Leishmania chagasi T Cell Antigens Identified Through a Double Library Screen

Department of Biochemistry and Health Graduate Program, Federal University of Rio Grande do Norte, Natal, RN, Brazil, and Departments of Internal Medicine, Biochemistry, Microbiology and Epidemiology, University of Iowa and Veterans' Administration Medical Center, Iowa City, IA, 52242, USA

^* To whom correspondence should be addressed. Email: mary-wilson{at}uiowa.edu.

	Abstract

Control of human visceral leishmaniasis in endemic regions is hampered in part by limited accessibility to medical care and emerging drug resistance. There is no available protective vaccine. Leishmania species protozoa express multiple antigens recognized by the vertebrate immune system. Since there is not one immunodominant epitope recognized by most hosts, strategies must be developed to optimize selection of antigens for prevention and immunodiagnosis. For this reason, we generated a cDNA library from the intracellular amastigote form of Leishmania chagasi, the cause of South American visceral leishmaniasis. We employed a two-step expression screen of the library to systematically identify T cell antigens and T-dependent B cell antigens. The first step was aimed at identifying the largest possible number of clones producing an epitope-containing polypeptide by screening with a pool of sera from Brazilians with documented visceral leishmaniasis. After removal of clones encoding heat shock proteins, positive clones underwent a second step screen for their ability to cause proliferation and IFN- responses of T cells from immune mice. Six unique clones were selected from the second screen for further analysis. The corresponding antigens were derived from glutamine synthetase, a transitional endoplasmic reticulum ATPase, elongation factor 1, kinesin K-39, repetitive protein A2, and a hypothetical conserved protein. Humans naturally infected with L. chagasi mounted both cellular and antibody responses to these proteins. Preparations containing multiple antigens may be optimal for immunodiagnosis and protective vaccines.