The reovirus-specific cytotoxic T cell response is not restricted to serotypically unique epitopes associated with the virus hemagglutinin

Production of Alexa Fluor 488-labeled reovirus and characterization of target cell binding, competence, and immunogenicity of labeled virions

Respiratory enteric orphan virus (reovirus) has been used to study many aspects of the biology and genetics of viruses, viral infection, pathogenesis, and the immune response to virus infection. This report describes the functional activity of virus labeled with Alexa Fluor 488, a stable fluorescent dye. Matrix assisted laser desorption-time of flight analysis indicated that Alexa Fluor 488 labeled the outer capsid proteins of reovirus. Labeled virus bound to murine L929 fibroblasts as determined by flow cytometry and fluorescence microscopy, and the specificity of binding were demonstrated by competitive inhibition with non-labeled virus. Labeled reovirus induced apoptosis and cytopathic effect in infected L929 cells. Mice infected with labeled virus mounted robust serum antibody and CD8(+) T-cell responses, indicating that labeled virus retained immunogenicity in vivo. These results indicate that Alexa Fluor 488-labeled virus provides a powerful new tool to analyze reovirus infection in vitro and in vivo.

Regulation of polymeric immunoglobulin receptor expression by reovirus

Polymeric immunoglobulin receptor (pIgR) transcytoses dimeric IgA and IgA-coated immune complexes from the lamina propria across epithelia and into secretions. The effect of reovirus infection on regulation of pIgR expression in the human intestinal epithelial cell line HT-29 was characterized in this report. Both replication-competent and UV-inactivated reovirus at m.o.i. equivalents of 1-100 p.f.u. per cell upregulated pIgR mRNA by 24 h post-infection and intracellular pIgR protein was increased at 48 h following exposure to UV-inactivated virus. Binding of virus to HT-29 cells was required, as pre-incubating virus with specific antiserum, but not non-immune serum, inhibited reovirus-mediated pIgR upregulation. Endosomal acidification leading to uncoating of virus is a required step for pIgR upregulation, as ammonium chloride or bafilomycin A1 pre-treatment inhibited virus-induced pIgR upregulation. Inhibition experiments using the calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal suggested that calpains are involved in reovirus-mediated pIgR upregulation. Upregulation of pIgR following virus infection appears to be an innate immune response against invading pathogens that could help the host clear infection effectively. Signalling induced by microbes and their products may serve to augment pIgR-mediated transcytosis of IgA, linking the innate and acquired immune responses to viruses.

Experimental intestinal reovirus infection of mice: what we know, what we need to know

Reovirus, a member of the Reoviridae family, is a ubiquitous virus in vertebrate hosts. Although disease caused by reovirus infection is for the most part mild, studies of reovirus have particularly been valuable as a model for understanding the local host response to replicating foreign antigen in intestinal and respiratory sites. In this article, a brief overview is presented of the basic features of reovirus infection, as will the host's humoral and cellular immune response during the infectious cycle. New information regarding the interactions and involvement of immune response molecules during reovirus infection will be presented based on multiple analyte array studies from our laboratory.

Prolonged induction of IL-8 gene expression in a human fibroblast cell line infected with reovirus serotype 1 strain Lang

Viruses which infect mucosal surfaces commonly infect these particular anatomical sites based on both the virion structure and the interaction of the virus with a particular microenvironment. We infected a human lung epithelial cell line, a human gut epithelial cell line, and a human lung fibroblast cell line with reovirus 1/L to explore how this natural isolate of both the lung and the gut may interact with mucosal surfaces. While reovirus infection of the gut and lung epithelial cell lines was lytic, a chronic infection was established in the human lung fibroblast cell line. All three cell lines also produced interleukin-8 (IL-8) after infection with reovirus 1/L, and IL-8 production was not dependent upon viral replication. A prolonged production of IL-8 was observed in the chronically infected lung fibroblast cell line, suggesting that this mucosal population may be involved in the generation of inflammatory responses after the resolution of the initial lytic infection of the epithelium. These studies provide an in vitro model system for analyzing the interaction of reovirus 1/L with resident mucosal cell populations.

Predominant T-cell receptor Vbeta usage of intraepithelial lymphocytes during the immune response to enteric reovirus infection

Previous studies have found that intraepithelial lymphocytes (IEL) contain virus-specific cytotoxic T lymphocytes (CTL) that increase dramatically during the course of virus infection. In the present study, the T-cell receptor (TCR) V beta pattern used by IEL against reovirus enteric infection was investigated both in conventional and in germfree mice. IEL were isolated by a modified rapid method, and their expression of 13 TCR V betas was examined by flow cytometric analysis. The virus-specific CTL activity of each TCR V beta subset was assessed by subtraction with coated Dyna beads by a nonradioactive assay. There was a preferential perturbation of TCR V betas following virus challenge, including increases in cells expressing V beta7, -12, -14, and -17 in conventional mice and V beta2, -12, and -17 in germfree mice. In conventionally reared mice, IEL maintained and restimulated in culture had a preferential use of TCR V beta9, -12, and -17. TCR V beta2 and -17 subfamilies were found amplified in all conditions. Furthermore, TCR V beta12 and -17 accounted for 37 and 77% of the virus-specific CTL activity, respectively, after in vitro restimulation. This study provides evidence that virus-specific CTL activity may be due to the oligoclonal expansion of TCR V beta subfamilies in IEL. Our findings suggest that in vivo infection selectively presents few T-cell epitopes and that the correct identification of these T-cell epitopes would increase the likelihood of success when designing subunit vaccines.

The reovirus nonstructural protein sigma1NS is recognized by murine cytotoxic T lymphocytes

The cytotoxic T-lymphocyte (CTL) response in reovirus-infected C3H mice was investigated by using reovirus-vaccinia virus recombinants. Results of cytotoxicity assays indicated that the nonstructural protein sigma1NS elicited a significant CTL response. Experiments with sigma1NS-specific CTL lines showed that both strain-specific and cross-reactive epitopes exist in the sigma1NS protein.

Clonal analysis of the cytotoxic T-lymphocyte response to reovirus

Reovirus has previously been classified into three serotypes based on hemagglutination inhibition assays. In the present study, the specificity of cytotoxic T lymphocytes (CTL) generated in reovirus type 3-infected C3H/HeN mice was investigated at the population and clonal levels. Short-term CTL lines generated in response to reovirus type 3 preferentially lysed cells infected with reovirus type 1 or 3 and, in some instances, type 2-infected cells as well. Eleven CTL clones established from the lines demonstrated two unique patterns of recognition. A single clone was exquisitely specific for reovirus type 3-infected cells and did not cross-react on reovirus type 1- or 2-infected cells. Ten of the clones recognized reovirus type 1- and type 3-infected cells. These clones had low levels of cross-reactivity on reovirus type 2-infected cells that was revealed only at high effector:target cell ratios. Precursor frequency analysis further revealed that the majority of the CTL generated against reovirus type 3 could cross-react on both reovirus type 1- and type 2-infected cells. Some CTL could be detected that had a more restricted pattern of recognition and recognized reovirus type 3-infected cells exclusively or recognized reovirus type 3-infected cells and either reovirus type 1- or type 2-infected cells. These results indicate that a minimum of four epitopes are recognized by reovirus-specific CTL and that the response is dominated by CTL that recognize an epitope common to all three serotypes of reovirus.

H-2 restriction and serotype crossreactivity of anti-reovirus cytotoxic T lymphocytes (CTL)

Murine anti-reovirus cytotoxic T lymphocytes (CTLs) were analyzed for H-2 restricted recognition of virus infected target cells and for potential cross-reactivity with cells infected by reovirus serotype 1 (T1; Lang strain) or by serotype 3 (T3; Dearing strain). Anti-reovirus CTL specifically lysed virus infected cells and lysis was shown to be H-2 restricted by the H-2Dd, H-2Ld, H-2Kd, H-2Kb, and H-2Kk antigens. No H-2 antigens were identified which failed to restrict virus recognition by anti-reovirus CTL. Anti-T1 and anti-T3 CTLs were also shown to crossreact completely with cells infected with the opposite virus serotype. Thus, anti-reovirus CTLs are restricted by a broad spectrum of H-2 antigens and they detect common rather than unique structural components of these two viral serotypes.