Substance P in pathogenesis of cryptosporidiosis in AIDS

描述（由申请人提供）：隐孢子虫病由原生动物寄生虫隐孢子虫引起，在正常宿主中自限性，但在艾滋病患者中可引起危及生命的慢性腹泻。对于与晚期AIDS相关的隐孢子虫病，尚未成功开发出安全有效的治疗方法。C.细小病毒感染引起肠道生理变化，如增加的氯阴离子分泌（Cl）和上皮屏障破坏，导致水样腹泻。 P物质（SP）是一种神经肽，是一种疼痛递质，可引起人肠组织中C1-离子的分泌。我们先前研究了SP在伴有自然严重隐孢子虫病的艾滋病患者和正常志愿者空肠活检中的表达。小病（轻度疾病）。与轻度自限性隐孢子虫病的正常志愿者相比，艾滋病患者的SP表达更强。我们假设SP是艾滋病相关隐孢子虫病慢性肠道症状的关键介质。我们还推测，免疫缺陷宿主的肠道组织中SP的表达会因隐孢子虫病感染而升高，单独的HIV感染不会引起SP表达的升高。为了验证这些假设，我们建议使用隐孢子虫病的免疫缺陷动物模型，即。患有艾滋病（实验性SIV感染后）和隐孢子虫病的灵长类动物作为机会性自然发生的感染。动物模型的优点是，从动物模型获得大的组织样品比从患有隐孢子虫病的AIDS患者获得大的组织样品更容易，并且，旨在确定负责疾病发病机制的分子靶点和特异性拮抗剂的初始治疗测试的研究可以最好地使用动物来源的组织进行研究。本项目的目的是检验SP介导免疫缺陷宿主隐孢子虫病严重症状的假设。具体目标1：确定与无隐孢子虫病的免疫缺陷动物或患有亚临床实验性隐孢子虫病的正常免疫活性猕猴相比，患有慢性自然感染隐孢子虫病的免疫缺陷动物的肠道SP是否上调。将比较有和没有自然发生C的免疫缺陷猕猴（患有艾滋病）之间的回肠SP mRNA表达和蛋白质水平。parvum感染和正常猕猴与和没有亚临床实验C。细小病毒感染具体目标2：检验SP是介导肠道生理改变的关键因子的假设，该改变导致与免疫缺陷宿主相关的自然发生的慢性隐孢子虫病的水样腹泻。将在有和没有天然存在的C的SIV感染的猕猴（患有AIDS）的回肠组织之间比较C1-离子分泌和屏障完整性。通过Ussing小室技术，在存在和不存在SP受体拮抗剂的情况下观察小孢子虫感染。这些研究将进一步明确SP在C.小虫引起腹泻。表明SP参与疾病过程的证据将支持使用SP受体拮抗剂作为与AIDS相关的隐孢子虫病和可能的其他肠道病原体相关的危及生命的疾病的治疗。

DESCRIPTION (provided by applicant): Cryptosporidiosis, caused by the protozoan parasite, Cryptosporidium parvum, is self-limited in normal hosts but can cause life threatening, chronic diarrhea in AIDS patients. No safe and effective treatment has been successfully developed for cryptospofidiosis associated with advanced AIDS. C. parvum infection causes intestinal physiologic changes like, increased chloride anion secretion (CI) and epithelial barrier disruption that leads to watery diarrhea. Substance P (SP), a neuropeptide, is a pain transmitter and can cause C1- ion secretion in human intestinal explants. We have previously studied SP expression in jejunal biopsies of AIDS patients with natural severe cryptosporidiosis and normal volunteers experimentally challenged with C. parvum (mild disease). SP expression was stronger in AIDS patients compared to normal volunteers with mild self-limited cryptosporidiosis. We hypothesize that SP is a key mediator of chronic intestinal symptoms in AIDS associated cryptosporidiosis. We also hypothesize that SP expression will be elevated in intestinal tissues of immunodeficient hosts because of cryptosporidiosis infection, HIV infection alone will not cause increased SP expression. To verify these hypotheses, we propose to use an immunodeficient animal model of cryptosporidiosis, ie. primates with AIDS (after experimental SIV infection) and cryptosporidiosis as an opportunistic naturally occurring infection. Advantage of an animal model is that, it is easier to procure large tissue samples from an animal model to that from AIDS patients with cryptosporidiosis, and, studies aimed at defining molecular targets responsible for disease pathogenesis and initial therapeutic testing of specific antagonists can best be studied using animal derived tissues. The goal of this project is to test the hypothesis that SP mediates severe symptoms of cryptosporidiosis in immunodeficient hosts. Specific aim 1: To determine if intestinal SP is upregulated in immunodeficient animals with chronic naturally infected cryptosporidiosis as compared to immunodeficient animals without cryptosporidiosis or normal immunocompetent macaques with subclinical experimental cryptosporidiosis. Ileal expression of SP mRNA and protein levels will be compared between immunodeficient macaques (with AIDS) with and without naturally occurring C. parvum infection and in normal macaques with and without subclinical experimental C. parvum infection. Specific aim 2: To test the hypothesis that SP is a key factor that mediates intestinal physiological alterations that lead to watery diarrhea in naturally occurring chronic cryptosporidiosis associated with immunodeficient hosts. C1- ion secretion and barrier integrity will be compared between ileal tissues from SIV infected macaques (with AIDS) with and without naturally occurring C. parvum infection in the presence and absence of SP receptor antagonist by the Ussing chamber technique. These studies will determine the role of SP in the pathogenesis of C. parvum induced diarrhea. Evidence implicating SP in the disease process would support the use of SP receptor antagonists as a therapy for the life threatening illness associated with AIDS related cryptosporidiosis and perhaps other intestinal pathogens.