首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Oral administration of F4 fimbriae of Escherichia coli induces intestinal mucosal immune responses in F4 receptor-positive (F4R(+)) pigs, but not in F4R(-) pigs. We examined whether F4 fimbriae in F4R(-) animals behave like a food antigen and can induce oral tolerance. Therefore, F4R(+) and F4R(-) pigs were fed 2mg of F4 and challenged i.m. to evaluate the effect of oral F4 on the systemic immune system. As control antigen, two different oral doses (2 and 600 mg) of OVA were used. Thirty days after the i.m. OVA challenge, the OVA-specific serum IgG titre in 600 mg-fed pigs was lower than that in non-fed animals, indicating that tolerance was induced. Conversely, in the 2mg-fed pigs a rapid increase of OVA-specific IgG with higher titres than those in non-fed pigs was seen following challenge, indicating a priming of the systemic immune system. A similar priming was seen in both F4-fed F4R(-) and F4R(+) pigs. Upon challenge, non-fed pigs displayed a primary immune response with a slow increase of F4-specific serum IgG, whereas F4-fed F4R(-) and F4R(+) pigs showed secondary responses with a rapid increase of serum IgG. This was expected in F4R(+) pigs, as in these animals oral F4 induces F4-specific antibody-secreting cells in the spleen, suggesting a priming of the systemic immune system. However, also the F4-fed F4R(-) pigs displayed a secondary response, despite the failure to detect a response upon oral F4 administration. These findings suggest that the F4 antigen, at a dose of 2 mg, behaves like a common food antigen in F4R(-) pigs, namely it induces a systemic priming.  相似文献   

2.
Oral immunization of both humans and animals with non-replicating soluble antigens often results in the induction of oral tolerance. However, receptor-dependent uptake of orally administered soluble antigens can lead to the induction of an antigen-specific immune response. Indeed, oral immunization of pigs with recombinant FaeG (rFaeG), the adhesin of the F4(K88) fimbriae of enterotoxigenic Escherichia coli (ETEC), induces an F4-specific humoral and cellular immune response. This response is accompanied with a reduction in the excretion of F4(+)E. coli following challenge. To improve the immune response against F4, rFaeG was orally co-administered with the mucosal adjuvant cholera toxin (CT). Oral immunization of pigs with rFaeG and CT significantly improved the induction of an F4-specific humoral and cellular immune response and also significantly reduced the faecal F4(+)E. coli excretion following F4(+) ETEC challenge as compared to rFaeG-immunized pigs. Therefore, the present study demonstrates that CT can act in pigs as a mucosal adjuvant for antigens that bind to the intestinal epithelium by a CT-receptor-independent mechanism.  相似文献   

3.
The F4 fimbrial antigen of Escherichia coli and its receptors   总被引：11，自引：0，他引：11  
F4 or K88 fimbriae are long filamentous polymeric surface proteins of enterotoxigenic Escherichia coli (ETEC), consisting of so-called major (FaeG) and minor (FaeF, FaeH, FaeC, and probably FaeI) subunits. Several serotypes of F4 have been described, namely F4ab, F4ac, and F4ad. The F4 fimbriae allow the microorganisms to adhere to F4-specific receptors present on brush borders of villous enterocytes and consequently to colonize the small intestine. Such ETEC infections are responsible for diarrhea and mortality in neonatal and recently weaned pigs. In this review emphasis is put on the morphology, genetic configuration, and biosynthesis of F4 fimbriae. Furthermore, the localization of the different a, b, c, and d epitopes, and the localization of the receptor binding site on the FaeG major subunit of F4 get ample attention. Subsequently, the F4-specific receptors are discussed. When the three variants of F4 (F4ab, F4ac, and F4ad) are considered, six porcine phenotypes can be distinguished with regard to the brush border adhesiveness: phenotype A binds all three variants, phenotype B binds F4ab and F4ac, phenotype C binds F4ab and F4ad, phenotype D binds F4ad, phenotype E binds none of the variants, and phenotype F binds F4ab. The following receptor model is described: receptor bcd is found in phenotype A pigs, receptor bc is found in phenotype A and B pigs, receptor d is found in phenotype C and D pigs, and receptor b is found in phenotype F pigs. Furthermore, the characterization of the different receptors is described in which the bcd receptor is proposed as collection of glycoproteins with molecular masses ranging from 45 to 70 kDa, the bc receptor as two glycoproteins with molecular masses of 210 an 240 kDa, respectively, the b receptor as a glycoprotein of 74 kDa, and the d receptor as a glycosphingolipid with unknown molecular mass. Finally, the importance of F4 fimbriae and their receptors in the study of mucosal immunity in pigs is discussed.  相似文献   

4.
The intestinal mucosal immune system can discriminate actively between harmful pathogenic agents and harmless food antigens resulting in different immune responses namely IgA production and oral tolerance, respectively. Recently, a pig model has been developed for studying intestinal mucosal immune responses in which F4 fimbrial antigens of enterotoxigenic Escherichia coli (F4 ETEC) are used as oral antigens. A unique feature of this model is that soluble F4 antigens can be administered to pigs which have a receptor for this fimbriae (F4R(+)) on their small intestinal villous enterocytes and pigs which do not have this receptor (F4R(-)). Oral administration of F4 to the F4R(+) pigs results in an intestinal mucosal immune response that completely protects the pigs against a challenge infection. In F4R(-) pigs such an intestinal mucosal immune response does not occur. However, a priming of the systemic immune system can be seen similar to the priming in pigs fed with the same dose of a food antigen, suggesting that F4 in F4R(-) pigs behaves as a food antigen. The fact that different mucosal immune responses can be induced with soluble F4, makes it an interesting model to study mucosal immune mechanisms in the pig.  相似文献   

5.
F4 enterotoxigenic Escherichia coli (ETEC) cause diarrhoea and mortality in piglets leading to severe economic losses. Oral immunization of piglets with F4 fimbriae induces a protective intestinal immune response evidenced by an F4-specific serum and intestinal IgA response. However, successful oral immunization of pigs with F4 fimbriae in the presence of maternal immunity has not been demonstrated yet. In the present study we aimed to evaluate the effect of maternal immunity on the induction of a systemic immune response upon oral immunization of piglets. Whereas F4-specific IgG and IgA could be induced by oral immunization of pigs without maternal antibodies and by intramuscular immunization of pigs with maternal antibodies, no such response was seen in the orally immunized animals with maternal antibodies. Since maternal antibodies can mask an antibody response, we also looked by ELIspot assays for circulating F4-specific antibody secreting cells (ASCs). Enumerating the F4-specific ASCs within the circulating peripheral blood mononuclear cells, and the number of F4-specific IgA ASCs within the circulating IgA+ B-cells revealed an F4-specific immune response in the orally immunized animals with maternal antibodies. Interestingly, results suggest a more robust IgA booster response by oral immunization of pigs with than without maternal antibodies. These results demonstrate that oral immunization of piglets with F4-specific maternal antibodies is feasible and that these maternal antibodies seem to enhance the secondary systemic immune response. Furthermore, our ELIspot assay on enriched IgA+ B-cells could be used as a screening procedure to optimize mucosal immunization protocols in pigs with maternal immunity.  相似文献   

6.
F18(+)Escherichia coli have the ability to colonize the gut and cause oedema disease or post-weaning diarrhoea by adhering to specific F18 receptors (F18R) on the porcine epithelium. Although it is well established that a DNA polymorphism on base pair 307 of the FUT1 gene, encoding an alpha(1,2)fucosyltransferase, accounts for the F18R phenotype, the F18R nature is not elucidated yet. The aim of the present study was to investigate the correlation between the presence of H-2 histo-blood group antigens (HBGAs) or its derivative A-2 HBGAs on the porcine gut epithelium and F18(+)E. coli adherence. A significant positive correlation was found between expression of both the H-2 (r=0.586, P<0.01) and A-2 (r=0.775, P<0.01) HBGAs and F18(+)E. coli adherence after examination of 74 pigs aged from 0 to 23 weeks. The majority of the genetically resistant pigs (FUT1M307(A/A)) showed no HBGA expression (91.7%) and no F18(+)E. coli adherence (83.3%). In addition, it was found that F18R expression levels rise with increasing age during the first 3 weeks after birth and that F18R expression is maintained in older pigs (3-23 weeks old). Taken together, these data suggest that, apart from H-2 HBGAs, A-2 HBGAs might be involved in F18(+)E. coli adherence.  相似文献   

7.
To prevent enterotoxigenic Escherichia coli (ETEC) induced postweaning diarrhoea, the piglet needs an active mucosal immunity at the moment of weaning. In the present study, the feasibility of oral vaccination of suckling piglets against F4+ETEC infection with F4 fimbriae was studied. Furthermore, oral vaccination with enteric-coated pellets of F4 fimbriae was compared to vaccination with F4 fimbriae in solution. Therefore, piglets were orally administered 1mg F4 fimbriae in pellets or in solution during three successive days at the age of 7 and 21 days, whereas control piglets were not vaccinated. Five days postweaning (33 days of age), all animals were orally challenged with F4+ETEC. Despite the induction of an immune response upon oral administration of both F4 fimbriae in pellets as in solution, the colonisation of the small intestine by F4+ETEC upon oral challenge could not be prevented. However, a marginal but significant reduction in F4+ E. coli faecal excretion was found in the piglets vaccinated with F4 fimbriae in pellets, indicating that the use of an enteric-coat which protects the F4 fimbriae against inactivation by milk factors and degradation by enzymes and bile improves vaccination.  相似文献   

8.
Enterotoxigenic and verotoxigenic F18+ Escherichia coli colonising the pig small intestine, adhere to receptors on intestinal villous enterocytes by F18 fimbriae. The aim of the present study was to define the F18R nature. The knowledge on the nature of this receptor could be important for the development of receptor-based treatments against F18+ E. coli-induced disease. The adhesion of F18+ E. coli to pig intestinal villous enterocytes was analysed in an in vitro assay. The adhesion of F18+ E. coli but not of F4ac+ E. coli was strongly inhibited by monoclonal antibodies (mAb) with blood group H-2 specificity. Conversely, blood group H-1 specific mAb could not inhibit the adhesion of F18+ E. coli nor F4ac+ E. coli. Moreover, the blood group H-2 trisaccharide strongly inhibited the adhesion of F18+ E. coli, but only partially the adhesion of F4ac+ E. coli. These data demonstrate that the F18 receptor contains the blood group antigen H-2 (-fuc-(1-2)-β-Gal-(1-4)-GlcNAc) as major carbohydrate.  相似文献   

9.
The present study analysed quantitatively the mucin 4 polymorphism for determining the F4ac/ab receptor status of a total of 63 pigs by comparing it with the in vitro villous adhesion assay. The probability of a susceptible genotype for the mucin 4 increases significantly with increasing F4ab or F4ac ETEC adhesion per 250 microm villi (P=0.029 for F4ab, P=0.030 for F4ac), with the odds ratio for each unit increase of F4ab or F4ac equal to, respectively, 1.036 (95% CI [1.004-1.069]) and 1.018 (95% CI [1.002-1.034]). In the phenotypic in vitro villous adhesion test, a cut-off value of 5 bacteria was chosen as a criteria for the distinction between an F4R positive and F4R negative pig. The sensitivity and specificity for the in vitro villous adhesion test, with the genotyping test for mucin 4 as golden standard, is 100% and 24%, respectively, for F4ab as well as F4ac. Absence of adhesion of F4ac and F4ab ETEC to the villous brush borders was not associated with genotypic resistance suggesting that there is at least one other receptor for F4ab/ac Escherichia coli. As a consequence, not only mucin 4 gene polymorphism but also expression of these other receptor(s) has to be included in a screening assay for F4ac/ab receptor negative pigs.  相似文献   

10.
Post-weaning diarrhoea and oedema disease in weaned piglets are caused by infection with F4+ or F18+ Escherichia coli strains. There is no commercial vaccine available, but it is shown that oral immunization of weaned piglets with purified F4 fimbriae induces a protective mucosal immune response. In the present study, piglets were orally and nasally immunized with purified F18 fimbriae in the presence of the mucosal adjuvant LT(R192G) or CTA1-DD, respectively. This immunization could not lead to protection against F18+ E. coli infection. The induced F18-specific immune response was directed towards the major subunit FedA and weakly towards the adhesive subunit FedF. The results of these experiments demonstrate that it is difficult to induce protective immunity against F18+ E. coli using the whole fimbriae due to the low response against the adhesin.  相似文献   

11.
Segmented filamentous bacteria preferentially attached to the follicle-associated epithelium overlying the lymphoid tissue in samples of the terminal ileum from seven horses examined by scanning electron microscopy. The bacteria adhered to the apical membrane of the enterocytes by a holdfast segment. Each filament tended to be of uniform diameter, but the filaments ranged from 0·7 to 1·4 μm in diameter. The bacteria were usually absent from the adjacent villous epithelium.  相似文献   

12.
Bovine colibacillosis caused by enterotoxigenic Escherichia coli (ETEC) is a worldwide problem. Adhesion of ETEC to intestinal cell receptors mediated by the surface protein F5 fimbriae is the initial step in the establishment of colibacillosis. Prevention of ETEC F5+ adhesion to enterocytes protects newborn calves against collibacillosis. On the enterocytes, the F5 fimbriae bind to a ganglioside that is also found on horse red blood cells. Thus, the presence of F5 fimbriae induces haemagglutination, which is useful as an indicator in a functional assay system. In this study, recombinant anti-F5 scFv antibody fragment produced in E. coli HB2151 reacted with F5 fimbriae in ELISA and Western immunoblot, and prevented haemagglutination induced by the binding of the F5 fimbriae to its natural host receptors on horse red blood cells. Given the ease with which recombinant antibodies can be mass-produced, the presently described scFv may hold promise as a prophylactic agent for colibacillosis.  相似文献   

13.
Different procedures for preparing and purifying F4ac fimbriae of the enterotoxigenic Escherichia coli strain GIS 26 (O149:K91:F4ac LT+Sta+STb+) were performed and the purity and yield of F4ac were compared. Fimbriae were prepared by either mechanical shearing or heatshock treatment of concentrated bacterial suspensions (10(11) bacteria/ml). The mechanical shearing procedure resulted in approximately 1.7 mg fimbriae (i.e. 74.4% of the isolated protein) and 0.6 mg (25.6%) contaminating proteins per 10(12) bacteria, whereas the yield of fimbriae following heatshock treatment was lower (0.3 mg per 10(12) bacteria, i.e. 26.2%) and the relative contamination higher (1.0 mg per 10(12) bacteria, i.e. 73.8%). A further purification consisted of either anion exchange chromatography (AEC) or electro-elution from SDS-polyacrylamide gels. The electroelution procedure was performed under reducing and denaturing conditions, so that purified FaeG subunits, the major subunit of F4, were finally obtained. The binding activity of fimbriae, nonpurified as well as purified, and FaeG to F4-specific receptors on isolated intestinal villi was assessed in an inhibition adhesion assay. Native fimbriae as well as major subunits were able to bind to the receptors, and the specificity of the binding was demonstrated by blockage with F4ac-specific MAb.  相似文献   

14.
致病性F18大肠杆菌黏附素受体易感性仔猪的体外鉴定   总被引：5，自引：0，他引：5  
在PCR-RFLP方法分析了不同猪个体FUT1基因M307位点等位基因多态性的基础上，制备M307位点为GG和AG2种类型仔猪小肠上皮细胞分别与表达F18ab菌毛的野生型大肠杆菌、表达F18ac菌毛含fed操纵子全基因的重组大肠杆菌及表面分泌表达F18ab菌毛FedF亚单位的重组大肠杆菌进行体外黏附和黏附抑制试验。结果表明，上述野生菌或重组菌对GG和AG2种基因型的30～35日龄断奶仔猪小肠上皮细胞均具有较好的黏附能力。上述3种大肠杆菌分别与抗F18ab纯菌毛血清、F18ac纯菌毛血清及抗F18ab菌毛FedF亚单位单因子血清作用后．则丢失黏附小肠上皮细胞能力。而GG基因型的3日龄仔猪小肠上皮细胞不能很好的黏附上述野生菌或重组菌．但是可以很好地黏附表达987P菌毛的大肠杆菌。  相似文献   

15.
Parenteral immunisation normally induces a systemic antibody response characterised by high IgG and low IgA responses. In the present study, the effect of different doses of F4-fimbriae on the isotype-specific antibody response after intramuscular immunisation was studied in pigs. Pigs were injected twice with a 9 weeks interval with either 1, 0.1 or 0.01 mg of F4-ETEC fimbriae. The dose of 1mg F4 induced significantly lower primary F4-specific IgG and IgM responses than the doses of 0.1 and 0.01 mg F4, but primed for an enhanced F4-specific IgM serum antibody response after the booster immunisation. Furthermore, the dose of 0.1mg induced the highest F4-specific IgA serum response which was significantly higher than after injection with 0.01 and 1mg F4. Moreover, both lower doses (0.1 and 0.01 mg) showed a higher number of F4-specific IgA and IgG antibody secreting cells (ASC) in the local draining lymph nodes of the pigs. This study demonstrated that low doses of purified F4-ETEC fimbriae, especially the 0.1mg dose, are optimal for inducing F4-specific IgA responses after IM immunisation.  相似文献   

16.
Newly weaned piglets can be orally immunised against F4+ enterotoxigenic Escherichia coli (ETEC) infection with F4 fimbriae. However, to efficiently develop a vaccine against ETEC induced postweaning diarrhoea, knowledge of the stability of the F4 fimbriae to different pH and gastric digestion is needed. The gastrointestinal pH in suckling and recently weaned piglets was measured and the stability of F4 fimbriae to different pH and to pepsin was assessed in vitro. In the stomach the lowest pH was found in the fundus gland region. Gastric pH values below 2.5 were not found in suckling piglets or at the day of weaning, in contrast to piglets 1 and 2 weeks postweaning. Along the first half of the small intestine and in the caecum, a negative correlation was found between pH and age. The F4 fimbriae were stable to pH 1.5 and 2 for 2 h, whereas longer incubation periods resulted in conversion of the multimeric forms into monomers. The F4 fimbriae were partially degraded by incubation for 15-30 min in simulated gastric fluid at pH 1.5 and 2, and completely digested from 3 h onwards. At pH 3, the fimbriae maintained their antigenicity for at least 4h. The results demonstrate that gastric digestion will only have a limited impact on oral immunisation since liquid passes through the stomach relatively quickly (50% within 2 h). However, we previously demonstrated that the transit times are prolonged shortly after weaning. Shortly after weaning it could be necessary to protect the F4 fimbriae against gastric digestion to obtain efficient oral immunisation of the piglets.  相似文献   

17.
Immunoprophylaxis of porcine oedema disease and post-weaning diarrhoea caused by strains of Escherichia coli expressing fimbriae F18 is an unsolved problem. The study was designed to examine whether vaccination with a live F18ac vaccine of unweaned pigs born to sows with F18ac antibody in the colostrum requires preformed fimbriae in the vaccine, and whether protection against the heterologous fimbrial variant F18ab is induced as well. Genetically susceptible pigs were vaccinated orally on three consecutive days, beginning 10 days before weaning with 10(11) CFU of an F18ac culture. Challenge with a dose of 10(7) CFU of E. coli F18 on three consecutive days was initiated 9 or 11 days after weaning. Eighteen pigs given the fimbriated F18ac vaccine and challenged with a strain of the homologous fimbrial variant were protected against colonization; mean faecal viable counts of the challenge strain were >3 log10 lower than those from the 17 non-vaccinated control pigs. The vaccinated pigs developed a significant rise of F18ac IgA serum antibodies. The 23 pigs which had received the non-fimbriated vaccine showed no significant protection and exhibited much lower serum F18ac IgA ELISA reactivities. Eighteen pigs vaccinated with the fimbriated F18ac and challenged with an F18ab strain had faecal viable counts nearly as high as those from 16 non-vaccinated control pigs. It is concluded that only oral vaccines having preformed fimbriae induce protection limited to the homologous fimbrial variant.  相似文献   

18.
《Veterinary microbiology》1997,54(2):133-144
Enterotoxigenic (ETEC) and enterotoxaemic (ETEEC) Escherichia (E.) coli that express F18 (F107) fimbriae colonize the small intestine and cause diarrhoea and/or oedema disease in weaned pigs. So far, two antigenic variants of F18 can be distinguished with a common antigenic factor designated ‘a’ and two specific factors called ‘b’ and ‘c’. In this study the existence of crosswise anti-colonization immunity between E. coli strains that express F18ab or F18ac fimbrial variants, respectively, was demonstrated. Weaned pigs of susceptible genotype with respect to susceptibility to adhesion of E. coli with fimbriae F18 were inoculated with E. coli strains 3064STM (O157:K-:H-:F18ab; resistant to streptomycin) and 8199RIF (O141ab:K-:H4:F18ac; resistant to rifampicin). The faecal shedding was compared subsequent to immunization and homologous or heterologous challenge. An enzyme-linked immunosorbent assay (ELISA) was applied to measure IgA, IgM and IgG antibodies against the F18ab and F18ac antigens in saliva, faeces, serum and intestinal wash samples. About 8 log CFU/g of the inoculated strains were found in faeces of all pigs following immunization as well as in non-immunized controls after challenge. Bacterial counts of the inoculated strains after challenge were between 2 and 5 log lower, without any difference between homologous and heterologous challenge. Intestinal colonization with fimbriated E. coli resulted in production of significantly increased levels of anti-fimbrial antibodies, especially IgA, in serum and intestinal wash samples. There were higher levels of homologous than of heterologous anti-fimbrial antibodies. Production of antibodies against F18a or against another common fimbrial antigen is probably responsible for crosswise anti-colonization immunity between E. coli strains with F18ab and F18ac fimbrial variants. Serum F18-specific IgA may be a useful indicator of a mucosal immune response directed against F18 fimbriae.  相似文献   

19.
猪肠毒素大肠杆菌F4(ETEC F4)是引起1～2周龄仔猪黄、白痢最普遍、危害最大的大肠杆菌。ETEC F4能否致病,决定于猪的小肠上皮细胞有无ETEC F4受体。本文综述了ETEC F4的黏附模式,F4特异受体在猪小肠中的分布,受体的生化特性,受体编码基因的定位、克隆现状及存在的问题,并对今后F4受体的研究方向及应用前景进行了展望。  相似文献   

20.

Diarrhoea, a significant problem in pig rearing industry affecting pre- and post-weaning piglets is caused by enterotoxigenic Escherichia coli (ETEC). The ETEC are classified as per the fimbriae types which are responsible for bacterial attachment with enterocytes and release of toxins causing diarrhoea. However, genetic difference exists for susceptibility to ETEC infection in piglets. The different phenotypes found in pigs determine their (pigs’) susceptibility or resistance towards fimbrial subtypes/variants (F4ab, F4ac, F4ad and F18). Specific receptors are present on intestinal epithelium for attachment of these fimbriae, which do not express to same level in all animals. This differential expression is genetically determined and thus their genetic causes (may be putative candidate gene or mutations) render some animals resistant or susceptible to one or more fimbrial subtypes. Genetic linkage studies have revealed the mapping location of the receptor loci for the two most frequent variants F4ab and F4ac to SSC13q41 (i.e. q arm of 13th chromosome of Sus scrofa). Some SNPs have been identified in mucin gene family, transferring receptor gene, fucosyltransferase 1 gene and swine leucocyte antigen locus that are proposed to be linked mutations for resistance/susceptibility towards ETEC diarrhoea. However, owing to the variety of fimbrial types and subtypes, it would be difficult to identify a single causative mutation and the candidate loci may involve more number of genes/regions. In this review, we focus on the genetic mutations in genes involved in imparting resistance/susceptibility to F4 or F18 ETEC diarrhoea and possibilities to use them as marker for selection against susceptible animals.

  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号