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PubMedDate not supplied

Human T-lymphotropic retroviruses.

The first human retroviruses have been discovered during the past six years. They cause two diseases which involve disturbances of the growth of the T4 lymphocyte, a remarkably specific target cell type. This cell, which is central to the regulation of the immune system, is induced by human T-lymphotropic virus type I (HTLV-I) to excessive proliferation (leukaemia) and by HTLV-III to premature death (acquired immune deficiency syndrome, AIDS). Both also seem to be indirectly involved in several other disorders. The genetic structures of these retroviruses and the mechanisms by which they usurp host-cell functions are novel among retroviruses.

Acquired Immunodeficiency Syndrome↗
PubMed1979

Cell cycle-dependent chronic infection of human cytomegalovirus in human osteogenic sarcoma cells.

Human osteogenic sarcoma cells transformed by murine sarcoma virus (R970) showed restricted growth of human cytomegalovirus (HCMV). Virus was attached to the same extent as in human fibroblasts. HCMV growth was blocked at early stages after virus penetration. Splitting of infected R970 cultures resulted in infection of all cells. In experiments using synchronized R970 cells it was found that factor(s) associated with the S-phase of the cell cycle might be necessary for establishment of the infection.

Adsorption↗
PubMed1985

Vesicular stomatitis virus-infected cells fuse when the intracellular pool of functional M protein is reduced in the presence of G protein.

Five highly cytolytic strains of both Indiana and New Jersey serotypes of vesicular stomatitis virus were shown to induce cell fusion in BHK-21 and R(B77) cells. Inhibition of protein synthesis after the eclipse period of viral replication is a prerequisite for vesicular stomatitis virus-induced cell fusion. Pulse-chase experiments showed that inhibition of protein synthesis would lead to a drastic reduction in the intracellular pool of M protein as compared with other proteins. A temperature-sensitive mutant defective in M protein function (G31) was the only mutant of the five complementation groups to spontaneously induce polykaryocytes at the nonpermissive temperature. Previously, G protein has been shown to play a role in vesicular stomatitis virus-induced cell fusion. These results suggest that the combination of the presence of G protein on the virus-infected cell surface and the absence of functional M protein or a reduced level of intracellular M protein promotes cell fusion. On the basis of this study, we propose that vesicular stomatitis virus infection can induce cell fusion when the functional M protein pool declines to a critical level while G protein remains on the cell surface.

Amino Acids↗
PubMed1987

Identification of a nonproductive, cell-associated form of measles virus by its resistance to inhibition by recombinant human interferon.

Subacute sclerosing panencephalitis (SSPE) is a fatal disease in children and young adults that is caused by persistent infection of the central nervous system (CNS) by a nonproductive, cell-associated form of measles virus. Using an experimental model for SSPE (LEC viral strain in newborn hamsters), we have shown previously that establishment of such CNS infections involves selective elimination from the CNS of productively infected cells by host defensive mechanisms, coupled with the selective sparing of cells carrying nonproductive viral forms. That interferon (IFN) may play a role in this process was suggested by the disappearance of productively infected cells from the CNS tissues prior to the appearance of antiviral antibodies and by the demonstration of cell-associated, IFN-resistant viral variants in the virus stocks that were used. Results of this study support these conclusions by showing that similar IFN-resistant viral variants are present in the HBS strain of SSPE-derived measles virus and that these variants, in the presence of IFN, have properties that are similar to those of naturally occurring cell-associated strains of SSPE viruses, e.g., DR, IP3, and Biken. These IFN-resistant forms of HBS virus were isolated and were shown to maintain their resistance to inhibition by IFN after cloning. However, on removal of IFN, they reverted to productive forms similar to the parental HBS virus. The potential role of such viral forms in the pathogenesis of SSPE is discussed.

Animals↗
PubMed1993

Prolonged replication in the mouse central nervous system of reoviruses isolated from persistently infected cell cultures.

We examined pathogenic characteristics of plaque-purified reoviruses isolated from persistently infected L-cell cultures (PI viruses) after intracranial inoculation into newborn mice. The PI viruses were isolated from independent cultures initiated with high-passage stocks of the wild-type (wt) strain, type 3 Dearing. The virulence of most PI viruses was equivalent to that of the wt strain. However, replication of PI viruses in the central nervous system of infected mice was prolonged to 25 (but not 50) days postinoculation. Thirty-eight percent (n = 186) of mice inoculated with the PI viruses had residual virus detectable in brain tissue 25 days after inoculation, in contrast to only 16% (n = 57) of mice inoculated with wt virus (P = 0.009). Mean residual brain titers were more than 20-fold higher in mice inoculated with PI viruses compared with wt virus (4.3 x 10(4) versus 2.1 x 10(3); P = 0.006). Tropism of PI virus within the brain resembled that of wt virus, and the distribution of PI virus antigen in the brain did not change over time. The extent of necrosis in the brains of mice harboring PI virus 25 days after inoculation was minimal, despite continued presence of high titers of infectious virus. The latter observation resembles the absence of cytopathicity seen in L-cell cultures persistently infected with reovirus. These observations suggest that the interaction of PI viruses with cells can be altered in vivo as well as in cell culture, but virus is eventually cleared from the infected animal.

Ammonium Chloride↗
PubMed1992

The 19-kilodalton adenovirus E1B transforming protein inhibits programmed cell death and prevents cytolysis by tumor necrosis factor alpha.

The adenovirus E1A and E1B proteins are required for transformation of primary rodent cells. When expressed in the absence of the 19,000-dalton (19K) E1B protein, however, the E1A proteins are acutely cytotoxic and induce host cell chromosomal DNA fragmentation and cytolysis, analogous to cells undergoing programmed cell death (apoptosis). E1A alone can efficiently initiate the formation of foci which subsequently undergo abortive transformation whereby stimulation of cell growth is counteracted by continual cell death. Cell lines with an immortalized growth potential eventually arise with low frequency. Coexpression of the E1B 19K protein with E1A is sufficient to overcome abortive transformation to produce high-frequency transformation. Like E1A, the tumoricidal cytokine tumor necrosis factor alpha (TNF-alpha) evokes a programmed cell death response in many tumor cell lines by inducing DNA fragmentation and cytolysis. Expression of the E1B 19K protein by viral infection, by transient expression, or in transformed cells completely and specifically blocks this TNF-alpha-induced DNA fragmentation and cell death. Cosegregation of 19K protein transforming activity with protection from TNF-alpha-mediated cytolysis demonstrates that both activities are likely the consequence of the same function of the protein. Therefore, we propose that by suppressing an intrinsic cell death mechanism activated by TNF-alpha or E1A, the E1B 19K protein enhances the transforming activity of E1A and enables adenovirus to evade TNF-alpha-dependent immune surveillance.

Adenovirus Early Proteins↗
PubMed1974

Identity of a newly isolated human polyomavirus from a patient with progressive multifocal leucoencephalopathy.

Isolation of a strain of polyomavirus, designated COL, from the brain of a patient with progressive multifocal leucoencephalopathy is described. The COL strain is antigenically similar to JC polyomavirus, previously isolated from a brain affected by progressive multifocal leucoencephalopathy and is unrelated to BK, another human polyomavirus isolated from urine. Immunological cross testing of viruses in the Polyomavirus genus shows that there are at least six antigenic types in this group.

Agglutination Tests↗
PubMed1987

Persistent infection of Vero cells by paramyxoviruses. A morphological and immunoelectron microscopic investigation.

Two Vero cell lines persistently infected with canine distemper virus (CDV) or with both CDV and canine parainfluenza (CPI) viruses were investigated. Cells in the CPI-CDV cell line were 90-100% positive for CPI antigen and exhibited 10-80% CPI hemadsorption. Cytoplasmic CDV antigen expressed in both singly and dually infected monolayers varied weekly from 1 to 100%. Numerous cytolytic crises were observed in both cell lines. Cell replication was severely depressed in both cell lines when compared with uninfected Vero cells. Infrequent interfering activity against lytic CPI virus was present in the CPI-CDV cell line but not between lytic CDV and progeny virus from the CDV or the CPI-CDV cell line. Ultrastructurally, Vero cells persistently infected with both paramyxoviruses contained two types of viral nucleocapsids (NC). By immunoelectron microscopy, smooth NC were identified as CPI virus and rough NC were of CDV origin. The viral NC never intermingled but rather were restricted to discrete cytoplasmic areas containing either one type of NC or the other.

Animals↗
PubMed1990

Serological survey of the Iriomote cat (Felis iriomotensis) in Japan.

The Iriomote cat (Felis iriomotensis) was first discovered on Iriomote Island in the Yaeyama Islands of Japan in 1965. Ten male and 11 female adult cats were captured during the 6 yr period from 1983 to 1988. These were examined for evidence of viral and mycoplasmal infections. Neither Mycoplasma sp. nor Ureaplasma sp. were detected in swab samples of oropharyngeal and urogenital regions. A foamy virus was isolated from the oropharyngeal swab of a female cat examined in 1988. Feline leukemia virus was not detected in any of the cats. All cats were negative for serum antibodies to feline panleukopenia virus, feline herpesvirus, feline immunodeficiency virus and rotavirus. Eleven of 19 (58%), 14 of 17 (82%) and 6 of 17 cats (35%) had serum antibodies against feline calicivirus, coronavirus and feline syncytium forming virus, respectively.

Animals↗
PubMed1993

Phocine distemper in harbor seals (Phoca vitulina) from Long Island, New York.

The first occurrence of phocine distemper (PD) disease in harbor seals (Phoca vitulina) from the United States is reported. Two seals stranded on Long Island, New York (USA) in February 1992 with clinical signs of respiratory distress, fever, and depression. Pneumonia and diffuse pulmonary congestion were the most significant post mortem findings. On histologic examination one seal had a diffuse broncho-interstitial pneumonia with formation of syncytia. The principal lesion in the second animal was nonsuppurative meningoencephalitis. Using immunoperoxidase staining, PD viral antigen was found in the cytoplasm of bronchiolar epithelium and cerebral cortex neurons. With a differential virus neutralization test, there were higher titers against phocine distemper virus (PDV) than against canine distemper virus. Thus, PDV is the most likely agent responsible for the observed lesions.

Animals↗
PubMed1979

[Transforming activity and the oncogenicity of simian adenovirus SA7 DNA].

The transforming and oncogenous activity of uncleaved DNA of simian adenovirus SA7 (AdSA7) and the products of its restriction by endonucleases R. Bam HI and R. SalI was studied. It was shown that uncleaved virus DNA transformed the rat kidney cells and rat embryo fibroblasts and induced tumors in newborn hamsters. AdSA7 DNA, hydrolysed by R. Bam HI, posessed the transforming activity. The mixture of DNA fragments, obtained after hydrolysis by R. SalI was oncogenous in hamsters.

Adenoviridae↗
PubMedDate not supplied

Reproducibility of a virus-neutralization test for infectious laryngotracheitis virus.

A virus-neutralization test for infectious laryngotracheitis virus was performed in microtiter plates using standard techniques. To assess the reproducibility of the test, 11 sera were each titrated repeatedly once a week for 8 weeks, and the results were compared to a standard. The standard used for reproducibility was that the 95% logarithmic confidence intervals of the mean calculated from three titrations of the same serum had to be smaller than the logarithmic distance "within" two microtiter plate wells. For the virus neutralization test to give reproducible results, such confidence intervals had to fall "within" two wells at least 75% of the time. Over the 8 weeks, percent reproducibility varied from 43.5% to 81.5%. The infectious laryngotracheitis virus-neutralization test did not meet our defined standard of reproducibility with positive antisera. Results with negative control sera were reproducible, however. Percent reproducibility varied from 31.8% to 93.8% for different sera tested, but it was not related to the titer of the sera.

Animals↗
PubMed1988

Typing of cytopathic and noncytopathic bovine viral diarrhea virus reference and Canadian field strains using a neutralizing monoclonal antibody.

Cytopathic and noncytopathic reference strains as well as Canadian field isolates of bovine viral diarrhea virus were analyzed by neutralization and immunofluorescence tests using a bovine viral diarrhea virus-specific neutralizing monoclonal antibody. Results on reference strains indicated three major antigenic groups: I) NADL-like, II) New York 1-like and III) Oregon C24V-like. Field isolates could be segregated into groups I and II and none could be typed into the group III. It appears that most bovine viral diarrhea virus strains share a common antigen which carries a major neutralization epitope. These characteristics would make this monoclonal antibody a useful reagent for taxonomic and epizootiological studies.

Animals↗
PubMedDate not supplied

[The isolation of a concentrated and purified rotavirus preparation by using bentonite].

The preparation obtained when cultivating virus SA-11 in the transplantable cell culture SPEV has been purified and concentrated by means of bentonite. The virus adsorption at acidic values of pH (4.0-4.5) and elution at alkaline values of pH (8.5) were the main stages of production of the concentrated and purified rotavirus preparation. The paper embraces data on the infective activity of the virus protein content, amount of the rotavirus antigen, results of the electron and immunoelectron microscopy, characterizing the method efficiency.

Animals↗