Tissue memory B cell repertoire analysis after ALVAC/AIDSVAX B/E gp120 immunization of rhesus macaques

The ALVAC prime/ALVAC + AIDSVAX B/E boost RV144 vaccine trial induced an estimated 31% efficacy in a low-risk cohort where HIV-1 exposures were likely at mucosal surfaces. An immune correlates study demonstrated that antibodies targeting the V2 region and in a secondary analysis antibody-dependent cellular cytotoxicity (ADCC), in the presence of low envelope-specific (Env-specific) IgA, correlated with decreased risk of infection. Thus, understanding the B cell repertoires induced by this vaccine in systemic and mucosal compartments are key to understanding the potential protective mechanisms of this vaccine regimen. We immunized rhesus macaques with the ALVAC/AIDSVAX B/E gp120 vaccine regimen given in RV144, and then gave a boost 6 months later, after which the animals were necropsied. We isolated systemic and intestinal vaccine Env-specific memory B cells. Whereas Env-specific B cell clonal lineages were shared between spleen, draining inguinal, anterior pelvic, posterior pelvic, and periaortic lymph nodes, members of Env-specific B cell clonal lineages were absent in the terminal ileum. Env-specific antibodies were detectable in rectal fluids, suggesting that IgG antibodies present at mucosal sites were likely systemically produced and transported to intestinal mucosal sites.