Pathogenesis of SARS-CoV-2 and Immune Response in COVID-19

Abstract

SARS-CoV-2, which emerged in Wuhan province of China for the first time in December 2019 and spread rapidly all over the world, is still causing an epidemic. SARS-CoV-2 is the third coronavirus outbreak we encountered after SARS-CoV and MERS-CoV infections. Due to SARS-CoV and MERS-CoV infections, we have gained experience about the pathogenesis and immune responses of coronaviruses. However, studies have shown that, unlike the information derived from our experience, SARS-CoV-2 is both very infectious and its effect on cells is different. Therefore, we aimed to compile the data of the published studies on the pathogenesis of SARS-CoV-2 and the resulting host immune response. In many studies, it has been reported that not only the presence of the host ACE2 receptor is sufficient for the infection of the host cell, but also the cleavage of the structural S protein by proteases should be materialized. It has been shown that, unlike SARS-CoV-2, SARS-CoV and MERS-CoV, it contains different protease cleavage systems and amino acid sequences in the ACE2 receptor binding site. In SARS-CoV-2 infection, as reported in studies conducted up to now, Th1 and Th2-mediated cytokine and chemokine levels in the host are different than SARS-CoV infection, and also different chemokines can be upregulated compared to other CoVs. Considering that effective vaccines have not been developed for the infectious RNA viruses despite the ongoing trials for many years, in order to reveal all these differences in the pathogenesis and immune response process and to develop effective antivirals against SARS-CoV-2 within a short time. the need for comprehensive studies on host immune response is evident.