Restricted replication of adenovirus type 2 in mouse Balb/3T3 cells.

The nature of the infection of mouse B3T3 cells by adenovirus type 2 (Ad2) has been studied in vitro. Following infection with an adsorbed MOI of 225, more than 90 percent of the cells synthesized both early and late virus-specific antigens. In contrast, the yield of progeny virus varied from only 2 X 10(4) to 2 X 10(6) FFU/2 X 10(5) cells. The range in yields was related, in part, to the number of cell generations from the time of the initial subcloning, the yield increasing with passage level. Infectious center analysis suggested that fewer than 0.5 percent of infected cells synthesized progeny virus. Analysis of DNA synthesis in infected multiplying B3T3 cells demonstrated that cellular DNA synthesis began to be shut off at 12 hours p.i., a time when viral DNA synthesis was beginning. The maximum rate of viral DNA synthesis was approximately 12 percent of that in infected human cells. In contrast to infected multiplying cells, infection of quiescent B3T3 cell cultures resulted in the induction of cellular, along with viral, DNA synthesis. Analysis of late gene expression detected synthesis of most viral polypeptides, but revealed greater than 90 percent reductions in the rate of synthesis of polypeptides II, III, IV, and IX, as compared with infected human cells.

The induction of cellular DNA synthesis in G1-arrested BKH21 cell infected with adenovirus type 2.

G1-arrested BHK21 cells infected with adenovirus type 2 were studied to determine the effect of infection on host DNA synthesis in a productive cycle of infection. At various intervals following infection, analysis of the intracellular DNA was carried out by zonal sedimentation centrifugation through alkaline sucrose gradients. In addition to material which sedimented to the position of the virus markers (34S), a class of high mol. wt. DNA (40 to 100S) was found to be synthesized beginning approx. 13 h p.i. and continuing up to about 35 h p.i. DNA--DNA hybridization studies on this newly synthesized DNA showed it to be cellular DNA. When this material was density labelled with 5-bromodeoxyuridine and centrifuged to equilibrium through alkaline CsCl gradients, it was found to be the product of semi-conservation replication and not of repair synthesis.

Adenovirus tumorigenesis: role of the viral genome in determining tumor morphology.

Adenovirus type 12 transforms the fibroblastic BHK21 (baby hamster kidney) cell line into rounded or cuboidal cells that give rise in hamsters to undifferentiated small cell sarcomas indistinguishable from those induced in newborn hamsters by inoculation of the virus itself. In contrast. cells from this line transformed by polyoma virus retain their fibroblastic morphology and induce fibrosarcomas in hamsters. This suggests that the morphology of tumors induced by the adenovirus-transformed cells from this line may be determined by the viral genome and that such mechanism may also explain the remarkably uniform microscopic appearance which seems to characterize tumors induced in hamsters by direct inoculation of adenovirus type 12.