表达幽门螺杆菌粘附素保守区的减毒鼠伤寒沙门菌免疫治疗作用的研究

探讨表达幽门螺杆菌（Helicobacter pylori,Hp）粘附素保守区（AB）的减毒鼠伤寒沙门菌X4072（pYA248-AB）的免疫治疗效果,以及可能的免疫治疗机制,以确定X4072（pYA248-AB）在Hp疫苗研制中的应用价值.建立Hp感染小鼠模型,在该模型中评价X4072（pYA248-AB）治疗Hp感染的效果,运用细菌培养法观察Hp根除率及定植量的改变,流式细胞术分析免疫后小鼠脾细胞亚型,IL-2和IL-4细胞依赖株的细胞测活法检测细胞因子,ELISA法检测小鼠血清及肠液中抗AB抗体产生情况.结果表明,免疫治疗后疫苗治疗组根除率为53.3%,显著高于X4072（pYA248）和PBS对照组（P＜0.01）.未根除Hp的小鼠,疫苗治疗组Hp的定植密度明显低于其他两组（P＜0.01）.应用流式细胞仪分析免疫小鼠脾CD4⁺/CD8⁺ T淋巴细胞的比值时,发现疫苗治疗组和鼠伤寒菌对照组的比值均显著高于PBS对照组（P＜0.05）,而疫苗治疗组的比值又显著高于鼠伤寒菌对照组（P＜0.05）.进一步对细胞因子进行分析发现,与PBS对照组相比免疫治疗组和鼠伤寒菌对照组IL-2和IL-4明显升高(P＜0.05).同时,免疫治疗组与鼠伤寒菌对照组相比,IL-4增高明显(P＜0.05).针对AB的抗体测定结果发现,仅在免疫治疗组的小鼠肠液中检测到了IgA抗体.免疫治疗组IgG抗体滴度较其他两组明显升高,第二次加强免疫后2周即上升至1∶10 000.动物实验表明,X4072（pYA248-AB）能根除或显著降低Hp在小鼠胃内的定植,其可能的免疫治疗机制包括提高CD4⁺/CD8⁺比值,诱导Th1和Th2反应以及产生针对AB的特异性抗体.     

宋内I相抗原和霍乱CT—B共表达的免疫保护效果观察

将编码宋内氏痢疾菌(Shigella sonnei)l相O抗原的基因和霍乱弧菌(Vibrio cholerae)的CT—B基因克隆至带asd基因的质粒PYA248．得重组质粒PMGLl05。将该重组质粒转入asd基因缺失的减毒伤寒沙门氏茵X4072．构成了一个不带抗药性基因的载体-宿主平衡致死景统。一系列实验表明．该重组苗X4072(PMGLl05)能稳定地表达宋内I相O抗原和霍乱弧菌的CT-B抗原．小鼠免疫保护实验表明,该重组菌对有毒的宋内氏I相痢疾杆菌及霍乱弧菌的攻击均具有良好保护作用。     

鼠伤寒沙门氏菌asd基因的克隆及序列分析

以鼠伤寒沙门氏茵标准株基因组DNA作为模板,用PCR的方法扩增鼠伤寒沙门氏菌的asd基因并克隆入质粒pUCl9,并对其进行测序,序列与献报道一致。同时将质粒pYA248上的链球菌asd基因进行了置换,观察了分别含有链球菌asd基因与鼠伤寒沙门氏菌asd基因的质粒在减毒鼠伤寒沙门氏菌X4072中的生长情况,结果表明含有鼠伤寒沙门氏菌的asd基因的高拷贝质粒pUCl9的菌株生长情况更好。为完善染色体／质粒平衡致死系统,构建减毒鼠伤寒沙门氏活菌疫苗奠定了基础。     

表达大肠杆菌LT-B/ST融合抗原的减毒鼠伤寒沙门氏菌株的构建

编码LT-B/ST融合抗原的基因插入pYA248载体中,构建了重组质粒pXZL66。该重组质粒转入无毒鼠伤寒沙门氏菌SR-11,ΔCya,Δcrp,Δasd菌株X4072。此无抗药性的杂合菌株X4072(pXZL66)表达的LT-B/ST融合抗原具有LT和ST抗原性而没有生物毒性,可望成为预防ETEC腹泻和相应的沙门氏菌病双价口服活疫苗候选株。     

表达乙型脑炎病毒E蛋白重组减毒沙门菌活载体疫苗株的构建

目的:构建表达乙型脑炎病毒(JEV)E蛋白的口服重组减毒鼠伤寒沙门菌活载体疫苗株。方法:克隆JEV E基因,将其插入表达载体pYA3341中,构建重组质粒pYA3341-E,将重组质粒电转入鼠伤寒沙门菌疫苗株X4550(缺失asd、cya、crp基因),获得重组疫苗菌株X4550(pYA3341-E);鉴定重组菌E蛋白的表达,测定重组菌的稳定性、生长曲线、安全性,以及小鼠的免疫试验和血清中和试验。结果:酶切鉴定和序列测定证实重组质粒构建成功;SDS-PAGE检测有目的蛋白条带;Western印迹证实表达的E蛋白能与猪抗JEV阳性血清特异性结合;重组菌株在体外营养选择压力下,可稳定地携带重组质粒传代繁殖,在体内可较稳定地定居于肠系膜淋巴结和脾脏;小鼠口服试验证实重组菌无毒性作用,安全可靠;小鼠口服重组菌免疫,ELISA检测产生了抗JEV抗体;中和试验表明产生的抗体具有中和活性。结论:构建了能稳定表达JEV E蛋白的口服减毒鼠伤寒沙门菌疫苗株X4550(pYA3341-E),为研究乙型脑炎口服基因工程疫苗奠定基础。     

减毒鼠伤寒沙门菌三型分泌表达系统的构建及其特性

为开发新型重组减毒鼠伤寒沙门菌口服活疫苗载体,本研究以pYA3493质粒为基础,用鼠伤寒沙门菌sopE_(Nt100)基因及其启动子替代原有的P_(trc)启动子,构建沙门菌三型分泌表达载体pYA-sopE_(Nt100);再将质粒pYA-sopE_(Nt100)电转入沙门菌ΔcrpΔasd SL1344,构建减毒鼠伤寒沙门菌ΔcrpΔasd SL1344(p YA-sop E_(Nt100))三型分泌表达系统,研究其生物学特性,进一步将报告基因egfp克隆入sop E基因下游,构建重组菌株ΔcrpΔasd SL1344(p YA-sop E_(Nt100)-egfp),感染Vero细胞,用Western blotting分析该系统递呈外源抗原的能力。PCR、酶切及测序结果表明,减毒鼠伤寒沙门菌ΔcrpΔasd SL1344(p YA-sop E_(Nt100))三型分泌表达系统构建成功;生物学特性鉴定结果表明,其血清型与亲本株Δcrp SL1344及野生株SL1344保持一致;其生化特性与亲本株基本相近,但与野毒株相比发生明显变化;生长速度也更为缓慢;重组菌株ΔcrpΔasd SL1344(p YA-sop E_(Nt100))的LD50较野生株SL1344降低了7.0×104倍;Western blotting结果发现,重组菌培养上清中能检测到Sop E_(Nt100)-egfp融合蛋白(37 k Da);重组菌株感染Vero细胞后,可以同时检测到Sop E_(Nt100)-egfp融合蛋白(37 k Da)和EGFP蛋白(27 k Da)。以上结果证实,本研究成功构建了新型减毒鼠伤寒沙门菌ΔcrpΔasd(p YA-sop E_(Nt100))三型分泌表达系统,其能够有效递呈外源抗原,该重组菌株有潜力作为安全、稳定、高效表达外源基因的口服重组活疫苗载体。     

表达霍乱CT-B和LPS-O抗原的鼠伤寒菌苗株的构建

编码霍乱CT—B和LPSO抗原的基因与载体质粒pYA248重组后,转入△cya△crp △ asd减毒鼠伤寒疫苗株x4072,构建成无药物抗性、带双价抗原的工程菌株x4072(pMG306)。该菌株能分泌表达特异的霍乱CTB抗原,并且在菌体表面同时表达霍乱和鼠伤寒的。抗原。小鼠腹腔免疫和攻击试验表明该菌苗株对霍乱毒株的攻击具有良好的保护作用。本研究为新型霍乱／鼠伤寒双价口服活疫苗的构建打下了基础。     

鼠伤寒沙门菌SL1344株环化腺苷酸合成酶缺失株平衡致死系统的构建及其雏鸡免疫保护试验

摘要:【目的】为构建鼠伤寒沙门菌环化腺苷酸合成酶缺失株平衡致死系统,并对其生物学特性进行检测。【方法】以鼠伤寒沙门菌SL1344Δcya株为亲本株,利用重组自杀性质粒(pREΔasd)介导的同源重组技术,经两步法缺失并筛选asd基因缺失株(SL1344Δcya Δasd)。将含asd基因且无抗性的pYA3493质粒电转化至缺失株SL1344ΔcyaΔasd,构建重组菌株SL1344ΔcyaΔasd (pYA3493)。【结果】试验结果表明,重组菌株SL1344ΔcyaΔasd(pYA3493)生化特性和生长速度与参考株SL1344相比差异较大,与亲本株SL1344Δcya基本一致,SL1344ΔcyaΔasd(pYA3493)失去了利用麦芽糖、乳糖、山梨醇等碳源的能力,也不能分解H2 S、半乳糖和鼠李糖,但仍保留了利用葡萄糖的能力。对1日龄雏鸡攻毒试验表明,SL1344ΔcyaΔasd(pYA3493)毒力较参考株SL1344降低了约104倍。免疫保护试验显示,1日龄雏鸡免疫SL1344ΔcyaΔasd(pYA3493)后第17天,利用鼠伤寒沙门菌参考株攻毒,保护率为62.5%。【结论】鼠伤寒沙门菌SL1344株环化腺苷酸合成酶缺失株平衡致死系统构建成功,且具有较好的免疫保护性,为深入研究以鼠伤寒沙门菌为载体的口服疫苗奠定基础。     

携带HCV核心蛋白原核表达质粒与真核表达质粒的减毒伤寒沙门菌诱导小鼠免疫应答之比较

丙型肝炎病毒（HCV）核心蛋白是丙肝疫苗的重要候选抗原,然而,该蛋白因具有免疫调控作用而影响免疫应答的诱导。构建了HCV核心蛋白的两种表达质粒,一种是体内激活型原核表达质粒pZW-C,另一种是真核表达质粒pCI-C。将该两种质粒转化减毒鼠伤寒沙门菌SL7207,得到重组菌SL7207/pZW-C和SL7207/pCI-C,分别将重组菌口服接种小鼠,检测小鼠的免疫应答,结果发现：① SL7207/pCI-C免疫鼠的CD3⁺CD4⁺ T细胞持续降低,而SL7207/pZW-C免疫鼠的CD3⁺CD4⁺ T细胞无明显改变;② SL7207/pCI-C免疫只诱导低水平抗HCV核心蛋白抗体,加强免疫对抗体阳转率及抗体水平无明显影响,而SL7207/pZW-C免疫组所有小鼠均产生较高水平的抗核心蛋白抗体。③ SL7207/pCI-C免疫鼠脾细胞的体外增殖活性、细胞毒性T细胞活性以及加强免疫对细胞免疫应答的增强作用均明显不及SL7207/pZW-C免疫鼠。结果提示：携带真核表达质粒pCI-C的沙门菌因在小鼠细胞内表达天然形式（结构以及磷酸化修饰）的HCV核心蛋白,可能通过对T细胞的免疫抑制作用而弱化免疫应答。而以携带原核表达质粒pZW-C的沙门菌免疫可避免这一问题,并具有接种方便,成本低廉等优点,从而可望作为基于HCV核心蛋白为靶抗原的HCV疫苗的候选免疫方式。     

宋内Ⅰ相抗原和霍乱CT-B共表达的免疫保护效果观察

将编码宋内氏痢疾菌(Shigella sonnei)I相O抗原的基因和霍乱弧菌(Vibrio choler-ae)的CT-B基因克隆至带asd基因的质粒PYA248,得重组质粒PMGL105。将该重组质粒转入asd基因缺失的减毒伤寒沙门氏菌X4072,构成了一个不带抗药性基因的载体-宿主平衡致死系统。一系列实验表明,该重组菌X4072(PMGL105)能稳定地表达宋内I相O抗原和霍乱弧菌的CT-B抗原。小鼠免疫保护实验表明,该重组菌对有毒的宋内氏I相痢疾杆菌及霍乱弧菌的攻击均具有良好保护作用。     

霍乱毒素B亚单位基因在鼠伤寒沙门氏菌中的表达

本工作成功地将霍乱毒素B亚单位(ctx B)基因插入到带有天门冬氨酸β-半醛脱氢酶基困(asd+)的pYAZ48质粒中,并将它转化至天门冬氨酸β-半醛脱氢酶突变(asd-)鼠伤寒沙门氏菌中。实验结果表明,ctx B亚单位基因能在鼠伤寒沙门氏菌中高效表达,并且表达的蛋白能分泌到细胞外。动物实验结果也表明：该疫苗菌株能在肠粘膜细胞定居;口服及全身免疫均能产生较高的抗体,并能增强动物细胞的免疫功能;对伤寒、霍乱有毒株的攻击有良好的保护效果。该系统的应用为疫苗基因工程提供了一个新的途径。     

伤寒─鼠伤寒重组株Vi4072在小鼠中定居及血清学效果观察试验

以伤寒─鼠伤寒双价重组株Ｖｉ４０７２的３×１０８ＣＦＵ一次口服感染ＢＡＬＢ／Ｃ小鼠,４天后即可从小鼠的集合淋巴结、肝、脾中分离到该菌,４９天后该菌始被小鼠机体彻底清除。血清和小肠匀浆液中Ｖｉ抗体检测结果证明Ｖｉ４０７２菌株有刺激特异性免疫应答的功能。血清、小肠匀浆液中Ｖｉ抗体明显升高。     

伤寒─鼠伤寒重组株Vi4072在小鼠中定居及血清学效果观察试验

以伤寒─鼠伤寒双价重组株Ｖｉ４０７２的３×１０８ＣＦＵ一次口服感染ＢＡＬＢ／Ｃ小鼠,４天后即可从小鼠的集合淋巴结、肝、脾中分离到该菌,４９天后该菌始被小鼠机体彻底清除。血清和小肠匀浆液中Ｖｉ抗体检测结果证明Ｖｉ４０７２菌株有刺激特异性免疫应答的功能。血清、小肠匀浆液中Ｖｉ抗体明显升高。     

Development of a protein secretion system with the application of sec-dependent protein secretion components

In order to induce high levels of protein secretion, we have constructed a recombinant plasmid, designated pBP244, into which was incorporated key components of the type-II Sec-dependent secretion system, including LepB (signal peptidase), SecA (ATPase), and SecB (chaperone). The biological activities of the LepB, SecA, and SecB components expressed from genes harbored by pBP244 appeared to play their normal roles. In order to evaluate the protein secretion, a pspA (Streptococcus pneumoniae surface protein A) gene was cloned into pBP244, resulting in pBP438. S. typhimurium harboring pBP438 grown until the stationary phase, secreted a higher level of PspA into the culture supernatants than did the strain harboring pYA3494. The strain harboring pBP438 secreted a supernatant amount 1.71-fold, a periplasmic space amount 1.47-fold, and an outer membrane amount 1.49-fold higher than that of pYA3494. S. typhimurium chi8554 kept the Asd+ plasmid pBP244 and pBP438 for 60 generations in LB broth harboring DAP, thereby indicating that pBP244 and pBP438 were quite stable in the Salmonella strain.     

Removal of antibiotic resistance of live vaccine strain Escherichia coli MM-3 and evaluation of the immunogenicity of the new strain

MM-3 was a live vaccine strain candidate for protecting neonatal piglets from diarrhea.Designed in the 1980s,a high degree of protection from colibacillosis was afforded to piglets in a challengestudy and field trials.However MM-3 had a drawback of carrying the antibiotic resistance gene (chloramphenicolacetyltransferase gene,cat).The introduction of a host-plasmid balanced lethal system into the vaccine wasa good idea to solve the problem.The λ-Red recombination system was adopted in this study to realize thereplacement of cat by aspartate-semialdehyde dehydrogenase gene (asd) in the plasmid pMM085.The newplasmid named pMMASD was introduced into an Escherichia coli strain χ6097 and Salmonella typhimuriumχ4072 where the asd gene had been knocked out in their chromosomes.Cultured in an Erlenmeyer flask,expression levels of two antigens K88ac fimbriae and heat-labile enterotoxin B subunit (LTB) in cell lysatewere similar among MM-3,χ4072(pMMASD) and χ6097(pMMASD).However,χ4072(pMMASD) possessedthe more effective secretion mechanism to transport LTB enterotoxin into culture liquid.The relatively higherstability of pMMASD in Salmonella typhimurium χ4072 than that of pMM085 in MM-3 was determined bothin vitro in the absence of selective pressure,and in vivo following oral inoculation.Oral immunization ofBALB/c mice with χ4072(pMMASD) or χ6097(pMMASD) was sufficient to elicit IgA responses in mucosaltissues as well as systemic IgG antibody responses to the K88 fimbriae,while MM-3 failed to elicit specificantibody responses to K88 fimbriae in mucosal tissues.Among three live strains,only χ4072(pMMASD)could develop strong humoral responses against LTB enterotoxin.The results suggest that χ4072(pMMASD)is expected to be a promising live vaccine strain.     

Immune responses dependent on antigen location in recombinant attenuated Salmonella typhimurium vaccines following oral immunization

The subcellular location of a recombinant antigen in recombinant attenuated Salmonella vaccines may influence immunogenicity dependent on exposure of the recombinant antigen to cells involved in systemic immune responses. It has been shown that a recombinant attenuated Salmonella vaccine secreting the recombinant Streptococcus pneumoniae PspA (rPspA) antigen specified by pYA3494 induced protective anti-rPspA-specific immune responses (Kang et al. (2002) Infect. Immun. 70, 1739-1749). A recombinant plasmid pYA3496 specifying a His(6)-tagged rPspA (His(6)-rPspA) protein (no apparent signal sequence) caused the rPspA antigen to localize to the cytoplasm of Salmonella. Salmonella vaccines carrying pYA3494 or pYA3496 expressed similar amounts of rPspA. After a single oral immunization in BALB/c mice with 10(9) colony-forming units (CFU) of the recombinant Salmonella vaccines carrying pYA3494 or pYA3496, IgG antibody responses were stimulated to both rPspA and Salmonella lipopolysaccharide (LPS) antigens. The anti-rPspA IgG titer induced by Salmonella carrying pYA3494 (1.9 x 10(7)) was 10(4) times higher than induced by Salmonella carrying pYA3496 (<2.4 x 10(3)).