A HUMAN MONOCLONAL-ANTIBODY SPECIFIC FOR THE V3 LOOP OF HIV TYPE-1 CLADE-E CROSS-REACTS WITH OTHER HIV TYPE-1 CLADES

To ascertain the antigenic relationship between HIV-1 viruses belongin g to various genetically defined subgroups (clades), shared epitopes n eed to be defined, Human monoclonal antibodies (MAbs) are particularly useful for this purpose because they can detect complex regions of vi ral proteins that may be missed by sequence analysis and because, by d efinition, they react with epitopes that stimulate the human immune sy stem, Monoclonal antibodies derived from the cells of HIV-1 clade B-in fected subjects have been used extensively for this purpose, Here we d escribe the first human MAb derived from a clade E-infected individual ; the MAb is specific for the V3 loop, recognizing a core epitope repr esented by the amino acids TRTSVR on the N-terminal side of the crown of the V3 loop, The IgG(1)(kappa) MAb, designated 1324E, binds to the clade E consensus V3 loop, to rgp120 proteins from clade E and to peri pheral blood mononuclear cells infected in vitro with the virus that i nfected the subject from whose cells the MAb-producing heterohybridoma was derived, Strong cross-reactivity of the MAb to the V3 peptides, r gp120 proteins, and native monomeric gp120s representing clades A and C, as well as to cells infected with a clade C primary isolate, reveal ed a shared V3 epitope between these clades, When tested for its neutr alizing ability, MAb 1324E neutralized a clade E isolate that had been adapted for growth in H9 cells but failed to neutralize five clade E primary isolates.