Recognition of human cytomegalovirus gene products by HCMV-specific cytotoxic T cells.

The antigen specificity of HCMV-specific cytotoxic T cells (CTL) was investigated in healthy adult seropositive donors by analyzing the frequency of CTL precursors (CTLp) against six different HCMV-encoded proteins. HCMV-specific, CD8+ CTL clones from two donors were also characterized. Thje precursor frequency analysis showed that a major phosphoprotein of HCMV, pp65 (UL83), was the immunodominant CTL target antigen in healthy seropositive adults. The frequency of CTLp specific for different HCMV proteins ranged from 1/12,000 for pp65 to > 1/100,000 for gB (UL55), gH (UL75), pp50 (UL44), and pp28 (UL98). Characterization of the HCMV-specific CTL clones from two donors revealed that the majority of clones lysed targets expressing pp65 and that none of the clones recognized other HCMV proteins.