Medium- and Long-Term Immune Responses in the Small Intestine in Piglets from Oral Vaccination against .

Post-weaning stress, together with , are two of the key factors in the occurrence of post-weaning diarrhea. There are different commercial vaccines that induce immunity at the local or systemic level, improving farm health and avoiding economic losses in the pork industry. That is why the objective of this study was to evaluate the effect of an oral enterotoxigenic F4/F18 vaccine on immunity and intestinal integrity in the middle and long term after inoculation. The gene expression of the biomarkers indicative of cellular infiltration (calprotectin, CAL), tight junction proteins (occludin, OCL; zonulin, ZON; and claudin, CLA) and a panel of proinflammatory (interleukins, IL: IL1α, IL1β, IL6, IL8, IL12p35 and IL12p40; interferons, IFN: IFNα and IFNγ; and tumoral necrosis factor, TNF: TNFα) and anti-inflammatory mediator cytokines (TGFβ and IL10) were analyzed, as well as histomorphology in jejunum and ileum, the cell density of goblet cells, intraepithelial lymphocytes and IgA-producing cells. Differences were observed in ZON, CLA and CAL, with greater gene expression in observed in vaccinated piglets at 42 days post vaccination (dpv) in the ileum. Regarding the expression of cytokines, the vaccinated animals showed significant differences in IL1α, IL6, IL12p35, IL12p40, IFNα, IFNγ, TNFα and TGFβ at 42 dpv in the jejunum or ileum. The villi showed greater height in the vaccinated piglets and the ratio between villus height and crypt depth was significantly greater in the vaccinated group in the jejunum at 84 dpv. The count of IgA-producing cells shows higher values for the unvaccinated group in the ileum, while intraepithelial lymphocytes show a significant increase in both jejunum and ileum in vaccinated piglets. We can conclude that oral vaccination against produces an evident effect, which manifests itself even in the middle and long term after the challenge, including immune response, decrease in antimicrobials usage, better histological structure in intestine and the improvement of performance.