Detection of early antigens in nuclei of cells infected with cytomegalovirus or herpes simplex virus type 1 and 2 by anti-complement immunofluorescence, and use of a blocking assay to demonstrate their specificity.

Skin fibroblasts exposed to cytosine arabinoside (Ara C) were infected with either cytomegalovirus (CMV) or herpes simplex virus (HSV) type 1 and 2. Herpesvirus-determined early antigens (HV-EA), detected by anti-complement immunofluorescence (ACIF), occurred primarily in the nuclei, and the specificity of these results was established by an ACIF blocking reaction using F(ab')2 fragments of human and hyperimmune reference sera. Direct tests with selected sera and cross-blocking experiments between early antigenic systems of CMV, HSV-1 and the Epstein-Barr virus (EBV) did not demonstrate common HV-EA.