Biological expression of antigenic determinants of murine leukemia virus proteins gp69-71 and p30

Antisera to purified structural proteins of Rauscher murine leukemia virus, the major envelope glycoprotein, gp69/71, and the major internal protein, p30, were studied by immunofluorescence of viable and fixed virus-infected cells and by virus neutralization. Group-specific and type-specific determinants of gp69/71 were demonstrated by immunofluorescence and virus neutralization tests, indicating that these determinants are located in the cytoplasm and probably on the cell surface as well as on virus envelope. Antisera against p30 showed anti-group and anti-interspecies activities by immunofluorescence with no virus-neutralizing activity. Both antigenic determinants of gp69/71 were sensitive to guanidine-hydrochloride and to a lesser degree to ether treatment, whereas the group-specific determinants of p30 were relatively stable to these treatments.

Expression of the major internal viral polypeptide in cells transformed by wild-type and temperature-sensitive murine sarcoma virus

Phenotypic expression of the murine intraspecies and interspecies antigenic determinants of the major type C viral structural 30,000-dalton polypeptide, p30, was measured by radioimmunoassay inhibition in cell lines from different species. Uninfected normal rat kidney (NRK) cells did not contain detectable levels of murine intraspecies and interspecies p30 antigen, whereas rat cells transformed by and producing murine sarcoma virus (MSV)-Moloney leukemia virus (M-MSV-MuLV) contained high levels of both murine intraspecies and interspecies p30 antigen. Significant amounts of murine intraspecies and interspecies p30 antigen were detected in wild-type MSV-transformed nonproducer NRK cells. The control of p30 antigen expression was examined in temperature-sensitive MSV-transformed nonproducer cells [NRK(MSV-1b)] which are cold sensitive for maintenance of the transformed phenotype. Both murine intraspecies and interspecies p30 antigens were detected in NRK(MSV-1b) cells when grown at the permissive (39 C) or nonpermissive (33 C) temperature, suggesting that p30 antigen expression is not correlated with maintenance of the transformed phenotype. The results demonstrate that previously undetectable p30 antigens are expressed in MSV-transformed nonproducer NRK cells, and suggest that the expression of p30 antigen may be a useful marker for viral gene expression in mammalian cells.

Structure of the mouse mammary tumor virus: characterization of bald particles

The polypeptide, antigenic, and morphological structure of the mouse mammary tumor virus was studied following protease digestion of intact virions. Intact, untreated virions (rho = 1.17 g/ml) had characteristic envelope spikes, five major polypeptides, and were precipitated by antisera against gp52. Two of the major polypeptides, with molecular weights of 52,000 (gp52) and 36,000 (gp36), had carbohydrate moieties. Protease treatment resulted in spikeless, "bald" particles (rho = 1.14 g/ml), which had altered surface antigenicity and which contained neither gp52 nor gp36. These data indicated that gp52 and gp36 were on the viral envelope. Bald particles retained a 28,000 dalton polypeptide (p28) which was proposed as the major internal polypeptide.

Cold-sensitive mutants of bacteriophage phi x174. II. Comparison of two cold-sensitive mutants

Cold-sensitive bacteriophage phiX174 mutants, another class of conditional lethals, were examined with regard to growth parameters, DNA synthesis, and particle properties. Two mutants, cs70 and cs82, were examined. Mutant cs70 was eclipse defective, showing altered eclipse kinetics at permissive temperature (40 C) and failing entirely to eclipse at restrictive temperature (25 C). Mutant cs70 replicated well at 25 C if allowed prior eclipse at 40 C. Mutant cs82 had wild-type eclipse at both temperatures but was defective in single-strand synthesis at 25 C, which led to delayed progeny phage appearance, decreased progeny phage synthesis rate, and greatly reduced burst size. The cs82 block could not be bypassed by temperature shift. Since complementation analysis of cs70 and cs82 was not feasible due to the unique properties of these mutants, those phiX174 properties affected by the virus coat were examined as an index of a mutation in a coat protein gene. Mutant cs70 had aberrant attachment kinetics at both 25 C and 40 C, evidence of a coat protein alteration. Mutant cs70 also exhibited significantly decreased thermal stability, further evidence of an altered virus structure. Mutant cs82 had increased thermal stability, but the difference was not sufficient to allow unequivocal assignment of this mutant to a coat protein gene. Both mutants had wild-type antiserum inactivation and host range, although cs70 was subject to less of (low-level) plating restriction by endogenous F(+) factors.

The viral envelope glycoprotein of murine leukemia virus and the pathogenesis of immune complex glomerulonephritis of New Zealand mice

The use of monospecific antisera for the analysis by radioimmunoassay and immunofluorescence study of two major viral proteins, gp69/71 and p30 of murine leukemia virus, that could be of significance in the pathogenesis of immune complex glomerulonephritis of mice, particularly NZB and B/WF(1) hybrid mice, yielded the following conclusions. A remarkably high concentration of viral envelope glycoprotein, gp69/71, was detected in the spleen and serum of New Zealand mice (NZB, NZW, B/WF(1), and W/BF(1)); the concentration in the spleen was 10-fold greater than that found in AKR mice and 30-fold greater than that present in C57BL/6 mice. The gp69/71 was deposited along with bound immunoglobulins, apparently as an immune complex, in the diseased kidneys of mice, and the glomerular site and extent of deposition of gp69/71 was related to the severity of the glomerulonephritis. This study suggests that the pathogenesis of immune complex glomerulonephritis (and vasculitis) in mice is related to the expression of this specific viral envelope glycoprotein and to the host immune response to this protein.

Type C viral expression in primate tissues

Nucleic acid sequences homologous to a [(3)H]DNA transcript prepared from an endogenous baboon type C virus are readily detected in both the cellular DNA and RNA of several different Old World monkeys. Competitive radioimmunoassays for the major viral protein (p30) of baboon type C viruses detect viral antigen in a normal stumptail spleen and a rhesus ovarian carcinoma. The p30 antigen from these tissues is closely related by several immunologic criteria to the p30 protein of baboon type C viruses. The results indicate that normal primate tissues transcribe endogenous viral-specific RNA and translate at least one viral structural protein.

SV40: T antigen, the A function and transformation

T antigen, a protein found in the nuclei of SV40-transformed and -infected cells, can be purified and characterized. Our data suggest that T antigen in transformed cells is found at least in part in a large 22S complex, suggesting that this 22S form may contain T antigen complexed with other viral or host proteins. We prefer the assumption that T antigen is correlated with the A function, although a definitive in vitro proof for this hypothesis is still missing. Mutants in the A function most likely interfere with the maintenance of transformation, a result inviting the interpretation that the A function may indeed govern DNA synthesis of the transformed cell or influence the cell's ability to pass from G1 (or G0) to S. Thus transformation by SV40 may be a direct consequence of the introduction of the SV40 replicon and the presence of its initiator function which is used by the transformed cell.

Endogenous primate and feline type C viruses

1. Endogenous type C viruses have been detected in a wide variety of mammalian species. Multiple copies of related, but not identical, virogene sequences can be found in the DNA of these species. 2. The endogenous type C virogenes are subject to the pressures of natural selection, and closely related species possess related virogene sequences. These genes evolve as cellular entities diverging from one another in a manner which correlates well with taxonomic relatedness of the species. 3. The endogenous type C viruses of baboons and domestic cats are related, but they can be distinguished by biologic and immunologic criteria and by partial nucleic acid sequence homology. Virogene sequences in the DNA of Old World monkeys and domestic cats also show a degree of relatedness not shared by the unique sequence DNA of these species. The data suggest that progenitors of domestic cats were exogenously infected by a type C virus that also gave rise to present-day endogenous type C viruses of Old World monkeys. 4. The genomes of exogenously infectious viruses replicating in permissive host cells appear to evolve much more rapidly than endogenous virogenes which replicate as cellular genes. Laboratory strains of efficiently oncogenic type C viruses are presumed to be derived from activated endogenous viruses which have been selected for virulence and which, in certain cases, have acquired the capacity to replicate in the host's own cells. 5. The ubiquitous presence of endogenous type C viruses among vertegrates and their preservation throughout millions of years of evolution suggests that these genes express normal physiologic functions which provide a selective advantage to the species.

Detection of antibodies to Herpesvirus saimiri late antigens in human sera

One hundred fifty sera from handlers of squirrel monkeys and 100 sera from individuals who had never handled monkeys were tested by immunofluorescence for antibodies reactive to structural proteins of Herpesvirus saimiri (HVS). Eleven (7.3%) of the occupationally exposed group and 4 (4%) of the noncontact group were seropositive for HVS by immunofluorescence assay, and 10 of these 15 (6.7 and 2%, respectively) were also seropositive for either the major glycoprotein (140 kD) or the major capsid protein (160 kD) of HVS by radioimmunoprecipitation assay. Two sera from handlers of squirrel monkeys, however, recognized many different HVS structural antigens by immunoprecipitation, and it seems unlikely that they could also be cross-reactive antibodies. Since these two sera did not contain antibodies to HVS early antigens or to the nonstructural antigens present in infected owl monkey kidney cells, and follow-up sera collected from the same individuals several months later were negative for antibodies to HVS, these individuals do not appear to have been infected by the virus. The risk that HVS poses to humans appears to be very low.