Effect of caffeine on the replication of nonirradiated and ultraviolet-irradiated cytomegalovirus.

The effect of caffeine on cytomegalovirus (CMV) replication in human embryo lung (HEL) and human embryo kidney (HEK) cells was studied. In HEL cultures, nonirradiated CMV yielded up to 6.7 times more plaques in caffeine-treated cultures than in control cultures. Virus growth curves exhibited different profiles, depending on the time of treatment of the cultures with the drug. Incorporation of [3H]TdR into virus DNA was enhanced and began about 24 h earlier in the caffeine-treated cultures than in the untreated cultures. A relationship between decreased incorporation of [3D]TdR into cellular DNA caused by caffeine and increased virus replication was observed in the HEL cells. In caffeine-treated HEK cultures, CMV replicated better than in untreated cultures in which virus growth was transitory and decreased after 10 days of incubation. The infectivity of CMV irradiated with UV light doses of 3,120-12,480 erg/mm2 decreased as a function of the UV dose. The extent of multiplicity reactivation of the irradiated virus increased when irradiated with higher UV doses. The effect of caffeine on the infectivity of UV-irradiated CMV depended on the dose with which the virus was irradiated. Caffeine increased the infectivity of CMV irradiated with lowest UV dose (3,120 erg/mm2) but did not increase the infectivity of virus irradiated with 12,480 erg/mm2. Multiplicity reactivation of the UV-irradiated CMV was inhibited by caffeine regardless of the UV dose with which the virus was irradiated.