Clonal analysis of human anti-V3 monoclonal antibodies selected by a V3 tetramer.

The production of human monoclonal antibodies (mAbs) has been improved recently using the single B cell and PCR technology. A number of new anti-HIV-1 mAbs directed to various epitopes were produced by selecting single B cells from HIV positive individuals using the HIV-1 envelope (Env) proteins, and we tested whether the peptide can select B cells specific to a particular Env epitope. Using the fluorescently-labeled peptide tetramer representative of the V3 loop of HIV-1 Env gp120 for staining the B cells derived from one HIV-1 infected donor, four clonal human mAbs were produced with specificity to the V3 region. The clonality of the four V3 mAbs was based on the usage of the same immunoglobulin genes and almost identical sequence of CDRs. The amino acid changes were present only in the framework and, possibly, they could be related to the differences observed in the relative affinity binding of these four mAbs to V3 antigen. One representative V3 mAb displayed very potent neutralizing activity to one of two viruses tested. This study shows the feasibility of utilizing a peptide tetramer to select epitope-specific B cells and produce mAbs.