CD4+ T cell dysfunction during visceral leishmaniasis

项目总结/摘要 内脏利什曼病是一种毁灭性的，被忽视的热带疾病，最终导致多器官衰竭， 如果不治疗的话就会死亡。与许多寄生虫感染一样，开发有效疫苗的努力已经取得了进展。 仍然没有成功。与一些可以通过中和来控制的传染性病原体相比， 抗体和/或细胞毒性CD8 + T细胞，对利什曼病的保护主要是由辅助性T细胞1介导的 分化的CD4 + T细胞，但如何CD4 + T细胞的活化，分化和功能的调节， 内脏利什曼病仍然是未知的。这些研究的一个主要局限性是无法 在实验模型系统中准确鉴定利什曼特异性CD4 + T细胞，以评估T细胞 在感染过程中和感染后的寿命和功能。在这里，使用最近发现的MHC-II 表位在利什曼原虫物种中保守，我们表明与皮肤形式的利什曼病相反， 抗原特异性CD4 + T细胞在内脏利什曼病期间功能耗尽，产生IL-10， 表达高水平的抑制性受体PD-1和CTLA-4。这表明，与其保持 “隐藏的”、高寄生虫负荷和/或抗原负荷使适应性免疫系统达到这样的程度， 抗原特异性CD4 + T细胞失去产生必要的促炎细胞因子的能力， 寄生在巨噬细胞内。因为目前没有有效的疫苗和有限的治疗方法 为了治疗利什曼病，我们已经产生了重组牛痘病毒（VacV）载体， 免疫显性利什曼原虫表位靶向MHC-II呈递，以研究CD4 + T细胞对 这种寄生虫感染开始研究CD4 + T细胞活化的机制并确定策略 为了逆转或限制内脏利什曼病期间的T细胞功能障碍，我们将1）确定功能和基因， 抗原特异性CD4 + T细胞的表达谱，这些细胞在皮肤或内脏免疫后被激活。 利什曼原虫感染和2）确定治疗性病毒免疫联合免疫治疗是否能恢复 在内脏利什曼病期间对CD4 + T细胞的功能。本项目的总体目标是开始定义 内脏利什曼病期间调节CD4 + T细胞功能和功能障碍的机制， 有助于我们改进针对这种复杂寄生虫的疫苗设计和疗法的长期目标。

PROJECT SUMMARY/ABSTRACT Visceral leishmaniasis is a devastating, neglected tropical disease, ultimately leading to multiorgan failure and death when left untreated. As with many parasitic infections, efforts to develop an effective vaccine have remained unsuccessful. In contrast to a number of infectious pathogens which can be controlled by neutralizing antibodies and/or cytotoxic CD8+ T cells, protection against leishmaniasis is largely mediated by T helper 1 differentiated CD4+ T cells, but how CD4+ T cell activation, differentiation, and function are regulated during visceral leishmaniasis is still largely unknown. A major limitation to these studies has been the inability to accurately identify Leishmania-specific CD4+ T cells in experimental model systems in order to assess T cell longevity and functions during and after the course of the infection. Here, using a recently identified MHC-II epitope conserved across Leishmania species, we show that in contrast to cutaneous versions of leishmaniasis, antigen-specific CD4+ T cells become functionally exhausted during visceral leishmaniasis, produce IL-10, and express high levels of the inhibitory receptors PD-1 and CTLA-4. This suggests that rather than remaining “hidden”, high parasite burden and/or antigen load overwhelms the adaptive immune system to the point where antigen-specific CD4+ T cells lose the capacity to produce the necessary pro-inflammatory cytokines to kill parasites residing within macrophages. Because there is currently no effective vaccine and limited treatment options for leishmaniasis, we have generated recombinant Vaccinia virus (VacV) vectors expressing the immunodominant Leishmania epitope targeted for MHC-II presentation to study the CD4+ T cell response against this parasitic infection. To begin to investigate the mechanisms of CD4+ T cell activation and to identify strategies to reverse or limit T cell dysfunction during visceral leishmaniasis, we will 1) define the functions and gene expression profiles of antigen-specific CD4+ T cells that become activated following either cutaneous or visceral Leishmania infections and 2) determine if therapeutic viral immunization combined with immunotherapy restores function to CD4+ T cells during visceral leishmaniasis. The overall goal of this project will be to begin to define the mechanisms that regulate CD4+ T cell function and dysfunction during visceral leishmaniasis, which will contribute to our long-term goal of improving vaccine design and therapies against this complex parasite.