Submitted to: Journal of Veterinary Medicine Series B
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Some types of the bacteria Escherichia coli (E. coli) are important causes of diarrhea in animals and people. These E. coli stick to the small intestine and produce toxins that cause fluid to be secreted into the intestine. The ability of E. coli to stick to the intestine and make toxins is essential to cause diarrhea. Some E. coli, made by recombinant DNA methods, stick but do not make toxins. In this study we found an E. coli that stuck to the intestine, did not make toxins, and did not cause diarrhea. Further, we found that this E. coli caused cells in the pig intestine that are involved in protection from disease to increase greatly in number. These are exciting findings, because this E. coli has the qualities necessary to produce a safe and effective vaccine. We found that one of the E. coli we used did not cause diarrhea and that the immune cells increase in number and change after the pigs had been infected. This study is an important step in the development of vaccines to prevent E. coli diarrhea in pigs. Pork producers would benefit from a vaccine that would protect pigs from E. coli. This would reduce costs of pig production by reducing losses due to disease.
Technical Abstract: The effects of genetically engineered non-enterotoxigenic Escherichia coli (non-ETEC) strains containing either wild-type (1466) or recombinant plasmid (2407) encoding F4ac antigen were studied in order to establish their role in (1) causing mucosal damage of the gut, (2) inducing an inflammatory reaction of the gut-associated lymphoid tissues (GALT), i.e., in the small intestinal lamina propria (LP) and ileal mesenteric lymph node (MLN), and (3) eliciting the protective immune responses mediated by CD+ leukocyte subsets in LP and MLN of experimentally infected weaned pigs. Unlike F4ac+ ETEC strain M1823, both non-ETEC strains (1466 and 2407) induced only a mild swelling of the small intestinal mucosa and a moderate leukocyte infiltration in jejunal/ileal LP. An increase of CD1+ and SWC2a+ cells was detected by single-color fluorocytometry (FCM) among B and T lymphocytes from LP and MLN of 2407-infected pigs. A strong proliferation of CD45+ cells was observed in LP/MLN of pigs infected with either 2407 or M1823 strain of E. coli. The use of non-ETEC strain 2407 was associated with a marked leukocytosis and proliferation of CD1+ and SWC2a+ cells in both tested compartments of porcine GALT. This strain neither caused lesions of jejunal/ileal villous epithelium nor produced diarheal disease in orally vaccinated pigs.