Spotted Fever Rickettsial Antigens

描述（由申请人提供）：严重斑点热立克次体病是一种危及生命的、由蜱传播的、新出现和再出现的人类感染，由细胞内立克次体引起，包括康氏雷克次体和立克次体。优秀的动物模型和现有的人类数据揭示了ifn - γ， CD8细胞毒性T淋巴细胞，树突状细胞（dc）和NK细胞在宿主对立克次体的保护性免疫中的重要作用。与自限性感染相比，急性致死性鼠斑疹热立克次体感染相关免疫抑制的证据得到了立克次体感染相关免疫抑制的支持，即在急性致死性鼠斑疹热立克次体感染中，IL-10产生CD4+CD25+ T调节细胞显著抑制淋巴细胞增殖和IL-2和ifn - γ的产生。目前尚不清楚为什么宿主防御系统不能控制致死性立克次体的细菌感染。本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感染的免疫调节机制。本提案的目的是确定dc介导缺陷先天和抑制适应性免疫反应的机制，包括T调节1细胞，这可能导致致命的立克次体感染。我们的具体目的1是确定受损DC-NK细胞串音在促进严重斑疹热立克次体缺陷先天免疫反应中的关键作用。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被清除）。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）在严重斑点热立克次体病中由dc和/或T调节细胞表达或产生的抑制T细胞反应中的作用。在特异性靶1中介导DC-NK细胞相互作用的toll样受体（TLRs）、细胞因子和趋化因子，以及dc与T调节细胞的相互作用在特异性靶2中通过抑制细胞因子和/或调节分子（包括PD-1/PD-L和IDO）介导受抑制的1型保护效应T细胞和/或凋亡中的作用，将通过体内和体外方法进行研究，包括流式细胞术、ELISPOT、ELISA、RT- real - time PCR、小鼠TLR PCR阵列、免疫组织化学染色、斑块测定、HPLC以及过继转移、免疫分子消耗和敲除小鼠。近年来，向美国疾病控制与预防中心报告的落基山斑疹热（已知最致命的立克次体疾病）病例数已达到历史最高水平。该项目旨在确定免疫反应的哪些组成部分导致致命感染中无法控制细菌生长，以允许未来的免疫调节治疗来提高生存率。

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.