Spotted Fever Rickettsial Antigens

描述（由申请方提供）：重度斑点热立克次体病是由专性细胞内立克次体（包括立克次体）引起的危及生命、蜱媒、新发和复发的人类感染。conorii和R.立克次氏体良好的动物模型和现有的人类数据揭示了IFN-γ、CD 8细胞毒性T淋巴细胞、树突状细胞（DC）和NK细胞在宿主针对立克次体的保护性免疫中的关键重要性。与自限性感染相比，在急性致死性鼠斑点热立克次体病中，产生IL-10的CD 4 + CD 25 + T调节细胞显著抑制淋巴细胞增殖和IL-2和IFN-γ产生，这支持了人类立克次体感染相关免疫抑制的证据。目前还不清楚为什么宿主防御系统不能控制致命性立克次体病的细菌感染。这项研究的长期目标是更好地了解宿主防御系统无法控制严重斑点热立克次体病感染的免疫调节机制。本提案的目的是确定DC介导涉及T调节1细胞的先天性缺陷和抑制的适应性免疫应答的机制，这可能导致致命的立克次体感染。我们的具体目标1是确定受损的DC-NK细胞串扰对促进严重斑点热立克次体病患者先天免疫应答缺陷的关键作用。我们将比较易感小鼠中有缺陷的DC-NK细胞串扰（导致细菌负荷逐渐增加）与耐药小鼠中有效的DC-NK细胞相互作用（导致先天反应期间细菌清除）。我们的具体目标2是确定免疫调节分子如PD-1/PD-L和吲哚胺2，3-双加氧酶（IDO）或细胞因子如IL-10表达或产生的DC和/或T调节细胞在严重斑点热立克次体病期间抑制T细胞应答中的作用。Toll样受体（TLR）、介导DC-NK细胞相互作用的细胞因子和趋化因子，具体目标1，以及DC与T调节细胞的相互作用在介导抑制的保护性效应子1型T细胞和/或通过抑制性细胞因子和/或调节分子（包括PD-1/PD-2）的凋亡中的作用。在特定目标2中，将使用体内和体外方法，包括流式细胞术、ELISPOT、ELISA、RT或真实的时间PCR、小鼠TLR PCR阵列、免疫组织化学染色、空斑测定、HPLC以及过继转移、免疫分子耗竭和基因敲除小鼠。近年来，向疾病预防控制中心报告的落基山斑疹热（已知最致命的立克次体病）病例数达到了历史最高水平。该项目旨在确定免疫反应的哪些成分导致无法控制致命感染中的细菌生长，以便将来进行免疫调节治疗以提高存活率。

DESCRIPTION (provided by applicant): Severe spotted fever rickettsioses are life-threatening, tick-borne, emerging and re-emerging human infections caused by obligately intracellular Rickettsia including R. conorii and R. rickettsii. Excellent animal models and the available human data reveal the critical importance of IFN-gamma, CD8 cytotoxic T lymphocytes, dendritic cells (DCs) and NK cells in host protective immunity against Rickettsia. Evidence for human rickettsial infection-associated immunosuppression is supported by remarkable suppression of lymphocyte proliferation and IL-2 and IFN-gamma production by IL-10 producing CD4+CD25+ T regulatory cells in acute fatal murine spotted fever rickettsiosis compared to self-limited infection. It remains unclear why the host defense system fails to control bacterial infection in fatal rickettsiosis. The long-term goal of this research is to better understand the immune regulatory mechanisms involved in the inability of the host defense system to control infection in severe spotted fever rickettsiosis. The objective of this proposal is to determine the mechanisms by which DCs mediate defective innate and suppressed adaptive immune responses involving T regulatory 1 cells, which may lead to fatal rickettsial infection. Our specific aim 1 is to determine the key effect of impaired DC-NK cell cross talk on promoting a defective innate immune response in severe spotted fever rickettsiosis. We will compare the defective DC-NK cell cross talk in susceptible mice, which causes progressively increased bacterial loads, with efficient DC-NK cell interaction in resistant mice, which lead to clearance of bacteria during the innate response. Our specific aim 2 is to determine the role of immunoregulatory molecules such as PD-1/PD-L and indoleamine 2,3-dioxygenase (IDO) or cytokines such as IL-10 expressed or produced by DCs and/or T regulatory cells in suppression of T cell responses during severe spotted fever rickettsiosis. Toll-like receptors (TLRs), cytokines and chemokines that mediate the DC-NK cell interaction in specific aim 1, and the role of interactions of DCs with T regulatory cells in mediating suppressed protective effector type-1 T cells and/or apoptosis via suppressive cytokines and/or regulatory molecules including PD-1/PD-L and IDO in severe spotted fever rickettsiosis in specific aim 2 will be investigated using in vivo and in vitro approaches including flow cytometry, ELISPOT, ELISA, RT- or real time PCR, mouse TLR PCR array, immunohistochemical staining, plaque assay, HPLC as well as adoptive transfer, depletion of immune molecules and knockout mice. PUBLIC HEALTH RELEVANCE In recent years the number of cases of Rocky Mountain spotted fever, the most lethal rickettsial disease known, reported to the CDC has reached the highest level in history. This project is designed to determine what components of the immune response are responsible for failure to control bacterial growth in fatal infections to allow future immunomodulatory treatment to enhance survival.