产肠毒素大肠杆菌混合载体疫苗的免疫原性评价

本研究在构建表达ETEC菌毛抗原CFA/I、CS6和CS3、融合肠毒素LTB/STm的混合活载体疫苗的基础上 ,以两株福氏志贺载体疫苗 ,同等剂量相混合进行免疫。通过口服免疫 ,该混合多价活疫苗能够诱导机体产生相应的抗ETEC特异的血清和黏膜抗原抗体反应 ,达到了与各单独疫苗株一致的免疫效果 ,同时保持了载体志贺菌自身的免疫原性。     

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.     

致泻大肠埃希菌实验室检测工作的探讨与分析

致泻大肠埃希菌引发的肠道感染疾病越来越多，在肠道病原菌中所占比重已超过志贺菌成为最常见的腹泻病原菌。近年来，嘉兴市陆续出现了多起由该菌引起的食物中毒和门诊病例，2002年本市所辖某县检出了一例由O157：H7（EHEC）引起的病例，2005年在本市食物中毒和门诊病例的腹泻病人标本中陆续检出3株与腹泻有关的O125：K70（EPEC）、O164：K？（EIEC）、O25：K19（ETEC），这引起了笔者的高度重视。为了更好地认识致泻大肠埃希菌的生物学特性，整理了检测工作中的记录，查阅了相关资料，并结合工作体会，从实验室角度对致泻大肠埃希菌的检测工作及其注意事项作了分析与探讨。     

Studies on the etiologic agents of infantile diarrhea in Riyadh

Rectal swabs from children, aged from 1 month to 5 yr with diarrhea brought to the outpatient clinic of the Children Hospital, Riyadh, Kingdom of Saudi Arabia were examined for the presence of common enteric pathogens both bacterial and viral. Important diarrheal pathogens were isolated from 30·6 per cent of the children. Rotavirus was detected from 16·7 per cent of the patients followed by EPEC 5·5 per cent, ETEC 4·6 per cent and Shigella sp. 3·7 per cent. No organism of Salmonella group was found in this group of children. Rotavirus was predominant in age groups between 1 month to 2 yr. Antibiotic resistance were less common in pathogenic bacteria but more prominent in the non pathogenic Esch. coli isolated from the stool. Fifty four of the Esch coli were resistant to 4–6 commonly used antibiotics such as tetracycline, ampicillin, chloramphenicol, kanamycin, streptomycin and cotrimoxazole. This high incidence of multiple resistance in the population may be attributed to indiscriminate use of antibiotics.     

肠毒素大肠杆菌LTh－STIb二价基因探针的克隆及其应用研究

在肠毒素大肠杆菌（ＥＴＥＣ）ＬＴｈ－ＳＴＩａ－ＳＴＩｂ三价基因探针的基础上，用限制性内切酶ＥｃｏＲｌ酶切，回收片段．重新构建ＬＴｈ－ＳＴＩｂ二价基因探针的克隆株。用辣根过氧化物酶复合物（ＨＲＰ）直接标记二价基因探针，建立了增强型化学发光反应（ＥＣＬ）检测ＥＴＥＣ的方法．其敏感性可测到０．１ｐｇ的质粒ＤＮＡ或由１０个菌体培养而来的ＥＴＥＣ细胞，与同位素标记杂交方法的敏感性一致．且此探针仅与产ＳＴＩｂ、ＬＴｈ肠毒素的人源性ＥＴＥＣ菌株杂交，与ＳＴＩａ肠毒素菌株及其它非ＥＴＥＣ菌株均无杂交信号．该探针与三价探针及ＬＴｈ单价探针联合使用，能间接将ＬＴｈ、ＳＴＩａ和ＳＴＩｂ３种肠毒素分型。结果表明该方法简便快速、特异敏感，无放射性污染，是ＥＴＥＣ实验室诊断及分子流行病学调查的有效工具。     

Outbreaks of cholera-like diarrhoea caused by enterotoxigenic Escherichia coli in the Brazilian Amazon Rainforest

The relationship between enteropathogens and severe diarrhoea in the Brazilian Amazon is poorly understood. In 1998, outbreaks of acute diarrhoea clinically diagnosed as cholera occurred in two small villages localized far from the main cholera route in the Brazilian rainforest. PCR was performed on some enteropathogens and heat-labile (LT) and/or heat-stable (STh) toxin genes, the virulence determinants of enterotoxigenic Escherichia coli (ETEC), were detected. Further characterization of ETEC isolates revealed the presence of two clones, one from each outbreak. One presenting serotype O167:H5 harboured LT-I and STh toxin genes and expressed the CS5CS6 colonization factor. The other, a non-typeable serotype, was positive for the LT-I gene and expressed the CS7 colonization factor. The current study demonstrates the importance of molecular diagnosis in regions such as the Amazon basin, where the enormous distances and local support conditions make standard laboratory diagnosis difficult. Here we also show that the mis-identified cholera cases were in fact associated with ETEC strains. This is the first report of ETEC, molecularly characterized as the aetiological agent of severe diarrhoea in children and adults in the Brazilian Amazon Rainforest.     

Clonal clustering and colonization factors among thermolabile and porcine thermostable enterotoxin-producing Escherichia coli

A considerable proportion of enterotoxigenic Escherichia coli (ETEC) do not possess identifiable colonization factors (CFs). Genetic fingerprint analyses based on repetitive sequence-based polymerase chain reaction (rep-PCR) showed that 9 of 10 such CF-negative isolates which produced the thermolabile and the porcine thermostabile enterotoxin could be divided into three clusters. Following transformation with a plasmid harbouring the gene encoding CfaR, a positive regulator for several ETEC adhesins, three of the six strains in the first cluster expressed coli surface antigen 20 (CS20). No CFs were identified on the two transformed strains in the second cluster while the transformants of the two strains in the last cluster expressed CS12, the N-terminal amino acid sequence of which was deciphered. The study illustrates the potential of using genetic fingerprinting to group ETEC into clusters of strains with genes encoding different CFs and confirms the ability of CfaR to induce the expression of several different CFs.     

The way forward for ETEC controlled human infection models (CHIMs)

In the absence of good animal models, Controlled Human Infection Models (CHIMs) are useful to assess efficacy of new vaccine candidates against Enterotoxic Escherichia coli (ETEC), as well as other preventive or therapeutic interventions. At the 2018 Vaccines Against Shigella and ETEC (VASE) conference, a workshop was held to further review and discuss new challenge model developments and key issues related to further model standardization. During the workshop, invited speakers briefly summarized for attendees recent developments and main agenda issues before workshop participants were divided into four groups for more focused discussions.The main issues discussed were: (1) whether there is a need for more ETEC strains to test a diversity of vaccine candidates, and if so, what criteria/qualities are desirable in strain selection; (2) how ETEC CHIMs could be more standardized to better support ETEC vaccine development; (3) how volunteer selection criteria and screening should be performed, and; (4) how an expanded sample collection schema and collaborative analysis plan may facilitate a more in-depth assessment of the role of antigen-specific humoral and cellular immune responses in ETEC infection, and provide better insights into ETEC pathogenesis and correlates of protection.The workshop concluded that additional challenge strains may need to be developed to better support new vaccines and therapeutics that are advancing in the development pipeline. In this regard, the need for a well characterized ST-only expressing ETEC strain was highlighted as a priority given that promising new heat stable toxoid based vaccine candidates are on the horizon. In addition, further standardization of the ETEC CHIMs was strongly encouraged, noting that it may not be realistic to standardize across all strains. Also, intensified volunteer screening may result in higher attack rates, although more stringent eligibility criteria may contribute to a more limited application of the model and diminish its representativeness. Finally, a sampling schedule and priority list for minimum set of samples was also proposed. Future workshops could be held to further refine standards for ETEC CHIMS and to facilitate more collaborative work on stored sample sets from previous and future ETEC CHIMs to maximize the contribution of these trials to our understanding of ETEC pathogenesis and our development of better prevention and control measures for this important pathogen.     

Clinical endpoints for efficacy studies

Well-established, validated and clinically meaningful primary and secondary endpoints are critical in advancing vaccines through proof of principal studies, licensure and pre-qualification. To that end, the field of vaccine development for Shigella, enterotoxigenic Escherichia coli (ETEC) as well as other enteric pathogens would benefit greatly from a focused review of clinical endpoints and the use of common endpoints across the field to enable study-to-study comparisons as well as comparative assessments between vaccine candidates. A workshop was conducted to review clinical endpoints from controlled human challenge studies, field studies in naïve adult travelers and pediatric studies in low-middle income countries and to develop a consensus on clinical endpoints for future vaccine trials.Following sequential presentations on different study designs (CHIM, travelers’ efficacy and pediatric efficacy), workshop participants broke into three simultaneous workgroups focused on those study designs to discuss a number of topics key to clinical endpoints specific to each study design. Previously utilized endpoints were reviewed with an eye towards potentially novel endpoints for future studies and consideration of the disease parameters and spectrum of disease targeted for prevention. The strength of support among workshop participants for the use of various endpoints is summarized as are recommendations for additional endpoints to be considered in future studies. It is anticipated that this report will facilitate endpoint determination in future efficacy trials of vaccine candidates.     

Preexisting antibodies to homologous colonization factors and heat-labile toxin in serum, and the risk to develop enterotoxigenic Escherichia coli-associated diarrhea

Preexisting serum immunoglobulin (Ig) A and IgG titers against colonization factors and heat-labile toxin of enterotoxigenic Escherichia coli (ETEC) were examined in young adults who subsequently developed ETEC-associated diarrhea and in healthy matched controls. The data suggest an inverse association between the antibody titers against colonization factors, but not heat-labile toxin, and development of ETEC-associated diarrhea.