Tobacco Seed-Based Oral Vaccination against Verocytotoxic O138 Escherichia coli as Alternative Approach to Antibiotics in Weaned Piglets.

Post-weaning diarrhoea and enterotoxaemia caused by Escherichia coli are serious threats in the pig ( Sus scrofa domesticus ) livestock industry and are responsible for economic losses related to mortality, morbidity and stunted growth. The aim of this study was to evaluate the effect of an engineered tobacco seeds-based edible vaccine in O138 Escherichia coli -challenged piglets throughout a multidisciplinary approach. Thirty-six weaned piglets were enrolled and randomly divided into two experimental groups, a control (C; n = 18) group and a tobacco edible vaccination group (T, n = 18), for 29 days of trial. At days 0, 1, 2, 5 and 14, piglets of the T group were fed with 10 g of the engineered tobacco seeds line expressing F18 and VT2eB antigens, while the C group received wild-type tobacco seeds. After 20 days, 6 piglets/group were orally challenged with the Escherichia coli O138 strain (creating four subgroups: UC = unchallenged control, CC = challenged control, UT = unchallenged tobacco, CT = challenged tobacco) and fed with a high protein diet for 3 consecutive days. Zootechnical, clinical, microbiological, histological and immunological parameters were assayed and registered during the 9 days of post-challenge follow up. At 29 days post-challenge, the CT group displayed a lower average of the sum of clinical scores compared to the CC group ( p < 0.05), while the CC group showed a higher average sum of the faecal score (diarrhoea) ( p < 0.05) than the CT group. A decreased number of days of shedding of the pathogenic strain was observed in the CT compared to the CC group ( p < 0.05). Specific anti-F18 IgA molecules were significantly higher in the CT group compared to the CC group's faecal samples during the post-challenge period ( p < 0.01). In conclusion, edible vaccination with engineered tobacco seeds showed a protective effect on clinical symptoms and diarrhoea incidence during the post-challenge period, characterized by a limited time of pathogenic strain shedding in faeces.