title: Distinct Immune Responses in Resistant and Susceptible Strains of Mice during Neurovirulent Alphavirus Encephalomyelitis.
abstract: Susceptibility to alphavirus encephalomyelitis is dependent on a variety of factors, including the genetic background of the host. Neuroadapted Sindbis virus (NSV) causes uniformly fatal disease in adult C57BL/6 (B6) mice, but adult BALB/c (Bc) mice recover from infection. In B6 mice, fatal encephalomyelitis is immune mediated rather than a direct result of virus infection. To identify the immunological determinants of host susceptibility to fatal NSV-induced encephalomyelitis, we compared virus titers and immune responses in adult B6 and Bc mice infected intranasally with NSV. B6 mice had higher levels of virus replication, higher levels of type I interferon (IFN), and slower virus clearance than did Bc mice. B6 mice had more neuronal apoptosis, more severe neurologic disease, and higher mortality than Bc mice. B6 mice had more infiltration of inflammatory cells and higher levels of IL1b, IL-6, TNFa, Csf2, and CCL2 mRNAs and interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), IFN-γ, and C-C motif ligand 2 (CCL2) protein in brains than Bc mice. However, Bc mice had more brain antibody at day 7 and a higher percentage of CD4(+) T cells. CD4(+) T cells in the brains of Bc mice included fewer Th17 cells and more regulatory T cells (Tregs) producing IL-10 than B6 mice, accompanied by higher levels of Il2 and Cxcl10 mRNAs. In the absence of IL-10, resistant Bc mice became susceptible to fatal encephalomyelitis after NSV infection. These studies demonstrate the importance of the immune response and its regulation in determining host survival during alphavirus encephalomyelitis.
  
  
  OBJECTIVE
  Mosquito-borne alphavirus infections are an important cause of encephalomyelitis in humans. The severity of disease is dependent both on the strain of the virus and on the age and genetic background of the host. A neurovirulent strain of Sindbis virus causes immune-mediated fatal encephalomyelitis in adult C57BL/6 mice but not in BALB/c mice. To determine the host-dependent immunological mechanisms underlying the differences in susceptibility between these two strains of mice, we compared their immune responses to infection. Resistance to fatal disease in BALB/c mice was associated with better antibody responses, more-rapid virus clearance, fewer Th17 cells, and more-potent regulatory T cell responses than occurred in susceptible C57BL/6 mice. In the absence of interleukin-10, a component of the regulatory immune response, resistant mice became susceptible to lethal disease. This study demonstrates the importance of the immune response and its regulation for host survival during alphavirus encephalomyelitis.
authors.affiliation: Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Kirsten A
authors.initials: KA
authors.lastname: Kulcsar
authors.affiliation: Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Victoria K
authors.initials: VK
authors.lastname: Baxter
authors.affiliation: W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Rachy
authors.initials: R
authors.lastname: Abraham
authors.affiliation: W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Nelson
authors.affiliation: Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA dgriffi6@jhu.edu.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Griffin
mesh_terms: D000524:Alphavirus / Q000472:pathogenicity*; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D016207:Cytokines / Q000235:genetics; D004198:Disease Susceptibility / Q000276:immunology*; D004679:Encephalomyelitis / Q000276:immunology* / Q000821:virology; D015870:Gene Expression; D018836:Inflammation Mediators / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D014774:Virulence
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators