Construction of a polyepitope fusion antigen of human cytomegalovirus ppUL32 and detection of specific antibodies by ELISA.

We have previously shown that single linear epitopes of the major human cytomegalovirus (HCMV) antigens, expressed as fusion proteins or synthesized as oligopeptides can be valuable diagnostic material in the serology of HCMV infection (5, 6, 13). In this work we fused sequences expressing two different epitopes (aa 1005-1048 and aa 595-614) contained in the basic phosphoprotein of 150 KD coded by UL32 (1, 2), (ppUL32), which has repeatedly been shown to be the strongest immunogen present in the viral particle. The fusion protein was tested by ELISA with HCMV-positive human sera in comparison with other fusion proteins of ppUL32. We found that the double epitope fusion protein was recognised by IgM present in a larger number of sera and with more intense reactions than all the other ppUL32 fusion proteins. The double epitope reacted positively with 81.3% and, when denatured, with 94.7% of IgM-positive sera respectively. IgG reactivity was also high, reaching a percentage of 90.7.