- Volume 36, Issue 2, 1977

The reverse transcriptase of Mason-Pfizer monkey virus (M-PMV) has been isolated and partially purified by ion exchange chromatography. Sera from rabbits immunized with the partially purified enzyme have been shown by microimmuno-diffusion analysis to be immunologically specific for the M-PMV polymerase. The immune serum also specifically inhibits M-PMV polymerase activity and this inhibitory activity has been shown to reside in the IgG fraction of the serum. The application of these reagents to examining virus identity and investigating the possible viral aetiology of human breast cancer is discussed.

In cell-free protein synthesizing systems from wheat embryos, messenger RNAs extracted from chick embryo fibroblasts infected with fowl plague virus direct the synthesis of nine virus-specific polypeptides, two of which may be related to the virus-specific glycopolypeptides. All of the mRNAs are complementary in sequence to virion RNA, and RNAs which do not contain poly A appear to be translated as efficiently as their polyadenylated counterparts. Under certain conditions of incubation, virion RNA also directs the synthesis of discrete polypeptides but these products are not detected in infected cells.

The infection of eggs, cell cultures or mice with a mixture of amantadine-resistant and amantadine-sensitive strains of influenza virus resulted in the transfer of amantadine-resistance or sensitivity between strains. The response of a recombinant virus to amantadine was not related to either of its surface antigens. Resistance to amantadine was transferred as an all-or-none character. It is concluded that amantadine-resistance is a useful genetic marker for influenza viruses.

Five temperature-sensitive mutants (ts 1 to 5) were isolated from a stock of the Moloney strain of murine sarcoma leukaemia virus complex which had been mutagenized by ultraviolet irradiation or N-methyl-N′-nitro-N-nitrosoguanidine. In mouse cells at the non-permissive temperature the mutants formed fewer foci of transformed cells than at the permissive temperature.

The ts mutants were characterized by testing: (1) murine leukaemia virus (MuLV) clones from the ts complex, (2) the effect of additional wild type MuLV on focus formation, (3) focus formation in rat cells and (4) focus formation with pseudotypes rescued from non-producer cells. Two mutants (ts 1 and ts 3) were found to be ts MuLVs which did not possess heat labile virion proteins and were not ts in post-penetration helper functions necessary for the fixation of sarcoma virus transformation. The remaining three mutants (ts 2, ts 4 and ts 5) were ts murine sarcoma viruses which, however, showed no temperature-sensitive effect on the maintenance of transformed cell morphology nor on colony forming efficiency in soft agar.

Seven structural proteins referred to as proteins 1 to 7 in order of increasing mol. wt. were detected following electrophoresis of disrupted purified virus preparations. Proteins 1 to 4 occurred in largest amounts, whereas protein 5, 6 and 7 occurred in small amounts. The estimated mol. wt. of proteins 1 to 5 were 27000, 52000, 58000, 78000 and about 90000, respectively. Proteins 2, 3, 4 and 5 are glycoproteins that reacted well with Schiff’s reagent whereas protein 1 reacted only weakly. A Schiff-positive zone migrating in front of bromophenol blue and behaving like glycolipid was obtained by extracting purified virus with chloroform plus methanol. Iodination of intact and Nonidet P40-disrupted virus resulted in differential labelling of proteins 1 to 4. The results were interpreted as indicating that protein 1 is located inside the virus envelope and that proteins 2, 3, 4 and 5 are on the envelope surface. An infectious component containing only protein 1 and, presumably, RNA was obtained by disrupting the virus with Nonidet P40.

The antigenic relationships between Epstein-Barr (EB) virus and herpesvirus saimiri (HVS) have been investigated in comparative immunofluorescence, microimmunodiffusion and serum neutralization tests. No similarity was detected between the structural antigens of the two herpesviruses but the results of micro-immunodiffusion tests showed that they shared a non-structural, virus-determined antigen. The implications of this finding are discussed in relation to the importance of HVS and its monkey lymphoma as a model system of herpesvirus oncogenesis.

Three new groups (phleum mottle virus, southern bean mosaic virus and carnation mottle virus groups) are proposed for plant viruses which have small spherical particles sedimenting as a single component and each containing a single RNA species. The grouping is based on a range of characters including sedimentation coefficient, stabilization of the capsid, banding behaviour in Cs2SO4, protein subunit molecular weight and distribution of particles within the cell.

A virus from Agrostis stolonifera (tribe: Aveneae) with filamentous particles about 685 nm long was serologically closely related to, and considered to be a strain of, ryegrass mosaic virus (RMV). This strain caused symptoms in Polypogon monspeliensis (tribe: Aveneae) more readily and in Lolium multiflorum (Italian ryegrass) less readily than did RMV from Lolium and Festuca spp. (tribe: Festuceae).

In L. multiflorum and P. monspeliensis the Agrostis isolate induced pinwheel inclusions with associated laminar aggregates and tubes, but Lolium isolates induced pinwheels with laminar aggregates only. The intracellular distribution of the pinwheels differed with the severity of host response. Thus, in plants with mild symptoms most pinwheels were contiguous with the plasmalemma close to plasmodesmata, but in plants with severe symptoms the pinwheels were free in the cytoplasm.

Virus particles occurred either randomly or in bundles in the cytoplasm of mesophyll and phloem companion cells. In P. monspeliensis infected with the Agrostis isolate, fibrous inclusions, possibly virus particles, occurred in some nuclei. When symptoms were severe, mitochondria and chloroplasts were amorphous and the latter had many marginal vesicles.

We have shown previously that a non-fatal outcome of infection with street rabies virus occurs more often when mice are exposed to a high ambient temperature (HAT = 35 °C) early in the course of the infection. To determine what influence the virus strain had on this protective effect of HAT, we have extended these observations to studies of a fixed rabies strain, CVS and several substrains of CVS virus derived from temperature-sensitive (ts) mutants. In all cases, mortality was reduced to some extent by exposure of the animals to HAT; however, dramatic strain-specific differences in the extent of the effect were noted. Although each of the virus substrains tested was revertant in the ts character (as tested in vitro using a non-permissive temperature of 40.5 °C), several substrains (ts 1, ts 4, RT51) caused disease that was sensitive (> 90% reduction in mortality) to HAT. Mortality induced by the parental CVS virus was reduced approx. 50% at HAT. A single CVS virus substrain, VSW89, caused disease that was less affected by HAT than was disease induced by the parental strain. As in previous studies with street virus, the incubation periods for infection with CVS virus substrains were consistently prolonged at HAT.

Interferon derived from human fibroblasts is readily inactivated during agitation and filtration. This inactivation has been shown to be largely a product of mechanical stress, and has been studied in detail by subjecting interferon to controlled shear stress using a rotational viscometer. The possible mechanism of this phenomenon is discussed.

Fibroblast interferon may be stabilized against many inactivating influences by the addition of certain simple sulphydryl reagents. The use of such easily removable and relatively non-toxic stabilizers should help in the preparation and purification of fibroblast interferon for clinical use.

Studies were performed to compare the therapeutic effectiveness of three antiviral drugs (ARA-A, ARA-C and IDU) on the course of fatal disseminated vaccinia virus infection in immunosuppressed mice. Treatment with ARA-A begun as late as 7 days after virus infection was significantly effective in preventing death; no antiviral effect of the other two drugs was demonstrated.

Unlike other strains tested, the RA 27/3 vaccine strain of rubella virus, attenuated in human fibroblasts, failed to inhibit superinfection with Newcastle disease virus (i.e. induce intrinsic interference). Since proteins of the input virion are known to lead to intrinsic interference, these may differ in the RA 27/3 strain from those in other rubella strains.

Potent preparations of bovine leucocyte and fibroblast interferons had substantial antiviral activity on monkey cells and low activity on human cells. Thus, interferon from a ‘lower’ phylogenetic species can have considerable antiviral activity in primate cells, but not all primate cells are equally sensitive.

Enveloped virions and dense bodies of human cytomegalovirus have been purified by centrifugation, using combination negative viscosity: positive density gradients. Light-scattering bands of each component were obtained, and when these were examined by immune electron microscopy minimal cross contamination was observed.

Periodate or nitrous acid treatment greatly decreases the ability of unfractionated Escherichia coli transfer RNA (tRNA) to be aminoacylated by tRNA-synthetases but these treatments do not affect their antiviral activity against encephalomyocarditis virus infection of mice. Bisulphite treatment of E. coli tRNA reduces its ability to be aminoacylated by 20% and has no effect on antiviral activity. Bromine water treatment of tRNA under conditions causing extensive base modifications eliminates aminoacylation and the antiviral activity of E. coli tRNA. Periodate treatment of yeast tRNA does not affect its antiviral activity and nitrous acid treatment increases its antiviral activity to that of E. coli tRNA. The ability to be aminoacylated does not therefore appear to be essential for antiviral activity of tRNA but extensive modification (bromine water treatment) does destroy antiviral activity.

Two functional groups on the potato virus X protein subunit were titrated between pH 7.0 and 5.5. Titration of these groups at 20 °C was the same as that at 4 °C. There was no evidence of polymerization of subunits in 0.1 m-KCl over the range pH 3.7 to 10.3.

The nuclear polyhedrosis viruses of Trichoplusia ni and Autographa californica produce plaques in monolayers of Spodoptera frugiperda cells under a solid overlay containing agarose as the solidifying agent. Plaques are visible macroscopically after staining the cells with neutral red or with the tetrazolium salt, INT, and a linear dose response is observed. The sensitivity of the assay is less than that obtained using an end-point dilution technique; however, plaque formation does provide a simple means of cloning virus.

Reverse transcriptase activity was detected in the supernatants of rat embryo fibroblast cell cultures transformed by HSV types 1 and 2 at either the sub-optimal temperature of 20 °C or the supra-optimal temperature of 42 °C. Rat cell clones which had been transformed at 20 °C contained higher levels of C-type virus DNA polymerase than did cell clones which had been transformed at 42 °C. Syncytia formation typical for C-type RNA viruses occurred at passages higher than 24. The activation of endogenous C-type RNA viruses was independent of the virus and transformation method used.