Thus, stabilization of the overall CDRH3 structure combined with a local flexibility at the base may contribute to the improved neutralization breadth and potency of CAP256-VRC26.25 compared to those of Batimastat (BB-94) the other lineage members. Open in a separate window FIG 5 Structural characteristics of CAP256-VRC26.25. members. This antibody, CAP256-VRC26.25, neutralized 57% of diverse clade viral isolates and 70% of clade C isolates with remarkable potency. Among the viruses neutralized, the median 50% inhibitory concentration was 0.001 g/ml. All 33 lineage members targeted a quaternary epitope focused on V2. While all known bNAbs targeting the V1V2 region interact with the N160 glycan, the CAP256-VRC26 antibodies showed an inverse correlation of neutralization potency with dependence on this glycan. Overall, our results highlight the ongoing evolution within a single antibody lineage and describe more potent and broadly neutralizing members with potential clinical utility, particularly in areas where clade C is usually prevalent. IMPORTANCE Studies of HIV-1 broadly neutralizing antibodies (bNAbs) provide valuable information for vaccine design, and the most potent and broadly reactive of these bNAbs Keratin 18 (phospho-Ser33) antibody have potential for clinical use. We previously described a family of V1V2-directed neutralizing antibodies from an HIV-1 clade C-infected donor. Here, we report around the isolation and characterization of new members of the family mostly obtained at time points of peak serum neutralization breadth and potency. One of the new antibodies, CAP256-VRC26.25, displayed a 10-fold greater neutralization potency than previously described lineage members. It neutralized 57% of diverse clade viral isolates and 70% of clade C isolates with remarkable potency: the median 50% inhibitory concentration was 0.001 g/ml. Our results highlight the ongoing evolution within a single antibody lineage and describe more potent and broadly neutralizing members with potential clinical utility, particularly in areas where clade C is usually prevalent. INTRODUCTION Neutralizing antibodies (NAbs) against HIV-1 are likely to be a major component of an effective vaccine-induced immune response. Cross-reactive NAbs commonly arise during HIV-1 contamination, though only a small subset of infected patients produces NAbs with a high neutralization breadth and potency (1,C4). In contrast, the HIV-1 envelope glycoprotein (Env) vaccine immunogens tested to date have failed to elicit cross-reactive neutralizing antibodies (5, 6). Thus, studying the development of broadly neutralizing antibodies (bNAbs) in infected individuals may provide important lessons for vaccine design (5, 7,C10). In addition, the isolation of bNAbs from selected donors has greatly aided our understanding of the HIV-1 Env structure (11,C13) and vulnerability to neutralizing antibodies (14,C16), and such antibodies have the potential to be used for the prevention or treatment of HIV-1 contamination (8, 17). NAbs directed to the V1V2 region of HIV-1 Env are of particular interest for vaccine design, as this site is usually antigenic and commonly targeted in HIV contamination (18, 19). To date, families of V1V2-directed bNAbs have been isolated from only four different donors (20,C23). These antibodies typically have Batimastat (BB-94) a long, anionic heavy chain complementarity-determining region 3 (CDRH3), which penetrates the glycan shield, and heavy chain variable (VH) gene mutation levels of 10 to 20%. They bind to the apex region of the intact trimer and bind poorly or not at all to most monomeric forms of the protein. Negative-stain electron microscopy studies show that such antibodies bind with a stoichiometry of one per trimer and likely interact with more than one protomer (21, 24), consistent with the location of V1V2 at the apex of the trimer (11, 12). This category of antibodies typically relies on glycan residues, specifically, N156 and N160 in V2 (23). Glycan dependence sometimes results in incomplete neutralization, referred to as the plateau effect (23, 25, 26), due in part to the microheterogeneity of glycoforms at these residues, resulting in a resistant subpopulation within a virus preparation (27). Our group has extensively studied the antibodies from donor CAP256, who developed high-titer plasma neutralizing antibodies to the V1V2 region that first appeared Batimastat (BB-94) at Batimastat (BB-94) 1 year and peaked at 3 years of HIV-1 contamination (21, 28, 29). This donor was infected with a clade C virus and 15 weeks later was superinfected with a different clade C virus. We isolated 12 V1V2-directed antibodies at multiple time points over 4 years of contamination; all were somatically related and termed the CAP256-VRC26 lineage, where CAP256 denotes the donor and VRC26 denotes the antibody lineage. Members of this antibody lineage have a very long CDRH3 of 35 to 37 amino acids.
