Vaccines against gastroenteritis,current progress and challenges

ABSTRACT

Enteric viral and bacterial infections continue to be a leading cause of mortality and morbidity in young children in low-income and middle-income countries, the elderly, and immunocompromised individuals. Vaccines are considered an effective and practical preventive approach against the predominantly fecal-to-oral transmitted gastroenteritis particularly in the resource-limited countries or regions where implementation of sanitation systems and supply of safe drinking water are not quickly achievable. While vaccines are available for a few enteric pathogens including rotavirus and cholera, there are no vaccines licensed for many other enteric viral and bacterial pathogens. Challenges in enteric vaccine development include immunological heterogeneity among pathogen strains or isolates, a lack of animal challenge models to evaluate vaccine candidacy, undefined host immune correlates to protection, and a low protective efficacy among young children in endemic regions. In this article, we briefly updated the progress and challenges in vaccines and vaccine development for the leading enteric viral and bacterial pathogens including rotavirus, human calicivirus, Shigella, enterotoxigenic Escherichia coli (ETEC), cholera, nontyphoidal Salmonella, and Campylobacter, and introduced a novel epitope- and structure-based vaccinology platform known as MEFA (multiepitope fusion antigen) and the application of MEFA for developing broadly protective multivalent vaccines against heterogenous pathogens.     

3CL hydrolase-based multiepitope peptide vaccine against SARS-CoV-2 using immunoinformatics

The present study provides the first multiepitope vaccine construct using the 3CL hydrolase protein of SARS-CoV-2. The coronavirus 3CL hydrolase (Mpro) enzyme is essential for proteolytic maturation of the virus. This study was based on immunoinformatics and structural vaccinology strategies. The design of the multiepitope vaccine was built using helper T-cell and cytotoxic T-cell epitopes from the 3CL hydrolase protein along with an adjuvant to enhance immune response; these are joined to each other by short peptide linkers. The vaccine also carries potential B-cell linear epitope regions, B-cell discontinuous epitopes, and interferon-γ-inducing epitopes. Epitopes of the constructed multiepitope vaccine were found to be antigenic, nonallergic, nontoxic, and covering large human populations worldwide. The vaccine construct was modeled, validated, and refined by different programs to achieve a high-quality three-dimensional structure. The resulting high-quality model was applied for conformational B-cell epitope selection and docking analyses with toll-like receptor-3 for understanding the capability of the vaccine to elicit an immune response. In silico cloning and codon adaptation were also performed with the pET-19b plasmid vector. The designed multiepitope peptide vaccine may prompt the development of a vaccine to control SARS-CoV-2 infection.     

弓形虫多表位基因重组抗原在弓形虫免疫检测中的应用

目的评价弓形虫多表位基因重组抗原在弓形虫感染诊断中的效果,探索多表位抗原在弓形虫免疫检测中的应用前景。方法以Ni-NTA Agarose和割胶电渗两步纯化法,获取弓形虫多表位基因的原核表达纯化产物rMAG,以适宜浓度的rMAG包被ELISA微孔板,分别检测弓形虫急性和慢性感染血清,评价试剂盒检测的敏感性和特异性。结果经Ni-NTAAgarose和割胶纯化,得到了纯度为95.86%的弓形虫多表位重组可溶性抗原。以3!g/ml的抗原浓度包被ELISA微孔板,对兔和小鼠的急慢性弓形虫感染血清进行了检测。结果检测小鼠血清141份,其中慢性感染弓形虫小鼠血清117份、正常小鼠血清24份,检测体系的敏感性为88.88%,特异性为91.67%,一致性为89.36%。检测兔血清24份,其中急性感染弓形虫兔血清18份,正常兔血清6份,阳性血清检出率为94.4%,总一致性为91.5%。结论以弓形虫多表位重组抗原构建的ELISA试剂盒既可以检测弓形虫急性感染血清,又可以检测弓形虫慢性感染血清,具有一定的应用前景。     

弓形虫多表位基因植物表达载体的构建

目的构建弓形虫多表位基因(TGMG)植物表达载体。方法①将TGMG亚克隆人pBAC55构建中间载体pB35MG,再将其中E35S/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pC35MG。②将番茄果实特异性启动子E81.1插入pB35MG构建中间载体pB35E1MG,再将其中E35SE81.1/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pC35E1MG。③将番茄果实特异性启动子E82.2插入pB35MG构建中间载体pBE2MG,再将其中E82.2/TGMG/NOS3′结构单元亚克隆人pCAMBIA2300构建植物表达载体pCE2MG。测序鉴定pB35MG、pC35E1MG、pCE2MG中的TGMG序列。④pC35MG、pC35E1MG、pCE2MG转化根癌农杆菌LBA404。结果重组质粒用酶切鉴定均得到预期片段,pB35MG、pC35E1MG、pCE2MG测序结果正确。结论成功构建TGMG中间载体pB35MG、pB35E1MG、pBE2MG,以及植物表达载体pC35MG、pC35E1MG、pCE2MG。并将3种植物表达载体导入根癌农杆菌。     

具有免疫反应性的弓形虫多表位抗原在大肠杆菌中的可溶性表达和鉴定

目的 获得弓形虫多表位基因在原核系统中可溶性表达产物,为弓形虫病重组抗原试剂盒的制备及疫苗的研究奠定基础.方法 以PCR法扩增弓形虫多表位基因,使其两端带有与载体pET2a相匹配的酶切位点,插入载体pET2a,酶切并测序鉴定后,转入大肠杆菌BL21(DE),以IPTG进行诱导,SDS-PAGE分析和鉴定该基因的表达水平、表达产物的可溶性及其相对分子质量,Western-blot分析表达产物的免疫反应性.结果 该基因在原核表达系统中经诱导,得到了M_r1000的可溶性融合表达产物.经Ni-NTA纯化,纯度可达90%以上.免疫印迹实验表明该产物能够被弓形虫B6感染的小鼠血清和弓形虫RH感染的兔血清特异识别.结论 弓形虫多表位基因在原核中的可溶性表达产物在弓形虫病诊断及疫苗研究中有潜在的应用价值.     

HBc与HBV多表位复合基因在肝癌细胞中的转染与表达

目的 观察HBc与HBV多表位复合基因在肝癌细胞株HepG2细胞内表达情况。方法 将构建的HBc与HBV多表位复合基因真核表达质粒pHBcMep以Lipofectamine介导转染HepG2细胞，通过间接免疫荧光、Western-blot检测表达产物。结果 经G418筛选的阳性转染细胞经间接免疫荧光染色后在紫外光激发时发出明显的荧光，而末转染质粒或转染pcDNA3．1的HepG2细胞则无明显荧光。Western-bot结果显示表达产物约为33kDa，并能与抗preS2多抗特异性结合。结论 HBc与HBV多表位复合基因在肝癌细胞内获得正确表达。     

HBV多表位复合基因在NS-1细胞的表达

目的 研究HB4颗粒为呈现载体的阳V多表垃复合基因在哺乳动物细胞NS-l内的表达。方法 PCR扩增HBc 1-72aa及93-183aa编码序列并合成HBV多表位复合基因，定向克隆至pcDNA3．1( )。经双酶切及核苷酸序列测定等方法筛选阳性克隆。阳性质粒以Lipofetamine介导转染NS-l细胞，通过ELISA及间接免疫荧光等方法检侧细胞表达产物。结果 双酶切及测序结果证实阳性质粒正确克隆了约890bp的HBc与HBV多表位复合基因的杂合基因。重组于成功转染NS-l细胞并表达HBc-Mep融合蛋白。结论 HBc颗粒为呈现载体的HBV多表位复合基因在哺乳动物细胞NS-l内正确表达目的蛋白。为研究pHBc-Mep作为DNA疫苗的免疫活性奠定基础。为后期检测核酸疫苗pHBcMep的细胞免疫效果提供靶细胞。     

多表位融合抗原检测结核分枝杆菌抗体的应用价值

目的应用由基因重组表达的结核分枝杆菌多表位融合抗原检测血清或血浆中的结核抗体,评价其在结核病快速诊断中的价值。方法用酶免法分别对361例结核病人和288例非结核病人的血清标本进行检测。结果肺结核患者结核抗体的阳性率显著高于非结核患者。结论本试剂盒的敏感性为70.4%,特异性为84.9%。即血清结核抗体的检测对结核病的诊断和鉴别具有一定的临床价值。     

重组结核分枝杆菌多表位肽的免疫原性研究

目的探讨纯化的重组结核分枝杆菌多表位肽激发细胞毒性T淋巴细胞(Cytotoxic Tlymphocyte,CTL)免疫应答的能力,为新型结核疫苗的设计打下基础。方法通过细胞增殖和细胞毒性实验,研究纯化的重组表达多表位肽刺激外周血单个核细胞(PBMC)产生的增殖反应和细胞毒活性,初步鉴定重组多表位肽的免疫原性。结果以刺激系数(SI)>3为界,多表位肽(10μmol)能刺激全部10例HLA-A*0201阳性(A2+)结核菌素阳性(PPD+)健康个体的PBMC发生增殖,SI为46.2±5.6;增殖反应明显高于单肽(平均SI为10.2±2.3)以及PPD(平均SI为15.6±3.6)引起的细胞增殖反应(P<0.01)。在多表位肽诱导的CTL细胞毒活性分析中以负载抗原肽(10μmol)的T2细胞作为靶细胞,多表位肽诱导的CTL作为效应细胞,多表位肽能诱导全部的10例A2+PPD+健康个体中CTL杀伤活性,平均活性分别为(86.2±9.6%),显著高于单肽[平均为(25.4±3.6)%]和PPD[平均为(22.6±2.8)%](P<0.01)。结论重组优化多表位肽在细胞水平具有较好的免疫原性,能有效刺激PBMC产生细胞增殖反应和细胞毒活性。     

Antibodies derived from an enterotoxigenic Escherichia coli (ETEC) adhesin tip MEFA (multiepitope fusion antigen) against adherence of nine ETEC adhesins: CFA/I,CS1, CS2, CS3, CS4, CS5, CS6, CS21 and EtpA

Diarrhea continues to be a leading cause of death in children younger than 5 years in developing countries. Enterotoxigenic Escherichia coli (ETEC) is a leading bacterial cause of children's diarrhea and travelers’ diarrhea. ETEC bacteria initiate diarrheal disease by attaching to host receptors at epithelial cells and colonizing in small intestine. Therefore, preventing ETEC attachment has been considered the first line of defense against ETEC diarrhea. However, developing vaccines effectively against ETEC bacterial attachment encounters challenge because ETEC strains produce over 23 immunologically heterogeneous adhesins. In this study, we applied MEFA (multiepitope fusion antigen) approach to integrate epitopes from adhesin tips or adhesive subunits of CFA/I, CS1, CS2, CS3, CS4, CS5, CS6, CS21 and EtpA adhesins and to construct an adhesin tip MEFA peptide. We then examined immunogenicity of this tip MEFA in mouse immunization, and assessed potential application of this tip MEFA for ETEC vaccine development. Data showed that mice intraperitoneally immunized with this adhesin tip MEFA developed IgG antibody responses to all nine ETEC adhesins. Moreover, ETEC and E. coli bacteria expressing these nine adhesins, after incubation with serum of the immunized mice, exhibited significant reduction in attachment to Caco-2 cells. These results indicated that anti-adhesin antibodies induced by this adhesin tip MEFA blocked adherence of the most important ETEC adhesins, suggesting this multivalent tip MEFA may be useful for developing a broadly protective anti-adhesin vaccine against ETEC diarrhea.