Submitted to: Regional Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 1995
Publication Date: N/A
Interpretive Summary: Diarrhea in weaned pigs is of major economic importance to the swine industry. Bacteria called Escherichia coli produce toxins that cause diarrhea in weaned pigs and must be able to bind to the small intestine to cause disease. Bacterial structures called K88 facilitate binding by some of the E. coli that cause diarrhea in neonatal and weaned pigs. When pregnant sows are vaccinated against K88, antibodies against K88 in their milk protect their suckling pigs from K88-mediated disease. Weaned pigs can no longer rely on maternal antibodies for protection, but must develop their own intestinal immunity. The objective of this study was to determine if a laboratory-derived K88-positive, nontoxigenic E. coli strain called strain 2407 that does not cause diarrhea, could invoke a cellular immune response in experimentally infected weaned pigs. Changes in the proportion and distribution of immune cell populations at the mucosal surface in pigs infected with strain 2407 mimicked changes seen following infection with a K88-positive enterotoxigenic strain. These results indicate that strain 2407 could be a source of K88 antigen for preparation of a live oral vaccine to protect weaned pigs from colibacillosis.
Distinct patterns of CD antigen expression on T lymphocyte subsets and distribution of CD**+ T cells in jejunal lamina propria (LP), Peyer's patches (PP), and ileal mesenteric lymph node (MLN) have been correlated with diarrheal disease or local protection due to enterotoxigenic Escherichia coli (ETEC)/non-ETEC infection/vaccination in 4-week-old pigs. An increase of CD2a**+, CD8a**+, in LP, and SWC1a**+ cells in MLN (p < 0.05, p < 0.01, respectively) of pigs infected with ETEC strain M1823 was observed. Non-ETEC strain 2407 stimulated a strong proliferation of cytolytic CD8a**+ cells in LP (p < 0.01) Pigs vaccinated with 2407 strain had more abundant SWC1a**+ and CD8a**+ cells in MLN (p < 0.05) or CD4a**+ cells in PP (p < 0.01), respectively. Numerous CWC1a**+ cells were found in LP of villous epithelium, PP, and paracortical/sinusoidal areas of MLN in M1823-treated pigs. In 2407-inoculated pigs marked infiltration/proliferation of CD8a**+ cells were demonstrated in LP/PP and paracortex of MLN. Recombinant nontoxigenic strain 2407 seems to be a good source of protective (fimbrial) antigen for development of a safe and effective live oral vaccine against postweaning colibacillosis in swine.