- Volume 61, Issue 1, 1982

The cyanophage AS-1 adsorbs to vesicles of known lipid composition. The lipids used included: phosphatidylcholine (from soybean); monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulphoquinovosyldiacylglycerol, and phosphatidylglycerol (from Anacystis nidulans); cholesterol. Adsorption required the presence of phosphatidylcholine and cholesterol but not the algal lipids.

Peritoneal macrophages isolated from Balb/c mice 1 day after infection with lactate dehydrogenase-elevating virus (LDV) exhibited a 5- to 10-fold enhancement of attachment and ingestion of sheep red blood cells coated with immunoglobulin (EAIgG) or immunoglobulin plus complement (EAIgMC). Macrophages isolated from mice 7 days after LDV infection or macrophages infected with LDV in culture were also slightly more active than macrophages from uninfected mice, but the differences were not significant. The results indicate that a specific increase in the number of Fc and C3 receptors on macrophages occurs during the acute phase of infection. This increase correlates with the transient appearance of interferon in acutely infected mice. We postulate that during the acute phase the productive infection of a subpopulation of macrophages that is permissive for LDV results in the synthesis of sufficient interferon to cause activation of the remaining non-permissive macrophages in the animal.

Canine parvovirus (CPV), feline panleukopenia virus (FPLV) and mink enteritis virus (MEV) were compared serologically, by determination of their host range in cell cultures, as well as by restriction enzyme analysis. Maps of the virus genomes were established using seven different restriction enzymes cutting at a total of 56 sites. MEV and FPLV gave maps which were identical except for one restriction site. The map of CPV is closely related to those of FPLV/MEV since their DNAs share about 80% of the restriction sites tested. However, CPV is clearly distinct from FPLV/MEV since either eight (German isolate) or nine (Belgian, Swiss and American isolates) restriction sites are different. The DNAs of six vaccine strains of FPLV and MEV were also analysed. They gave maps which closely resembled those of the respective wild-type strains. CPV and FPLV/MEV also differed with respect to antigenicity, as well as to host range in cell cultures.

Two antigenically indistinguishable strains, 171 and 308, of Kilham rat virus (KRV) have distinct host ranges and contain capsid proteins of identical size, but with different isoelectric points. The single-stranded DNA genomes of the viruses are also the same size but appear to have different secondary and tertiary structures. The genomes of the two strains have nearly identical cleavage maps for 11 restriction endonucleases, except for differences in five restriction sites in the region bracketed by 0.63 to 0.90 map units (from the 3' ends of the virus strands). However, there is a lack of extended heterology in the nucleotide sequence of the two virus genomes, as judged by electron microscopic analysis of the heteroduplex of the two virus DNAs. This suggests that very subtle differences in the sequences of the genome, and possibly of the capsid proteins, may play a role in the host specificity without affecting the antigenic similarity of KRV strains.

Radiation leukaemia virus, Rs strain (RadLV-Rs), is a virus complex derived from radiation-induced lymphoma of the C57BL/6 mouse. Several B-ecotropic retroviruses (T1223/B, T98/B and T128/B) were isolated from the RadLV-Rs and further cloned. They were found to be highly leukaemogenic and polymorphic in terms of XC cell fusion activity. To investigate a possible relationship between their phenotypical and genotypical properties, a serological characterization of their proteins was undertaken by means of interference, neutralization and type-specific radioimmunological experiments. In addition, these viruses were compared on the basis of the electrophoretic mobility of their proteins. They were also compared with the prototype endogenous N-ecotropic (BL6/NÌ) and xenotropic (T530/X) retroviruses of the C57BL/6 mouse as well as the AKR-MuLV and the RadLV/VL-3 (thymotropic leukaemogenic retrovirus involved in radio-induced lymphoma). With respect to the pl2, T1223/B and T128/B viruses were of xenotropic type as in RadLV/VL-3, whereas T98/B p12 displayed ecotropic and xenotropic type-specific antigenic determinants. The gp71 of all B-ecotropic virus isolates were indistinguishable and of the AKR-MuLV type. This latter result was further supported by interference and neutralization experiments. This supports the view that the B-ecotropic virus isolates originated by recombination (one or two events) between N-ecotropic and xenotropic endogenous retroviruses. The RadLV/ VL-3 possesses a unique envelope recombinant glycoprotein of which the antigenicity was not observed in the RadLV-Rs complex. Thus, it may be assumed that the leukaemogenic components of RadLV and RadLV-Rs arose by different recombinational mechanisms.

The xenotropic (X-tropic) mouse type C virus (MuLV) and its pseudotype of murine sarcoma virus (MSV) were inoculated into several fertilized developing Pekin duck eggs. The development of the duck embryos was substantially reduced in those receiving the X-tropic viruses compared to eggs inoculated only with tissue culture medium. Infectious virus was isolated from some of the adult animals; in others, evidence for integrated virus sequences in the tissues was noted. No specific pathology was found in the ducks that received X-tropic MuLV alone, but one duck developed multiple fibrosarcomas when inoculated at birth with the X-tropic virus pseudotype of MSV. Two ducks receiving X-tropic MuLV had signs of haematopoietic disorders. In addition, more virus-inoculated animals had evidence of hepatitis and encephalitis than control ducks. Antibody production to X-tropic MuLV was present in several ducks inoculated with virus either in embryo or at birth. Absence of antiviral antibodies was noted in those animals whose tissues contained replicating virus. These studies confirm the observations with X-tropic virus in tissue culture. They demonstrate in vivo that avian species are susceptible to infection by the mouse X-tropic virus and that their fibroblasts can be transformed by the X-tropic MuLV pseudotype of MSV.

Purified virus proteins from transformation-defective (td) mutants of Rous sarcoma virus PrA or PrB were trapped in human erythrocyte ghosts which, after resealing, were fusion-injected into hamster RBH cells or rat TWERC cells. These cell lines are non-productively transformed by subgroup C Rous sarcoma virus. After fusion injection the hamster RBH cells released transforming subgroup C Rous sarcoma virus. No infectious virus could be rescued from rat TWERC cells. Since previous experiments have shown that fusion injection of the purified Rous sarcoma virus protein p 15 into hamster RBH cells caused cleavage of the precursor protein pr76 to form the virus group-specific antigen (gag) but did not induce infectious virus, we conclude that in addition to p 15 other virus proteins are required to induce virus rescue in hamster RBH cells.

The genome of avian reoviruses is comprised of 10 segments of double-stranded (ds)RNA. Analysis by polyacrylamide gel electrophoresis of the genomic RNA from a small number of avian reoviruses has demonstrated a significant polymorphism in the migration pattern of the dsRNA segments among different isolates. Comparison of these patterns with that of the mammalian reovirus of serotype 1 has permitted calculation of the molecular weights of the avian dsRNA species.

We have generated several variants of the human lymphoid cell line Namalwa which were characterized as high producers, non-producers and spontaneous producers of interferon (IFN). All of them were stable for more than 1 year, suggesting chromosomal inheritance of their mutations. We show the kinetics and quantity of IFN production following treatment with several inducers, including polyriboinosinic-polyribocytidylic acid [poly(rI).poly(rC)].

Two avirulent mutants of the CVS strain of rabies virus were isolated from clones resistant to one neutralizing monoclonal antibody. The virulence of clones resistant to three other anti-glycoprotein monoclonal antibodies was similar to that of the wild-type.

It has been shown previously that the pathogenicity of avian influenza A viruses depends strictly on the proteolytic cleavability of their haemagglutinins (HAs) in infected cells. In this communication, pathogenic and non-pathogenic strains of the H7 subtype have been studied by comparing the genetic relatedness of their HA genes. Some of the cleavable HAs of pathogenic strains were genetically more closely related to the uncleaved HAs than to other cleavable HAs. These data clearly demonstrate that the overall evolution of the H7 haemagglutinins is different from the evolution of the specific cleavage site.

As demonstrated previously, a ‘beta particle’ fraction isolated from the cytoplasm of PLC/PRF/5 cells contains hepatitis B virus (HBV)-specific DNA. Here, further evidence is provided that the specificity of the DNA for HBV is represented at least by sequences coding for the surface and core antigen (HBsAg and HBcAg). This was shown by two different hybridization techniques. One of them, the technique of Southern, distinguished these hybrid molecules formed from those containing HBV DNA integrated into chromosomes. The HBV-specific beta particle DNA forms two distinct bands separate from the high molecular weight cellular DNA.

Replication of hepatitis A virus (HAV) in the human hepatoma-derived PLC/PRF/5 cell line was neither inhibited in the presence of various concentrations of guanidine or D-2-(α-hydroxybenzyl)benzimidazole (D-HBB), nor were the two chemicals effective in combination. Under identical conditions, however, replication of poliovirus type 1 was inhibited. Tracer experiments with radiolabelled guanidine and D-HBB also furnished no evidence that the two antiviral substances were metabolized gradually to inactive derivatives in PLC/PRF/5 cells. Therefore, it is concluded that resistance to the action of guanidine and D-HBB is an inherent characteristic of HAV. However, the insensitivity of HAV to these drugs does not exclude the virus from the family of picornaviruses.

The polypeptides secreted from cells infected with myxoma virus have been studied. Three virus-induced polypeptides were detected. One major and one minor polypeptide were synthesized and secreted in the absence of virus DNA synthesis; one minor polypeptide was not detected in the medium under such conditions. All these polypeptides were glycosylated and one was sulphated. Two precipitin lines were seen in Ouchterlony tests examining medium from infected rabbit cells and using serum from rabbits convalescent from myxoma virus infections. These antigens were unrelated to the virus-specific antigens released from cells infected with vaccinia virus. No major differences were detected in comparisons between the polypeptides secreted from cells infected with virulent and relatively avirulent strains of myxoma virus.

A mutant of herpes simplex virus type 1 [HSV- 1(HFEM)], tsB7, appears to have two temperature-sensitive functions. One is required during the first hour of infecting a cell (suggesting that it is performed by a virion protein) and the other is the non-essential function of ‘early shut-off’ of cellular protein synthesis, which is mediated by a virion protein. The latter function remained temperature-sensitive in a revertant virus (RC2) grown at the non-permissive temperature (39 °C). However, under these conditions RC2 did cause inhibition of host synthesis, showing that ‘delayed shut-off’, requiring virus protein synthesis, can occur independently of early shut-off, which is mediated by a virion protein. Early shut-off by u.v.-irradiated tsB7 was reversed when the temperature was raised, whereas delayed shut-off by intact tsB7 was not. Of two wild-type strains of virus examined, HSV-1 (F) also exhibited temperature-sensitive early shut-off, but HSV-2(G) did not.

B cell responses of Balb/c mice were suppressed using sheep anti-mouse IgM serum. At 4 weeks, both B cell-suppressed and normal littermates were infected in the ear pinna with herpes simplex virus type 1 (HSV-1). The B cell-suppressed mice failed to produce neutralizing herpes antibodies in their sera but had a normal cell-mediated immunity (CMI) response as measured by a delayed hypersensitivity skin test. Although the infection was eliminated from the ear in both B cell-suppressed and normal mice by day 10 after infection, there was an indication that B cell-suppressed mice had a more florid primary infection of the peripheral and central nervous system and also a higher incidence of a latent infection. These results support the hypothesis that antibody is important in restricting the spread of virus to the central nervous system, whereas CMI is important in clearing the primary infection in the ear pinna.

Adult athymic Nu/Nu mice showed increased susceptibility to lethal infection with murine cytomegalovirus (MCMV) when compared to their heterozygous T cell-competent Nu/+ littermates. However, the extent of this increase in susceptibility varied dramatically depending on the genetic background of the mice carrying the Nu/Nu gene. Genetically susceptible Balb/c (H-2 d) mice showed a greater than 316-fold difference between the LD50 of Nu/Nu and Nu/+ littermates. In marked contrast, the genetically resistant CBA (H-2 k) strain was characterized by only a 16-fold difference in resistance between Nu/Nu and Nu/+ mice, and furthermore, the athymic CBA Nu/Nu mice were no more susceptible than the T cell-competent Balb/c Nu/+ strain. These results together with previous observations strongly suggest that the (H-2 k)-associated resistance of the CBA strain is mediated by non-T cell-dependent early defence mechanisms.