No abstract

5-Bromodeoxycytidine (BrdC) and 5-iododeoxycytidine, at a concentration of 100 mug/ml, effectively inhibit the replication of varicella-zoster (VZ) virus in tissue culture. No toxicity could be demonstrated in uninfected cells under the same conditions. Studies on the enzymatic basis for this selective inhibition were undertaken. Infection of human embryonic lung cell monolayers with VZ virus-infected cells results in the induction of thymidine (dT), deoxycytidine (dC), and BrdC kinase activities (which are increased 10-, 40-, and 60-fold, respectively) and in a 70-fold stimulation in the incorporation of 3H nucleotide (5-bromodeoxyuridylate) derived from BrdC into DNA. The thermal stability of the VZ virus-induced activities differs significantly from the activities induced by herpes simplex virus type 1 and herpes simplex virus type 2 and those present in uninfected human embryonic lung cells. The VZ virus-induced dT, dC, and BrdC kinase are similarly affected by temperature and cofractionate upon Sephadex gel filtration, findings consistent with the hypothesis that these activities are the function of a single enzyme: a pyrimidine deoxyribonucleoside kinase. The molecular weight, calculated on the basis of the elution pattern on Sephadex G-150, is 70,000. Kinetic studies, demonstrating that dT and dC competively inhibit the phosphorylation of BrdC, are consistent with the phosphorylation of these substrates at a common active site. Kinetic parameters include: KidT = 0.6 MUM; KidC = 60 muM; KmBrdC = 8.5 muM. In contrast to its relatively high affinity for the VZ virus-induced kinase, BrdC is a relatively poor substrate for the host kinases. Therefore, the basis for the selective inhibition of VZ virus by 5-halogenated analogues of dC is reflected in the induction of a pyrimidine deoxyribonucleoside kinase with a high affinity for BrdC.

SUMMARYHuman adenovirus types I, 2, 3, 5, 6, 7, 12, 14, I6, and 21 failed to replicate beyond input titres in green monkey kidney (GMK) cells. Co-infection of the monkey cells with papovavirus SV4o stimulated replication of all the adenoviruses tested. Addition of the defective SV4o genome in the PARA particle carried by an adenovirus type 7 population enabled all the adenoviruses to replicate in the GMK cells. Growth kinetics of the adenoviruses in GMK cells co-infected with SV4o were similar to the kinetics of the virus following addition of PARA. A latent period of 16 to 24 hr was followed by an exponential increase in infectious virus between 24 and 48 hr after inoculation. Synthesis of the PAPA component closely paralleled that of the adenoviruses. Both the adenoviruses and PAPA remained largely cellassociated throughout the growth cycle. During the replication of the transcapsidants, the titre of the adenovirus was always greater than the titre of the PAPA component. Ratios were generally in the order of 5oo infectious units of adenovirus per infectious unit of PAPA. These results differed from those obtained with the parent PARA-adenovirus type 7 population in which the adenovirus to PAPA ratio was approximately 3 : I.

The effects of infection by the human cytomegaloviruses Ad-169 on the incorporation of [¹⁴C] acetate into the polar and neutral lipids of human embryonic lung cells and human saphenous vein smooth muscle cells were compared to [¹⁴C]acetate incorporation in mock-infected control cells. Cytomegalovirus infection caused a shift in the relative amounts of polar and neutral lipids, with infected cells having lower amounts of polar lipids and higher amounts of neutral lipids than mock-infected controls. When neutral lipids were separated into diglyceride (DG), cholesterol (C), fatty acid, triglyceride (TG) and cholesterol ester (CE) components, Ad-169-infected cells had lower levels of incorporation of label into CE, TG, and DG fractions, and higher levels of label incorporation into C than mock-infected cells.