Pathogenic and transcriptomic differences of emerging SARS-CoV-2 variants in the Syrian golden hamster model.. [PMID: 34268506 PMCID: PMC8282094 DOI: 10.1101/2021.07.11.451964]

Co-evolution of SARS-CoV-2 variants and host immune response trajectories underlie COVID-19 pandemic to epidemic transition

COVID-19 pandemic saw emergence of multiple SAR-CoV-2 variants. Exacerbated risk of severe outcome and hospital admissions led us to comprehend differential host-immune kinetics associated with SARS-CoV-2 variants. Longitudinal investigation was conducted through different time periods of Pre-VOC and VOCs (Delta & Omicron) mapping host transcriptome features. Robust antiviral type-1 interferon response marked Omicron infection, which was largely missing during Pre-VOC and Delta waves. SARS-CoV-2-host protein-protein interactions and docking complexes highlighted N protein to interact with HNRNPA1 in Pre-VOC, demonstrating its functional role for enhanced viral replication. Omicron revealed enhanced binding efficiency of LARP1 to N protein, probably potentiating antiviral effects of LARP1. Differential expression of zinc finger protein genes, especially in Omicron, mechanistically support induction of strong IFN (Interferon) response, thereby strengthening early viral clearance. Study highlights eventual adaptation of host to immune activation patterns that interrupt virus evolution with enhanced immune-evasion mutations and counteraction mechanisms, delimiting the next phase of COVID-19 pandemic.

The SARS-CoV-2 B.1.351 Variant Can Transmit in Rats But Not in Mice

Previous studies have shown that B.1.351 and other variants have extended the host range of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to mice. Sustained transmission is a prerequisite for viral maintenance in a population. However, no evidence of natural transmission of SARS-CoV-2 in wild mice has been documented to date. Here, we evaluated the replication and contact transmission of the B.1.351 variant in mice and rats. The B.1.351 variant could infect and replicate efficiently in the airways of mice and rats. Furthermore, the B.1.351 variant could not be transmitted in BALB/c or C57BL/6 mice but could be transmitted with moderate efficiency in rats by direct contact. Additionally, the B.1.351 variant did not transmit from inoculated Syrian hamsters to BALB/c mice. Moreover, the mouse-adapted SARS-CoV-2 strain C57MA14 did not transmit in mice. In summary, the risk of B.1.351 variant transmission in mice is extremely low, but the transmission risk in rats should not be neglected. We should pay more attention to the potential natural transmission of SARS-CoV-2 variants in rats and their possible spillback to humans.

Optimization of single dose VSV-based COVID-19 vaccination in hamsters

The ongoing COVID-19 pandemic has resulted in global effects on human health, economic stability, and social norms. The emergence of viral variants raises concerns about the efficacy of existing vaccines and highlights the continued need the for the development of efficient, fast-acting, and cost-effective vaccines. Here, we demonstrate the immunogenicity and protective efficacy of two vesicular stomatitis virus (VSV)-based vaccines encoding the SARS-CoV-2 spike protein either alone (VSV-SARS2) or in combination with the Ebola virus glycoprotein (VSV-SARS2-EBOV). Intranasally vaccinated hamsters showed an early CD8 + T cell response in the lungs and a greater antigen-specific IgG response, while intramuscularly vaccinated hamsters had an early CD4 + T cell and NK cell response. Intranasal vaccination resulted in protection within 10 days with hamsters not showing clinical signs of pneumonia when challenged with three different SARS-CoV-2 variants. This data demonstrates that VSV-based vaccines are viable single-dose, fast-acting vaccine candidates that are protective from COVID-19.