• Vaccine Name: E. coli heat-labile enterotoxin B-subunit (LB-T) Vaccine
• Target Pathogen: Escherichia coli
• Target Disease: Hemorrhagic colitis
• Vaccine Ontology ID: VO_0004144
• Type: Subunit vaccine
• Antigen: The antigen for this vaccine is a plant-optimized synthetic gene encoding for the E. Coli heat-labile enterotoxin B-subunit (LT-B) (Mason et al., 1998).
• Preparation: DNA plasmids were created, and the expression cassettes were purified. Potato plants were transformed by the leaf disc cocultivation method. Transformed lines were analyzed, and the best lines were clonally propogated. These plantlets were transferred to soil and grown. The tubers produced were the vaccine (Mason et al., 1998).

Cattle Response

• Vaccination Protocol: The authors used two independent transgenic lines of potato tubers, THllO-8 and THllO-51, and nontransformed tubers of line FL1607. Potato tubers were peeled and sliced before offering to mice as food. BALB/c mice were fasted overnight before feeding raw tuber slices. Tuber feedings were performed at weekly intervals for 3 weeks (days 0, 7 and 14). Mice were divided into four groups of five animals each. Each animal in Groups 1-3 received 5 g of FL1607, THllO-8 or THllO-51 tubers per feeding, respectively (Mason et al., 1998).
• Immune Response: Mice that ingested three doses of transformed tubers developed anti-LT-B faecal IgA and anti-LT-B serum IgG antibody responses equivalent to or greater than responses developed by mice gavaged orally with 5 micrograms purified LT-B. THllO-51 tubers, in contrast to THllO-8 tubers or purified LT-B, produced significantly higher anti-LT-B faecal IgA responses when ingested by mice. Control mice that were fed nontransformed potatoes had no detectable anti-LT-B faecal IgA or anti-LT-B serum IgG responses (Mason et al., 1998).
• Challenge Protocol: Mice were challenged by oral administration of 25 micrograms LT (heat-labile enterotoxin) (Mason et al., 1998).
• Efficacy: Compared to mice that were fed non-transformed tubers, mice that were immunized by gavage with purified bacteria LT-B had the greatest reduction in gut/carcass ratio on subsequent challenge. Mice that were fed transformed potatoes had somewhat less but still a significant reduction in fluid. No mouse was completely protected. Control mice fed nontransformed potatoes developed no anti-LT-B faecal or serum antibodies (Mason et al., 1998).