engleski

A role of porcine gut immune T, B, and null/ gamma delta TCR^+ cells in the protective immunity to fimbrial/toxin antigens of Escherichia coli

Protection of weaned pigs from F4^+ enterotoxigenic Escherichia coli (ETEC) will require the induction of mucosal immunity to prevent the development of postweaning diarrhea. Porcine T and B cells residing gut-associated lymphoid tissues (GALT) recognize capsular, fimbrial, and toxin antigens via their highly diverse protein receptors. The current study compares the proportion of T (CD4a^+ and CD8a^+), B (CD1^+ and CD21^+), and null (SWC5^+) cells in the GALT such as jejunal lamina propria (JLP), ileal Peyer"s patches (IPP), and mesenteric lymph node (MLN), and relates it to the development of protective (vaccinal) immunity against challenge infection with F4ac^+ hemolytic ETEC strain (O:149:K91:K88ac:987P:LT^+ STb^+) in 4-week-old pigs. Eight pigs per group were intragastrically vaccinated with 10^10 CFU/ml of F4ac^+ non-ETEC strain 2407 in 60 ml of Trypticase soy broth (TSB) or primed with either N-acetylglucosaminyl-(beta,1-4)-N-acetyl-muraminyl-L-alanyl-D-isoglutamine (GMDP) at Day 0 or copolymer of polyoxyethylene and polyoxypropylene (POE-POP) at Day -2 prior to the vaccination. At postvaccination Day 6 principal and control (received TSB only) pigs were orally challenged with F4ac^+ ETEC isolate and sampled (lymphocytes from JLP, IPP, and MLN) following euthanasia at Day 14. The JLP of pigs that were primed with POE-POP before the vaccination had significantly higher (p < 0.05) number of cytolytic CD8a^+ cells than did the nonvaccinated controls. Also, the MLN of these pigs and those that were just immunized with 2407 bacteria exhibited an increased (p < 0.05) quantity of SWC5^+ null/gamma delta TCR^+ cells. Conversely, the proportion of CD1^+ B cells was much lower in the MLN (p < 0.05; < 0.01) of the vaccinated pigs primed with either POE-POP or GMDP, respectively. However, the GMDP-treated 2407-vaccinated pigs had more CD21^+ B cells in the MLN (p < 0.001) than the controls. The helper CD4a^+ T cells were less abundant (p < 0.01) in the MLN of the vaccinated and challenged pigs. The phenotypic and functional expression of immune cell subsets in porcine GALT following the specific immunization with F4ac^+ non-ETEC strain 2407 against postweaning colibacillosis and the challenge infection with F4ac^+ ETEC strain seems to be antigen(s) driven process comprising both cellular (CD8a/SWC5^+ T/null cells) and humoral (CD21^+ B cells) protective immunity at the site of the enteric infection, i.e. jejunal mucosal surfaces or in the ileal MLN. Since the vaccinal strain of E. coli, particularly when immune response modifiers (POE-POP or GMDP) were given, protected weaned pigs from clinical disease it is logical to recommend it as the potential source of the replicating antigen(s) for the development of live oral vaccine against colidiarrhea.

Immune cells; protective immunity; E. coli; pigs

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