Journal of General Virology - Volume 9, Issue 3, 1970

Second Circular. At the 10th International Congress of the I.A.M.S. held in Mexico City from 9 to 15 August 1970, a new Section of Virology was created. The Section agreed to assume the responsibility for organizing and holding the Second International Congress for Virology in Budapest.

The Executive Committee of the Section and the Hungarian Host Committee have made the following arrangements:

Change in time and location. Because of the large number of preliminary registrants, the accommodation facilities of the Hotel DUNA Inter-Continental would have been inadequate. Thus, the location will be in a special congress building that can accommodate the plenary sessions for over 1000 participants. The building also contains 6 other meeting rooms of small sizes. It is located at 84 Dózsa György Street, Budapest.

The shift in location has necessitated a change in the time of the Congress to 27 June to 3 July 1971.

Eligibility for participation.

Production of Sendai virus and virus-induced ultrastructural changes were compared in infected chick embryo lung epithelial cells and chick embryo fibroblast cells. By 48 hr after infection, chick embryo lung cells made 100 times more infectious virus, as measured by plaque assay, than chick embryo fibroblast cells. The chick embryo lung cells showed little cytopathology up to 48 hr, while chick embryo fibroblast cells began to show severe cytopathic changes at 24 hr. Both cell types contained abundant cytoplasmic aggregates of virus nucleocapsids, but budding virus particles were more common on the surfaces of chick embryolung cells. The data indicate that late steps in virus maturation are relatively inefficient in chick embryo fibroblast cells.

Treatment of Semliki Forest virus with Nonidet-P40, sodium deoxycholate or Tween 80 + ether destroyed virus infectivity but preserved complement fixing, haem-agglutinating and neutralizing antibody blocking activities. All treatments split the virus into intact cores and fragments of envelope, but Nonidet gave the best separation of these components. Only the virus envelope had haemagglutinating and neutralizing antibody-blocking activities. Immunodiffusion tests showed that the envelope and core proteins were serologically distinct.

Further treatment of envelope fragments with dilute trypsin liberated at least three antigens, which could be separated by column chromatography. In immuno-diffusion tests, antigens 2 and 3 were serologically distinct, but both gave reactions of partial identity with antigen 1. All antigens fixed complement, but only antigen 1 was associated with haemagglutinating and neutralizing antibody-blocking activities. Sephadex gel filtration indicated that antigen 1 had a particle weight greater than 200,000 daltons, that antigen 3 had a molecular weight of about 9000, and that antigen 2 was intermediate in size.

Antiserum was prepared in rabbits against purified haemagglutinin obtained from A0/bel virus. The antiserum had potent virus-neutralizing and haemagglutination-inhibiting activity, but was free of antibody to A0/bel neuraminidase or to influenza A type-specific ribonucleoprotein. In immunodiffusion tests, the anti-haemagglutinin serum gave precipitin reactions with all A0 and A1 virus strains tested but did not react with human A2 viruses or avian or porcine influenza A viruses. The studies suggested a close immunological relationship between the haemagglutinins of A0 and A1 influenza viruses which was not revealed by haemagglutination-inhibition tests.

Four single-sporangium isolates of Olpidium brassicae were inoculated on 14 different plant species to determine their ability to infect and reproduce in each host and their ability to transmit two tobacco necrosis virus isolates. Two O. brassicae isolates, one from lettuce and one from tomato, were able to reproduce in most hosts and transmitted both tobacco necrosis virus isolates to all hosts. By contrast, a mustard isolate reproduced in only six species and was not a vector of tobacco necrosis virus. An oat isolate reproduced in six species (three in common with the mustard) and was a poor vector, transmitting one tobacco necrosis virus isolate to only two hosts and not transmitting the other tobacco necrosis virus isolate to any host.

Zoospores of the different fungus isolates were mixed with suspensions of virus, washed, negatively stained, and examined in the electron microscope. Virus adsorbed tightly to the surface membranes (plasmalemma of the body and axonemal sheath) of zoospores of isolates that transmitted it, but not to those of the non-vector (mustard) isolate. Zoospores of the poor vector (oat) isolate adsorbed fewer particles of the tobacco necrosis virus isolate they transmitted than did those of good vectors and did not adsorb the other tobacco necrosis virus isolate. Most, but not all, of the observed specificity of transmission of tobacco necrosis virus seems to be associated with the ability or inability of zoospores to adsorb the virus on their surfaces. None of these isolates adsorbed particles of turnip yellow mosaic, tomato bushy stunt or cucumber necrosis viruses. O. brassicae zoospores also adsorbed satellite virus particles. Zoospores of Olpidium cucurbitacearum adsorbed particles of cucumber necrosis virus, but not of tobacco necrosis virus, to their surfaces. Thus, in vitro acquisition consisted of a tight adsorption of virus to the zoospore surface membranes in each of the three known instances of this type of relationship.

Kinetic haemagglutination-inhibition tests were used to investigate possible antigenic variation between four strains of rubella virus which had been isolated in different years and in different geographical areas. No significant differences were detected using hyperimmune rabbit sera and human sera obtained following both naturally acquired infection and vaccination with an attenuated rubella vaccine. These results suggest that major antigenic variation is unlikely to constitute a problem with rubella.

Infectivity titration, sedimentation analysis in sucrose gradients and electron microscopy have been used to study virus maturation following the reversal of the inhibition of vaccinia virus growth by rifampicin.

Electron-dense inclusions containing tubular structures develop in the cytoplasm of infected BHK 21/C 13 cells maintained in rifampicin, but the formation of immature and mature virus particles is prevented. The removal of rifampicin is followed by a rise of the virus infectivity. Spicule-covered membranes appear at the periphery of the inclusions and both immature and mature virus particles are seen. A proportion of the DNA synthesized in the presence of rifampicin is incorporated into particles and becomes resistant to deoxyribonuclease I. If protein synthesis is inhibited, spicule-covered membranes and immature particles appear but no mature particles are seen; the virus infectivity does not increase and the DNA remains susceptible to deoxyribonuclease I. It is suggested that rifampicin binds reversibly to a virus-specified protein, thereby preventing the formation of immature virus particles. Possible effects of rifampicin on the subsequent stages of virus maturation are discussed.

Herpes viruses stimulate the activity of thymidine kinase (E.C.2.7.1.21) in a number of cell types (Kit & Dubbs, 1969) and a mutant virus which fails to produce the enzyme has been isolated (Dubbs & Kit, 1964). Simultaneous infection of cells with wild-type and mutant virus results in the inhibition of thymidine kinase activity (Munyon & Kit, 1965). A possible explanation of this inhibition is that thymidine kinase is composed of subunits and the mutant virus synthesizes an inactive subunit which competes with the active units (Kit & Dubbs, 1969; McAuslan, 1969). The postulated inactive subunit may be antigenically similar to or different from the active enzyme subunit. We have examined this possibility immunologically.

Wild-type herpes virus and the mutant (2006) (Dubbs & Kit, 1964) were grown in BHK 21 cells or RK13 cells (Watson et al. 1966). Antisera to RK13 cells infected with each virus were produced by the method of Watson (1969).

The defective nature of adeno-associated satellite virus (ASV) has been investigated in several laboratories. Heat- or u.v.-inactivated adenovirus does not support ASV growth (Hoggan, Blacklow & Rowe, 1966; Blacklow, Hoggan & Rowe, 1967). An incomplete growth cycle of human adenovirus 7 is known to take place in primary green monkey kidney (GMK) cells, where the virus DNA and some virus specific RNA are produced as well as the T antigen (Rapp, Feldman & Mandel, 1966; Baum, Weiss & Reich, 1968). Since ASV does not multiply in this system (Blacklow et al. 1967), it has been considered to date that ASV growth takes place only in cells co-infected with a competent helper adenovirus. We found that a temperature-sensitive mutant (ts 13) of human adenovirus 31 (Ad 31), recently isolated in our laboratory, helps ASV replication at its non-permissive temperature, 39.5°, as efficiently as the wild strain.

Phage 13vir is a sheath-tailed phage (Prozesky, de Klerk & Coetzee, 1965, Pl. 1, fig. 5) which arises from single clones of Proteus mirabilis strain 13 (Coetzee & Sacks, 1960). It forms large clear plaques on strain 13. The phage may carry a constitutive mutation in an operator gene which controls development of the prophage in strain 13. It is not inducible with ultraviolet light or mitomycin C but is often present in overnight broth cultures of strain 13. The phage is particularly troublesome in that strain 13 is the host of transducing phage 34 (Coetzee & Sacks, 1960) and lysates of the latter are usually contaminated with phage 13vir.

When high titre φ 13vir. 13 (prepared by infecting a broth culture of strain 13) is spotted on a lawn of a locally isolated P. mirabilis strain 5006 the bacteria are killed but serial dilutions of the phage only sporadically form plaques.

The effect of divalent cations on the susceptibility of mammalian cells to infection by viruses has been the subject of several investigations. Calcium enhances poliovirus plaque formation on rabbit embryo kidney cells (Cooper, 1961) and magnesium increases the susceptibility of monkey kidney cells to poliovirus (Wallis & Melnick, 1962). Plaque formation by certain rhinoviruses in HeLa cells is enhanced by higher concentrations of calcium and magnesium in the overlay medium (Fiala & Kenny, 1966; Stott & Tyrrell, 1968). The increased susceptibility of monkey kidney cells to poliovirus results from the earlier release of virus from infected cells (Wallis & Melnick, 1962), and the release of rhinovirus from HeLa cells is also greatly enhanced in the presence of high levels of MgCl2 (Fiala & Kenny, 1967). This communication provides evidence that MgCl2 also enhances plaque formation by human adenoviruses on HeLa cell monolayers and that the effect is due to an increase in the rate of virus release from infected cells.