title: Immune CD8(+) T cells prevent reactivation of Toxoplasma gondii infection in the immunocompromised host.
abstract: Toxoplasma gondii remains a serious cause of morbidity and mortality in individuals that are immunosuppressed, patients with AIDS in particular. The cellular immune response, especially by gamma interferon (IFN-gamma)-producing CD8(+) T cells, is an essential component of protective immunity against the parasite. In the present study the role of CD8(+) T cells during the reactivation of Toxoplasma infection in an immunocompromised murine model was evaluated. Chronically infected mice were challenged with LP-BM5 virus, and the kinetics of CD8(+) T-cell function was studied. At 10 weeks after viral infection, mice showed obvious signs of systemic illness and began to die. At this stage, CD8(+) T cells were unresponsive to antigenic stimulation and unable to kill Toxoplasma-infected targets. IFN-gamma production by the CD8(+) T cells from dual-infected animals reached background levels, and a dramatic fall in the frequency of precursor cytotoxic T lymphocytes was observed. Histopathological analysis of the tissues demonstrated signs of disseminated toxoplasmosis as a result of reactivation of infection. However, treatment of the dual-infected animals with immune CD8(+) T cells at 5 weeks post-LP-BM5 challenge prevented the reactivation of toxoplasmosis, and mice continued to live. Our study for the first time demonstrates a therapeutic role for CD8(+) T cells against an opportunistic infection in an immunocompromised state.
authors.affiliation: Department of Medicine, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA. Imtiaz.Khan@dartmouth.edu
authors.forename: I A
authors.initials: IA
authors.lastname: Khan
authors.forename: W R
authors.initials: WR
authors.lastname: Green
authors.forename: L H
authors.initials: LH
authors.lastname: Kasper
authors.forename: K A
authors.initials: KA
authors.lastname: Green
authors.forename: J D
authors.initials: JD
authors.lastname: Schwartzman
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005260:Female; D016867:Immunocompromised Host; D016219:Immunotherapy, Adoptive; D007371:Interferon-gamma / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D014123:Toxoplasmosis / Q000276:immunology*
chemical_list: D007371:Interferon-gamma