title: Persistent virus infection despite chronic cytotoxic T-lymphocyte activation in gamma interferon-deficient mice infected with lymphocytic choriomeningitis virus.
abstract: The role of gamma interferon (IFN-gamma) in the permanent control of infection with a noncytopathic virus was studied by comparing immune responses in wild-type and IFN-gamma-deficient (IFN-gamma -/-) mice infected with a slowly invasive strain of lymphocytic choriomeningitis virus (LCMV Armstrong). While wild-type mice rapidly cleared the infection, IFN-gamma -/- mice became chronically infected. Virus persistence in the latter mice did not reflect failure to generate cytotoxic T-lymphocyte (CTL) effectors, as an unimpaired primary CTL response was observed. Furthermore, while ex vivo CTL activity gradually declined in wild-type mice, long-standing cytolytic activity was demonstrated in IFN-gamma -/- mice. The prolonged effector phase in infected IFN-gamma -/- mice was associated with elevated numbers of CD8(+) T cells. Moreover, a higher proportion of these cells retained an activated phenotype and was actively cycling. However, despite the increased CD8(+) T-cell turnover, which might have resulted in depletion of the memory CTL precursor pool, no evidence for exhaustion was observed. In fact, at 3 months postinfection we detected higher numbers of LCMV-specific CTL precursors in IFN-gamma -/- mice than in wild-type mice. These findings indicate that in the absence of IFN-gamma, CTLs cannot clear the infection and are kept permanently activated by the continuous presence of live virus, resulting in a delicate new balance between viral load and immunity. This interpretation of our findings is supported by mathematical modeling describing the effect of eliminating IFN-gamma-mediated antiviral activity on the dynamics between virus replication and CTL activity.
authors.affiliation: Institute of Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Bartholdy
authors.forename: J P
authors.initials: JP
authors.lastname: Christensen
authors.forename: D
authors.initials: D
authors.lastname: Wodarz
authors.forename: A R
authors.initials: AR
authors.lastname: Thomsen
mesh_terms: D000818:Animals; D002908:Chronic Disease; D007371:Interferon-gamma / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008168:Lung / Q000821:virology; D008213:Lymphocyte Activation; D008216:Lymphocytic Choriomeningitis / Q000276:immunology / Q000821:virology*; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D013154:Spleen / Q000821:virology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D007371:Interferon-gamma