SARS-CoV-2 USA/WA1/2020 (WA-1) strain expressing Venus and a rSARS-CoV-2 expressing mCherry and containing mutations K417N, E484K, and N501Y found in the receptor binding domain (RBD) of the spike (S) glycoprotein of the South African (SA) B.1.351 (beta, {beta}) VoC, in bifluorescent-based assays to rapidly and accurately identify human monoclonal antibodies (hMAbs) able to neutralize both viral infections in vitro and in vivo. Importantly, our bifluorescent-based system accurately recapitulated findings observed using individual viruses. Moreover, fluorescent- expressing rSARS-CoV-2 and the parental wild-type (WT) rSARS-CoV-2 WA-1 had similar viral fitness in vitro, as well as similar virulence and pathogenicity in vivo in the K18 human angiotensin converting enzyme 2 (hACE2) transgenic mouse model of SARS-CoV-2 infection. We demonstrate that these new fluorescent-expressing rSARS- CoV-2 can be used in vitro and in vivo to easily identify hMAbs that simultaneously neutralize different SARS-CoV-2 strains, including VoC, for the rapid assessment of vaccine efficacy or the identification of prophylactic and/or therapeutic broadly NAbs for the treatment of SARS-CoV-2 infection.

microbiology↗

bioRxiv2021

Visualization of SARS-CoV-2 infection dynamic

Replication-competent recombinant viruses expressing reporter genes provide valuable tools to investigate viral infection. Low levels of reporter gene expressed from previous reporter-expressing rSARS-CoV-2 have jeopardized their use to monitor the dynamics of SARS-CoV-2 infection in vitro or in vivo. Here, we report an alternative strategy where reporter genes were placed upstream of the viral nucleocapsid gene followed by a 2A cleavage peptide. The higher levels of reporter expression using this strategy resulted in efficient visualization of rSARS-CoV-2 in infected cultured cells and K18 hACE2 transgenic mice. Importantly, real-time viral infection was readily tracked using a non-invasive in vivo imaging system and allowed us to rapidly identify antibodies which are able to neutralize SARS-CoV-2 infection in vivo. Notably, these reporter-expressing rSARS-CoV-2 retained wild-type virus like pathogenicity in vivo, supporting their use to investigate viral infection, dissemination, pathogenesis and therapeutic interventions for the treatment of SARS-CoV-2 in vivo.

microbiology↗

bioRxiv2021

Contribution of SARS-CoV-2 accessory proteins to viral pathogenicity in K18 hACE2 transgenic mice

Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) is the viral pathogen responsible for the current coronavirus disease 2019 (COVID-19) pandemic. To date, it is estimated that over 113 million individuals have been infected with SARS-CoV-2 and over 2.5 million human deaths have been recorded worldwide. Currently, three vaccines have been approved by the Food and Drug Administration for emergency use only. However much of the pathogenesis observed during SARS-CoV-2 infection remains elusive. To gain insight into the contribution of individual accessory open reading frame (ORF) proteins in SARS-CoV-2 pathogenesis, we used our recently described reverse genetics system approach to successfully engineer recombinant (r)SARS-CoV-2, where we individually removed viral 3a, 6, 7a, 7b, and 8 ORF proteins, and characterized these recombinant viruses in vitro and in vivo. Our results indicate differences in plaque morphology, with ORF deficient ({Delta}ORF) viruses producing smaller plaques than those of the wild-type (rSARS-CoV-2/WT). However, growth kinetics of {Delta}ORF viruses were like those of rSARS-CoV-2/WT. Interestingly, infection of K18 human angiotensin converting enzyme 2 (hACE2) transgenic mice with the {Delta}ORF rSARS-CoV-2 identified ORF3a and ORF6 as the major contributors of viral pathogenesis, while {Delta}ORF7a, {Delta}ORF7b and {Delta}ORF8 rSARS-CoV-2 induced comparable pathology to rSARS-CoV-2/WT. This study demonstrates the robustness of our reverse genetics system to generate rSARS-CoV-2 and the major role for ORF3a and ORF6 in viral pathogenesis, providing important information for the generation of attenuated forms of SARS-CoV-2 for their implementation as live-attenuated vaccines for the treatment of SARS-CoV-2 infection and associated COVID-19. IMPORTANCEDespite great efforts put forward worldwide to combat the current coronavirus disease 2019 (COVID-19) pandemic, Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) continues to be a human health and socioeconomic threat. Insights into the pathogenesis of SARS-CoV-2 and contribution of viral proteins to disease outcome remains elusive. Our study aims to determine the contribution of SARS-CoV-2 accessory open reading frame (ORF) proteins in viral pathogenesis and disease outcome, and develop a synergistic platform combining our robust reverse genetics system to generate recombinant (r)SARS-CoV-2 with a validated rodent model of infection and disease. We demonstrated that SARS-CoV-2 ORF3a and ORF6 contribute to lung pathology and ultimately disease outcome in K18 hACE2 transgenic mice, while ORF7a, ORF7b, and ORF8 have little impact on disease outcome. Moreover, our combinatory platform serves as the foundation to generate attenuated forms of the virus to develop live-attenuated vaccines for the treatment of SARS-CoV-2.

microbiology↗