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Production of rabbit antibodies against the viral capsid antigen (VCA) of the epstein‐barr virus (EBV)

Rabbits were immunized with nuclear or cyto‐plasmic extracts of the Epstein‐Barr virus (EBV)‐producing marmoset cell line B95‐8. Following extensive absorption with human EBV‐negative cells (Hep‐2, Ramos and BJAB), sera were obtained that no longer reacted with cellular or serum proteins of human origin, but gave a single precipitin band with extracts of the human EBV‐producing line, P3HR‐1. Immunofluorescence tests performed with appropriate parallel human serum controls showed that the rabbit serum contained no activity against EBNA + EA ‐ VCA ‐ Raji cells, or against P3HR‐1 virus superinfected, cytosine arabinoside‐treated Raji cells that contained EBNA and EA, but not VCA. The sera gave a brilliant indirect immunofluor‐escence reaction with the virus‐producing (EBNA+EA+ VCA+) P3HR‐1 lines. Two‐color fluorescence tests, performed with a direct TRITC‐labelled VCA conjugate and indirect FITC‐staining with the rabbit serum, showed that the same cells reacted in both red and green fluorescence, confirming that the rabbit serum was directed specifically against some antigen formed in the virus‐producer cells. Since the synthesis of the relevant antigen was prevented by cytosine arabinoside it cannot be EA and must be a late antigen. The morphology and localization of the antigen support the conclusion that the antigen is VCA or some part of the VCA complex.