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Infection and Immunity, July 2009, p. 2948-2956, Vol. 77, No. 7
0019-9567/09/$08.00+0 doi:10.1128/IAI.00154-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Department of Microbiology and Immunology, Institute for Human Infections and Immunity,1 Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, Texas 77555-1070,2 Departments of Medicine and Immunology, Baylor College of Medicine, Houston, Texas 770303
Received 9 February 2009/ Returned for modification 20 March 2009/ Accepted 6 April 2009
We have previously reported that Leishmania braziliensis infection can activate murine dendritic cells (DCs) and upregulate signaling pathways that are essential for the initiation of innate immunity. However, it remains unclear whether Toll-like receptors (TLRs) are involved in L. braziliensis-mediated DC activation. To address this issue, we generated bone marrow-derived DCs from MyD88–/– and TLR2–/– mice and examined their responsiveness to parasite infection. While wild-type DCs were efficiently activated to produce cytokines and prime naïve CD4+ T cells, L. braziliensis-infected MyD88–/– DCs exhibited less activation and decreased production of interleukin-12 (IL-12) p40. Furthermore, MyD88–/– mice were more susceptible to infection in that they developed larger and prolonged lesions compared to those in control mice. In sharp contrast, the lack of TLR2 resulted in an enhanced DC activation and increased IL-12 p40 production after infection. As such, L. braziliensis-infected TLR2–/– DCs were more competent in priming naïve CD4+ T cells in vitro than were their controls, findings which correlated with an increased gamma interferon production in vivo and enhanced resistance to infection. Our results suggest that while MyD88 is indispensable for the generation of protective immunity to L. braziliensis, TLR2 seems to have a regulatory role during infection.
Published ahead of print on 13 April 2009.
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