Antigen-specific B cells responding to pneumococcal polysaccharide vaccination in newly diagnosed HIV infected individuals. (P4264)

Abstract

Abstract The peripheral blood of newly diagnosed HIV infected individuals is subjected to high uncontrolled viral titers. The decimation of both T and B cells thus leaves these individuals highly susceptible to opportunistic infections, including Streptococcus pneumoniae, despite the availability of vaccines. We have previously shown using directly labeled fluorescent pneumococcal polysaccharides that the majority of pneumococcal polysaccharide-specific B cells in healthy individuals were IgM+ memory B cells. Using this method, we identified specific deficiencies in B cell populations responding to pneumococcal polysaccharide vaccination in HIV infected individuals. Namely, a significant decrease in pneumococcal polysaccharide-specific IgM+ memory B cells compared to healthy individuals. Consequently, HIV infected individuals showed reduced antibody response and opsonophagocytic titers compared to healthy individuals. Furthermore, we correlated changes in pneumococcal polysaccharide-specific B cell populations post-vaccination with individual CD4 T cell counts. We observed a decreasing trend in pneumococcal polysaccharide-specific IgM+ memory B cells with lower CD4 T cell counts. These data indicate that the loss of pneumococcal polysaccharide-specific IgM+ memory B cells in HIV infected individuals correlates with CD4 counts and results in poor responsiveness to pneumococcal vaccination.