PROJECT SUMMARY An effective HIV-1 remains an important but elusive goal. One promising approach to such a vaccine uses sequential immunization to guide B-cell receptor (BCR) maturation. To do so, one first amplifies immature unmutated precursors of a particular class of broadly neutralizing antibodies (bNAbs). These precursor BCR are then shepherded to recognize HIV-1 envelope glycoprotein (Env) using increasingly native Env antigens. Sequential immunization strategies for both VRC01- and V3-glycan-classes of bNAbs are being developed. Here we establish the foundations for using the same general strategy to elicit V2-glycan/apex antibodies. Apex bNAbs have properties that both complicate such an approach but ultimately make success more likely. Specifically these bNAbs bind Env largely through their long, acidic and tyrosine-sulfated heavy-chain CDR3 region. Thus there is less need for extensive somatic hypermutaion characteristic of V3-glycan and VRC01-class bNAbs. However, apart from their long sulfated CDR3 regions, apex bNAbs have few distinguishing features. Here we show that we can elicit antibodies in rats with long tyrosine-sulfated CDR3 regions using anti-sulfotyrosine antibodies as antigens. We propose to optimize this approach and use it in concert with oligomeric forms of Env trimers to elicit anti-apex antibodies. These studies will develop a potentially easier approach to generating broad and potent anti-HIV-1 antisera.

PROJECT NARRATIVE We have developed a novel approach for eliciting precursors to the V2-glycan/apex class of broadly HIV neutralizing antibodies. We test here the hypothesis that this approach and inoculation with an appropriate combination of antigens can generate this class of bNAbs in rats.