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腸出血性大腸桿菌(EHEC)O157:H7多價基因工程疫苗的實驗研究

發(fā)布時間:2018-04-18 06:04

  本文選題:腸出血性大腸桿菌(EHEC) + O157:H7; 參考:《第三軍醫(yī)大學》2005年碩士論文


【摘要】:O157:H7 大腸桿菌是腸出血性大腸桿菌(EHEC)的一個主要血清型,感染該菌可使人患腹瀉、出血性結(jié)腸炎(hemorrhagic colitis,HC),也可引發(fā)溶血性尿毒綜合征(hemolytic uremic syndrome , HUS) 及血栓形成性血小板減少性紫癜(thrombotic thrombocytopenic purpura,TTP)等嚴重并發(fā)癥,嚴重者可導致死亡。EHEC O157 的感染因具有暴發(fā)流行趨勢、強烈的致病性與致死性和抗生素治療可加劇病情的危險性等特點,已經(jīng)成為全球性的公共衛(wèi)生問題。目前EHEC O157:H7 的全基因組測序已經(jīng)完成,然而目前對其感染仍缺乏有效的防治方法,研究證明抗菌藥物可促使菌體破壞,釋放志賀毒素增加,從而使并發(fā)HUS 的危險性增加。因此,尋找有效的針對性防治方法如疫苗對防治O157:H7 的感染有著極其重大的意義。人類同病原微生物長期斗爭的歷史表明,疫苗是預防和抑制傳染病的有力武器。由于O157 的暴發(fā)流行和治療上的困難,疫苗研究就顯得尤其緊迫。 為了評估疫苗的保護效果,建立一個與人類病變相似的動物模型極為重要。對于O157 菌,其易感動物為牛、羊、豬等大型哺乳動物,不適合實驗室應用;而小型實驗動物如大鼠、小鼠等都不是O157 菌的天然易感動物,須降低其對O157 的抵抗力或增強O157 對其的致病力,才有可能建立相應的動物模型。 目前已公認的與EHEC 致病性有關的致病基因主要有eae 基因、stx 基因、溶血素hly 基因還有III 型分泌蛋白EspA、B、D 等。緊密粘附素(Intimin)介導細菌與腸上皮細胞的緊密粘附,是O157 最主要的定植因子,尤其是它的約C 端1/3 部分(Intimin-C)為胞外功能區(qū),與相應受體結(jié)合,且具有良好的免疫原性和免疫保護性,是理想的疫苗備選抗原之一。 EHEC O157可以產(chǎn)生兩種志賀毒素,志賀毒素Ⅰ(Stx1)和志賀毒素Ⅱ(Stx2)。其中Stx2為分泌型表達,由1個A亞單位和5個B亞單位組成,A亞單位具有細胞內(nèi)毒性,能與28S rRNA作用從而抑制蛋白質(zhì)合成,是大腸桿菌O157:H7引起臨床表現(xiàn)的病理基礎;B亞單位具有細胞結(jié)合特性,能與具有特定受體(Gb3)的細胞結(jié)合,從而引導A亞單位發(fā)揮作用。多數(shù)O157:H7細菌產(chǎn)生Stx2,與溶血性尿毒綜合征(HUS)及血栓形
[Abstract]:O157:H7 Escherichia coli is a major serotype of enterohemorrhagic Escherichia coli.Hemolytic uremic syndrome (HUSS) and thrombocytopenic purpura (TTP) can also be caused by hemorrhagic colitis. In severe cases, the infection of .EHECO157 may be caused by an outbreak of epidemic trend, which may lead to death in patients with hemorrhagic colitis, such as hemolytic uremic syndrome (HUSS) and thrombocytopenic purpura of thrombocytopenic purpura (thrombocytopenic purpura).The characteristics of strong pathogenicity and mortality, and antibiotic therapy can aggravate the risk of disease, has become a global public health problem.At present, the whole genome sequencing of EHEC O157:H7 has been completed. However, there is still no effective method to prevent and cure the infection of EHEC O157:H7. It has been proved that antimicrobial agents can induce the destruction of bacteria and increase the release of Shiga toxin, thus increasing the risk of concurrent HUS.Therefore, it is of great significance to find effective methods such as vaccine to prevent and cure O157:H7 infection.The long history of human struggle with pathogenic microorganisms shows that vaccine is a powerful weapon to prevent and suppress infectious diseases.Because of the outbreak of O 157 and treatment difficulties, vaccine research is particularly urgent.In order to evaluate the protective effect of the vaccine, it is very important to establish an animal model similar to human disease.For O157, the susceptible animals are large mammals, such as cattle, sheep and pigs, which are not suitable for laboratory use, while small laboratory animals such as rats and mice are not naturally susceptible to O157.It is necessary to reduce its resistance to O157 or to enhance its pathogenicity in order to establish corresponding animal models.At present, the main pathogenicity genes related to the pathogenicity of EHEC are eae gene, hemolysin hly gene and III type secretory protein, EspAgnib D, and so on.Tight adhesion between bacteria and intestinal epithelial cells mediated by close-adhesion hormone (Intimin) is the most important colonization factor of O157, especially its C terminal 1 / 3 part of Intimin-Cis is an extracellular functional region, binds to the corresponding receptor, and has good immunogenicity and immunogenicity.It is one of the ideal vaccine candidate antigens.EHEC O157 can produce two kinds of Shiga toxin, Shiga toxin 鈪,

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