Mechanisms for generating cell membrane antigens that are recognized by cytotoxic T lymphocytes

Studies with many viruses have revealed that viral specific protein synthesis is an obligatory step in generating antigens on target cells for antiviral cytotoxic T lymphocytes. This has been most clearly demonstrated with DI particles, virions that are structurally complete but lack infectious RNA. Adsorption of such particles onto target cell membranes does not render these cells susceptible to lytic attack by antiviral effector cells, unless some viral protein synthesis transpires. However, some viruses, such as Sendai virus, circumvent the requirement for viral protein synthesis via fusion of the viral envelope with the target cell membrane, a process mediated by a specialized fusion protein. Once inserted into the lipid bilayer, it is likely that viral components and self H-2 noncovalently associate so that the complex can be recognized by antiviral cytotoxic T cells. This idea is supported by the demonstration that viral proteins and H-2 containing membrane proteins, incorporated into reconstituted membrane vesicles or liposomes are recognized by cytotoxic T cells. These data further show that native rather than altered viral and H-2 molecules are the moieties recognized. Associations between antigen and H-2 have been detected by a variety of techniques and in some cases are not random but selective; that is, viral antigens perferentially associate with some H-2 alleles and not others. In summary, these findings indicate that although viral antigens are present in the mature virions, these components are not recognized by antiviral killer cells until integrated into the plasma membrane. This may be achieved either through direct fusion of the viral envelope with the target cell or following viral protein synthesis and insertion of viral antigens into the plasma membrane.

Role of glycosylation in the H-2-restricted cytolysis of virus-infected cells

The role of the oligosaccharide portions of cell surface glycoproteins in the susceptibility of virus-infected cells to H-2-restricted cytolysis was investigated by using the antibiotic tunicamycin (TM). TM inhibits the addition of sugars to the polypeptides of glycoproteins. TM treatment of P815 cells before and during infection with vesicular stomatitis virus (VSV) inhibited glycosylation of proteins and reduced by about 50% the lysis of infected P815 cells by VSV-immune, H-2-identical killer cells. In contrast, TM treatment had a modest inhibitory effect on cytolysis of P815 cells by alloimmune effector cells. TM treatment did not inhibit the surface expression of either H-2 or VSV glycoprotein. Thus, glycosylation of H-2 and/or viral glycoprotein is a prerequisite for the lysis of infected cells by H-2-identical, VSV-immune cytotoxic cells.

Synthesis in vitro of the full-length complement of defective-interfering particle RNA of vesicular stomatitis virus

Under appropriate reaction conditions in vitro, four different defective-interfering particles of vesicular stomatitis virus have been shown to synthesize the full-length complement of their RNAs. The reaction involved preinitiation of the core particles with ATP and CTP, followed by RNA chain elongation in the presence of the beta, gamma-imido analogue of ATP, AdoPP[NH]P, and the three normal ribonucleoside triphosphates. By hybridization of the in vitro synthesized plus strand with the standard genome RNA followed by RNase treatment of the heteroduplexes, we have shown that the RNA of a defective-interfering particle derived from the 3' end of the genome RNA has evolved by an internal deletion of the standard genome.

Proposal for a uniform nomenclature for defective interfering viruses of vesicular stomatitis virus

Defective interfering particles of vesicular stomatitis virus have been named according to their parental derivation and to their genomic length and physical properties. This suggested uniform nomenclature can be adapted for other virus systems.

Assembly of avian reticuloendotheliosis virus: association of the core precursor polypeptide with the intracellular ribonucleoprotein complex

A virus-specific ribonucleoprotein complex is present in the cytoplasm of reticuloendotheliosis virus-transformed chicken bone marrow cells. This ribonucleoprotein complex contains viral reverse transcriptase activity and may represent a precursor to the budding virion. The major viral polypeptide associated with the ribonucleoprotein complex was a polypeptide with a molecular weight of 63,000. This protein exhibited a precursor-product relationship with the major reticuloendotheliosis virus structural core protein p29. Core polypeptides were not associated with the intracellular ribonucleoprotein complex. Thus, p29 was incorporated into the virion in the form of its precursor Pr63. The cleavage of Pr63 in the ribonucleoprotein complex was accomplished either during the budding process of shortly after the release of particles from the cell.

Antigenuria in St. Louis encephalitis

Patients with St. Louis encephalitis may have urinary tract symptoms when they develop manifestations related to involvement of the central nervous system. During 1976, 12 patients with St. Louis encephalitis were studied for the presence of antigenuria, and compared to controls. Although virus isolation attempts were negative indirect immunofluorescence, electron microscopy, and immune electron microscopy demonstrated the presence of viral antigen in urine. Further study of antigenuria in St. Louis encephalitis is needed to delineate the pathophysiology of the lower urinary tract symptoms and to determine whether this phenomenon might furnish the basis for a rapid diagnostic test for the disease.

Isolation and characterization of a virus-specific ribonucleoprotein complex from reticuloendotheliosis virus-transformed chicken bone marrow cells

Chicken bone marrow cells transformed by reticuloendotheliosis virus (REV) produce in the cytoplasm a ribonucleoprotein (RNP) complex which has a sedimentation value of approximately 80 to 100S and a density of 1.23 g/cm3. This RNP complex is not derived from the mature virion. An endogenous RNA-directed DNA polymerase activity is associated with the RNP complex. The enzyme activity was completely neutralized by anti-REV DNA polymerase antibody but not by anti-avian myeloblastosis virus DNA polymerase antibody. The DNA product from the endogenous RNA-directed DNA polymerase reaction of the RNP complex hybridized to REV RNA but not to avian leukosis virus RNA. The RNA extracted from the RNP hybridized only to REV-specific complementary DNA synthesized from an endogenous DNA polymerase reaction of purified REV. The size of the RNA in the RNP is 30 to 35S, which represents the subunit size of the genomic RNA. No 60S mature genomic RNA was found within the RNP complex. The significance of finding the endogenous DNA polymerase activity in the viral RNP in infected cells and the maturation process of 60S virion RNA of REV are discussed.

Host function-dependent induction of defective interfering particles of vesicular stomatitis virus

Suppression of host cell function by treatment with actinomycin D prior to infection prevented the induction of defective interfering particles of vesicular stomatitis virus, which had been cloned and propagated in cell pretreated with actinomycin D. Replication of defective interfering particles already present in an infecting virus stock, however, was not affected by pretreatment of cells with actinomycin D. Thus, the induction, but not the replication, of defective interfering particles appears to be a host cell function-dependent phenomenon. The implications of this phenomenon for host defense mechanisms against virus infections are discussed.

Oligonucleotide fingerprints of RNA species obtained from rhabdoviruses belonging to the vesicular stomatitis virus subgroup

The relationships among the genomes of various rhabdoviruses belonging to the vesicular stomatitis virus subgroup were analyzed by an oligonucleotide fingerprinting technique. Of 10 vesicular stomatitis viruses, Indiana serotype (VSV Indiana), obtained from various sources, either no, few, or many differences were observed in the oligonucleotide fingerprints of the 42S RNA species extracted from standard B virions. Analyses of the oligonucleotides obtained from RNA extracted from three separate preparations of VSV Indiana defective T particles showed that their RNAs contain fewer oligonucleotides than the corresponding B particle RNA species. The fingerprints of RNA obtained from five VSV New Jersey serotype viruses were easily distinguished from those of the VSV Indiana isolates. Three of the VSV New Jersey RNA fingerprints were similar to each other but quite different from those of the other two viruses. The RNA fingerprints of two Chandipura virus isolates (one obtained from India and one from Nigeria) were also unique, whereas the fingerprint of Cocal virus RNA was unlike that of the serologically related VSV Indiana.

Pseudotypes of vesicular stomatitis virus with the mixed coat of reticuloendotheliosis virus and vesicular stomatitis virus

Vesicular stomatitis virus (VSV) forms pseudotypes with envelope components of reticuloendotheliosis virus (REV). The VSV pseudotype possesses the limited host range and antigenic properties of REV. Approximately 70% of the VSV, Indiana serotype, and 45% of VSV, New Jersey serotype, produced from the REV strain T-transformed chicken bone marrow cells contain mixed envelope components of both VSV and REV. VSV pseudotypes with mixed envelope antigens can be neutralized with excess amounts of either anti-VSV antiserum or anti-REV antiserum.

Comparative ultrastructural study of four reticuloendothelias viruses

The morphology and development of four members of the reticuloendotheliosis virus group were studied by transmission electron microscopy. Virions of duck spleen necrosis virus, duck infectious anemia virus, chicken syncytial virus, and reticuloendotheliosis virus strain T are sperical with a diameter of approximately 110 nm. They are covered with surface projections about 6 nm long and 10 nm in diameter. The center-to-center distance of surface projections is about 14 nm. The budding virions contain crescent-shaped electron-dense cores 73 nm in diameter with electron-lucent centers. After release of the virions the cores apparently become condensed to 67 nm in diameter. Virions were found budding at the plasma membrane and into smooth-walled, intracytoplasmic vesicles of productively infected cells. The distribution of budding reticuloendotheliosis viruses on cells appeared random over the cell surface, and occasionally aberrant multiple forms of budding virions were observed. The virions appear to resemble mammalian leukemia and sarcoma viruses more closely than avian leukosis-sarcoma viruses.

Characterization of endogenous RNA-directed DNA polymerase activity of reticuloendotheliosis viruses

Reticuloendotheliosis viruses (REV) contain an endogenous RNA-directed DNA polymerase activity. The endogenous DNA polymerase activity can be elicited in purified preparations of REV by treatment with nonionic detergents. The enzyme activity has a strong preference for manganous ions. Therefore, appreciable endogenous DNA polymerase activity can be demonstrated only if the reaction mixture contains appropriate concentrations of manganous ions. Enzyme activity can be inhibited by pretreatment with RNase or deletion of one or more deoxyribonucleoside triphosphates from the reaction mixture. In contrast, actinomycin D has little effect in initial DNA synthesis. The results from both velocity and equilibrium centrifugation indicate that the nascent chains of product DNA are associated with 60S viral RNA. The DNA product of the endogenous DNA polymerase reaction is hybridizable to REV RNA, but not to avian leukosis virus RNA.

Reticuloendotheliosis virus nucleic acid sequences in cellular DNA

Reticuloendotheliosis virus 60S RNA labeled with (125)I, or reticuloendotheliosis virus complementary DNA labeled with (3)H, were hybridized to DNAs from infected chicken and pheasant cells. Most of the sequences of the viral RNA were found in the infected cell DNAs. The reticuloendotheliosis viruses, therefore, replicate through a DNA intermediate. The same labeled nucleic acids were hybridized to DNA of uninfected chicken, pheasant, quail, turkey, and duck. About 10% of the sequences of reticuloendotheliosis virus RNA were present in the DNA of uninfected chicken, pheasant, quail, and turkey. None were detected in DNA of duck. The specificity of the hybridization was shown by competition between unlabeled and (125)I-labeled viral RNAs and by determination of melting temperatures. In contrast, (125)I-labeled RNA of Rous-associated virus-O, an avian leukosis-sarcoma virus, hybridized 55% to DNA of uninfected chicken, 20% to DNA of uninfected pheasant, 15% to DNA of uninfected quail, 10% to DNA of uninfected turkey, and less than 1% to DNA of uninfected duck.

Lack of sequence homology among RNAs of avian leukosis-sarcoma viruses, reticuloendotheliosis viruses, and chicken endogenous RNA-directed DNA polymerase activity

The relatedness of the RNAs of the three avian systems, including six avian leukosis-sarcoma viruses, four reticuloendotheliosis viruses, and the microsome fraction of normal uninfected chicken embryo cells, containing RNA and a DNA polymerase have been studied by nucleic acid hybridization. All six avian leukosis-sarcoma viruses have closely related nucleotide sequences; and all four reticuloendotheliosis viruses have closely related nucleotide sequences. But, almost no similarities were detected between the RNAs of avian leukosis-sarcoma viruses and reticuloendotheliosis viruses. The RNA template of the endogenous RNA-directed DNA polymerase activity of normal uninfected chicken cells had no detectable relationship to RNAs of avian leukosis-sarcoma and reticuloendotheliosis viruses.

Endogenous RNA-directed DNA polymerase activity in uninfected chicken embryos

Early chicken embryos that are either positive or negative for group-specific antigens of avian leukosis viruses contained endogenous RNA-directed DNA polymerase activity. This endogenous DNA polymerase activity was not increased after mixture of soluble DNA polymerases isolated from chicken embryos with disrupted chicken embryo cells. The endogenous activity was resistant to treatment with deoxyribonuclease, and the initial rate of DNA synthesis was partially resistant to actinomycin D. In contrast, over 90% of the endogenous polymerase activity was destroyed by ribonuclease in medium with high salt concentration. The DNA product of the endogenous DNA polymerase activity from chicken embryos did not hybridize with RNA of Rous sarcoma virus or reticuloendotheliosis virus, whereas about 40% of this DNA product hybridized with the RNA from the same chicken-cell fraction. Antibody against DNA polymerase of avian myeloblastosis virus did not neutralize the chicken endogenous DNA polymerase activity. These results demonstrate that uninfected chicken embryo cells contain endogenous RNA-directed DNA polymerase activity that is not derived from avian leukosis or reticuloendotheliosis viruses.