LAUSR

We attempted to determine whether or not F4ac+ nonenterotoxigenic Escherishia coli (non-ETEC) strains 2407 and 1466 tested as vaccine candidate strains are capable of priming porcine lymphocytes from jejunal lamina propria (JLP), ileal Peyer's patches (IPP), and mesenteric lymph node (MLN) to respond to in vitro stimulation with common mitogens (pokeweed mitogen, PWM and phytohemagglutinin, PHA) or specific antigens (F4 fimbrial antigen, peptidoglycan monomer, PGM and lipopolysaccharide, LPS). Five 4-week-old pigs per group were intragastrically inoculated with either F4ac+ (1466 or 2407) or F4-(1467) non-ETEC strains. The control pigs were given broth containing 1.2% sodium bicarbonate. At postinoculation Day 6 the pigs were killed, their gut lymphocytes were isolated and stimulated in vitro with. Also, the patterns of cluster of differentiation (CD) antigen expression on T and B cells in the single cell suspensions from JLP, IPP, and MLN were determined by flow cytometry using anti-swine CD-specific monoclonal antibodies. F4ac+ non-ETEC strain 2407 and, to a lesser extent 1466, activated lymphocytes from PP and MLN to respond better to common mitogens (PHA, PWM, LPS), F4ac fimbrial antigen or immune response modifier PGM. An increase of CD2a+ and CD8a+ T cells in JLP, and species-specific SWC1+ T cells in MLN (P<0.05) was detected in 2407-treated pigs. In conclusion, inoculation with non-ETEC strain 2407 exhibited stimulatory properties to porcine gut immune cells, and thus, could be used in the vaccination programs to control the postweaning colibacillosis in swine.