HIV-1 Env-Specific Memory and Germinal Center B Cells in C57BL/6 Mice

Continued efforts to define the immunogenic properties of the HIV-1 envelope glycoproteins (Env) are needed to elicit effective antibody (Ab) responses by vaccination. HIV-1 is a highly neutralization-resistant virus due to conformational and glycan shielding of conserved Ab determinants on the virus spike. Elicitation of broadly neutralizing Abs that bind poorly accessible epitope regions on Env is therefore extremely challenging and will likely require selective targeting of specific sub-determinants. To evaluate such approaches there is a pressing need for in vivo studies in both large and small animals, including mice. Currently, most mouse immunization studies are performed in the BALB/c strain; however, the C57BL/6 strain offers improved possibilities for mechanistic studies due to the availability of numerous knock-out strains on this genetic background. Here, we compared Env immunogenicity in BALB/c and C57BL/6 mice and found that the magnitude of the antigen-specific response was somewhat lower in C57BL/6 than in BALB/c mice by ELISA but not significantly different by B cell ELISpot measurements. We then established protocols for the isolation of single Env-specific memory B cells and germinal center (GC) B cells from immunized C57BL/6 mice to facilitate future studies of the elicited response at the monoclonal Ab level. We propose that these protocols can be used to gain an improved understanding of the early recruitment of Env-specific B cells to the GC as well as the archiving of such responses in the memory B cell pool following immunization.