title: T cell-, interleukin-12-, and gamma interferon-driven viral clearance in measles virus-infected brain tissue.
abstract: Genetic studies with immunocompetent mice show the importance of both T cells and gamma interferon (IFN-γ) for survival of a measles virus (MV) challenge; however, the direct role of T cells and IFN-γ within the MV-infected brain has not been addressed. Organotypic brain explants represent a successful ex vivo system to define central nervous system (CNS)-specific mechanisms of leukocyte migration, activation, and MV clearance. Within the heterogeneous, brain-derived, primed leukocyte population which reduced MV RNA levels in brain explants by 60%, CD3 T cells are the active antiviral cells, as purified CD3-positive cells are highly antiviral and CD3-negative leukocytes are unable to reduce the viral load. Neutralization of CCL5 and CXCL10 decreases leukocyte migration to areas of infection by 70%. However, despite chemokines directing the migration of T cells to infected neurons, chemokine neutralization revealed that migration is not required for viral clearance, suggesting a cytokine-mediated antiviral mechanism. In accordance with our hypothesis, the ability of leukocytes to clear the virus is abrogated when explants are treated with anti-IFN-γ neutralizing antibodies. IFN-γ applied to infected slices in the absence of primed leukocytes reduces the viral load by more than 80%; therefore, in brain tissue, IFN-γ is both necessary and sufficient to clear MV. Secretion of IFN-γ is stimulated by interleukin-12 (IL-12) in the brain, as neutralization of IL-12 results in loss of antiviral activity and stimulation of leukocytes with IL-12/IL-18 enhances their immune effector function of viral clearance. MV-primed leukocytes can reduce both West Nile and mouse hepatitis viral RNAs, indicating that cytokine-mediated viral clearance occurs in an antigen-independent manner. The IFN-γ signal is transduced within the brain explant by the Jak/STAT signaling pathway, as inhibition of Jak kinases results in a loss of antiviral activity driven by either brain-derived leukocytes or recombinant IFN-γ. These results reveal that primed T cells directly act to clear MV infection of the brain by using a noncytolytic IL-12- and IFN-γ-dependent mechanism in the CNS and that this mechanism relies upon Jak/STAT signaling.
authors.affiliation: Department of Molecular Biology, Case Western Reserve University School of Medicine W205, 10900 Euclid Avenue, Cleveland, OH 44106, USA. samantha.stubblefield@case.edu
authors.forename: Samantha R
authors.initials: SR
authors.lastname: Stubblefield Park
authors.forename: Mi
authors.initials: M
authors.lastname: Widness
authors.forename: Alan D
authors.initials: AD
authors.lastname: Levine
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Patterson
mesh_terms: D000818:Animals; D001921:Brain / Q000276:immunology / Q000821:virology*; D004195:Disease Models, Animal; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology*; D018664:Interleukin-12 / Q000276:immunology*; D008457:Measles / Q000276:immunology / Q000473:pathology / Q000821:virology*; D008459:Measles virus / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009924:Organ Culture Techniques; D013601:T-Lymphocytes / Q000276:immunology*; D019562:Viral Load
chemical_list: D018664:Interleukin-12; D007371:Interferon-gamma