Isolation and profiling of antibodies targeting SARS-CoV-2

A promising therapeutic and prophylactic strategy against COVID-19 is passive immunization through the transfer of anti-SARS-CoV-2 neutralizing antibodies and convalescent serum. However, there is growing evidence that antibody responses to the virus can also directly contribute to lethal immunopathology and hyperinflammation present in severe COVID-19 disease. Understanding the distinct mechanisms whereby humoral responses to SARS-CoV-2 provide protective antiviral immunity versus harmful immunopathology is thus essential in developing effective treatments for COVID-19. Furthermore, analysis of antibody responses in SARS-CoV-2-infected individuals will inform development of effective SARS-CoV-2 vaccines and reliable serological tests in the immediate future. Here, we propose to identify and characterize COVID19 patients' anti-SARS-CoV-2 antibodies and the epitopes on SARS-CoV-2 that are targeted by immune responses. The goals of the proposed research are to identify potent neutralizing antibodies against SARSCoV-2 that can be advanced as therapeutic drug candidates and elucidate potential roles for deleterious autoreactive cross-reactivity of humoral responses to the virus. Our working hypothesis is that anti-SARSCoV-2 antibody responses generate neutralizing protective antibodies in most subjects, whereas S1 spike protein-reactive antibodies may cross-react with self-antigens expressed on lung epithelial cells in patients severely affected by the virus as suggested by a previous SARS-Cov study. We therefore propose to isolate and produce in vitro anti-SARS-CoV-2-reactive neutralizing recombinant antibodies cloned from memory B cells and plasmablasts from the blood of patients and asymptomatic infected subjects. We will profile cloned recombinant antibodies and COVID-19 patient plasma samples for reactivity against a large panel of conformational SARS-CoV-2 antigens as well as extracellular/secreted human proteins to identify humoral responses that may contribute to viral clearance and COVID-19 immunopathology, respectively. Responses to extracellular SARS-CoV-2 antigens will be determined using a multiplex flow-cytometry based assay that enables simultaneous quantification of humoral responses against multiple viral proteins as well as a qualitative assessment of their ability to block the interaction of SARS-CoV-2 spike protein with its entry receptor ACE2. Potential autoreactive responses elicited by SARS-CoV-2 infection will be assessed using a technique called REAP (Rapid Extracellular Antibody Profiling), in which serum/antibodies are panned against a comprehensive library of >3,000 human extracellular proteins displayed on the surface of yeast. These studies will thus provide insight into the development of immune responses targeting SARS-CoV-2, identify potent neutralizing antibodies against SARS-CoV-2 that can be advanced as therapeutic drug candidates and may suggest therapeutic strategies to attenuate potentially pathogenic antibody responses.