UV-inactivation of Epstein-Barr virus: differences in early antigen expression in two different non-productive cell lines and influence of caffeine.

Two non-productive Epstein-Barr (EB) virus genome-carrying lymphoblastoid cell lines, namely Raji and NC37, were used for studying the effect of UV irradiation on the ability of P3HR-1 EB virus to induce early antigen (EA) formation. In NC37 cells infected with UV-irradiated virus the formation of EA was delayed; thus the slope of inactivation curve based on the early (24 hr) reading was steeper than that based on the late (72 hr) reading. This was not observed in Raji cells. Caffeine did not influence the percentage of EA positive cells in cultures infected with untreated virus; however, the drug exhibited a marked inhibitory effect on EA production after infection with UV-irradiated virus. The sensitivity to caffeine effect decreased more rapidly with time after infection of Raji than of NC37 cells, suggesting a higher degree of readiness of the host cell repair system in the former than in the latter cells. The caffeine effect was merely directed against the synthesis of R (restricted) component of EA; its influence on the D (diffuse) component formation was negligible.