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Abstract: 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 α(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. [Copyright &y& Elsevier]

Abstract: F18+ Escherichia coli cause postweaning diarrhoea and oedema disease in newly weaned piglets. Protection against these diseases can be established by preventing the fimbrial adhesion of these bacteria to the enterocytes of the porcine intestine. To test a vaccine against F18+ E. coli consisting of the adhesin of F18 fimbriae, FedF, the conservation of the FedF subunit had to be examined. Therefore, the fedF sequence of 37 F18+ E. coli isolates from different countries was determined and compared to the fedF gene of the F18ab reference strain F107/86. The amino acid sequence of the mature FedF from the individual F18+ E. coli isolates was 96–100% identical to that from E. coli F107/86, but the overall homology was 90.4%. Hyper variable regions were not found in the FedF sequence. The FedF sequence was conserved over the different countries and between the two antigenic variants, F18ab and F18ac, suggesting that F18ab and F18ac strains have the same receptor. Furthermore, the conserved C-terminal region in the FedF adhesin suggests that the F18 fimbriae, in analogy with type 1 and P pili, are assembled by a donor strand mechanism. In conclusion, the reported conservation of FedF supports the usefulness of the fimbrial adhesin as a subunit vaccine against F18+ E. coli infection. [Copyright &y& Elsevier]

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 (α-fuc-(1-2)-β-Gal-(1-4)-GlcNAc) as major carbohydrate. [Copyright &y& Elsevier]

Escherichia coli (E. coli) O157:H7 can cause haemorrhagic colitis and the haemolytic uremic syndrome in humans. Ruminants are the main reservoir for this bacterium: they can harbour the bacteria in the gastrointestinal tract without showing clinical symptoms. The reason for this persistence is still unclear, although it has been suggested that E. coli O157:H7 can suppress the immune system. To investigate the effects on the immune system of ruminants, an infection model is needed that mimics a long-term infection as it can occur in both sheep and cattle. As the terminal rectum has recently been identified as a primary colonisation site in cattle, we developed a rectal inoculation model for sheep and used this model to study immune responses against selected virulence factors of E. coli O157:H7 (intimin, EspA and EspB). Sheep were infected and re-infected when E. coli O157:H7 excretion was no longer detectable. The animals did not develop serum or local antibody responses but showed a cellular response against EspA and intimin respectively 9 and 16 days after infection. This response was also present 5 days after re-infection, albeit lower, and did not prevent animals from being re-infected. These results demonstrate that E. coli O157:H7 can be persistently present in the large intestine of sheep without inducing a clear protective immune response., (Copyright © 2010 Elsevier B.V. All rights reserved.)

F18(+)Escherichia coli infections causing post-weaning diarrhoea and/or oedema disease are a major cause of economic losses in pig industry. To date, no preventive strategy can protect pigs from F18(+)E. coli infections. One of the most attractive approaches to eliminate F18(+)E. coli infections is the selection for pigs that are resistant to F18(+)E. coli infections. However, this strategy was not believed to be favourable because of reports of genetic association with the stress-susceptibility gene in the Swiss Landrace. To investigate this potential association more thoroughly, 131 randomly selected Belgian hybrid pigs were genotyped for both the F18(+)E. coli resistance alleles (FUT1(A)) and the stress-susceptibility alleles (RYR1(T)) and their association was investigated by determining the linkage disequilibrium. This linkage disequilibrium (LD=-0.0149) is close to zero and does not differ significantly from 0 (likelihood ratio test chi(1)(2)=1.123, P=0.29), demonstrating no association between the FUT1(A) and RYR1(T) alleles. Furthermore, only a small fraction (4.6%) of the Belgian pigs was found to be resistant to F18(+)E. coli infections. Our results suggest that selection for F18(+)E. coli resistant pigs might be an attractive approach to prevent pigs from F18(+)E. coli infections, unlike to what has previously been postulated.

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.