ENHANCED ACTIVATION OF HUMAN T-CELL CLONES SPECIFIC FOR VIRUS-LIKE PARTICLES EXPRESSING THE HIV V3 LOOP IN THE PRESENCE OF HIV V3 LOOP-SPECIFIC POLYCLONAL ANTIBODIES

Recombinant virus-like particles (VLP), formed by the yeast Ty p1 prot ein, carrying the HIV gp120 V3 loop on their surface (V3-VLP) have bee n tested in vitro for immunogenicity and antigenicity by using VLP p1- specific human CD4(+) T cell lines and clones. VLP-specific human T ce ll lines and clones were generated from normal individuals, indicating that VLP-specific precursor cells present in the peripheral lymphocyt e pool can be induced to expand clonally upon antigen challenge in vit ro, in the absence of previous immunization. It was also shown that V3 -specific polyclonal antibodies enhance V3-VLP-induced activation of V LP-specific T cell clones. Antibody-dependent potentiation has been sh own previously in other antigen systems, and it depends on enhanced up take of complexed antigen by Fc receptor-positive antigen-presenting c ells. Since in this case antigen is internalized by presenting cells a s a complex, it can be inferred that a similar event of antibody-media ted antigen uptake can take place with V3-specific B cells, resulting in presentation by the B cells of T helper epitopes derived from proce ssing of the VLP p1 moiety. This suggests that T helper cells specific for the carrier VLP p1 protein can be activated to provide help to V3 -specific B cells in the presence of the appropriate antigen construct .