Structural Characterization of Coronavirus Antibodies Raised by Infection and Vaccination

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Project 3: Summary/Abstract SARS-CoV-2, a newly-emergent betacoronavirus in the sarbecovirus genus, resulted in a global pandemic in 2020, infecting millions and causing COVID-19 disease. Two other zoonotic betacoronaviruses, SARS-CoV (a sarbecovirus) and MERS-CoV (a merbecovirus), also resulted in outbreaks within the last 20 years. SARS-like viruses circulate in bats and serological surveillance of people living near caves where bats carry diverse coronaviruses demonstrate direct transmission of SARS-like viruses with pandemic potential, suggesting a pan- coronavirus vaccine is needed. In Project 3, the Bjorkman lab will use structural biology and biochemical approaches to understand the neutralization mechanisms of antibodies (Abs) elicited in humans by SARS-CoV- 2 infection or vaccination and in experimental animals by immunization. In Aim 1, using 3D structures of Ab Fabs bound to coronavirus spike (S) trimers, we will derive the structural correlates of neutralization/binding for monoclonal Abs (mAbs) and polyclonal plasmas isolated in Project 1 by Dr. Nussenzweig from (i) humans infected by SARS-CoV-2 after ~1 month, (ii) matured human Abs isolated ½ - 2 years after infection, (iii) humans vaccinated against SARS-CoV-2 with the Moderna vaccine, and (iv) animals immunized with vaccine candidates developed in Project 2 by Drs. Bieniasz and Hatziioannou or developed in this project's Aim 2 in the Bjorkman laboratory. Aim 2 of this project will follow up on our lab's evaluations of the potential for cross-reactive antibody responses to sarbecoviruses, for which we made homotypic nanoparticles presenting the receptor-binding domain (RBD) of only SARS-CoV-2 or co-displaying SARS-CoV-2 RBD along with RBDs from animal betacoronaviruses (mosaic nanoparticles; 4-8 distinct RBDs). By combining results of functional analyses of Ab neutralization derived from pseudotyped and authentic virus neutralization assays in collaboration with Dr. Rice with structural analyses of Abs isolated from RBD-nanoparticle–injected mice, we will refine our nanoparticle vaccine candidate(s) to increase their potential to protect against sarbecoviruses. Furthermore, we will develop additional vaccine candidates against merbecoviruses and/or alphacoronaviruses that will be evaluated along with the best pan-sarbecovirus vaccine in animal models of protection by Dr. Rice and/or our NIH collaborator, Dr. Vincent Munster. This highly-integrated project has the potential to contribute to creation of vaccine(s) that could avert future global pandemics.