Characterization of three monoclonal antibodies (VAK3-5) that identify p24, core protein of human immunodeficiency virus, and its precursors.

VAK3, VAK4 and VAK5 monoclonal antibodies (mAbs) were raised by using disrupted purified human immunodeficiency virus (HIV) as an antigen. These mAbs exclusively reacted with an HIV-infected cell line, H9/HIV, and did not react with human T cell lymphotropic virus (HTLV)-I or -II infected cell lines. Strip radioimmunoassay based on the Western blotting technique revealed that these mAbs recognize a single band that corresponds to a 24-kd (p24) core protein of HIV when disrupted viruses were used as antigens. When cell lysates of H9/HIV were used as antigens, these mAbs gave two bands with molecular weights of 40 kd (p40) and 57 kd (p57) in addition to p24. VAK5-conjugated Sepharose 4B beads precipitated non-glycosylated proteins, p24, p40 and p57 from [L-35S]methionine-labeled H9/HIV. P57 and p40 appear to be a precursor and an intermediate precursor of p24, respectively. Purified IgG of VAK3 and VAK4, and the serum from an individual infected with HIV inhibited the binding of VAK5 mAb to HIV. These findings suggest that p24 of HIV contains structure(s) with strong antigenicity.