Journal of General Virology - Volume 15, Issue 1, 1972

Twenty-eight bacteriophages from Rhizobium trifolii were found to be divisible into eleven distinct morphological groups. Four groups had long, non-contractile tails, five possessed a contractile tail, and two had tails of uncertain structure. The groups could be further distinguished from one another by head size and tail detail. Isolates of the same morphological type had similar plaque characteristics and host range. All types contained DNA.

A strain of foot-and-mouth disease virus (O1 bfs 1860) was found to be comparatively stable in aerosols at relative humidities above 55%: the inactivation rate was greater at lower relative humidities.

Virus precipitated with ammonium sulphate or methanol was considerably more unstable than untreated virus at relative humidities below 55%: this instability was not due to residual precipitant not removed by dialysis. Virus precipitated by polyethylene glycol or centrifuged at high speed was as stable as untreated virus. Possible reasons for the instability of virus precipitated by ammonium sulphate or methanol are discussed.

Comparisons were made of the aerosol stabilities of eight strains of foot-and-mouth disease (FMD) virus suspended in bovine salivary fluid. The strains used were O1 bfs 1860, O1 pacheco, O1 lombardy, O2 brescia, A5 eystrup (tübingen), A22 iraq 24/64, Cnoville and Clebanon 3/69. The strains were compared as aerosol clouds 1 sec. old at different relative humidities and during storage for up to 60 min. at 70% and 55% relative humidity (RH). In aerosol clouds 1 sec. old all virus strains showed maximum survival of infectivity at 60% RH and above. Below 60% RH, infectivity was reduced and little infectivity was detected below 20% RH. At low RH the aerosol survival of the A strains was about 10-fold higher than that for the O and C strains. The strains differed significantly in stability during storage of aerosols at 70% or 55% RH. Decay rates ranged from 1.1 log./hr (O1 pacheco) to 3.2 log./hr (O1 bfs 1860) at 70% RH and from 2.1 log./hr (O1 pacheco) to 3.3 log./hr (A22 iraq) at 55% RH. At 55% RH the infectivity recoveries of some strains were too low for decay rates to be determined.

We have investigated the effect of ethidium bromide (EB) on synthesis of nuclear, virus and mitochondrial DNA in permissive cells infected with simian virus 40 (SV 40). In the presence of EB, no newly formed, closed-circular, mitochondrial DNA (M-DNA) could be detected by isopycnic EB-CsCl gradient centrifugation. Synthesis of nuclear and virus DNA was not inhibited by a concentration of 8 µg./ml., even though SV40-DNA and M-DNA are similar in their tertiary structure, in that both are supercoiled, closed-circular, double-stranded molecules. The yield of SV40 progeny under these conditions was not reduced nor was their specific infectivity affected, as compared to control values.

The polypeptides of cells which had been infected with adenovirus and pulse labelled with high specific activity [35S]-methionine have been examined by polyacrylamide gel electrophoresis followed by autoradiography. Five virus-particle polypeptides and at least five other polypeptides which appeared to be specific for the infected cell could be discerned. One of the latter polypeptides could be detected very early in infection and is shown to be one of the major components of the previously described P antigen. The experiments also show that in the absence of arginine in the tissue culture medium, the infected cells fail to synthesize the arginine-rich core polypeptide.

Cytoplasmic nucleocapsids of Semliki Forest virus were formed in BHK21 cells treated with canavanine under such conditions that virus RNA synthesis continued but no infectious virus was released. On the other hand, envelope protein synthesis was strongly inhibited. The canavanine nucleocapsids formed sedimented at 140s and contained 42s virus RNA and a protein indistinguishable from the normal protein by polyacrylamide gel electrophoresis. The canavanine nucleocapsids were not released from the cells.

A skin disease of unknown aetiology appeared in a herd of 17 dairy cattle in northern Minnesota during late summer of 1970. The disease was characterized by small elevated nodules on all parts of the body with two animals showing teat lesions. The possibility of lumpy skin disease, a disease of cattle exotic to the United States, was considered.

Samples of excised nodules and whole blood were sent to Plum Island for investigation. Tissue cultures inoculated with these samples were passaged several times until cytopathic effects were seen. The results of the early tissue culture experiments were used to establish a preliminary diagnosis (Yedloutschnig et al. 1970). Electron microscopy of thin sections of such infected cells revealed a herpes virus. The present report describes the identification of this virus and compares it with other previously known bovine herpes viruses: bovine herpes mammillitis (BHM) (Martin et al. 1966; Pepper et al. 1966; Rweyemamu, Johnson & Tutt, 1966); Allerton (Polson &p, Kipps, 1967).

Genetic recombination between different strains of influenza A virus takes place readily under laboratory conditions (reviewed by Kilbourne, 1963) and this fact has recently found practical application in techniques for ‘tailor making’ antigenic ‘hybrid’ strains of influenza, the antigenic composition of which is pre-determined by the appropriate choice of parent strains (Tumova & Pereira, 1965; Kilbourne et al. 1967; Webster, 1970; McCahon & Schild, 1971). Recombination has also been suggested as a method for the production of strains with high growth capacity in the embryonated egg for use in the preparation of inactivated influenza vaccines (Kilbourne & Murphy, 1960) and recently Kilbourne (1969) has reported the isolation of a recombinant virus (X-31) using A0/pr8/34 virus and A2/hong kong/68 as parent viruses. X-31 was considered as appropriate for vaccine production since it exhibited the high yielding growth characteristics of A0/pr8 but was antigenically identical to the current epidemic virus A2/hong kong/68.

The morphogenesis of the vaccinia subgroup of poxviruses has been extensively examined using cell cultures and embryonated eggs (Joklik, 1966). However, Burnet (1955) pointed out that, at least for the formation of inclusion bodies, there is a marked difference between infected epithelial cells in vivo and cells infected in the laboratory. To clarify the structure and significance of poxvirus inclusions in vivo we have examined conventional and thin sections of pigeonpox lesions taken from a naturally infected bird. Sections of chorioallantoic membrane inoculated with the virus were examined for comparison.

Examination of the lesions in the pigeon by conventional microscopy showed that the epidermis was markedly thickened due to proliferation of stratified squamous cells. Single eosinophilic intracytoplasmic inclusions (Fig. 1) about the size of a cell nucleus or bigger were present in the majority of these cells. In contrast to the squamous cells, inoculated chorioallantoic membranes, although covered with pocks, had very few cells with recognizable inclusions; however, the few inclusions which were detected were similar to but much smaller than those seen in the original lesions.

Previous studies showed that several lines of cells of the same type differed greatly in the amounts of interferon produced when stimulated by the same inducer (Cantell & Paucker, 1963; Lockart, 1965). In our laboratory, one line of L cells, designated LTS, produced relatively small amounts of interferon when induced with either Newcastle disease virus (NDV) or the complex of polyriboinosinic and polyribocytidylic acids (poly IC); another line of L cells, designated Lpa, produced significantly larger amounts of interferon when exposed to either of these inducers. It appears, therefore, that LTS cells have less interferon-producing potential than have Lpa cells. We showed recently that cells were sensitized by incubation with interferon so that induction by an otherwise non-inducing virus resulted in greater yields of interferon (Stewart, Gosser & Lockart, 1971). Also, since interferon was made earlier and in response to subinducing concentrations of poly IC, we proposed that pretreatment with interferon somehow altered the induction process.

Cells exposed to the complex of polyinosinic and polycytidylic acid (poly IC) develop resistance to direct virus challenge and simultaneously release interferon (Field et al. 1967; Younger & Hallum, 1968). The mechanisms by which poly IC triggers the production of interferon are unknown. The effect of the time of exposure of cells to poly IC on interferon induction was examined in order to clarify the nature of ‘triggering’. Since all the antivirus activity of poly IC is not necessarily due to the induction of interferon (Kjeldsberg & Flikki, 1971), we determined simultaneously the yield of interferon and the intracellular resistance to virus as functions of the poly IC concentration and the time of exposure. Our results indicate that the critical adsorption of molecules of poly IC by human cells is much more rapid than previously suspected.

The polynucleotides poly I and poly C (Miles Laboratories) were dialysed before use for 24 hr at 4° against 0.001 m-sodium phosphate, pH 7.4.

Changes in the cell membranes after infection or transformation of cells by oncogenic viruses have been demonstrated using a plant agglutinin, Concanavalin A (Con. A) isolated from Jack beans. Upon infection or transformation of cells by oncogenic viruses, the cells agglutinate in the presence of Con. A (Inbar & Sachs, 1969; Ben-Bassat, Inbar & Sachs, 1970; Benjamin & Burger, 1970). Moore & Temin (1971) reported a lack of correlation between transformability by RNA tumor viruses and agglutinability of cells by Con. A. Recent evidence (Cline & Livingston, 1971; Ozanne & Sambrook, 1971; Arndt-Jovin & Berg, 1971; Inbar, Ben-Bassat & Sachs, 1971) has suggested that both normal and transformed cells have the same number of Con. A binding sites but agglutinate differentially to a given concentration of Con. A. Nicolson (1971) showed that single Con. A binding sites at the surface of normal cells are randomly distributed whereas in transformed cells the Con. A sites are present in clusters.

Three virus-coded structural antigens of the influenza virus have been previously described. The ribonucleoprotein (RNP) antigen, identified as the ‘soluble’ antigen of influenza by Hoyle & Fairbrother (1937), is located internally in the virus particle and is antigenically invariant and type-specific, providing the basis for the division of influenza viruses into types A, B and C. The haemagglutinin and neuraminidase antigens occur at the virus surface and are immunologically and morphologically (Laver & Valentine, 1969) distinct proteins which show a considerable degree of antigenic variation. In addition, Dimmock & Watson (1969) have presented evidence for a non-structural antigen induced by the influenza virus which appeared to be present in the nucleoli of cells early after infection with influenza. This report describes studies on an additional antigen of the virus which appears to be located internally in the particle.