The appearance of EBV-associated early and membrane antigens (EA and MA) was studied in EBV-infected Raji cells. Newly synthetized MA appeared on approximately 50% of the cells 20-24 hours after infection. Around the same time intranuclear EA appeared in 2-5% of the cells, spreading later into the cytoplasm. The appearance of MA and EA was not inhibited by Ara C and iododeoxyuridine, but was completely prevented by puromycin. Viral capsid antigen (VCA) synthesis was not observed during an observation period of 4 days. Unless DNA synthesis was inhibited, the frequency of MA- and EA-positive cells decreased continuously after 1 or 2 days; the infectious cycle was thus abortive. Exposure of EBV to sera with high anti-MA titers neutralized the virus, as judged by its inability to induce EA. The virusneutralizing titers could be reduced by absorbing the sera with an EBV carrying cell line containing a high frequency of MA-positive cells, but not with a line with few MA-positives. The frequency of VCA + EA + cells was approximately equal in both lines. This supports the hypothesis that MA may represent viral envelope components inserted into the cell membrane, in analogy with the HSV system.
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