幽门螺杆菌Cag致病岛hp0527基因的缺失株构建和鉴定

目的:构建幽门螺杆菌(H.pylori)Cag致病岛编码hp0527基因的突变株.为Cag致病岛致病机制及H.priori功能研究奠定基础.方法:利用基因同源重组方法将卡那霉素抗性基因(KanR)连接到PCR扩增hp0527两端区域产生的2个目的基因片段之间,构建hp0527基因缺失的自杀质粒pBlueKM40-△hp0527;将带有卡那霉素抗性标志的缺失突变载体,通过抗生素卡那霉素筛选出缺失hp0527基因的突变株,并经PCR方法鉴定后,采用野生株和突变株的幽门螺杆菌分别与胃癌上皮细胞BGC-823共培养后,分析它们对细胞毒素相关蛋白CagA转运能力的影响.结果:成功构建出幽门螺杆菌hp0527基因突变的自杀质粒,突变载体经内切酶酶切分析显示:产生的条带与设计结果完全一致;抗生素筛选并经PCR鉴定后,获得了hp0527基因缺失株;CagA蛋白转运分析表明基因hp0527缺失前后,可以导致细菌转运CagA蛋白能力的丧失.结论:成功构建出1株缺失hp0527基因的H.pylori突变株,对于阐明该基因的功能及其在H.pylori致病中的地位及作用具有重要的研究价值.     

LuxS基因缺失的变形链球菌突变株的构建及鉴定

目的 通过同源重组法构建LuxS基因缺失的变形链球菌(Streptococcus mutans)突变株.方法 运用基因同源重组方法将红霉素抗性基因(Eymr)连接到PCR扩增LuxS基因两端区域产生的2个基因片段之间,并共同插入到pUCl9载体的多克隆位点中,构建出带红霉素抗性标志的缺失突变载体pUCluxKO.将突变载体转化到含完整LuxS基因的突变受体变形链球菌标准株中,红霉素筛选出LuxS基因缺失的变形链球菌突变株,并经PCR、生物荧光检测及DNA测序鉴定.结果 构建的突变载体经限制性内切核酸酶酶切分析显示,产生的条带与设计结果完全一致.PCR方法扩增突变株LuxS和Eymr基因显示,LuxS基因已被完整敲除掉,经生物荧光检测,突变株不能诱导哈氏弧菌(Vibrio harveyi)BBl70的生物发光,说明不能产生信号分子AI-2(autoinducer-2).DNA测序证实筛选得到了LuxS基因缺失的变形链球菌突变株.连续传代培养后证实,变形链球菌LuxS基因突变株具有良好的稳定性.结论 成功构建出LuxS基因缺失的变形链球菌突变株,为研究LuxS基因对变形链球菌致龋毒力的影响奠定了基础.     

变异链球菌LuxS基因缺陷株的建立及其耐酸能力的研究

目的 建立LuxS基因缺失的变异链球菌突变菌株,并对突变株的耐酸能力进行研究.方法 以变异链球菌UA159为材料,运用基因重组方法将红霉素抗性基因(Eymr)与LuxS基因上下游区域的2个基因片段按一定顺序重组到质粒载体PUC19的多克隆位点中,获得了具有红霉素抗性的重组质粒,将载体质粒转化到含完整LuxS基因的变异链球菌UA159中,利用红霉素抗性筛选出LuxS基因缺失的突变株.检测变异链球菌LuxS基因突变菌株在不同pH环境下生长情况,并以正常菌株为对照.结果 PCR基因扩增结果显示,突变株LuxS基因已被Eymr基因完全替换,不能再编码合成AI-2(autoinducer 2)信号分子,扩增产物经DNA测序证实筛选得到了LuxS基因缺失的突变株,并且突变株不能诱导V.harveyi BB170的生物发光.与变异链球菌标准菌株相比,LuxS基因突变株的生长情况随着pH的降低受到明显抑制.结论 本研究成功构建LuxS基因缺失的变异链球菌突变株,LuxS感应信号系统参与变异链球菌耐酸能力的调控,LuxS基因缺失菌株耐酸能力降低.     

采用基因打靶技术构建结核分枝杆菌新基因Rv0901缺失株的研究

目的：利用基因打靶技术构建基因打靶载体和基因缺失株，用于结核分枝杆菌基因Rv0901功能的研究。方法：结核分枝杆菌标准株H37Rv体外培养，对其Rv0901基因及两侧序列进行体外扩增，连接载体及目的片段，切除目的基因，再引入筛选标志构建重组自杀质粒，分别用酶切及PCR鉴定；用电穿孔法将重组自杀质粒转入结核杆菌H37Rv株，用PCR鉴定。结果：经鉴定PCR产物及插入片段大小与预期值相符，且为所需目的基因片段，成功切除靶片段；蓝白斑筛选证实标记基因插入片段插入方向正确；Rv0901基因缺失株用PCR鉴定成功缺失了目的基因片段2.5 kb。结论：成功构建了用于结核分枝杆菌基因打靶的置换型载体和Rv0901新基因缺失株，为Rv0901基因功能的研究奠定了基础。     

大肠杆菌qseC基因敲除及其缺陷株生物被膜形成的研究

目的 通过Red同源重组法构建qseC基因缺失的大肠杆菌突变株,并探讨qseC基因对大肠杆菌生物被膜形成的影响.方法 PCR扩增两翼与目的基因上下游同源、含有氯霉素抗性基因片段,电击转化人大肠杆菌MC1000,在Red同源重组酶作用下,用含同源臂的氯霉素抗性片段置换目的基因qseC,并利用FLP位点专一性重组将氯霉素抗性基因删除.结晶紫染色半定量法分析qseC基因缺失株生物被膜形成能力的变化.结果 PCR及DNA测序结果表明,qseC基因已被成功敲除.在LB培养基中,qseC基因缺陷株的生长状况与亲株无明显差异.MC1000与MC1000 △qseC基因缺失株生物被膜形成能力半定量A值的结果分别为1.00±0.15和0.47±0.10.结论 成功构建大肠杆菌qseC基因缺失突变株,且qseC基因对细菌生物被膜的形成具有调控作用.     

无标记的变异链球菌的clpP基因缺陷株的构建

目的 构建无标记的clpP基因缺陷的变异链球菌(简称变链菌)突变株.方法 设计引物PCR扩增大观霉素(Sp)抗性基因,使loxP位点位于Sp抗性基因的两侧,构建出大观霉素抗性基因盒(loxP-Sp-loxP).将clpP基因克隆到pGEM-T-Easy TA载体后,双酶切以去除clpP基因的部分序列,并连入loxP-Sp-loxP,得到clpP基因缺陷的同源重组载体pIB△clpP-Sp.将该载体线性化并电转变链菌标准株,大观霉素筛选得到clpP基因缺陷株.再以温敏质粒pCrePA电转缺陷株,Cre重组酶表达并删除选择标记基因,继而在限制性温度下培养以消除pCrePA,获得无标记的clpP基因缺陷株,并进行PCR及DNA测序鉴定.结果 PCR及DNA测序结果表明clpP基因内部分序列已被删除,且无Sp抗性基因,该部位只留有一个34 bp的loxP位点.结论 在变链菌中成功构建出无标记的clpP基因缺陷株,为进一步研究clpP基因的功能及其在变链菌致龋过程中的作用奠定了基础.     

赖型钩端螺旋体017株外膜蛋白新基因ompL17基因靶向敲除及其突变株的构建

目的将外膜蛋白新基因ompL17靶向敲除并构建该基因的突变株。方法提取钩端螺旋体017株基因组DNA，扩增出外膜蛋白新基因ompL17，与打靶载体p2NIL重组，并插入氨苄抗生素抗性基因伽”使外膜蛋白新基因ompL17失活，构建重组的基因打靶质粒p2NIL17A。电穿孔转化入钩体017株中构建突变株，通过豚鼠模型观察该突变株的毒力变化。结果PCR、Dot blot和酶切分析，证实构建了以氨苄青霉素抗性基因DNA为标记探针的基因打靶载体，并构建外膜蛋白新基因ompL17敲除的钩体017株突变株。结论成功将钩体外膜蛋白的新基因ompL17进行靶向敲除，并构建钩体017株突变株，为进一步进行该基因的功能研究和阐明赖型钩体致病的分子机制奠定了基础。     

O139群霍乱弧菌TLC、CTX、RTX基因簇缺失株的构建及鉴定

目的构建O139群霍乱弧菌TLC、CTX、RTX基因簇缺失株。方法PCR扩增TLC上游片段（TLCup）、RTX下游片段（RTXdown）,克隆入pU18中,再在两者间插入氯霉素抗性（Cm）基因,获得重组质粒pUC18-TLC up—Cm-RTX down。酶切回收TLC up—Cm—RTX down片段,克隆入自杀质粒pDS132,构建重组自杀质粒pDS132-TLC up-Cm—RTX down。通过接合将重组自杀质粒转入O139群霍乱弧菌ZJ199693,20％蔗糖选择培养基（Cm抗性）筛选TLC、CTX、RTX基因缺失株。结果PCR、酶切证明重组自杀质粒pDS132-TLC up-Cm-RTX down构建正确。PCR证实O139群霍乱弧菌ZJ199693TLC、CTX、RTX毒力基因簇成功缺失。结论成功缺失O139群霍乱弧菌ZJ199693TLC、CTX、RTX基因簇．为进一步研究其功能和疫苗构建打下基础。     

HPI毒力岛缺失的EAggEC17-2突变菌株的构建及其功能研究

目的 构建HPI毒力岛缺失的EAggEC17-2突变株，初步研究EAggEC菌株携带的耶尔森菌HPI毒力岛合成铁载体Ybt的功能。方法以EAggEC17-2为出发菌株，irp8基因部分序列作为同源重组的一侧序列，irp5基因序列作为同源重组的另一侧序列，中间插入有氯霉素（Can）抗性基因（cat基因）标记。通过接合转移和同源重组，构建了缺失约24kb的HPI毒力岛功能核心区区域EAggEC17-2的仝岛缺失株EA85。应用流式细胞技术（FACS）检测指示菌株WA-CS irp1：：KN（pC3G3．3N）荧光强度的变化情况，对EA85缺失株和出发菌株进行了合成Ybt的功能比较研究。结果成功构建了EAggEC17-2HPI全岛缺失株EA85。EAggEC17-2菌株具有表达Ybt的功能，而缺失株EA85丧失了合成Ybt的能力。结论EAggEC17-2HPI毒力岛的缺失，使Ybt的合成彻底阻断。EAggEC17-2具有的合成Ybt的功能是由其染色体携带的HPI毒力岛所决定的。     

携带幽门螺杆菌ureB和IL-2质粒DNA的减毒鼠伤寒沙门菌疫苗构建

目的　构建编码幽门螺杆菌 (Helicobacterpylori,H .pylori)尿素酶B亚单位 (ureB)基因和小鼠IL 2基因以减毒鼠伤寒沙门菌为载体的核酸疫苗 ,体外转染Cos 7细胞 ,鉴定其表达蛋白的免疫性。方法　应用聚合酶链式反应 (PCR)技术从H .pylori标准菌株CCUG1 7874基因组DNA扩增ureB基因 ,从重组质粒 pCIneo IL 2扩增小鼠IL 2基因 ,通过T A克隆分别插入 pUCmT载体 ,检测ureB及IL 2的核苷酸序列 ,通过酶切、连接反应分别克隆入真核表达载体 pIRES ,PCR和酶切反应进行鉴定 ;重组载体 pIRES ureB和 pIRES ureB IL 2转入减毒鼠伤寒沙门菌LB50 0 0 ,抽提质粒 ,再次转入SL72 0 7,反复传代 ,鉴定核酸疫苗载体菌的稳定性。通过脂质体法将重组载体 pIRES ureB和pIRES ureB IL 2转染Cos 7细胞 ,SDS PAGE及Westernblot法检测表达蛋白的免疫性。结果　扩增出长约 1 70 0bp的ureB基因和 51 0bpIL 2 ,测序结果表明 ,扩增出的ureB基因与基因库H .pyloriureB序列一致 ,IL 2序列和小鼠的IL 2序列一致 ,PCR和酶切鉴定结果证实ureB和IL 2基因克隆入真核表达载体 pIRES ,并成功构建了稳定的幽门螺杆菌ureB和IL 2基因以减毒鼠伤寒沙门菌为载体的核酸疫苗 ,并且以Westernblot检测到特异性的相对分子质量 (Mr)为 6 6× 1 0 3的UreB蛋白     

Assessment of the cag pathogenicity island status of Helicobacter pylori infections with serology and PCR

The serological characterisation of Helicobacter pylori strains has been questioned, e.g., when the presence or absence of the cag pathogenicity island (PAI) is determined. This study compared CagA-reactive serum antibodies, assessed with immunoblot, with cag PAI status, as determined by PCR. CagA serology results were available for 101 individuals contributing 202 bacterial samples for cag PAI PCR. There was a high degree of correlation between the two methods (kappa coefficient, 0.82; 95% confidence interval, 0.68-0.97). Combined with suggested biological explanations for the discrepancies, this finding supports the application of well-evaluated serological assays in the assessment of the cag PAI status of H. pylori infections in clinical and epidemiological studies.     

implication of the structure of the Helicobacter pylori cag pathogenicity island in induction of interleukin-8 secretion

Helicobacter pylori virulence is associated with the presence of the cag pathogenicity island (PAI). The cag PAI is involved in the ability to induce interleukin-8 (IL-8) secretion by human cells, which is implicated in the inflammatory response of the gastric mucosa to H. pylori infection. The aim of this study was to determine whether the genetic structure of the cag PAI is conserved and whether it is linked to IL-8 induction ability. Detection of specific markers (cagA, picB, cag13-cag14, virD4, and IS605) by PCR and dot blot hybridization and long-distance PCR determination of the presence of cagI, cagII, and the middle region of the cag PAI were performed on 153 strains isolated from adults suffering from ulcers (n = 79) or gastritis (n = 74). IL-8 induction ability was evaluated by coculture of the strains with HEp-2 cells. Eighty-three strains (54.3%) had an entire cag PAI, 12 strains (7.8%) had the cag PAI split in two, 49 strains (32%) had no cag PAI, and 9 strains exhibited other structural combinations. The presence of an entire cag PAI was statistically correlated with the presence of IS605 (P = 0.006) and the ability to induce IL-8 secretion but not with clinical presentation of the infection. The structure of the cag PAI appears to be rather conserved and is related to the proinflammatory power of a strain. The existence of strains inducing IL-8 secretion regardless of the cag PAI structure suggests that this region is not the only requirement for IL-8 secretion.     

Genetic diversity in the Helicobacter pylori cag pathogenicity island and effect on expression of anti-CagA serum antibody in UK patients with dyspepsia

AIMS: To investigate variation within the cag pathogenicity island (PAI) of Helicobacter pylori isolated from patients with dyspepsia in mid-Essex, and to evaluate the effect on expression of anti-CagA antibody. METHODS: Sixty two isolates of H pylori cultured from gastric biopsies were screened by specific PCR assays for the presence of cagA and other gene markers (cagD and cagE, and virD4) in the cag PAI. An enzyme linked immunosorbent assay (ELISA) kit (Viva Diagnostica helicobacter p120) was used to test for anti-CagA IgG antibody in matching sera. Isolates were also genotyped by vacuolating cytotoxin polymerase chain reaction (PCR) analysis, and tested for absence of the complete cag PAI (empty site PCR assay). RESULTS: Forty one of the H pylori isolates had a cag PAI containing cagA. One strain had no cagA but other cag PAI loci were present, whereas the remaining 20 strains had no detectable cag PAI markers. Anti-CagA IgG antibody was detected in 34 sera by the ELISA assay, and when compared with the cag PAI genotype of the infecting strain, accuracy, sensitivity, and specificity were 92%, 87%, and 100%, respectively. The seven discrepant or borderline strains in the ELISA were all vacA s1 but differed in other genotypic markers. CONCLUSIONS: The cag PAI was widely distributed in H pylori from patients with dyspepsia in mid-Essex who had different gastric pathologies. Infection with a strain having an uninterrupted cag PAI was associated with the presence of anti-CagA antibody in most patients. Discrepant ELISA results, mostly for elderly patients with duodenal ulcers, were attributed to cagA associated variation, particularly to the presence of mixed cagA+/cagA- cell variants in the infecting strain population. Tests for anti-CagA serum antibody were unreliable for predicting severity of clinical disease associated with H pylori infection in this series of patients.     

Genomic Comparison of cag pathogenicity island (PAI)-positive and -negative Helicobacter pylori strains: identification of novel markers for cag PAI-positive strains

In an analysis of Helicobacter pylori genomic DNA by macroarray methodology, genomic DNA from a panel of cag pathogenicity island (PAI)-negative H. pylori clinical isolates failed to hybridize with 27 genes located outside the cag PAI in a cag PAI-positive reference strain. PCR analyses confirmed that HP0217 (encoding a lipopolysaccharide biosynthetic protein) and HP1079 (encoding a protein of unknown function) were present significantly more frequently in cagA-positive strains than in cagA-negative strains. A low G+C content of these two genes suggests they were acquired by horizontal transfer events.     

Epithelial Intestinal Cell Apoptosis Induced by Helicobacter pylori Depends on Expression of the cag Pathogenicity Island Phenotype

Helicobacter pylori has been shown to induce chronic active gastritis and peptic ulcer and may contribute to the development of duodenal ulcer. Previous studies have shown that H. pylori mediates apoptosis of gastric epithelial cells via a Fas-dependent pathway. However, evidence for the induction of such a mechanism in intestinal epithelial cells (IEC) by H. pylori infection has not been demonstrated yet. This study was performed (i) to ascertain that H. pylori can induce IEC apoptosis; (ii) to delineate the role of the cag pathogenicity island (PAI), cagE, and vacA gene products in this process; and (iii) to verify whether the Fas-dependent pathway is involved in this phenomenon. When T84 cells were exposed to VacA(+)/cag PAI(+) H. pylori strains (CCUG 17874 and 60190), they exhibited apoptosis hallmarks as assessed by morphological studies, as well as annexin V and 3,3'-dihexyloxacarbocyanine iodide staining. In contrast, few or no apoptotic features could be detected after incubation with an isogenic mutant of strain 60190 in which the cagE gene was disrupted (60190:C(-) strain) or with a VacA(-)/cag PAI(-) H. pylori strain (G21). In addition, activation of caspase-3 during infection with VacA(+)/cag PAI(+) H. pylori strains was inhibited by pretreatment of IEC with an antagonistic anti-Fas antibody (ZB4). Taken together, these findings indicate that H. pylori triggers apoptosis in IEC via a Fas-dependent pathway following a process that depends on the expression of the cag PAI.     

Characterization and immunogenicity of the CagF protein of the cag pathogenicity island of Helicobacter pylori

Helicobacter pylori infection causes severe gastroduodenal diseases in humans. Its virulence is strongly increased by the presence of the cag pathogenicity island (cag PAI). It has been shown that CagA, a major antigen in humans, is translocated to the host cell via a secretion system encoded by the cag PAI. The roles of many of the proteins encoded within the cag PAI are not known. Here we report on the cloning and expression of CagF, one of those proteins. We show that CagF is associated to the outer membrane of H. pylori G27 and that the protein is always expressed with electrophoretic mobility variations among the 20 strains tested here. We have also found that natural infection with H. pylori is able to induce antibodies against CagF.     

Distinct diversity of the cag pathogenicity island among Helicobacter pylori strains in Japan

The severity of Helicobacter pylori-related disease is correlated with the presence of a cag pathogenicity island (PAI). Genetic diversity within the cag PAI may have a modifying effect on the pathogenic potential of the infecting strain. We analyzed the complete cag PAI sequences of 11 representative Japanese strains according to their vacA genotypes and clinical effects and examined the relationship between the diversity of the cag PAI and clinical features. The cag PAI genes were divided into two major groups, a Western and a Japanese group, by phylogenetic analysis based on the entire cag PAI sequences. The predominant Japanese strains formed a Japanese cluster which was different from the cluster formed by Western strains. The diversity of the cag PAI was associated with the vacA and cagA genotypes. All strains with the s1c vacA genotype were in the Japanese cluster. In addition, all strains with the East Asian-type cagA genotype were also in the Japanese cluster. Patients infected with the Japanese-cluster strain had high-grade gastric mucosal atrophy. These results suggest that a distinct diversity of the cag PAI of H. pylori is present among Japanese strains and that this diversity may be involved in the development of atrophic gastritis and may increase the risk for gastric cancer.