Physiologic and immunologic consequences of exposure to ETEC enterotoxins

描述（由申请人提供）：产肠毒素大肠杆菌（ETEC）是世界范围内发病和死亡的重要原因，特别是在发展中国家的儿童中。世界卫生组织估计，发展中国家五岁以下儿童每年因ETEC造成的腹泻负担约为2.1亿例，38万人死亡。ETEC通过定植因子（CFs）和产生热不稳定（LT）或热稳定（ST）肠毒素在小肠定植而引起疾病。大多数临床分离株同时产生肠毒素，同时暴露于这两种强效肠毒素的生理或免疫后果尚不清楚。我们的初步数据表明，当LT和ST同时存在时，它们加在一起起作用，增加水进入肠道的运动，超过单独使用任何一种毒素所观察到的水平。我们的初步数据还表明，在暴露于这两种肠毒素的动物中，肠上皮细胞（IECs）对LT的反应产生的炎症细胞因子水平显著降低。根据我们的初步研究结果，我们对拟进行的研究的假设是：1)与单独使用任何一种毒素相比，LT与ST结合可以增加液体运动（腹泻），从而增加cGMP； 2) LT/ST ETEC产生ST可以显著降低宿主发起有效先天免疫反应的能力；3)LT/ST ETEC产生ST可以显著降低宿主发起有效适应性免疫反应的能力(例如：血清和粘膜抗体)对抗感染生物体（定植因子或LPS）或其热不稳定的毒素。具体目的是：1)确定LT/ST对T84细胞环核苷酸积累的作用；2)确定LT/ST对小鼠肠道先天免疫应答的作用；3)确定LT/ST对产肠毒素大肠杆菌适应性免疫应答的作用。在这些研究的结论中，我们将更好地了解同时暴露于这些生物体（LT和ST）产生的两种强效肠毒素的生理和免疫后果，并将获得过渡到非人灵长类动物研究或人体试验所需的信息。

DESCRIPTION (provided by applicant): Enterotoxigenic E. coli (ETEC) are a significant cause of morbidity and mortality world-wide, especially in children in developing countries. The World Health Organization estimates that the annual diarrhea burden due to ETEC in children less than five years of age in the developing world is approximately 210 million cases and 380,000 deaths. ETEC cause disease by colonizing the small intestine by means of colonization factors (CFs) and by production of either a heat-labile (LT) or heat-stable (ST) enterotoxin. The majority of clinical isolates produce both enterotoxins and the physiologic or immunologic consequences of simultaneous exposure to these two potent enterotoxins are unknown. Our preliminary data indicate that when LT and ST are both present, they work additively, increasing movement of water into the intestine over and above levels observed with either toxin alone. Our preliminary data also demonstrate that the levels of inflammatory cytokines produced by intestinal epithelial cells (IECs) in response to LT are significantly reduced in animals exposed to both enterotoxins. Based on our preliminary findings, our hypotheses for the proposed studies are 1) LT combined with ST increases fluid movement (diarrhea) when compared to either toxin alone by increasing cGMP, 2) the production of ST by LT/ST ETEC can significantly reduce the ability of the host to mount an effective innate immune response and 3) the production of ST by LT/ST ETEC can significantly reduce the ability of the host to mount an effective adaptive immune response (e.g., serum and mucosal antibody) against the infecting organisms (colonizing factors or LPS) or its heat-labile toxins. The specific aims are 1) Determine the role of LT/ST on accumulation of cyclic nucleotides in T84 cells; 2) Determine the role of LT/ST on innate immune responses in the murine intestine; and 3) Determine the role of LT/ST on adaptive immune responses to enterotoxigenic E. coli. At the conclusion of these studies, we will have a better understanding of the physiologic and immunologic consequences of simultaneous exposure to the two potent enterotoxins made by these organisms (LT and ST) and will have the information necessary to transition into non-human primate studies or human trials.