Study of antibody repertoires to the CD4 binding site of gp120 of a Chinese HIV-1-infected elite neutralizer, using 454 sequencing and single-cell sorting.

Broadly neutralizing antibodies (NAbs) against the CD4 binding site of HIV gp120 (CD4bs) have provided important information for vaccine design. In this study, we combined deep sequencing and single memory B cell sorting to isolate CD4bs-directed NAbs from a Chinese HIV-1-infected elite neutralizer. We first performed 454 pyrosequencing to capture the IGHV1, IGKV, and IGLV germline gene families. IGHV1-2*02, the heavy chain germline V gene (VH) of the CD4bs-directed bNAb VRC01, was found to have a relatively low somatic mutation rate. When an identity/divergence plot was used to interrogate the 454 sequencing data, no VRC01-like sequences were found within the dataset. We next used a pair of CD4bs-specific probes (RSC3/ΔRSC3) to sort the B cells from this Chinese donor and identified a CD4bs-directed Ab that showed limited neutralization capability. Interestingly, the VH gene of this weak NAb belongs to the IGHV5-51 lineage, with a somatic mutation rate of 7.99 %. Our study thus demonstrates that CD4bs-directed NAbs can be produced by rearrangement from other VH genes, such as IGHV5-51 in this donor, rather than IGHV1-2*02. The 454 sequencing data and NAb obtained from this study will provide useful insights into the CD4bs-directed B-cell response during HIV-1 infection as well as the diversity of neutralizing antibodies.