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J L Leibowitz

Publications and source records attributed to J L Leibowitz.

At least 73 records · Page 4Linked to original sources
PubMed1985

Characterization, molecular cloning, and physical mapping of the Shope fibroma virus genome.

Five strains of Shope fibroma virus (SFV), a strain of rabbit myxoma virus, and a strain of vaccinia virus were compared by restriction endonuclease digestion of their viral DNAs. Restriction digest patterns revealed that SFV and rabbit myxoma, both members of the Leporipoxvirus genus, were distinct from vaccinia, an Orthopoxvirus. All strains of SFV examined had a high degree of nucleotide sequence homology as shown by conservation of restriction sites within their genomes. However, restriction patterns of SFV and myxoma were quite different from one another suggesting that the genomes from these two viruses of the Leporipoxvirus genus do not share a large, highly conserved region of homology as do the viruses belonging to the Orthopoxvirus genus. Restriction mapping identified inverted terminal repeats of approximately 12 kb in length. Restriction fragments representing all but 400 bp of the termini were cloned in plasmid vectors.

Animals↗
PubMed1985

Recombination between nonsegmented RNA genomes of murine coronaviruses.

We have isolated a recombinant virus between the A59 and JHM strains of mouse hepatitis virus, which contain a single species of nonsegmented RNA genome. This recombinant was derived by mixed infection of DBT cells with temperature-sensitive mutants of A59 and JHM at nonpermissive temperature. Viruses recovered at this temperature were screened by oligonucleotide fingerprinting of their genomic RNAs. One recombinant virus, B1, was found to contain mostly A59-derived sequences, but the 3 kilobases at the 5' end of the genomic RNA was derived from JHM. Thus, the crossover point in the B1 genome is located within gene A, which codes for the viral RNA polymerases. The study of the intracellular RNA species of B1 virus revealed that probably all of the virus-specific subgenomic mRNA species contained the body sequences of strain A59 but the leader sequences of JHM. This result indicates that the JHM leader RNA, which differs from the A59 leader RNA, could be fused to the mRNAs of a different virus strain during RNA transcription. Furthermore, B1 virus-infected cells contain an additional subgenomic mRNA species which is transcribed from a new initiation site within gene C, suggesting that the leader RNA could determine the site of initiation for coronavirus mRNAs. These data represent a first report of RNA recombination between viruses, other than picornaviruses, which contain nonsegmented RNA genomes.

Base Sequence↗
PubMed1985

The immune response to mouse hepatitis virus: expression of monocyte procoagulant activity and plasminogen activator during infection in vivo.

After infection with 10(3) plaque-forming units of mouse hepatitis virus strain 3 (MHV-3) in vivo, peripheral blood mononuclear cells and splenic cells expressed procoagulant activity (PCA) in a pattern directly correlating with susceptibility to disease. Mononuclear cells from BALB/cJ mice, a strain which is fully susceptible to MHV-3, expressed a greater than 500-fold increase in PCA. PCA was first detected within 12 hr of infection; prior to histologic evidence of disease and viral replication, it reached maximal levels 48 hr post-infection (p.i.) and persisted until the death of the animals 5 to 7 days p.i. Mononuclear cells from C3HeB/FeJ mice expressed a significant but lesser titer of PCA, with elevated PCA persisting throughout the chronically infected state until death of the animals 4 to 6 mo p.i. Basal levels of PCA were detected in mononuclear cells from fully resistant A/J mice despite the presence of large amounts of virus in livers, spleens, and sera from these animals. When mononuclear cells expressing high PCA were subfractionated, monocytes were found to be the cellular source of greater than 96% of the PCA activity. Increased plasminogen activator activity was found in monocytes from resistant A/J mice at the time when PCA was markedly elevated in BALB/cJ and C3HeB/FeJ mice. This activity persisted for 5 to 7 days p.i., but was undetectable 10 days p.i. at a time when the mice had cleared the virus from their blood streams. These observations suggest that monocyte PCA may be important in the pathogenesis of MHV-3 disease, whereas the production of monocyte plasminogen activators may contribute to resistance of A/J mice to MHV-3-induced liver disease.

Animals↗
PubMed1984

Biological and macromolecular properties of murine cells persistently infected with MHV-JHM.

A persistently-infected neuroblastoma culture [Neuro-2A( JHMV )] was established with the murine hepatitis virus JHM [MHV-JHM]. After 100 days of passage, the endogenous virus [Neuro-2A( JHMV ) end] released by this culture was unable to induce the syncytia typical of MHV-JHM and the endogenous virus was not temperature-sensitive. The Neuro-2A( JHMV ) culture was cured of virus production by passage under neutralizing antibody [Neuro-2A( JHMV )Ab]. The Neuro-2A( JHMV ) and the Neuro-2A ( JHMV ) Ab cultures were as susceptible to heterologous infection with mengovirus and vesicular stomatitis virus as the uninfected Neuro-2A culture. However, the Neuro-2A ( JHMV ) and Neuro-2A( JHMV ) Ab cultures were partially resistant to homologous superinfection by MHV-JHM and the closely related MHV-A59. Virus related to MHV-JHM was rescued from the antibody-cured cells by cell fusion. The synthesis of MHV-JHM specific antigens by Neuro-2A( JHMV ) cells, Neuro-2A( JHMV ) Ab cells and 17 Cl-1 cells infected by Neuro-2A( JHMV ) end was studied by SDS-PAGE. The genomic RNAs of MHV-JHM and Neuro-2A( JHMV ) end were compared by oligonucleotide mapping. The results of the protein and RNA studies indicated that the genome of Neuro-2A( JHMV ) end was substantially modified from the genome of MHV-JHM, but the modifications did not significantly alter the molecular size of the viral-specific proteins.

Animals↗
PubMed1984

Protein synthesis in cells infected by murine hepatitis viruses JHM and A59: tryptic peptide analysis.

The structural and intracellular proteins of the murine hepatitis viruses MHV-JHM and MHV-A59 were studied by tryptic peptide mapping. The results demonstrated that the virions contained three distinct proteins: the two related chains of the E2 complex, the nucleocapsid protein and the heterogeneous E1 complex. Five distinct virus-specific proteins were synthesized by infected cells. Three of the five intracellular proteins contained tryptic-peptides with properties similar to the three structural proteins. Models describing the evolution of the proteins are proposed. Although the pathogenic properties of MHV-JHM and MHV-A59 differ greatly, the tryptic peptide maps of the corresponding proteins of these MHV strains were remarkably similar.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Persistent infection of oligodendrocytes in Theiler's virus-induced encephalomyelitis.

Mice infected with Theiler's murine encephalomyelitis virus (TMEV) develop a chronic relapsing demyelinating myelitis. To determine the localization of viral antigen in infected cells of the spinal cord, we studied TMEV-infected SJL/J mice using immunoelectron microscopic peroxidase-antiperoxidase techniques. Viral antigens were expressed in the cytoplasm of neurons and astrocytes 4 and 11 days postinfection. At 28 days postinfection, macrophages, astrocytes, and oligodendrocytes showed viral antigen in their cytoplasm. At 45, 83, 270, and 360 days postinfection, most infected cells were oligodendrocytes as revealed ultrastructurally by immunoperoxidase staining of prominent glial loops that connect with myelin lamellae. Some of these sheaths also showed Schmidt-Lanterman incisures that stained for viral antigen. Virus could be recovered at low titers for the duration of the illness. The findings indicate that TMEV induces persistent infection of oligodendrocytes which could then become the target of immune-mediated injury resulting in demyelination.

Animals↗
PubMed1983

A sensitive radioimmunoassay for the determination of antibodies to mouse hepatitis virus.

A solid-phase radioimmunoassay is described for the detection of antibodies to mouse hepatitis virus. Viruses were purified by velocity and isopycnic gradient centrifugation and 96-well plastic plates were coated with viral antigens. To allow the detection of most serotypes of low titered antisera, a pool of antigens from several viral serotypes were employed. The second antibody, an affinity-purified goat antimouse immunoglobulin, detects IgG, IgM and IgA antibodies. This assay is more sensitive than either the plaque reduction assay or the commercially available enzyme-linked immunosorbant assay and proved to be useful for screening mouse colonies for the presence of mouse hepatitis virus, following seroconversion in experimental animals and in the production of monoclonal antibodies to both structural and nonstructural proteins.

Animals↗
PubMed1983

Characterization of murine coronavirus RNA by hybridization with virus-specific cDNA probes.

Genome RNA of mouse hepatitis virus (MHV) strain A59 has been used as a template to synthesize two virus-specific probes: cDNArep, representing the majority of sequences of the genome RNA and cDNA3', representing the 3' end of the genome RNA. Molecular hybridization with these cDNAs was used to characterize both genome RNA and intracellular virus-specific RNAs. Hybridization of genome RNAs of MHV strains A59, JHM, and MHV-3 with A59 cDNArep showed that, although these three strains exhibit different pathogenicities, they contain closely related nucleotide sequences. Hybridization of intracellular RNA from MHV-infected cells with virus-specific cDNA shows that (i) the majority of virus-specific RNA is polyadenylated, (ii) virus-specific intracellular RNA contains six subgenomic species of the same polarity as genome RNA and (iii) all subgenomic RNAs contain the same 3' sequences as the genome RNA and thus form a nested set of RNAs.

Animals↗
PubMed1983

Immunologic dysfunction during viral oncogenesis. I. Nonspecific immunosuppression caused by malignant rabbit fibroma virus.

Malignant rabbit fibroma virus (MV) is a potent oncogenic poxvirus that produces a rapidly progressive syndrome of disseminated myxosarcoma, immunosuppression, and fatal gram-negative infection. MV is probably a recombinant between Shope fibroma virus (SFV) and rabbit myxoma virus, and is capable of preventing or aborting the in vitro proliferative responses of rabbit lymphocytes to B and T lymphocyte mitogens. Proliferative responses to sheep erythrocytes (SRBC) are similarly affected, although MV does not alter ongoing antibody responses to SRBC. Splenic lymphocytes from MV tumor-bearing rabbits suppress antibody and proliferative responses to SRBC when added to lymphocytes from SRBC-primed rabbits. Finally, lysates of cultured splenic lymphocytes from rabbits given MV suppress both proliferative and antibody-forming responses to SRBC. When MV is removed from these lysates by UV inactivation or by centrifugation, the suppressive activity remains. We therefore conclude that MV induces immunologic unresponsiveness in rabbits by at least two mechanisms. First, a direct suppressive effect of added virus on in vitro lymphocyte proliferation is seen. There is no effect in this situation if an antibody response is already in progress. Second, spleen cells exposed to MV in vivo produce one or more soluble factors capable of suppressing both proliferative and antibody responses of normal lymphocytes.

Animals↗
PubMed1983

Malignant rabbit fibroma virus causes secondary immunosuppression in rabbits.

Shope fibroma virus (SFV) causes a localized, self-limited, fibroblastic proliferation in adult rabbits. Extracts of Shope fibroma tumors were found to contain a second virus that induces a rapidly progressive disseminated tumor. Dissemination of this malignant fibroma is associated with activation of commensal mucosal infection with Pasteurella multocida, causing purulent conjunctivitis and rhinitis and resulting in death from nasal obstruction. We have isolated this new agent by two cycles of plaque purification. It is a poxvirus that is antigenically virtually identical to SFV as measured by a plaque reduction assay, but behaves differently both in vivo and in vitro. We have called this virus malignant rabbit fibroma virus (MV). Electrophoresis of restriction digests made with HIND III indicates that despite the antigenic similarity of SFV and MV, the locations of HIND III sites in the two viral genomes are quite different. These experiments have enabled us to determine that MV was present in small quantities in our initial uncloned stock of Patuxent strain SFV. Lymphocytes from rabbits bearing MV-induced tumors responded poorly to both B and T lymphocyte mitogens. This nonspecific immunologic dysfunction is evident at or before the time when metastases and Gram-negative infection develop, and it becomes more profound as the disease progresses. MV-induced tumors may provide a model for Gram-negative infection and decreased immunologic responsiveness associated with malignancies.

Animals↗
PubMed1983

Malignant rabbit fibroma virus: observations on the culture and histopathologic characteristics of a new virus-induced rabbit tumor.

The clinical, histopathologic, and cultural characteristics of a newly isolated poxvirus, malignant rabbit fibroma virus (MV), were investigated. MV was isolated from tumors induced by an uncloned stock of Shope fibroma virus (SFV). MV, SFV, and rabbit myxoma virus were compared. Similarly to myxoma virus, MV grew to higher titer in vitro than did SFV and produced plaques rather than foci on rabbit kidney cell monolayers. Unlike the local, self-limited fibroblastic proliferations observed in SFV recipients, MV and myxoma caused a fulminant clinical syndrome characterized by malignant histology, metastases, and supervening fatal gram-negative infection with Pasteurella multocida. MV induced a large, protuberant local tumor and discrete metastases histologically resembling myxosarcomas. Draining lymph nodes contained metastases and showed diffuse cortical hyperplasia. Kupffer's cells were prominent in the liver, and macrophages were abundant in the splenic sinusoids. The lungs and trachea were spared, but the conjunctiva and nasal mucosa showed squamous metaplasia and atypia, with overlying Pasteurella infection and underlying tumor. Myxoma virus infection produced similar mucosal changes, but both of these as well as the epidermis overlying the myxomas showed cytoplasmic virus inclusions. Neither the skin nor the epithelial surfaces overlying MV-induced tumors nor the tumors themselves contained virus inclusions. Thus the tumor syndrome caused by MV differed from other known rabbit tumors. Endonuclease restriction digests showed that the MV genome resembled, but was distinct from, rabbit myxoma virus. Opportunistic infection associated with MV-induced disseminated tumor may be an experimental model for the infectious complications that often supervene in host-tumor relationships.

Animals↗
PubMed1983

Neonatal infection with the Daniels strain of Theiler's murine encephalomyelitis virus.

The clinical and pathologic manifestation of Theiler's murine encephalomyelitis are age related. Animals infected during the first week of life die of a fulminant encephalitis analogous to human poliomyelitis. By contrast, animals infected within 2 and 4 weeks of age survive but develop chronic relapsing demyelination and persistent infection of the central nervous system. The neonatal infection results in widespread necrosis beginning with neuronal vacuolar degeneration followed by inflammatory infiltrates. Electron microscopy reveals paracrystalline arrays of 27-nm viral particles characteristic of picornaviruses within neurons and macrophages. In addition, oligodendrocytes show reactive changes and intracytoplasmic vacuoles. Immunoperoxidase studies show viral antigen primarily localized within neurons of the cerebral cortex, basal ganglia, hippocampus, and anterior horn cells. Viral antigen is found within the apical dendrites and axonal projections of hippocampal pyramidal cells suggesting that Theiler's murine encephalomyelitis may travel intraaxonally.

Animals↗
PubMed1982

Genetic analysis of murine hepatitis virus strain JHM.

We performed a genetic analysis of 37 temperature-sensitive mutants of murine hepatitis virus strain JHM. Of our mutants, 32 did not induce murine hepatitis virus-specific RNA synthesis in infected cells at the restrictive temperature, 39 degrees C. By complementation testing we have identified at least seven nonoverlapping complementation groups. Six of the genes identified in this way are required for murine hepatitis virus-specific RNA synthesis. The seventh complementation group is made up of five mutants which induced virus-specific RNA synthesis at 39 degrees C.

Electrophoresis, Agar Gel↗
PubMed1982

Cell-free translation of murine coronavirus RNA.

The coding assignments of the intracellular murine hepatitis virus-specific subgenomic RNA species and murine hepatitis virion RNA have been investigated by cell-free translation. The six murine hepatitis virus-specific subgenomic RNAs were partially purified by agarose gel electrophoresis and translated in an mRNA-dependent rabbit reticulocyte lysate, and the cell-free translation products were characterized by gel electrophoresis, immunoprecipitation, and tryptic peptide mapping. These studies have shown that RNA 7 codes for the nucleocapsid protein, RNA 6 codes for the E1 protein, RNA 3 codes for the E2 protein, and RNA 2 codes for a 35,000-dalton nonstructural protein. Genomic RNA directs the cell-free synthesis of three structurally related polypeptides of greater than 200,000 in molecular weight.

Animals↗