Development of an inactivated, oral immunogenic product against post-weaning colibacillosis caused by enterotoxigenic Escherichia coli in piglets.

BACKGROUND

Post-weaning diarrhea (PWD) caused by enterotoxigenic Escherichia coli (ETEC) expressing F4 and F18 fimbriae remains a major challenge in pig production, contributing to economic losses and increased antimicrobial use. This study aimed to preliminary evaluate the immunogenic potential of an orally administered formulation comprising heat-inactivated ETEC strains expressing F4 and F18 fimbriae, combined with low-dose recombinant human interferon-alpha (IFN-α) as a mucosal adjuvant, in piglets. Piglets from two different litters were allocated into two experimental groups: a treated group (T) receiving the inactivated ETEC formulation with IFN-α for 26 days, and a control group (C) receiving only IFN-α. According to the farmer, the sows had not been vaccinated. Immune responses were evaluated in the sows colostrum and piglet serum, saliva, and feces by ELISA. In mesenteric lymph nodes anti-F4/F18 IgA and IgG antibodies were quantified by ELISPOT.

RESULTS

The inactivated product preserved fimbrial antigenicity and remained sterile. Colostrum from both sows displayed elevated levels of fimbriae-specific IgA and IgG despite neither sow being vaccinated against E. coli. Treated piglets showed a transient serum IgA increase against F4 whereas serum IgG levels were often comparable to the controls. Notably, elevated mucosal IgA responses were observed in saliva and feces against both F4 and F18 (P < 0.01) in T group, accompanied by enhanced IgA-secreting B-cell activity in mesenteric lymph nodes. ELISA validation confirmed high assay reproducibility (R² > 0.98; CV < 10%). ELISPOT analysis underscored the adjuvant role of F4 and IFN-α in stimulating mucosal immunity.

CONCLUSIONS

Our preliminary findings may represent a promising strategy to control PWD and reduce antimicrobial use in pig production.