- Volume 22, Issue 3, 1974

The arginine analogue canavanine strongly inhibited the replication of herpes simplex virus in BSC-1 cells. Virus absorption and entry of the virus DNA into the cell nucleus were unaffected. However, changes qualitatively similar to those produced by arginine deprivation did occur. There was little inhibition of protein synthesis but the transport of proteins from cytoplasm to nucleus was substantially reduced. Virus DNA synthesis which was extremely sensitive early in the growth cycle was little affected at late times although virus maturation was still prevented. Possible modes of action of the drug are discussed.

Polyadenylic acid tracts were shown to be present in the 42S 38S, 33S and 26S single-stranded RNA species found in cells infected with Semliki Forest virus, as well as in the 20S double-stranded (RF) RNA. The average polyadenylic acid content of the 42S and 26S RNAs purified on oligo(dT)-cellulose columns was 100 to 110 and 63 to 67 residues, respectively.

The plaquing characteristics of a comprehensive range of influenza viruses in epithelial cell cultures of bovine and specific-pathogen-free chicken kidney are described. All type B viruses produced standard large plaques with high efficiency in bovine kidney cell cultures. They also plaqued in chicken kidney, but morphology was more varied and efficiency was slightly reduced. By comparison, the behaviour of a range of influenza A viruses was heterogeneous. Five out of 16 viruses failed to plaque in calf kidney cell cultures and the plaque morphology of the remainder varied with individual isolates and not with serotypes. E.o.p. was variable. Results in chicken kidney cell cultures were better and there were relatively fewer non-plaque-formers. Influenza A recombinants generally behaved like other influenza A viruses and it was concluded that plaquing capacity was genetically determined.

We have studied some properties of Nudaurelia capensis β virus, a non-occluded isometric RNA virus isolated from the infected larvae of the Pine Emperor moth, Nudaurelia cytherea capensis (Lepidoptera: Saturniidae). The virus was degraded by treatment with formic acid, and the mol. wt. of the coat protein was estimated by polyacrylamide gel electrophoresis to be between 60000 and 62000. The virus contains 11% single-stranded RNA with a nucleotide composition of 28% guanylic acid, 23% uridylic acid, 25% cytidylic acid, and 24% adenylic acid. The cryptogram of the virus is R/1; 1.8/11; S/S; I/O.

Electrophoresis of measles virus on SDS-polyacrylamide gels demonstrated the presence of six polypeptides, two of which were glycoproteins. The glycoproteins were present on the surface of the virus and could be removed by treatment of the virus with bromelain. The released glycoprotein component contained H.A. antibody blocking activity but no haemolytic or cell fusion activities. Treatment of purified virus with Tween 20 solubilized the envelope glycoproteins and part of the envelope lipids. The solubilized envelope fragments had a sedimentation coefficient of 4 to 10S and contained H.A. antibody blocking activity and low H.A. activity. When the Tween 20 was removed by gel-filtration through Sephadex G200 the envelope fragments were shown to have haemolytic and cell-fusion activities. After equilibrium density centrifuging of the solubilized envelopes in CsCl the lipids remained at the top of the gradient and the glycoproteins which contained only H.A. activity banded at a buoyant density of 1.26 g/ml. However, haemolytic and cell-fusion activities could be regenerated after extensive dialysis of the glycoproteins with the virus lipid fraction or with phosphatidylethanolamine.

Conditions favouring the infection of isolated tobacco mesophyll protoplasts by potato virus X (PVX) were studied in detail, and a procedure to effect infection in 70% of protoplasts was developed. PVX required higher concentrations of both inoculum virus and poly-l-ornithine than tobacco mosaic virus (TMV) or cucumber mosaic virus (CMV). PVX infection showed a unique response to varying pH of the inoculation medium. The time course of PVX multiplication in protoplasts resembled that of TMV. Unlike the infection by TMV and CMV, PVX infection was partially inhibited by actinomycin D. Inclusion bodies characteristic for PVX infection were present in the infected protoplasts, but their involvement in virus production appeared to be unlikely.

Two high mol. wt. double stranded RNA species have been discovered in yeast; some strains possess both species (killers) whilst other strains possess only one. Strains of the latter type have been isolated which possess relatively large amounts of dsRNA. Cell fractionation experiments utilizing these strains have shown that the dsRNA is associated with isometric virus-like particles similar to those found in other fungi. Similar particles, containing both species of dsRNA, have been isolated from a killer strain. The two species of dsRNA appear to be separately encapsidated.

Several new virus-specified polypeptides of high mol. wt. were detected in cells infected with Semliki Forest virus by use of pulse-chase methods in cells which had been either incubated at an elevated temperature in the presence of tosyl-l-phenylalanylchloromethane or treated with an inhibitor of glycoprotein synthesis, or an inhibitor of proteolytic enzyme activity, or five amino acid analogues, or an inhibitor of protein synthesis. The new polypeptides had estimated mol. wt. of 165000, 127000 and 105000 and were shown to be converted to lower mol. wt. polypeptides in pulse-chase experiments. These polypeptides, together with known non-structural polypeptides of mol. wt. of 97000, 78000 and 63000 are incorporated into a proposed cleavage mechanism for the synthesis of the virus structural proteins.

Phage ST-1 and a host range mutant, ST-1 h, the only members of the ϕX174 class of bacteriophage capable of growth on male strains of Escherichia coli, were characterized with respect to their growth requirements and physical properties. These phage were found to be separable on the basis of host range and antigenic properties but not by density or morphology. Phage ST-1 showed a strict requirement for the presence of divalent cations in order for growth to occur. This requirement was shown to be at the attachment stage in the infection process. Maximal adsorption kinetics occurred in the presence of 0.016 m-CaCl2 and both ST-1 and ST-1 h showed a greater response to divalent cations than did ϕX174. The interaction of these phage with isolated bacterial cell walls showed that the adsorption site involved the lipid layers but not the muramic acid portion of the cell wall. The growth of phage ST-1 on the mutant bacterial strain w-3110/1 revealed a strict requirement for the presence of calcium at a period after attachment.

Polyacrylamide gel electrophoresis of the solubilized proteins of IPN virus revealed at least seven polypeptide components of mol. wt. ranging from 34000 to 125000.

Temperature phage ΦD326, a new natural isolate, resembles λ and Φ80 in particle structure, inducibility by u.v. light, capacity to recombine, and ability to transduce specific regions of the bacterial chromosome. It has the same immunity specificity as Φ80. In respect to DNA base sequence, host range, tail antigens, interaction with unrelated prophages, chromosomal location of prophage, and genes transduced, ΦD326 resembles Φ80 more closely than λ.

As the generation time of Escherichia coli is increased, lysis caused by RNA phage infection occurs later after infection and decreases in amount. RNA phage is unable to cause lysis of E. coli approaching or in stationary phase. A mechanism of lysis is suggested.

The existence of defective interfering (DI) particles has been well documented for a number of virus systems (Huang & Baltimore, 1970). Such particles are currently of great interest since their ability to cause homologous interference has been implicated as a possible regulatory factor in the establishment of chronic or persistent virus disease (Huang & Baltimore, 1970). We have recently reported that about 50 cell generations after infection of BHK 21/13S cells with either lymphocytic choriomeningitis virus (LCMV) or Parana virus, infective virus could no longer be detected in either the cells or the culture medium (Staneck et al., 1972). However, LCMV-infected cultures continued to produce particles with an interference activity which closely resembled DI virus (Welsh, O′Connell & Pfau, 1972). The data presented here indicate that Parana, another arenavirus (Rowe et al., 1970), can initiate the nearly exclusive synthesis of DI virus under the same conditions.

The capsid polypeptides of Penicillium stoloniferum virus S (PsV-S) and P. stoloniferum virus F (PsV-F) were examined by SDS-polyacrylamide gel electrophoresis. PsV-S contained one major (S2) and one minor (S1) polypeptide with mol. wt. 42500 and 55500, while PsV-F contained one major (F2) and one minor (F1) polypeptide with mol. wt. 47000 and 59000, respectively. Mol. wt. of S2 and F2 polypeptides calculated from amino acid analyses were 41500 and 48000, respectively. PsV-S capsid was estimated to contain 120 molecules of polypeptide S2 and 1 molecule of polypeptide S1.

The 22 nm virus seen in the faeces of people with and without gastroenteritis has been shown to have the electron microscopic appearance of porcine parvovirus (PPV) and of mink enteritis virus (MEV). In CsCl gradients the density of the human virus (1.34 to 1.42 g/ml) was similar to that of PPV (1.31 to 1.39 g/ml).

Newcastle disease and influenza viruses were purified by centrifuging in sucrose and potassium tartrate gradients and analysed for polyamines by thin-layer chromatography of dansyl derivatives. It has been shown that both viruses contained spermine, spermidine and putrescine in concentrations sufficient to neutralize 30 to 40% of virus RNA phosphates.

Vesicular stomatitis virus was disrupted by 0.1% SDS into RNA, lipid and the individual virus polypeptides. If the virus was first treated with 0.4% formaldehyde, the particles retained their bullet shape on treatment with 0.1% SDS, although they were extensively penetrated by phosphotungstic acid. Radiochemical analysis using virus labelled with [14C]-amino acids or [14C]-choline or [3H]-glucosamine indicated that about 82% of the glycoprotein and about 96% of the protein was retained in the formaldehyde pre-treated particles, which were then treated with SDS, although more than 90% of the lipid was lost. With Sinbis virus also the overall structure of the particles was retained when the virus which had been pre-treated with formaldehyde was treated with 0.1% SDS. With this virus, about 60% of the glycoprotein was retained in the SDS-treated formalinized particles despite the loss of all the lipid. These results suggest that the surface projections are located in close proximity to the core protein.