Genetic Assessment of B-cell Responses Following Immunization with HIV Env Protein and Adjuvants or SHIV (AD8) Infection in Nonhuman Primates

Abstract

OA16.04 Background: An effective preventive vaccine for HIV-1 should generate potent neutralizing antibody responses against the HIV envelope (Env). However, broadly-neutralizing antibodies from HIV+ individuals often have unique characteristics such as extensive somatic hypermutation (SHM), long CDRH3 regions and VH gene restriction. Therefore, we monitored the development of these characteristics in the preclinical setting. Methods: NHP were immunized with HIV Env clade C protein alone, or with a panel of clinical adjuvants or were infected with SHIV(AD8) virus. Env-specific B cells were sorted, barcoded, deep sequenced, and analyzed using a newly curated NHP Ig reference database. In total we analyzed VH gene usage, SHM, and CDRH3 length from over 58,000 unique Ig heavy chains. Results: The adjuvants tested here did not significantly increase germline divergence compared to unadjuvanted protein, nor did they give rise to B cells with long CDRH3 regions. However, animals and individual reads with higher SHM showed evidence of a narrowed VH gene repertoire and were enriched in the IGHV3Q gene. By comparison, antibodies from SHIV infected animals showed an increase in SHM in animals with better neutralization responses. Better neutralization responses further correlated with higher viral loads and viral Env diversity, indicating that chronic antigen stimulation and diversity is likely a driving force for higher SHM and the development of antibody potency and breadth. Finally, we correlated the presence of 3 VH genes: IGHV4A, 4D and 3J with better neutralization, indicating it may be possible to identify a VH gene signature of neutralization. Conclusions: This study is the first comprehensive comparison of antibody genetics using vaccine and infection models in NHP. Our data suggest that future vaccine regimens should be designed to mimic chronic viral infection, utilizing heterologous Env immunogens and prolonged innate and antigen stimulation to drive affinity maturation and neutralization breadth.