title: IL-9 is a susceptibility factor in Leishmania major infection by promoting detrimental Th2/type 2 responses.
abstract: IL-9 is a cytokine produced by Th2 cells, induced during Leishmania major infection. Because the role of IL-9 in leishmaniasis is currently unknown, IL-9-deficient mice were generated by immunization with mouse IL-9 coupled to OVA. This produced strong and long-lasting neutralizing anti-IL-9 Abs in vivo. Anti-IL-9 vaccination showed protective effects, because it enabled L. major-infected nonhealer BALB/c mice to better resist to leishmaniasis with doubling the time span until pathological disease progression occurred. Increased resistance was also demonstrated by moderate footpad swelling and histopathology due to reduced parasite burden compared with sham-immunized BALB/c mice. Mechanistically, IL-9 neutralization in BALB/c mice resulted in a reduction of detrimental Th2/type 2 responses with an observed shift toward protective Th1 immune responses. This led to an alteration from alternative to classical macrophage activation with subsequent enhanced killing effector functions, as demonstrated by increased NO production but reduced arginase 1-mediated macrophage responses. Conclusively, the data show that IL-9 is a susceptible factor in leishmaniasis. They further suggest that IL-9 is able to influence Th dichotomy in leishmaniasis by promoting detrimental Th2/type 2 responses in BALB/c mice. The results extend efforts made to generate autoantibodies capable of regulating biological processes, with IL-9 a potential drug target against leishmaniasis.
authors.affiliation: University of Cape Town, Health Science Faculty, Institute of Infectious Disease and Molecular Medicine, Cape Town, South Africa.
authors.forename: Berenice
authors.initials: B
authors.lastname: Arendse
authors.forename: Jacques
authors.initials: J
authors.lastname: Van Snick
authors.forename: Frank
authors.initials: F
authors.lastname: Brombacher
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000502:physiology; D004198:Disease Susceptibility / Q000276:immunology; D007106:Immune Sera / Q000008:administration & dosage / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology; D016906:Interleukin-9 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000276:immunology / Q000502:physiology*; D018320:Leishmania major / Q000254:growth & development / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology* / Q000469:parasitology / Q000517:prevention & control; D008262:Macrophage Activation / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000096:biosynthesis / Q000633:toxicity; D016052:Protozoan Vaccines / Q000008:administration & dosage / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism; D018418:Th2 Cells / Q000276:immunology* / Q000378:metabolism*; D015534:Trans-Activators / Q000502:physiology
chemical_list: D001323:Autoantibodies; D004268:DNA-Binding Proteins; D007106:Immune Sera; D016906:Interleukin-9; D016052:Protozoan Vaccines; D015534:Trans-Activators; D009569:Nitric Oxide