- Volume 64, Issue 10, 1983

Cloned cells of the rat kidney fibroblast line designated NRK-49F, which requires epidermal growth factor (EGF), fibronectin, insulin, and retinoic acid for rapid multiplication in serum-free culture, were transformed by polyoma virus. Cells from two independent transformation events were isolated and cloned, as were cells from two corresponding control untransformed cultures not treated with virus. Tests in serum-free culture showed that the two transformed subclones required EGF and fibronectin but not insulin or retinoic acid for rapid multiplication, whereas the two control subclones retained the requirements for all four factors. Although EGF at 10 to 50 ng/ml stimulated the multiplication of all four subclones, EGF at 500 ng/ml strongly inhibited multiplication of the two transformed subclones but not the two control subclones.

Human α-interferons (IFN-αs) made in bacteria were examined for antiviral activity against herpes simplex virus type 2 (HSV-2) infections of mouse L-cells in vitro, and acute cervicovaginal and lethal systemic HSV-2 infections of BALB/c mice. The recombinant DNA-derived hybrid interferon IFN-αAD(Bgl) showed pronounced antiviral activity in vitro, exceeding the activity of either of the parental subtypes IFN-αA and IFN-αD and that of the other hybrids IFN-αAD(Pvu). A combination of topical and systemic treatments with IFN-αA and IFN-αAD(Bgl) failed to protect mice from subsequent challenge with an acute cervicovaginal infection of HSV-2. Protection from lethal systemic HSV-2 infection in mice was observed when IFN-αAD(Bgl) and IFN-αAD(Pvu) were administered systemically, whereas IFN-αA failed to confer protection. These results suggest that for protection against infection with HSV-2, the routes of introduction of the virus and of the interferon influence the host response to interferon therapy.

A retrovirus that causes pulmonary adenomatosis, a contagious lung tumour of sheep, contains a 25000 mol. wt. polypeptide which cross-reacts with the major core protein (p27) of Mason-Pfizer monkey virus and mouse mammary tumour virus.

Inhibitors of bacterial DNA gyrase and eukaryotic DNA topoisomerase (novobiocin and nalidixic acid) were investigated with respect to their effect on the activity of RNA-dependent DNA polymerases from murine and avian retroviruses. Purified RNA-dependent DNA polymerase from AKR virus was inhibited more than 90% by 0.3 mg/ml and almost completely by 1 mg/ml of the drugs when poly(A).oligo(dT)12–18 was used as a template-primer. In contrast to the enzyme from AKR virus, purified enzyme from avian myeloblastosis virus was less sensitive, i.e. nearly 50% activity remained even in the presence of 1 mg/ml of the drugs with the same template-primer. RNA-dependent DNA polymerase activity in AKR virus particles was inhibited, but was resistant to low concentrations of the drugs. The inhibition was not due to specific interaction between drugs and the template-primer or labelled precursor, since RNA-dependent DNA polymerase was inhibited by the drugs with activated calf thymus DNA or poly(C).oligo(dG)12–18 as the template. Endogenous DNA synthesis by AKR virus particles was inhibited by novobiocin to the same extent.

The distribution of measles virus antigens in an auto-degenerating persistently infected human cell line (AV3Al/MV) was examined by a direct fluorescent antibody technique. The appearance of virus antigens in cell nuclei increased with time and passage number, and correlated to a decrease in cell replication rates and increases in cellular pathology and mortality. Nuclei which had been invaded by virus antigens were frequently swollen and the cells tended to have round rather than cuboidal morphologies. The correlation between cell degeneration and viral nuclear invasion in this system suggests that quantification of viral nuclear invasion may be useful as a pathological marker of relative cell morbidity in persistent measles virus infections.

Following isoelectric focusing, poliovirus can be detected at two pH values. The acidic form consists of poliovirus aggregates and the neutral form of single virions.

Attempts were made to determine more precisely the structure and properties of a closterovirus, beet yellows virus (BYV), and a luteovirus, beet mild yellowing virus (BMYV), by scanning transmission electron microscopy, optical diffraction of electron images and acrylamide gel electrophoresis. It was shown that BYV has a mol. wt. of 76.5 × 106, including an RNA of 4.15 × 106. The pitch of the helix is 3.7 nm and there would be 8.5 protein subunits per turn. BMYV particles have a diameter of 26 nm and a total mol. wt. of 6.5(±0.45) × 106. The mol. wt. of the protein subunit is about 24000 and that of the RNA 2 × 106.