- Volume 44, Issue 2, 1979

A strain of parainfluenza virus type 3 (para 3) that had undergone a series of undiluted passages failed to produce syncytia when inoculated on to Vero cells at a high m.o.i. The strain repeatedly produced stable persistent infections. Persistently infected cells were resistant to superinfection by homologous virus, showed the presence of virus-specific antigen and shed low quantities of infectious virus into the supernatant fluid. The undiluted passage parainfluenza virus type 3 strain produced a substance that inhibited syncytium formation by homologous virus and by measles virus but appeared to have no effect on virus replication. This inhibitor had no demonstrable effect on unrelated viruses, including some that produced syncytia. It had a mol. wt. between 3500 and 14000, was acid- and heat-labile, and was inactivated by anti-para 3 serum.

Poliovirus capsid proteins comprise 15.1 lysines in VP1, 5.6 lysines in VP2, 11.7 lysines in VP3 and 5.5 lysines in VP4. Treatment with the monofunctional reagent N-succinimidyl 2,3-3H-proprionate leads to the modification of 3.4 lysines in VP1, 0.6 lysines in VP2, 2.0 lysines in VP3 and 0.03 lysines in VP4. Chemical modification with the monofunctional reagent N-succinimidyl 3-(4-hydroxy,5-125I-iodophenyl)propionate results in a predominant labelling of VP1 and VP3, whereas VP2 is less accessible and VP4 is not modified. Cross-linking of poliovirus with bifunctional imidoesters, dimethyl suberimidate (DMS, 1.1 nm) and dimethyl adipimidate (DMA, 0.8 nm) leads to a new protein complex of mol. wt. which corresponds to the sum of VP1 and VP3. By cleavage with ammonia and electrophoresis on polyacrylamide gels in SDS, the proteins are identified as VP1 and VP3. This result gives evidence for a direct neighbourhood of VP1 and VP3 in the virus capsid. Treatment of the virus with the mono- and bifunctional reagents has no influence on the stability of the particle. The infectivity is reduced only by the bifunctional reagent.

A virus-like particle was observed in two continuous cell lines derived from the marsupial Sminthopsis crassicaudata (Fat-tailed Dunnart). The development of the particle was similar to the development of D-type oncoviruses. Initially, a crescent of nucleoid material was observed near the nucleus in the region of the Golgi apparatus. This crescent developed into a doughnut-shaped A-type particle which migrated through the cytoplasm towards the cell membrane where it budded either into a smooth membrane cytoplasmic vacuole or from the cell membrane. Only enveloped A-type particles were observed; no mature B-type, C-type or D-type particles were detected.

The haemolysin of measles virus, either in the virion or in infected cells, is functionally and antigenically sensitive to acetone. Absorption of human sera with acetone-treated, measles virus-infected cells removes antibodies to all measles virus structural antigens except haemolysin. The antibody titres of absorbed sera give good correlation in HLI, neutralization and fluorescent antibody staining on unfixed infected cells.

The ribonucleic acids of cowpea chlorotic mottle virus were separated by rate zonal centrifugation, followed by polyacrylamide gel electrophoresis. They were then translated in wheat germ extracts and rabbit reticulocyte lysates. It was confirmed that RNA 4 codes for a polypeptide of approx. 19000 and RNA 3 is translated into a polypeptide of 32000 daltons. RNAs 2 and 1 were each shown to code for polypeptides of approx. 105000 daltons. Several smaller polypeptides were also synthesized and these are probably incomplete products. Of the two minor RNA components (RNAs 5 and 6) found in isolated virions only RNA 5 could be translated, the major product being approx. 68000 daltons.

Latent murine cytomegalovirus (MCMV) infection of BALB/c mouse spleens was studied using several methods including an explant tissue culture technique, co-cultivation on allogeneic and syngeneic cell cultures and nucleic acid hybridization. BALB/c mice experience latent infection which persists for at least 6 months and involves only a small fraction of spleen cells. The explant culture technique proved to be much more sensitive than other methods for detecting latent infection of lymphoid tissues.

An immunoprecipitation method coupled with SDS-polyacrylamide gel electrophoresis (SDS-PAGE) was used to identify the serologically cross-reactive polypeptides in Orthopoxvirus (vaccinia and cowpox viruses) and Leporipoxvirus (Shope fibroma virus). Two early and four late polypeptides in cells infected with vaccinia or cowpox virus were specifically immunoprecipitated with antiserum against Shope fibroma virus. Two early and two late polypeptides in cells infected with Shope fibroma virus cross-reacted with both antiserum against vaccinia virus and antiserum against cowpox virus. The possibility of the common polypeptides being related to nucleoprotein antigen in these cross-reactive polypeptides was discussed.

When purified turnip yellow mosaic virus was inoculated mechanically on to Chinese cabbage leaves, using known numbers of virus particles in 0.1 to 1.0 µl volumes of inoculum, as few as 10 to 30 particles were required to produce a single local lesion. A simple procedure is described for obtaining local lesions from the virus in single infected protoplasts.

Two types of plant virus particles, sugar beet yellows virus and pea early-browning virus, show nucleocapsids joined by cross bridges when viewed in the electron microscope. Sugar beet yellows virus particles preferentially aggregate in pairs which are joined by up to ten cross bridges originating from a morphologically different end of the virus particle. The long virus particles of pea early-browning infections were found to possess crystalline aggregates in the plant cytoplasm and many of the virus particles were linked by cross bridges extending the whole length of the virus particle.

The EBV DNA integrated into the host genome from cells of an African Burkitt lymphoma biopsy has been compared to the corresponding fraction of EBV DNA from the cell line SU-AmB-2 which is of American Burkitt lymphoma origin. It is shown that while, in the case of the African biopsy, large pieces of EBV DNA sequences are integrated into the host DNA, much smaller pieces of virus DNA are integrated into the DNA of the SU-AmB-2 cells. The possibility that this difference might be related to the fact that EBV is rarely associated with Burkitt lymphomas outside East Africa is discussed.