Studies in L. major–infected BALB/c mice have identified TCR Vα8+ Vβ4+ CD4+ T cells as the major source of early IL-4 production by recognizing the Leishmania antigen LACK (Leishmania homologue of receptors for activated C kinase) (19,20), although such T cells appeared to be primed by cross-reactive antigens derived from the gut flora (21). Even in L. major–infected resistant C57BL/6 mice, LACK-specific T cells were also found to be the source of early IL-4 production when mice were given anti-IFN-γ or anti-IL-12 at the onset of infection (22). Thus far, there is little information on the characterization of TCR usage in Leishmania-specific, IFN-γ-producing Th1
cells. In this study, we used C57BL/6 mice and investigated the TCR diversity of CD4+ T cells from a nonhealing model associated with La infection and a self-healing disease model associated with
Lb infection. Furthermore, we characterized IFN-γ-producing Th1 cells based on TCR usage during MI-503 order primary infection with these two parasite species, respectively, and during secondary La infection following pre-exposure to Lb parasites. Our results support a view Selleck RXDX-106 that the magnitude of CD4+ T-cell activation, rather than the TCR diversity, is the main determining factor for the outcome of Leishmania infection. Female C57BL/6J (B6) mice, at 6∼8 weeks old from the Jackson Laboratory (Ben Harbor, ME), were used in this study. Mice were maintained under specific pathogen-free conditions and used for experimentation, according to protocols approved by the institutional Animal
Care and Use Committees. The following mAbs were purchased from eBioscience (San Diego, CA) unless stated otherwise: FITC- or PE-conjugated anti-IFN-γ (XMG1.2); PerCP Cy5.5-conjugated anti-IL-17 (eBio17B7); APC anti-CD4 (GK1.5) and PE-Cy7 anti-CD3 (145-2C11), as well as isotype control Abs, including FITC-conjugated rat IgG1, PE-conjugated rat IgG1 and PerCP Cy5.5-conjugated rat IgG2a. The Mouse Vβ TCR screening panel kit those (Abs conjugated with FITC) and PE-conjugated TCR Vβ4 (KT4), Vβ6 (RR4-7), Vβ7 (TR310) and Vβ8 (F23.1) were purchased from BD Biosciences (San Jose, CA, USA). Infectivity of L. amazonensis (MHOM/BR/77/LTB0016) was maintained by regular passage through BALB/c mice (Harlan Sprague-Dawley, Indianapolis, IN, USA) and L. braziliensis (MHOM/BR/79/LTB111) by regular passage through Syrian golden hamsters (Harlan Sprague-Dawley). Promastigotes were cultured at 23°C in Schneider’s Drosophila medium (Invitrogen, Carlsbad, CA, USA), pH 7.0, supplemented with 20% FBS (Sigma, St. Louis, MO, USA), 2 mm L-glutamine, and 50 μg/mL gentamicin. Stationary promastigote cultures of less than five passages were used for animal infection. To prepare promastigote lysates, parasites (2 × 108/mL in PBS) were subjected to six freeze-thaw cycles and a 15-min sonication. The soluble parasite antigens were stored in aliquots at −20°C until use.