title: Recombinant interleukin 12 cures mice infected with Leishmania major.
abstract: Resistant C57BL/6 mice infected with Leishmania major are self-healing, whereas susceptible BALB/c mice fail to contain cutaneous infection and subsequently undergo fatal visceral dissemination. These disparate outcomes are mediated by dissimilar expansions of T helper type 1 (Th1) and Th2 CD4+ T lymphocyte subsets in vivo during cure and progression of disease. Because interleukin 12 (IL-12) has potent T cell growth and interferon gamma (IFN-gamma) stimulatory effects, we studied its effect on CD4+ T cell differentiation during murine leishmaniasis. Treatment with recombinant murine (rMu)IL-12 during the first week of infection cured 89% of normally susceptible BALB/c mice, as defined by decreased size of infected footpads and 1,000-10,000-fold reduced parasite burdens, and provided durable resistance against reinfection. Cure was associated with markedly depressed production of IL-4 by lymph node cells cultured with antigen or mitogen, but preserved or increased production of IFN-gamma relative to untreated mice. IL-4 and IFN-gamma mRNA associated with CD4+ T lymphocytes isolated from infected lymph nodes showed similar reciprocal changes in response to rMuIL-12 therapy. A single injection of anti-IFN-gamma monoclonal antibody abrogated the protective effect of rMuIL-12 therapy and restored Th2 cytokine responses. We conclude that rMuIL-12 prevents deleterious Th2 T cell responses and promotes curative Th1 responses in an IFN-gamma-dependent fashion during murine leishmaniasis. Since BALB/c leishmaniasis cannot be cured with rMuIFN-gamma alone, additional direct effects of IL-12 during T cell subset selection are suggested. Because rMuIL-12 is uniquely protective in this well-characterized model of chronic parasitism, differences in IL-12 production may underlie heterogenous host responses to L. major and other intracellular pathogens.
authors.affiliation: Department of Medicine, Case Western Reserve University, Cleveland, Ohio.
authors.forename: F P
authors.initials: FP
authors.lastname: Heinzel
authors.forename: D S
authors.initials: DS
authors.lastname: Schoenhaut
authors.forename: R M
authors.initials: RM
authors.lastname: Rerko
authors.forename: L E
authors.initials: LE
authors.lastname: Rosser
authors.forename: M K
authors.initials: MK
authors.lastname: Gately
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D018664:Interleukin-12; D007378:Interleukins / Q000627:therapeutic use*; D007895:Leishmania tropica; D016773:Leishmaniasis, Cutaneous / Q000276:immunology / Q000628:therapy*; D008198:Lymph Nodes / Q000166:cytology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000627:therapeutic use; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007378:Interleukins; D011994:Recombinant Proteins; D018664:Interleukin-12; D007371:Interferon-gamma