Oral immunisation of naive and primed animals with transgenic potato tubers expressing LT-B

The efficacy of edible vaccines produced in potato tubers was examined in m ice. Transgenic plants were developed by Agrobacterium tumefaciens-mediated transformation. The antigen selected was the non-toxic B subunit of the Es cherichia coli enterotoxin (recLT-B). A synthetic gene coding for recLT-B w as made and optimised for expression in potato tubers and accumulation in t he endoplasmic reticulum. Introduction of this gene under control of the tu ber-specific patatin promoter in potato plants resulted in the production o f functional. i.e. Gm1-binding, recLT-B pentamers in tubers. Selected tuber s containing about 13 mug of recLT-B per gram fresh weight were used for im munisation. subcutaneous immunisation with an extract of recLT-B tubers yie lded high antibody titres in serum that were similar to those obtained with bacterial recLT-B. The efficacy of oral administration of recLT-B tubers w as determined by measuring mucosal and systemic immune responses in naive a nd primed mice. Animals were primed by subcutaneous injection of an extract of recLT-B tuber plus adjuvant. Naive and primed mice were fed 5 g of tube rs (similar to 65 mug of recLT-B) or were intubated intragastrically with 0 .4 mi of tuber extract (similar to 2 mug of recLT-B). In naive mice, feedin g recLT-B tubers or intubation of tuber extract did not induce detectable a nti-LT antibody titres. In primed animals. however, oral immunisation resul ted in significant anti-LT IgA antibody responses in serum and faeces. Intr agastric intubation of tuber extract revealed higher responses than feeding of tubers. These results indicate clearly that functional recLT-B can be produced in p otato tubers, that this recombinant protein is immunogenic and that oral ad ministration thereof elicits both systemic and local IEA responses in paren tally primed, but not naive, animals. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.