title: An in vitro model of antibody-enhanced killing of the intracellular parasite Leishmania amazonensis.
abstract: Footpad infection of C3HeB/FeJ mice with Leishmania amazonensis leads to chronic lesions accompanied by large parasite loads. Co-infecting these animals with L. major leads to induction of an effective Th1 immune response that can resolve these lesions. This cross-protection can be recapitulated in vitro by using immune cells from L. major-infected animals to effectively activate L. amazonensis-infected macrophages to kill the parasite. We have shown previously that the B cell population and their IgG2a antibodies are required for effective cross-protection. Here we demonstrate that, in contrast to L. major, killing L. amazonensis parasites is dependent upon FcRγ common-chain and NADPH oxidase-generated superoxide from infected macrophages. Superoxide production coincided with killing of L. amazonensis at five days post-activation, suggesting that opsonization of the parasites was not a likely mechanism of the antibody response. Therefore we tested the hypothesis that non-specific immune complexes could provide a mechanism of FcRγ common-chain/NADPH oxidase dependent parasite killing. Macrophage activation in response to soluble IgG2a immune complexes, IFN-γ and parasite antigen was effective in significantly reducing the percentage of macrophages infected with L. amazonensis. These results define a host protection mechanism effective during Leishmania infection and demonstrate for the first time a novel means by which IgG antibodies can enhance killing of an intracellular pathogen.
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Katherine N
authors.initials: KN
authors.lastname: Gibson-Corley
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Marie M
authors.initials: MM
authors.lastname: Bockenstedt
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Paola M
authors.initials: PM
authors.lastname: Boggiatto
authors.affiliation: Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Yashdeep
authors.initials: Y
authors.lastname: Phanse
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Petersen
authors.affiliation: Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Bryan H
authors.initials: BH
authors.lastname: Bellaire
authors.affiliation: Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Jones
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology*; D000936:Antigen-Antibody Complex / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D007074:Immunoglobulin G / Q000276:immunology; D066298:In Vitro Techniques; D007894:Leishmania mexicana / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology / Q000469:parasitology; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000469:parasitology; D051379:Mice; D018345:Mice, Knockout; D019255:NADPH Oxidases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D017452:Receptors, IgG / Q000378:metabolism; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism
chemical_list: D000913:Antibodies, Protozoan; D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D017452:Receptors, IgG; D013481:Superoxides; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases