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Infection and Immunity, October 2005, p. 6620-6628, Vol. 73, No. 10
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.10.6620-6628.2005

Antigen Requirements for Efficient Priming of CD8⁺ T Cells by Leishmania major-Infected Dendritic Cells

Sylvie Bertholet,^1, Alain Debrabant,^2, Farhat Afrin,^1, Elisabeth Caler,¹ Susana Mendez,^1, Khaled S. Tabbara,^1,¶ Yasmine Belkaid,¹ and David L. Sacks^1*

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892,¹ Division of Emerging and Transfusion Transmitted Diseases, OBRR, CBER, U.S. Food and Drug Administration, Bethesda, Maryland 20892²

Received 2 December 2004/ Returned for modification 21 February 2005/ Accepted 14 June 2005

CD4⁺ and CD8⁺ T-cell responses have been shown to be critical for the development and maintenance of acquired resistance to infections with the protozoan parasite Leishmania major. Monitoring the development of immunodominant or clonally restricted T-cell subsets in response to infection has been difficult, however, due to the paucity of known epitopes. We have analyzed the potential of L. major transgenic parasites, expressing the model antigen ovalbumin (OVA), to be presented by antigen-presenting cells to OVA-specific OT-II CD4⁺ or OT-I CD8⁺ T cells. Truncated OVA was expressed in L. major as part of a secreted or nonsecreted chimeric protein with L. donovani 3' nucleotidase (NT-OVA). Dendritic cells (DC) but not macrophages infected with L. major that secreted NT-OVA could prime OT-I T cells to proliferate and release gamma interferon. A diminished T-cell response was observed when DC were infected with parasites expressing nonsecreted NT-OVA or with heat-killed parasites. Inoculation of mice with transgenic parasites elicited the proliferation of adoptively transferred OT-I T cells and their recruitment to the site of infection in the skin. Together, these results demonstrate the possibility of targeting heterologous antigens to specific cellular compartments in L. major and suggest that proteins secreted or released by L. major in infected DC are a major source of peptides for the generation of parasite-specific CD8⁺ T cells. The ability of L. major transgenic parasites to activate OT-I CD8⁺ T cells in vivo will permit the analysis of parasite-driven T-cell expansion, differentiation, and recruitment at the clonal level.

Editor: J. F. Urban, Jr.

These two authors contributed equally to this work.

Present address: Centre for Biotechnology, Jamia Hamdard, Hamdard University, New Delhi, India.

Present address: Department of Microbiology and Tropical Medicine, George Washington University, Washington, D.C.

^¶ Present address: Arabian Gulf University, College of Medicine, Manama, Bahrain.

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