INDUCTION OF V3-SPECIFIC CYTOTOXIC T-LYMPHOCYTE RESPONSES BY HIV GAG PARTICLES CARRYING MULTIPLE IMMUNODOMINANT V3 EPITOPES OF GP120

Efforts to develop a vaccine to prevent infection of human immunodefic iency virus (HIV) have focused on the induction of neutralizing antibo dies. In our previous study, we reported that chimeric gag-env virus-l ike particles (VLPs) induce neutralizing antibodies which block HIV in fection. In addition to the neutralizing antibodies, the cytotoxic T-l ymphocyte (CTL) response is considered to be another major immune defe nse mechanism required for recovery from many different viral infectio ns. In the present study, we have constructed chimeric fusion proteins using HIV-2 gag precursor protein with (I)four neutralizing epitopes from HIV-1 gp160; (2) three tandem copies of consensus V3 domain, whic h have been derived from 245 different isolates of HIV-1 and carries b oth the principal neutralizing determinant (PND) and CTL epitopes; and (3) V3 domains from HIV-1(IIIB), HIV-I-MN, HIV-1(RF), and HIV-1(SF2). These chimeric fusion proteins were expressed in a large quantity wit hin insect cells, and released as VLPs into the cell culture medium. T he purified gag-env VLPs from all three constructs appear to be spheri cal particles similar to immature HIV but slightly larger than the gag VLPs. Immunoprecipitation analysis showed that the chimeric proteins were recognized not only by HIV-I positive patient sera, but also by m onoclonal and polyclonal antisera raised against V3 peptides of HIV-1( IIIB), HIV-1(MN), HIV-1(RF), and the gp120 antiserum against HIV-1(SF2 ). Balb/C mice immunized with these chimeric VLPs successfully induced CTL activity against V3 peptide-stimulated target cells. In addition, a high degree of cross-reactivity was observed among the four differe nt strains of HIV-I V3 domain, indicating that the tandem multiple con sensus V3 peptide sequence carried by HIV-2 gag can be used as a poten tial HIV vaccine against various HIVs. (C) 1998 Academic Press.