Fine Structure of Cells Infected with Human Cytomegalovirus After Treatment with 9-(1,3-Dihydroxy-2-propoxymethyl)guanine

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Abstract
Infection with human cytomegalovirus (CMV) is characterized by cytological changes which are readily visualized by electron microscopy using ultrathin sections of infected cells. Treatment of such cells with 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), a potent inhibitor of CMV, is effective when initiated at early or late times after infection and the response to such treatment has been studied by fine structural analysis. Inhibition of viral DNA synthesis by DHPG treatment (50 .mu.M) late in virus infection resulted in a cessation of virus growth accompanied by a lack of development and possible regression in skein-like intranuclear inclusions together with a depletion in cytoplasmic dense bodies. Such changes were accompanied by the appearance of nuclear dense bodies. These were also present when virus growth was reduced (5 .mu.M-DHPG) rather than completely inhibited (50 .mu.M-DHPG) by treatment initiated from the time of infection. The nuclear bodies were predominantly of a reticular type structure after the early treatment but mainly of a homogeneous form when virus growth was interrupted at late times. Their presence appeared to be connected with the ability of infected cells to initiate the synthesis of late proteins and their morphology may relate to the extent of such protein synthesis. Unlike cytoplasmic dense bodies, provisional findings on the characterization of the nuclear bodies suggested that the 69K matrix protein was not present in abundance.