Cytokine induction during T-cell-mediated clearance of mouse hepatitis virus from neurons in vivo

Abstract

To investigate the mechanism by which viruses are cleared from neurons in the central nervous system, we have utilized a mouse model involving infection with a neurotropic variant of mouse hepatitis virus (OBLV60). After intranasal inoculation, OBLV60 grew preferentially in the olfactory bulbs of BALB/c mice. Using in situ hybridization, we found that viral RNA localized primarily in the outer layers of the olfactory bulb, including neurons of the mitral cell layer. Virus was cleared rapidly from the olfactory bulb between 5 and 11 days. Athymic nude mice failed to eliminate the virus, demonstrating a requirement for T lymphocytes. Immunosuppression of normal mice with cyclophosphamide also prevented clearance. Both CD4+ and CD8+ T-cell subsets were important, as depletion of either of these subsets delayed viral clearance. Gliosis and infiltrates of CD4+ and CD8+ cells were detected by immunohistochemical analysis at 6 days. The role of cytokines in clearance was investigated by using an RNase protection assay for interleukin-la (IL-la), IL-10i, IL-2, IL-3, IL-4, IL-5, IL-6, tumor necrosis factor alpha (TNF-o), TNF-I, and gamma interferon (IFN-,y). In immunocompetent mice there was upregulation of RNA for IL-la, IL-11", IL-6, TNF-a, and IFN-y at the time of clearance. Nude mice had comparable increases in these cytokine messages, with the exception of IFN-y. Induction of major histocompatibility complex class I (MHC-I) molecules on cells in infected brains was demonstrated by immunohistochemical analyses in normal and nude mice, suggesting that IFN-y may not be necessary for induction of MHC-I on neural cells in vivo.

Differential roles of CCL2 and CCR2 in host defense to coronavirus infection

“…Both CD4 + and CD8 + T cells are required for optimal clearance of virus from the brains of MHV-infected mice Lane et al, 2000;Pearce et al, 1994;Williamson and Stohlman, 1990;Yamaguchi et al, 1991). To assess the contributions of CCR2 and CCL2 to T cell migration and accumulation within the CNS of MHVinfected mice, brains were removed at defined times pi and T cell infiltration determined by flow cytometry.…”

“…Intracranial instillation of MHV into the CNS of susceptible mice results in widespread replication of virus in neurons and glia accompanied by a robust inflammatory response consisting of neutrophils, NK cells, T cells, and macrophages (Williamson and Stohlman, 1990). T cells are required for reduction of viral burden within the brain and this process is mediated by secretion of IFN-g and perforinmediated lysis of infected cells Parra et al, 1999Parra et al, , 2001Pearce et al, 1994;Williamson and Stohlman, 1990;Yamaguchi et al, 1991). Clearance is incomplete and surviving mice will often develop an immune-mediated demyelinating disease characterized by viral persistence in white matter tracts accompanied by lesions of white matter damage (Dales and Anderson, 1995;Fazakerley and Buchmeier, 1993;Lane and Buchmeier, 1997).…”

Coronavirus Spike Proteins in Viral Entry and Pathogenesis

“…The unstable JHM virus is set apart from its tissue culture-adapted variants in its ability to cause a rapid, disseminated, and lethal panencephalitis (Fazakerley et al, 1992;Pearce et al, 1994;see Fig. 2).…”

Pathogenesis of neurotropic murine coronavirus is multifactorial

“…1 obviously form the syncytia [15] that are observed during RIS in cell lines. Several strains of JHM with mutations in S2 have lost the ability to perform RIS and are less neurovirulent than wild-type JHM.SD (J.C. Tsai, unpublished data) [48,49], but many are also deficient in CEA-CAM1a-dependent fusion [41,50,51], are less able to use CEACAM1b as an alternative receptor [52], or resist neutralization by soluble receptor (i.e. are not triggered by receptor binding) [53] despite wild-type receptor-binding domains, which implies defects in receptor-dependent fusion as well as RIS.…”