- Volume 57, Issue 1, 1981

Human adenovirus type 5 caused acute hepatocellular damage when injected intravenously into C57B1/6 mice. Early protein (P) and late virus protein (V) antigen staining by immunofluorescence was located principally, if not exclusively, in hepatocytes. Autoradiography following incorporation of tritiated thymidine into Ad5-infected liver cells in vivo indicated that DNA synthesis was initiated in hepatocytes. Flow cytometry showed that cells with a 4n DNA content prior to infection were highly susceptible to infection, with 75% being lost from the liver cell population by 5 days post-infection. This observation was correlated with the observed pathology during the course of the infection.

Syncytia formation induced by the bovine leukaemia virus (BLV) has been classified as ‘early’ or ‘late’ polykaryocytosis. Early polykaryocytosis arises in the first 24 h in mixed cultures of BLV-infected cells with indicator cells. Late polykaryocytosis is observed 4 to 8 days after infection of sensitive cells with cell-free infectious BLV. Our results demonstrate that the two phenomena proceed from different mechanisms. Late polykaryocytosis results from an active process dependent on the integrity of the virus genome. In contrast, early polykaryocytosis is a passive process which does not require any de novo virus synthesis but is dependent on the presence of virus proteins in inducer cells.

Five human interferon-α (leukocyte) subtypes derived from genes cloned in Escherichia coli have been compared for their ability to induce antiviral activity against vesicular stomatitis virus infection of various mammalian cell cultures. These interferons, designated LeIF-A (IFN-α 2), -B, -C, -D (IFN-α 1) and LeIF-F, show different relative activities when assayed on human, bovine, hamster, mouse, rabbit and monkey cell lines. As with a natural human buffy-coat interferon-α preparation, three subtypes (LeIF-B, -C and -D) showed considerable activity on RK-13 rabbit cells, but two (LeIF-D and -F) also showed some activity on mouse L-929 cells. Of the five interferon subtypes examined, LeIF-F demonstrated the highest degree of species specificity.

Glycophorin, the major sialoglycoprotein in the human erythrocyte surface membrane, can serve as a red cell receptor for both wheat-germ agglutinin (WGA) and encephalomyocarditis (EMC) virus since glycophorin bound to WGA–Sepharose can at the same time bind EMC virus. In contrast, glycophorin bound to WGA–Sepharose cannot bind EMC virus in the presence of SDS. The evidence suggests that virus binding to glycophorin-WGA–Sepharose occurred in the absence of SDS because glycophorin was present in aggregated complexes which were large enough either to accommodate both EMC virus and WGA at the same time, or alternatively to provide sufficient attachment sites for multivalent binding of virions.

Deoxycytidine (dC) deaminase activity has been previously reported to be induced in herpes simplex virus (HSV)-infected cells (Chan, 1977). In contrast, we report here that HSV infection of either hamster cells naturally deficient in this enzyme activity or mouse cells containing a low level of activity never resulted in appearance or stimulation of dC deaminase, whereas thymidine kinase (TK) was always induced. Surprisingly, dC deaminase activity, which differed by electrophoretic mobility from the mouse or human cell enzyme, was discovered in some cells selected for the presence of HSV TK after infection with u.v.-irradiated HSV. Evidence is presented which suggests that the appearance of this new enzyme was not due to the presence of virus genes but rather to mycoplasma contamination.

Clover yellow mosaic virus (CYMV) protein encapsidates its RNA at pH 7.5, low ionic strength and at a temperature of 25 °C. Protected RNA fragments extracted from the initiation complexes contained the cap structure m7GpppGp in the stoichiometric proportions expected for fragment sizes. These results were consistent with the location of the initiation site for assembly at or near the 5′ end of RNA; consequently, the maturation process is polar (5′ to 3′ direction). This strengthens the case for polar initiation as an alternative to internal initiation in the assembly of helical plant viruses.

Small isometric virus-like particles have been detected in thin sections of phloem transfer cells of subterranean clover plants infected with subterranean clover red leaf virus (SCRLV). Virus-like particles similar in size and appearance but serologically distinct from those of potato leafroll virus, were also detected in purified preparations from SCRLV-infected plants. The morphology of the particles and their distribution in infected cells is consistent with SCRLV being a member of the luteovirus group, as previously suggested by its biological properties.