Primary induction of human cytotoxic lymphocytes against a synthetic peptide of the human immunodeficiency virus type 1 protease

Identification of in vitro immunogenic T-cell epitopes is important for the design of immunotherapeutics targeted to specific antigenic sites. To identify candidate cytotoxic T-lymphocyte (CTL) epitopes in the protease of human immunodeficiency virus type 1 (HIV-1) strain MN, we synthesized 9-mer and 10-mer peptides containing the HLA-A*0201 binding motif. Binding affinity of the peptides was measured by HLA-A*0201 up-regulation on T2 cells. Peptides with high binding-affinity were tested for their ability to stimulate primary CTLs from healthy HIV-negative blood donors. Peptide-specific CTLs were obtained from five out of six donors by stimulation with a g-mer (LVGPTPVNI) or a 10-mer (VLVGPTPVNI) peptide derived from a highly conserved amino acid stretch in the C-terminal region of the protease. Addition of peptide-specific CTLs to acutely HIV-infected lymphocytes resulted in inhibition of p24(gag) production. In conclusion, a highly conserved HIV protease peptide regularly elicits peptide-specific CTLs. Targeting immune responses against defined epitopes in non-variable regions may be a feasible way to minimize the risk of virus escape from immune surveillance.