Determining the role of antibody epitope specificity in regulating Fc effector functions

Proposal Summary/Abstract Antibody (Ab) Fc-mediated effector functions are an important correlate of protection against viral pathogens such as SARS-2. Methods such as systems serology are used to evaluate what kind of effector responses are protective for Abs against SARS-2 and other viruses, though crucial information about the epitope specificity those protective Abs are targeting is missing. To develop the most effective variant-proof or broad vaccines against sarbecoviruses, it is essential to determine which epitope specificities, when combined with Fc effector responses, can offer the most broad and robust protection. In this proposal, I aim to integrate deep mutational scanning (DMS) into systems serology, offering an innovative approach to map the epitope specificities within distinct IgG subclass and FcγR binding compartments of serum obtained from animals immunized with RBD-based protein nanoparticles and SARS-2 mRNA-Spike vaccines. This integration will facilitate the correlation between the binding epitopes of Fab regions in polyclonal Abs and the resulting Fc mediated functional responses. Although it is typically assumed there is no connection between the epitope specificity and the Fc subclass, preliminary findings surprisingly indicate variations in epitope specificity across different subclass compartments within the serum response, implying potential functional implications. The proposal will further involve the profiling of Ab-secreting cells at the single cell level to explore antigen specificity, IgG subclass, and FcγR binding properties, enabling the isolation and characterization of monoclonal antibodies (mAbs) with diverse antigen breadth and Fc characteristics. This multifaceted analysis will unveil patterns in epitope specificity and Fc properties at the monoclonal level. Finally, the project will assess the protective efficacy of serum and mAbs with distinct epitope specificity/Fc properties against homologous and heterologous SARS-2 infections, shedding light on the influence of epitope-specific Fab binding on Fc-mediated protection. Altogether, this proposal will make it possible to design immunization strategies that can more precisely modulate both Ab targeting and functional responses elicited, which will allow for a new generation of broadly protective vaccines. The mentoring phase of my proposal will take place in the lab of Dr. Pamela Bjorkman at Caltech. I will be advised by and collaborate with Dr. Jesse Bloom for DMS, Dr. Galit Alter for systems serology, and Dr. Mike Diamond for protection studies, gaining additional training required for this proposal. The research and mentorship proposed here will support me in reaching my overall career goal to establish my own academic research lab, with a focus on understanding the basic immunology of Abs targeting of viruses and designing better viral vaccines and therapeutics.