- Volume 2, Issue 3, 1968

Two strains of foot-and-mouth disease virus, distinguishable by four marker characteristics in addition to their antigenic subtype, could be separated by countercurrent distribution in an aqueous polymer phase system. This technique of separation was applied to the analysis of the progeny virus obtained from pig kidney cells simultaneously infected with these two strains.

Selection for recombinant virus yielded a number of isolates with the appropriate recombinant phenotype. These isolates subsequently segregated into a number of clones of various phenotypes including parental and recombinant types. Possible interpretations of this phenomenon are discussed. It is suggested that the segregating isolates may have originated from foci of infection inititated by viral aggregates.

The serological data suggest that the frequency of recombinants in the progeny may be greater than indicated by multiple marker exchanges.

The relationship of group-specific (hexon) antigen, type-specific (fibre) antigen, soluble haemagglutinin (dodecon) and purified virus particles of adenovirus 19 was studied by cross complement-fixation, haemagglutination- inhibition and neutralization with antisera prepared against purified antigens.

The fibre antigen reacted as an indirect haemagglutinin, producing haemag- glutination in the presence of selected heterologous adenovirus immune sera. Dodecon and fibre antigen were closely related, while hexon antigen showed no relationship to fibre and possibly a weak relationship to dodecon antigen. Neutralizing antibodies were found in antisera to hexon and dodecon, but not in fibre antisera.

The reproduction of a mutant of A2/SINGAPORE/57, selected after repeated passages in monkey kidney cells, and the synthesis of its subviral components were followed in two systems : in monkey kidney cells, in which new infectious virus is formed, and in human diploid cells, in which the growth cycle of this virus is abortive. The formation of subviral antigens was investigated by both immunofluorescence and complement-fixation tests. No marked differences were found between the kinetics of synthesis of the V and S antigens and their total yields in both systems. Migration of the S antigen from the nuclei was observed in A2/singapore virus infected by human diploid cells.

This investigation has been focused on the significance of residual growth in the latent period after ultraviolet irradiation of a lysogenic strain of Staphylococcus aureus (111). It was shown that the organisms divide once or twice before the development of free phage and the number of infective centres are increased by about 100 % in 30 min. after irradiation.

When celbenin (sodium 6-(2,6 dimethoxy benzamido) penicillinate) was added to the culture after irradiation, the number of infective centres decreased progressively, and no free phage developed. A delay of 10, 20 or 30 min. in introduction of the drug allowed an increasing fraction of the infective centres to develop and to yield free phage.

These observations lead to the suggestion that ultraviolet irradiation inhibits the synthesis of new repressor of vegetative phage development, but has no influence on repressor molecules present beforehand. Residual growth of the irradiated bacteria serves to dilute the intracellular repressor concentration below an effective level.

Established (laboratory) strains and fresh isolates of herpes simplex virus from patients with skin and genital lesions were classified into four groups depending on their effects on the social interaction among infected hep-2 cells. The groups comprised strains causing (1) rounding of cells but no adhesion or fusion, (2) loose aggregation of rounded cells, (3) tight adhesion of rounded cells, and (4) fusion of cells into polykaryocytes. Protype strains from each group were found to differ with respect to immunologic specificity, buoyant density in CsCl solutions and stability at 4°.

The replication of Sindbis virus was studied in primary chick embryo fibroblasts treated with actinomycin D. The cellular site of viral RNA and coat protein synthesis was found to be localized in the cytoplasmic reticulum. Two different species of RNA were identified in association with the reticulum, namely a double-stranded RNA with a sedimentation constant of 20 S and RNA with a sedimentation constant of 25 S. The single-stranded RNA molecules extracted from the 130 S virus particles had a sedimentation coefficient of 40 S. The time course of the association of viral RNA and coat proteins demonstrated that both components appear simultaneously in the 130 S viral ribonucleoprotein particles within 15 min.

A quantitative immunofluorescent cell-counting technique was used to investigate the virustatic effect of aminoadamantane, ammonium acetate and a number of aliphatic amines on the development of influenza virus antigens in BHK-21 cell monolayers. Influenza virus strains A2/SCOTLAND/49/57, A/nws and B/ENGLAND/939/59 were used at high multiplicities of infection in the tests. Quantification of the activity of the antiviral compounds was provided by the direct estimation of the proportion of infected cells in which the production of influenza virus fluorescent antigens was blocked. Comparable results were obtained for A2/SCOTLAND/49/57 virus using the immunofluorescent technique and the more conventional method of measuring antiviral activity by the reduction in the ability of the virus to multiply in tissue culture in the presence of the test compounds.

Serological relationships between neuraminidases of representative strains of influenza virus isolated between 1930 and 1967 were studied, using rabbit antisera. The neuraminidases of type A strains formed three antigenic groups, sw, A0-A1 and A2, with antigenic drift within these groups. The neuraminidases of type B strains were unrelated to those of type A strains, and also showed antigenic drift. Four subgroups could be distinguished in haemagglutination-inhibition tests, sw, Ao, A1 and A2. Antigenic drift occurred within each of these subgroups; antigenic changes in the neuraminidase and haemagglutinin occurred independently.

The neuraminidases of different strains as well as variants of a single strain varied greatly in their heat stability, which had no direct relation to the antigenic changes or the time of isolation of the strains. Both the antigenicity and the enzymic activity of the neuraminidases of certain strains (nsw, wse) were heat-labile and it was necessary to use freshly prepared virus suspensions for preparing antisera to their neuraminidases.

The several kinds of the two- and three-dimensional crystalline forms produced by the satellite virus of tobacco necrosis virus are described and discussed.

Extracts of rabies-infected suckling mouse brains purified by precipitation at pH 4·5, freed from smaller antigens by sedimentation at 161, 180g and digested with RNase, DNase and trypsin show in the ultracentrifuge a component of S 20 ≈ 16 to 18 which is lacking in extracts of normal suckling mouse brains similarly treated. The largest rabies soluble antigen (‘outer antigen’: Mead, 1962b) has a sedimentation constant S 20 ≈ 16 estimated by the ‘biological’ method of Polson & van Regenmortel (1961). The purified antigen appears to consist of rings or possibly single-turn helices about 100 Å in diameter containing about 0·57 μ g. pentose (as ribose) per μg. total nitrogen. The antigen also appears to contain deoxypentose. It is resistant to pancreatic RNase, DNase, trypsin and chymotrypsin, has a density of about 1·34 g./cm3. in CsCl and an electrophoretic mobility about 7/8 that of rabbit serum albumin at pH 8·5.

Preparative density-gradient centrifugation in the analytical rotor of the Model E Spinco centrifuge is described. This allows the method to be applied to smaller particles than can be treated in the S.W. 39 rotor.

Satellite Tobacco Necrosis Virus is the smallest virus known to date. It has a mean diameter of 180 Å with icosahedral symmetry which was determined from shadow-cast and negatively contrasted specimens. Immunological complexes of virus and anti-virus (IgG) were freed from non-specific IgG by particle sieve chromatography. The individual antibody molecules could be detected by electron microscopy in the small complexes formed with slight antigen excess. IgG molecules either bridged adjacent virus particles by their ends or were combined to a single virus particle by one of its ends, thus radiating out from the virus capsid. A few subunits could be discerned on the IgG molecules arranged in different structural configurations.