Engineering Immunity for Broad Protection Against Betacoronaviruses

Abstract In the past decade three highly virulent human betacoronaviruses have emerged, including SARS-CoV-2 which has caused a devastating pandemic and is responsible for the deaths of over 6 million people worldwide. Current vaccines and monoclonal antibody (mAb) treatments for SARS-CoV-2 are susceptible to mutations in the virus which can lead to decreased efficacy of these therapies. Two other highly pathogenic human betacoronaviruses, SARS-CoV and MERS-CoV, have no approved vaccines or therapeutics. There is an urgent need for broadly acting antibodies and vaccines which can protect against new variants of SARS-CoV-2 or future emerging human betacoronaviruses. Our current vaccines and mAbs for SARS-CoV-2 target the viral spike protein. The spike (S) is necessary and sufficient to mediate entry of the virus into host cells. S is comprised of two subunits. S1 is the receptor binding subunit and a major target of antibodies produced by current vaccines and mAb therapies. S2 is the membrane fusion subunit and is highly conserved among betacoronaviruses. Little is known about S2 targeting antibodies and their potential use in protecting against betacoronavirus infections. In this project we will identify and design broadly acting S2 antibodies as well as investigate Fc-effector functions of these antibodies. A multipronged approach using neutralization assays, in vitro Fc-effector function assays and systems serology will evaluate the functional properties of S2 antibodies from mice immunized with S2 immunogens. Using a panel of replication competent vesicular stomatitis virus (rVSV) pseudotype viruses expressing the spike protein from a wide range of betacoronaviruses (rVSV-CoVs) we will be able to identify antibodies that are broadly acting. Finally, by using what we learn in our analysis of endogenously produced S2 antibodies we will design bispecific S2 targeting antibodies to develop novel therapeutics broadly targeting betacoronaviruses. This project will significantly add to our knowledge of the role S2 antibodies play in infection with betacoronaviruses and how these antibodies can be utilized for future pandemic preparedness.