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Biomedical subjects

B N Fields

Publications and source records attributed to B N Fields.

At least 127 records · Page 7Linked to original sources
PubMed1981

Intestinal M cells: a pathway for entry of reovirus into the host.

Thirty minutes after inoculation of reovirus type 1 into the intestinal lumen of the mouse, viruses were found adhering to the surface of intestinal M cells but not other epithelial cells. Within 1 hour, viruses were seen in the M cell cytoplasm and were associated with mononuclear cells in the intercellular space adjacent to the M cell. These findings suggest that M cells are the site where reovirus penetrates the intestinal epithelium.

Animals↗
PubMed1981

Genetics of Reovirus.

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Cytotoxicity, Immunologic↗
PubMed1981

Role of the host cell in persistent viral infection: coevolution of L cells and reovoirus during persistent infection.

Mutant L cells, designated LR cells, were isolated after "curing" a persistently infected cell line (L/C) with antireovirus serum. The LR cells were shown to be virus-free; no reovirus was detectable by infectious center assays, plaque assays, presence of viral proteins, presence of viral dsRNA and immunofluorescence studies. Persistent infections were readily established n LR cells following infection with either cloned, low passage wild-type reovirus or cloned, low passage reovirus isolated from carrier cultures. Reovirus isolated from carrier cultures, however, grew much better than wild-type reovirus in LR cells and showed complete dominance over wild-type reovirus in coinfection experiments. Infection of LR cells with wild-type reovirus resulted in a low-level persistent infection with inefficient viral replication; these mutant L cells were partially resistant to infection with wild-type reovirus. In contrast, infection of the mutant L cells with virus isolated from the persistently infected cells resulted in a persistent infection accompanied with efficient viral replication. Infection of the original L cells with either wild-type reovirus or reovirus isolated from the persistently infected cells resulted in a lytic infection with no surviving cells. Thus the host cell plays a crucial role in the maintenance of persistent reovirus infection. Our results show that there is a coevolution of both mutant L cells and mutant reovirus during persistent infection.

Animals↗
PubMed1981

Type-specific reovirus antiserum blocks the cytotoxic T-cell-target cell interaction: evidence for the association of the viral hemagglutinin of a nonenveloped virus with the cell surface.

It has previously been demonstrated that spleen cells from mice immunized with reovirus type 1 or 3 generate virus-specific cytotoxic T lymphocytes (CTL) after in vitro restimulation. Such cytotoxic T cells lyse H-2 identical targets that are infected with the appropriate reovirus type. Viral recombinants were used to demonstrate that the S1 gene is the predominant viral gene determining the specificity of the CTL. Reoviruses are nonenveloped, non-membrane-maturing viruses; therefore, it was important to determine whether viral products were being recognized by CTL on the surface of target cells. Antiserum blocking was utilized to investigate this issue. Using viral recombinants and antisera to reoviruses types 1 and 3, we were able to demonstrate that the major viral antigen recognized by the CTL on the target cell surface is the sigma 1 polypeptide encoded by the S1 genome segment. Thus, viral antigens on the target cell membrane seem to be important in the CTL response to a nonenveloped, non-membrane-maturing virus.

Animals↗
PubMed1981

Tryptic peptide analysis of outer capsid polypeptides of mammalian reovirus serotypes 1, 2, and 3.

We studied the structural relationships among the outer capsid polypeptides of prototype strains of mammalian reovirus serotypes 1, 2, and 3 by tryptic peptide mapping. The micron1C polypeptide showed an extraordinary degree of conservation of its methionine-containing tryptic peptides. In contrast, the most abundant viral polypeptide, sigma 3, contained both conserved and unique methionine-containing tryptic peptides. The viral type-specific antigen, the sigma 1 polypeptide, contained both conserved and unique methionine- and tyrosine-containing tryptic peptides. These results suggested that the mammalian reovirus genome segments encoding each of the viral outer capsid polypeptides were derived from common ancestral segments which have diverged to different degrees.

Antigens, Viral↗
PubMed1981

Reovirus inhibition of cellular DNA synthesis: role of the S1 gene.

Type 3 reovirus inhibits L cell DNA synthesis, whereas type 1 reovirus exerts little or no effect on L cell DNA synthesis. By using recombinant viruses containing both type 1 and type 3 double-standard RNA segments, we determined that one double-stranded RNA segment, the reovirus type 3 S1 double-stranded RNA segment which encodes the viral hemagglutinin, segregates with and is responsible for the capacity of reovirus type 3 to inhibit L cell DNA synthesis.

Animals↗
PubMed1981

Immunologic tolerance after oral administration of reovirus: requirement for two viral gene products for tolerance induction.

We have demonstrated that reovirus type 1, but not type 3, generates serotype-specific immunologic tolerance for DTH responses following oral administration of UV-inactivated virus. As shown by adoptive transfer experiments, the tolerance is secondary to the generation of viral-specific suppressor T cells that are present in spleen and mesenteric lymph nodes. No tolerance was generated when live virus was administered orally. Using recombinant viral clones, it was found that 2 viral gene products were required for tolerance induction; serotype specificity is a property of the viral hemagglutinin (the product of the S1 dsRNA segment). The inability of type 3 reovirus to induce suppression following oral administration is a property of the mu 1C polypeptide (the product of the M2 dsRNA genome segment).

Administration, Oral↗
PubMed1980

Molecular basis of reovirus virulence. Role of the M2 gene.

The mammalian reoviruses (serotype 1, strain Lang and serotype 3, strain Dearing) differ in their sensitivity to digestion by chymotrypsin. We have found that the M2 double-stranded RNA (dsRNA) genome segment (encoding the micro1C outer capsid polypeptide) is responsible for this property. In addition to determining response to protease treatement in vitro, we have found that the M2 genome segment also determines the ability of these two viruses successfully to initiate local and systemic infection in newborn mice after peroral inoculation. Thus the M2 dsRNA segment defines a new virulence gene of the mammalian reoviruses.

Animals↗
PubMed1980

Specific disruption of vimentin filament organization in monkey kidney CV-1 cells by diphtheria toxin, exotoxin A, and cycloheximide.

We have examined the effect of diphtheria toxin, Pseudomonas aeruginosa exotoxin A, and cycloheximide on the CV-1 cell cytoskeleton. Within a few hours after producing an inhibition of cellular protein synthesis, all these agents specifically disrupted the organization of the vimentin filament system with no discernable effect on microtubules or microfilaments during the period of observation. Furthermore, just as the inhibition of protein synthesis by cycloheximide is reversible, so was the disruption of vimentin filaments by cycloheximide.

Animals↗
PubMed1980

Absolute linkage of virulence and central nervous system cell tropism of reoviruses to viral hemagglutinin.

That the hemagglutinin (HA) of reovirus, encoded in the S1 gene, determines the central nervous system (CNS) cell tropism of reovirus type 1 and 3 was shown using recombinant clones containing nine genes from one serotype and the S1 gene from the other. Clone 1.HA3 contains nine genes from type 1 and the S1 gene from type 3; 3.HA1 is the reciprocal clone. Type 3 and 1.HA3 cause a fatal encephalitis in newborn mice with neuronal destruction but no ependymal cell damage, whereas type 1 and 3.HA1 cause a nonfatal ependymal infection but no neuronal damage. Immunofluorescent studies showed no viral antigen in ependymal cells of mice infected with type 3 or 1.HA3 or in neuronal cells of mice infected with type 1 or 3.HA1. With type 3 or clones containing the type 3 HA, maximal brain titers were 10(10) plaque-forming units; maximal titers were 10(8) plaque-forming units for type 1 or clones containing the type 1 HA. This pattern of reovirus virulence for CNS probably relates to the specific interaction of viral HA with neuronal or ependymal surface receptors.

Animals↗
PubMed1980

Genetic variation during lytic reovirus infection: high-passage stocks of wild-type reovirus contain temperature-sensitive mutants.

Wild-type clones of reovirus serotypes 1 (Lang), 2 (Jones), and 3 (Dearing) were serially passaged in L cells at a high multiplicity of infection, and the virus population was examined at passage levels 2, 5, and 11 for the presence of temperature-sensitive (ts) mutants. By passage 11 all three serotypes contained ts mutants that were not present in the original wild-type stock. ts mutants representing three mutant groups were identified. The majority of these mutants were in group G. Our results show that high-passage stocks of reovirus consist of a genetically heterogeneous population.

Genes, Viral↗
PubMed1980

Genetic variation during persistent reovirus infection: presence of extragenically suppressed temperature-sensitive lesions in wild-type virus isolated from persistently infected L cells.

Persistent reovirus infection of L cells was established with a serially passaged stock of temperature-sensitive (ts) mutant C(447) containing greater than 90% defective interfering particles. Within a month after establishment of the carrier culture, the ts mutant was replaced by virus that expressed the wild-type (ts(+)) temperature phenotype (R. Ahmed and A. F. Graham, J. Virol. 23:250-262, 1977). To determine whether the ts(+) phenotype of the virus was due to intragenic reversion or to the presence of an extragenic mutation suppressing the original ts defect, several clones were backcrossed to wild-type reovirus, and the progeny of each cross were screened for temperature sensitivity. The results indicated that the original tsC lesion had reverted. However, in two of the seven clones examined, new ts lesions were found. These new ts lesions appeared phenotypically as ts(+) due to the presence of extragenic suppressor mutations. Temperature-sensitive mutants representing three different groups were rescued from one suppressed clone, indicating that this ts(+) clone contained multiple ts lesions. Among the ts mutants rescued were the initial isolates of a new recombination group which we have designated H. Some of the ts mutants rescued from the suppressed clones are capable of interfering with the growth of wild-type reovirus and may play a role in maintaining the carrier state. The results of this study show that persistently infected L cells contain a genetically heterogeneous population of reovirus even though all virus clones express the ts(+) phenotype. It is thus critical to distinguish between genotype and phenotype when analyzing viruses that emerge during persistent infection.

Animals↗
PubMed1980

Delayed hypersensitivity in mice infected with reovirus. I. Identification of host and viral gene products responsible for the immune response.

Delayed-type hypersensitivity (DTH) can be demonstrated in mice infected with reovirus by challenging primed animals in the footpad with virus. Maximal responses occur 7 days after immunization with as little as 10(5) viral particles. DTH to reovirus is transferable by lymph node cells and is mediated by T cells as the transfer of reactivity can be abrogated by treatment of cells with anti-Thy 1.2 plus complement. DTH to reovirus is serotype specific, animals infected with reovirus type 1 or 3 only develop DTH responses when challenged with the same serotype with which they were infected. Using recombinant viral clones containing genes from both parental serotypes, we have demonstrated that the S1 gene, the gene encoding the viral hemagglutinin, determines serotype specificity. Furthermore, in adoptive transfer experiments between mice of varying histocompatibility backgrounds, it was found that D or K, IA-IB region identity was required for the transfer of reactivity. These studies demonstrate that specific host and viral genes determine the in vivo cellular immune response to reovirus and should allow a more precise definition of the host cellular immune response to viral antigens.

Animals↗