title: Virus-specific and bystander CD8 T cells recruited during virus-induced encephalomyelitis.
abstract: Neurotropic coronavirus-induced encephalitis was used to evaluate recruitment, functional activation, and retention of peripheral bystander memory CD8+ T cells. Mice were first infected with recombinant vaccinia virus expressing a non-cross-reactive human immunodeficiency virus (HIV) epitope, designated p18. Following establishment of an endogenous p18-specific memory CD8+ T-cell population, mice were challenged with coronavirus to directly compare recruitment, longevity, and activation characteristics of both primary coronavirus-specific and bystander memory populations trafficking into the central nervous system (CNS). HIV-specific memory CD8+ T cells were recruited early into the CNS as components of the innate immune response, preceding CD8+ T cells specific for the dominant coronavirus epitope, designated pN. Although pN-specific T-cell numbers gradually exceeded bystander p18-specific CD8+ T-cell numbers, both populations peaked concurrently within the CNS. Nevertheless, coronavirus-specific CD8+ T cells were preferentially retained. By contrast, bystander CD8+ T-cell numbers declined to background numbers following control of CNS virus replication. Furthermore, in contrast to highly activated pN-specific CD8+ T cells, bystander p18-specific CD8+ T cells recruited to the site of inflammation maintained a nonactivated memory phenotype and did not express ex vivo cytolytic activity. Therefore, analysis of host CD8+ T-cell responses to unrelated infections demonstrates that bystander memory CD8+ T cells can comprise a significant proportion of CNS inflammatory cells during virus-induced encephalitis. However, transient CNS retention and the absence of activation suggest that memory bystander CD8+ T cells may not overtly contribute to pathology in the absence of antigen recognition.
authors.affiliation: Department of Neurology, University of Southern California Keck School of Medicine, 1333 San Pablo St., MCH 148, Los Angeles, CA 90033, USA.
authors.forename: Audrey M
authors.initials: AM
authors.lastname: Chen
authors.forename: Nivedita
authors.initials: N
authors.lastname: Khanna
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Stohlman
authors.forename: Cornelia C
authors.initials: CC
authors.lastname: Bergmann
mesh_terms: D000818:Animals; D001921:Brain / Q000276:immunology / Q000821:virology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000821:virology*; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000276:immunology*; D005434:Flow Cytometry; D006678:HIV / Q000276:immunology; D007156:Immunologic Memory; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000276:immunology / Q000821:virology