Elucidating the impact of immune imprinting on SARS-CoV-2 variant vaccination strategies using a humanized mouse model

PROJECT SUMMARY / ABSTRACT: Rationale: Continued evolution of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has led to immune-evasive variants that pose a persistent threat to global public health. Updated vaccines are needed to provide improved immune responses against emerging variants, but current approaches targeting the Omicron BA.4/5 variant may have limited effectiveness due to immune imprinting caused by prior immune system exposure to ancestral D614G variant antigens. Our preliminary data suggests that bivalent boosters targeting BA.4/5 do not provide superior neutralizing antibody (NAb) responses to SARS-CoV-2 variants compared to the original monovalent vaccine. This mentored career project aims to elucidate the impact and molecular basis of immune imprinting following primary D614G vaccination on subsequent humoral responses to variant antigens. Candidate: As an Infectious Diseases physician with a PhD in Microbiology and Immunology, I am uniquely positioned to bridge the gap between biomedical research and patient care to advance our knowledge of humoral immune responses to SARS-CoV-2. Further training in virology, structural biology, bioinformatics, and monoclonal antibody characterization will be crucial for completion of the proposed research and my development as an independent physician-scientist specializing in humoral immunity to pathogens of global importance. I have a globally recognized mentor in Dr. David Ho and benefit from an outstanding multidisciplinary team of experts to guide my training and research progress. Environment: The Ho laboratory at the Columbia University Irving Medical Center (CUIMC) is a leading group in the study of SARS-CoV-2, with expertise in the characterization of viral variants and monoclonal antibodies. This enriching environment provides access to a large network of collaborators including experts in cryo-electron microscopy, single cell sequencing, and antibody repertoire analysis. CUIMC also has a strong track record of enabling junior physician-scientists to develop independent and successful careers in academic medicine. Approach: Our central hypothesis is that primary vaccination targeting the SARS-CoV-2 D614G strain induces immunological imprinting that restricts antibody responses to subsequently encountered viral variant antigens. In Aim 1, we will test the impact of imprinting on NAb responses following BA.4/5 boosting strategies in a humanized mouse model. In Aim 2, we will characterize the antibody repertoires of immunized mice to identify imprinting effects using single B cell sequencing and bioinformatic approaches. In Aim 3, we will use high- throughput techniques to produce monoclonal antibodies, determine their neutralizing activity, and identify epitopes associated with imprinting responses though structural and binding assays. Through these aims, we will expand understanding of the immunologic and structural basis underlying imprinting in SARS-CoV-2. Our results should inform novel strategies for structure-based vaccine design to circumvent imprinting responses and produce broader immunity to SARS-CoV-2 variants and possibly other antigenically variable pathogens.