ABSTRACT
The gag encoded p24 protein of human immunodeficiency virus-1 (HIV-1) is a major constitutent of the viral core, and is also known as one of the most immunodominant antigens in the host immune response against the HIV-1. Based on the neutralizing ability of anti-p24 antibodies as well as their rapid appearance in human serum after viral infection, the development of vaccines and diagnostic tools targeting the p24 protein and anti-p24 antibodies is of great interest. For the characterization of the immunological properties of the HIV-1 p24 protein, in a previous study, putative B-cell epitopes were identified by screening the reactivity of a goat anti-p24 antiserum to a large array of overlapping synthetic peptides covering the whole p24 sequence. Four peptides were identified for their abilities to elicit a strong B-cell response, which sequences comprises the regions p24 (164-182), (202-221), (217-236) and (232-256), respectively. In the present study, the immunogenicity and differential properties of each of these individual epitopes were further characterized. To evaluate the time course of the antibody response, BALB/c mice were immunized with the HIV-1 p24 protein and their serum titers against each of these peptides were determined. The earliest immune response was observed against the p24 (202-221) peptide, which also showed the highest antibody titer against the immunized antigen. Furthermore,. enzyme-linked immunosorbent assay with HIV-1 p24 protein coated microtiter plates revealed that anti-p24 (202-221) antiserum has the most pronounced reactivity against the native p24 protein. Since the p24 (202-221) epitope has also been reported to include a cytotoxic T-lymphocyte epitope, it is suggested that this region might represent a powerful antigenic site responsible for eliciting both T- and B-cell immune response. The possible application of this specific epitope in vaccine development or AIDS diagnosis is discussed.