溶组织内阿米巴引起每年约10万人死于阿米巴病，是WHO持续关注的公共卫生问题，但其致病机理尚未完全阐明。我们前期研究发现在该原虫表面存在一种富含CXXC基序半乳糖／乙酰氨基半乳糖特异性凝集素中间亚单位，证实其具有疫苗和靶抗原作用，但其致病功能有待深入。为此假设：共有CXXC基序的凝集素中间亚单位与跨膜蛋白激酶形成复合体而成为致病的“双信号模式”，一方面与宿主免疫细胞相互作用引起宿主细胞病变，另一方面启动免疫调控信号传导系统，引起特异性的抗原变异和诱导抗补体作用，使疾病呈持续性感染状态。本项目将动态解析中间亚单位与跨膜蛋白激酶复合体在阿米巴不同培养阶段及单个滋养体的变化，研究其对宿主细胞免疫调节作用和抗补体的作用；进行该基因转染、结构突变和基因置换研究其对滋养体体内外毒力的影响，分析其与下游效应分子的关系和免疫保护作用。揭示中间亚单位与跨膜蛋白激酶复合体在溶组织内阿米巴的致病和免疫调控作用。

Amebiasis is a global health concern with large domestic impacts. The World Health Organization (WHO) estimates that approximately 50 million people worldwide suffer from invasive amebic infection each year, resulting in 40–100 thousand deaths annually. Studies conducted in China indicated it may affect over 1% of the population. It is an infection caused by the protozoan parasite Entamoeba histolytica, and could be classified as amebic colitis and/or liver abscess clinically. Early studies demonstrated that tissue surface adhesion of Trophozoites on colonic mucus and epithelial cells is the first and most critical step of infection, and a Gal/GalNAc-specific lectin was implicated in this process. .The E. histolytica Gal/GalNAc lectin was originally identified as a heterodimer of transmembrane heavy (Hgl) and GPI-anchored light (Lgl) glycoproteins linked by disulfide bonds. In 1998, the applicant identified a 150-kD protein that was associated with the Gal/GalNAc lectin by non-covalent bond. The protein, also known as the heterodimer intermediate subunit (Igl) of the Gal/GalNAc lectin complex, was a useful target antigen in diagnosis of amoebiasis and a suitable vaccine for its prevention. It is of interesting to note that the Igl gene contained special CXXC and CXC motifs shared with transmembrane protein kinases (TMK) genes. As the collective data produced in our laboratory indicated that Igl is a critical component for both tissue surface adhesion and pathogenesis, we hypothesized that CXXC motifs may function as a second and critical signal that complement the lectin signal for surface adhesion, invasion and pathogenesis of E. histolytica. It will interact with the host immune cells, and caused host cell and tissue lesions. For another, it will start immune regulation of signal transduction system, occur specific antigen variation and induction of anti-complement function, make the disease become to persistent infection..A series of studies will be included in the current project. Both mRNA and protein expression levels of Igl and TMKs will be monitored at different stages or single trophozoites of infection in the context of the other known virulence factors. The effects of Igl and TMK on immune systems will be assayed by in vitro expressed proteins. Through gene transfection, gene mutation and gene replacement technique, the influence of both genes on in vivo and in vitro virulence of amoeba will be researched. The results will provide required evidences to verify whether surface CXXC Igl and TMK are the core factors in the pathogenicity of Entamoeba histolytica.