- Volume 65, Issue 1, 1984

Using the immunofluorescence technique with antisera directed against markers on mouse brain cells, polyoma virus was found to infect in vitro, type 1 astrocytes, brain fibroblasts and leptomeningeal cells but not oligodendrocytes, type 2 astrocytes or neurones.

The involvement of lysosomes in infection by mouse hepatitis virus 3 (MHV3) was studied. L cells were infected with MHV3 in the presence of NH4Cl or chloroquine, weak bases which increase the intralysosomal pH and impair lysosomal functions. NH4Cl significantly inhibited virus-induced cytopathic effects and MHV3 replication, but did not prevent the attachment of 3H-labelled virus. No inhibition of MHV3 replication by NH4Cl and chloroquine was observed when lysosomotropic agents were added later than 3 h post-infection, suggesting the direct involvement of lysosomes in release of the viral genome into cytoplasm. These results, together with the lack of antibody-mediated immune lysis of MHV3-infected cells, suggest that MHV3 entered cells by an endocytic pathway (viropexis) followed by internalization into cellular lysosomes.

The RNA segments of bovine rotavirus (UK Compton strain) were measured by electron microscopy in mixtures containing φX174 double-stranded DNA as an internal reference molecule. The numbers of base pairs per segment were calculated and compared with data obtained by other procedures (comparative RNA gel electrophoresis; co-electrophoresis of cDNAs in denaturing gels; sequencing).

The buoyant density, nucleic acid, and proteins of the human serum parvovirus-like agent were investigated. Evidence is presented which suggests that the virus has genomic single-stranded DNA, and that complementary strands may be encapsidated in separate virions. Three proteins of 48000, 68000 and 80000 mol. wt. were found to co-purify with viral antigen at a density of 1.43 g/ml on CsCl gradients. On the basis of these properties it is suggested that this virus is a parvovirus.

An interferon-sensitive mutant of mengovirus has been shown to specifically induce interferon in infected cells. Although this appears to account for the sensitivity to interferon observed by others in an L(Y) cell line, it cannot account for the even greater sensitivity observed in our G3 line of mouse L cells.

RNAs of soil-borne wheat mosaic virus (SBWMV) from virions 281 nm, 138 nm and 92 nm long (designated here by relative lengths as 1.0L, 0.5L and 0.35L, respectively), were isolated and purified by three cycles of sucrose density gradient centrifugation. Infectivity assays with these RNAs proved the bipartite nature of SBWMV, the combination of 1.0L and either 0.5L or 0.35L RNAs being required for infection and for multiplication of progeny viruses. The 0.5L RNA underwent deletion mutation, producing smaller variants with various sizes, of which 0.4L and 0.35L RNAs were confirmed to be functional in combination with 1.0L RNA. The coat proteins of all isolates had mol. wt. of 19700. The mol. wt. of 1.0L, 0.5L, 0.4L and 0.35L RNAs, determined under denaturing conditions, were 2.28 × 106 (6500 bases), 1.23 × 106 (3500 bases), 0.97 × 106 (2800 bases) and 0.86 × 106 (2450 bases), respectively. A new virus group, furovirus (fungus-borne rod-shaped virus), is proposed for SBWMV.