No abstract

RNA polymerase activity capable of synthesizing long-chain, heteropolymeric RNA is associated with specific ribonucleoprotein complexes present in the cytoplasm of cells infected with vesicular stomatitis virus (VSV). The synthesis is independent of added exogenous template and the product labelled with GTP precursors can be totally annealed with excess virion RNA. The enzyme activity is therefore a transcriptase similar to that observed in association with the mature VSV virion.

Several nononcogenic cyt mutants of adenovirus type 12 induced the same ElA (55,000 [55K] and 25K) and E1B polypeptides (55K, 19K, and 17K) as did the wild-type virus, except that cyt 68 did not induce the E1B 19K protein. Tumorigenicity tests showed cells transformed by cyt 68 to be highly oncogenic in vivo. Therefore, it was concluded that the E1B 19K polypeptide is not necessary for tumor induction but may be involved in the efficiency of transformation. Human adenovirus type 12 (Adl2) is highly oncogenic in rodents, and it has been shown that cells transformed by the left 16% of the viral genome containing both ElA and E1B are sufficient to induce tumors (5, 9, 17). The mechanism for tumor induction by these viral gene products is not known. Recently, it has been reported that the protein translated from the 13S mRNA from the Adl2 ElA region is crucial in tumor induction (2). Expression of the EiB region is also necessary since it has been reported that rat cell line 3Y1 transformed by ElA (the left 4.5%) failed to induce tumors in animals (15). Using plasmids containing ElA of Adl2 and EBB of AdS and vice versa, Bernards et al. also showed that Adl2 EBB is important in oncogenesis (1), and it appears that the E1B 56,000 (56K)-dalton polypeptide is required (5). However, 3Y1 cells and primary rat kidney cells transformed by the left 6.7% can induce tumors in vivo (14; unpublished data). Thus, it is not clear which of the Adl2

The intracellular transcriptase complex of vesicular stomatitis virus-infected L cells synthesized RNA complementary to the entire infectious virus genome at either 370C or 280C in vitro. Not all sequences were present at the same frequency, however; copies of that segment of the genome common to the LT defective particles were present at 20 to 100 times higher frequently than copies of the genome segment common to the ST defective particle. The less frequent region was transcribed somewhat more effectively at 28°C than at 370C. The results suggest that transcriptional regulation rather than selective degradation is responsible for the differential accumulation of RNA.

Newcastle disease virus (NDV) and chikungunya virus (CV) replicated in monolayers of human umbilical vein endothelium to peak titres of 104.5 TCD50 per ml in 24 and 48 hours respectively following inoculation of 106 TCD50/ml of virus. The cultures demonstrated no cytopathic effects after 6 days incubation. Analysis of intracellular protein from virus-infected endothelial cells by polyacrylamide gel electrophoresis of 35s-methionine labelled extracts of infected and uninfected cells indicated that at 22 hours after infection, normal cellular protein synthesis was shut down and virus-specific protein was found inside the cells. In contrast, Influenza A viruses (HK and PR 8) did not replicate in endothelial cells. Endothelial cells exposed to a high dose of NDV were severely damaged as illustrated by rounding and stranding. Influenza A and CV did not exhibit this toxic effect. Although both NDV and CV demonstrated replication, they showed contrasting thrombo- genic effects in virus endothelium platelet reactions. Larger amounts of radioactivity were associated with endothelial cells when washed suspensions of 51Cr-labelled human platelets were added 24 hours after infection with NDV than when exposed to heat inactivated NDV or allantoic fluid. Platelets added to cultures infected with non-toxic doses of NDV or influenza virus adhered singly and in clumps to the surface of the endothelial cells, but not to those infected with CV. Identical results were attained when platelets, pre-incubated with virus, were placed on uninfected endothelial cell monolayers, then washed with buffer. The mechanism by which this adhesion takes place may be due to virus bridging or modification of endothelial cell membranes by viral neuraminidase leading to a depression of endothelial cell properties responsible for antiadhesiveness.