Demonstration of two distinct components in the early antigen complex of epstein‐barr virus‐infected cells

Examination of numerous sera from patients with infectious mononucleodis (IM), Burkitt's lymphoma (BL) or nasopharyngeal carcinoma (NPC) for antibodieh to Epstein‐Barr virus (EBV) induced early antigens (EA) revealed two distinct patterns of immunofluorescence in abortively EBV‐infected Raji cells. One showed diguse (D) staining of the nucleus and cytoplasm of invaded cells, the other (R) was restricted to masses in the cytoplasm. Although D‐ or R‐reactive Raji cells became detectable at similar times after exposure to EBV, the percentages of D‐positive cells initially exceeded R‐positive cells but ultimately both were nearly equal in number. R‐positive cells almost invariably contained also D. In EBV‐exposed RPM1 64–10 cells, frequently only D was synthesized. D antigen, in contrast to R, resisted fixation by methanol or ethanol, whereas R proved more resistant than D to proteolytic enzymes. Comparative serum titration on acetone, respectively ethanol‐fixed Raji‐EBV cell smears revealed that the transitory anti‐EA response observed in many IM patients was restricted almost exclusively to anti‐D. Anti‐EA positive sera from NPC patients also showed dominantly anti‐D activity whereas, in BL sera, anti‐R was usually, but not always, dominant, often being the only antibody to the EA complex present. Preliminary tests with pronase‐treated Raji‐EBV cell smears indicated that dominantly anti‐D reactive sera from IM patients were free of anti‐R whereas such sera from NPC or BL patients usually gave positive reactions which in part, however, failed to conform with the R pattern. The possible implications of these results have been discussed.