Oral administration and evaluation in piglets of tobacco seeds expressiong antigenic proteins against Oedema disease

The vaccination is an important and cost-effective way to control animal and human infectious disease. The use of transgenic plants as delivery system for vaccine proteins is attractive for its simplicity and increases likelihood for local immune response at sites of infection. In particular in livestock, vaccination allows to reduce antibiotic treatments, as suggested by EC Regulation 1831/2003. The aim of this study was to evaluate the transgenic tobacco seeds as edible vaccine in piglets. Tobacco seeds were previously transformed via agroinfection for the expression of antigenic proteins of Escherichia coli strains responsible of Pig Oedema disease: the F18 fimbriae adhesive and the VT2e-B subunit. 43 piglets, weaned at 202 days, were allocated in pens in the same environmental conditions and randomly divided in 4 experimental groups: Control Group (CG), Treatment 1 group (T1), Treatment 2 group (T2, Treatment 3 group (T3). Treatments were represented by different lines of tobacco seeds: F18 positive tobacco seeds (F18+), VT2e-B positive tobacco seeds (VT2e-B+) and wild type tobacco seeds (WT). Treatments were administered by oral route on days 0,1,2,14. T1 received 10 grams F18+ and 10 grams of VT2e-B+ containing about 6mg of F18 and 6mg of VT2e-B. T2 received 10 grams of VT2e-B+ containing about 6mg of VT2e-B. T3 received 25 grams of VT2e-B+ containing about 15mg of VT2e-B. CG received 20 grams of WT. Animals were fasted 3 hours before and 3 hours after the treatment administration. The amount of antigenic proteins was estimated by western blotting. On day 22 piglets were infected with 1*1010 CFU of O138 Escherichia coli strain, previously evaluated by polymerase chain reaction (PCR). In the pre-challenge phase faecal and blood samples were collected weekly to evaluate IgA and IgG amount by ELISA assays. After challenge faecal consistency and colour, body temperature, clinical signs related to oedema disease (eyelids, epiphora, neurological and respiratory symptoms, vitality) were determined individually thought specific points scales daily for 15 days. Zootechnical performances and haematocrit percentage (HT) were evaluated during all the experimental period. T1 showed a significant higher level of IgA in faeces than the other experimental groups in pre-challenge period. After challenge average individual body weight, average daily gain and feed intake were higher in T1 and T2 than CG. No differences were observed in body temperature, faecal evaluation and HT. After challenge CG showed scores of symptoms related to oedema disease worse than T1, T2 and T3 and treated piglets showed a rapider recovery. In conclusion we showed that oral administration of recombinant tobacco seeds expressing antigenic proteins against oedema disease can induce the increase of mucosal antibodies and a protective effect against the challenge strain in piglets.