齿龈内阿米巴对大白鼠牙龈组织的致病作用

目的观察齿龈内阿米巴(Eg)对实验动物的致病作用,了解其发病机制,研究Eg感染与牙周病的关系。方法从牙周病患者的牙周袋内容物分离Eg虫株并培养,分组人工感染大白鼠,观察Eg、共生菌(sb)和生理盐水的致病作用以及组织病理改变。结果Eg组s、b组及生理盐水对照组大白鼠牙周组织炎症发病率分别为87.50%、68.75%和12.50%,差异有统计学意义(P<0.01)。结论宿主免疫力低下时,Eg感染可导致牙龈组织炎症发生。     

Acute appendicitis caused by amebiasis

We report a case of appendicitis caused by amebiasis in a 45-year-old Japanese man. He presented to our hospital with bloody stools in June 1998. Sigmoidoscopy disclosed erosion, and a biopsy of the erosion showed colitis caused by Entamoeba histolytica infection. Four months later, he was admitted to our hospital with a small elastic mass and severe pain in the lower quadrant of the abdomen, which was diagnosed as acute appendicitis. He underwent appendectomy. Histopathological examination revealed numerous E. histolytica trophozoites, and we diagnosed acute appendicitis caused by E. histolytica. The patient has been free of symptoms, colonoscopy has revealed no erosion, and biopsy has revealed no E. histolytica for 12 months after the operation. Received: August 25, 1999 / Accepted: February 25, 2000     

Lysis of pathogenic and nonpathogenic Entamoeba histolytica by human complement: methodological analysis

The effect of nonimmune human serum on Entamoeba histolytica trophozoites was studied: (a) using whole serum in the presence of Ca and Mg ions allowing complement activation via both the alternative and classical pathways or in the presence of MgEGTA permitting alternative pathway activation only; (b) using different E. histolytica isolates; (c) varying serum and trophozoite concentrations and the time of incubation; and (d) using three different methods to quantify lysis, i.e., microscopic inspection, flow cytometry and 111In release. All three methods yielded similar results, with flow cytometry being most sensitive in identifying membrane damage and 111In release being most valid in determining cell death. Microscopic analysis was reliable only when a chamber was used to calculate the number of complement treated cells in relation to the initial cell count. E. histolytica isolates were classified into three groups according to their susceptibility to lysis by complement: (i) pathogenic isolates after long term cultivation in vitro were susceptible; (ii) pathogenic isolates after recent in vivo passage were less susceptible; and (iii) nonpathogenic isolates were nearly unaffected by exposure to the alternative pathway alone. The extent of lysis of the various isolates correlated with the degree of complement consumption in the serum samples, suggesting that unlysed isolates did not activate complement under the conditions employed. In general, lysis of susceptible trophozoites increased with the serum concentration and with the time of incubation. However, when the trophozoite concentration was 10(6)/ml or higher, lysis no longer reflected complement susceptibility because of exhaustion of the complement supply.     

Evaluation of dot-ELISA for serological diagnosis of amebiasis

 We improved the dot enzyme-linked immunosorbent assay (dot-ELISA) reported by Itoh and Sato, and assessed the usefulness of this test for the diagnosis of amebiasis. The sensitivity of dot-ELISA was compared with that of plate ELISA, the indirect hemagglutination test (IHA), and the indirect fluorescent antibody test (IFA) for the diagnosis of amebiasis. Of 37 serum samples from patients with documented amebiasis, 36 (97.3%) were positive by dot-ELISA. There was consistency among the results of dot-ELISA, plate ELISA, and IFA, although the positive rate of IHA was lower than that of the others (78.4%; 29 of 37 cases were positive). The specificities of dot-ELISA and plate ELISA were assessed using a total of 68 sera, collected from 38 patients infected with seven different parasites other than Entamoeba histolytica, 10 patients showing diarrhea or liver abscess without parasitic infection, and 20 healthy individuals. The two assays showed no false-positive results. There were no differences in sensitivity and specificity between dot-ELISA and plate ELISA. However, the dot-ELISA technique seems to be more feasible for clinical application than plate ELISA techniques, because the assay does not require any specific equipment. Received: July 8, 2002 / Accepted: December 7, 2002 RID="*" ID="*" A summary of this paper was presented at the 74th General Meeting of the Japanese Association for Infectious Diseases (Fukuoka, April 2000). Acknowledgments The authors are indebted to Professor Tsutomu Takeuchi and Dr. Seiki Kobayashi, Department of Tropical Medicine and Parasitology, Keio University School of Medicine, for supplying E. histolytica antigen, and to Dr. Hiroshi Yamasaki, Department of Parasitology, Juntendo University School of Medicine, for supplying recombinant Toxocara canis antigen for this study.     

齿龈内阿米巴的连续培养及其生长情况

目的： 建立齿龈内阿米巴（ Ｅｎｔａｍｏｅｂａ ｇｉｎｇｉｖａｌｉｓ， Ｅｇ） Ｆ Ｊ４ 的连续培养方法， 并观察其生长情况。方法： 在不同培养条件下观察 Ｅｇ虫体大小及其存活时间。结果： Ｅｇ在改良的 Ｌｏｃｋｅ ｅｇｇ ｓｅｒｕｍ 与改良的ｙｏｌｋ ｅｇｇ ｓｅｒｕｍ 培养基中生长良好， 建立了福建３ 株 Ｅｇ（ Ｆ Ｊ２ 、 Ｆ Ｊ３ 及 Ｆ Ｊ４） ， 虫体大小均值为１３１９ μｍ ～４３９３ μｍ ×９８８ μｍ ～３０７４ μｍ 。 Ｅｇ最适宜培养条件为ｐ Ｈ 在６４ ～６７ 、改良的 Ｌｏｃｋｅ ｅｇｇ ｓｅｒｕｍ 或蛋黄液含２０ ％ 小牛血清加青霉素、链霉素及米粉。虫体繁殖高峰为ｄ４ ， 其在上述培养液体中可存活１２０ ｈ ～１６８ ｈ 。结论： Ｅｇ在 Ｌｏｃｋｅ ｅｇｇ ｓｅｒｕｍ 与 Ｙｏｌｋ ｅｇｇ ｓｅｒｕｍ 培养基中生长良好， 每４ ｄ 转种１ 次， 可达到长期培养的效果。     

Fulminant amebic colitis

Nine patients with fulminating amebic colitis who were treated surgically from 1975 to 1982 are presented. Only those who had bowel resections with exteriorization of the cut ends survived. The pertinent literature is reviewed briefly.     

The interaction of human T-lymphocytes and Entamoeba histolytica: killing of virulent amoebae by lectin-dependent lymphocytes

Clinical and experimental studies indicate that following invasive disease due to Entamoeba histolytica, development of human cell-mediated immune mechanisms may provide protective immunity. Activated, human monocyte-derived macrophages in vitro can kill virulent axaenic amoebic trophozoites. This study describes the interaction of lectin-stimulated T-lymphocytes and E. histolytica trophozoites (virulent strain HM1-IMSS). Amoebae progressively killed unstimulated nonimmune T-lymphocytes over 18 h incubation with no effect on amoebic viability. T-lymphocytes, stimulated with phytohaemagglutinin (PHA), were progressively cytotoxic for virulent HMI amoebae over 18 h incubation, but were also reduced in viability themselves. Lymphocyte cytotoxicity for amoebae was absent if PHA was removed before or added only during the assay. PHA-stimulated T-lymphocytes killed amoebae at cell ratios of lymphocytes to amoebae as low as 50:1 and cytotoxicity was antibody-independent. PHA-stimulated T-lymphocytes, depleted of T8-bearing cells by complement-mediated lysis, were unable to kill amoebae. Adherence of PHA-stimulated T-lymphocytes to amoebae was greater than with unstimulated T-lymphocytes. Inhibition of the amoebic adherence lectin with N-acetyl-D-galactosamine decreased lymphocyte-amoebic adherence and resulted in increased lymphocyte amoebicidal activity and lymphocyte survival. Suspension of amoebae with or without adherent PHA-stimulated T-lymphocytes in a 10% dextran solution indicated that cytotoxicity was contact dependent. In summary, PHA-stimulated T-lymphocytes of the T8-phenotype can kill virulent axaenic E. histolytica trophozoites through a contact-dependent, antibody-independent mechanism.     

齿龈内阿米巴引起牙周炎的实验研究

目的　探讨齿龈内阿米巴 (Entamoeba ,gingivalis ,E .g .)的致病性及其与牙周炎之间的关系。方法　大白鼠用免疫抑制剂处理 1周 ,其下颌中切牙颈部用不锈钢丝栓扎后 ,随机分为 3组 ,分别于牙龈涂拭E .g .,共生菌 (Symbioticbacteria ,S .b .)及生理盐水 ,观察各组大白鼠发生牙周炎状况 ,同时检查脓液中有无活的病原体 ,实验结果进行病理学分析。结果　E .g .组大白鼠牙周炎发病率高于S .b .组和对照组 (P <0 .0 5 ) ,S .b组大白鼠牙周炎发病率高于对照组 (P <0 .0 5 ) ;脓液镜检或培养均查见相应的病原体 ;病理证实E .g .可引发牙周炎。结论　E .g .是条件致病病原体 ,当宿主免疫力低下时 ,在口腔内细菌协同作用下可使宿主发生牙周炎。     

Calpain‐dependent cleavage of SHP‐1 and SHP‐2 is involved in the dephosphorylation of Jurkat T cells induced by Entamoeba histolytica

Host cell death induced by Entamoeba histolytica is an important mechanism for both host defence and microbial immune evasion during human amoebiasis. However, the signalling pathways underlying cell death induced by E. histolytica are not fully understood. This study investigated the involvement of the protein tyrosine phosphatases (PTPs) SHP‐1 and SHP‐2 in the dephosphorylation associated with E. histolytica‐induced host cell death. Incubation with E. histolytica resulted in a marked decrease in protein tyrosine phosphorylation levels and degradation of SHP‐1 or SHP‐2 in Jurkat cells. Pre‐treatment of cells with a calpain inhibitor, calpeptin, impeded the amoeba‐induced dephosporylation and cleavage of SHP‐1 or SHP‐2. Additionally, inhibition of PTPs with phenylarsine oxide (PAO) attenuated Entamoeba‐induced dephosphorylation and DNA fragmentation in Jurkat T cells. These results suggest that calpain‐dependent cleavage of SHP‐1 and SHP‐2 may contribute to protein tyrosine dephosphorylation in Jurkat T cell death induced by E. histolytica.     

Cytopathogenicity of entamoeba histolytica: The role of amebic adherence and contact-dependent cytolysis in pathogenesis

The mechanisms by which Entamoeba histolytica trophozoites adhere to and lyse target cells are reviewed from the perspective of pathogenesis. Adherence via the galactose and N-acetyl -galactosamine inhibitable amebic lectin and possible additional amebic adhesin molecules is followed by target cell death. Inhibition of the Gal/GaINAc lectin with GaINAc inhibits amebic cytolysis of target cells. Amebic activities implicated in the cytolysic event include vesicle exocytosis and maintenance of an acid pH, pore forming proteins, phospholipase A and proteases. Increased knowledge of the sequence of events leading to target cell lysis should lead to more effective treatment or prevention of infection by this enteric parasite and add to our basic understanding of eukaryotic cell-cell interactions.Corresponding author.