Production and immunogenicity assessment of a ToxA-based multiepitope plant-made protein targeting enteric pathogens

Around 1.7 million people die annually due to enteric infections, which are mainly caused by ETEC (Enterotoxigenic E. coli ), V. cholera , V. parahaemolyticus , and Salmonella . There are currently licensed vaccines against cholera and salmonella, whose distribution is chain-dependent making difficult to efficiently distribute them in poor countries. In this context plants are attractive hosts for the synthesis and delivery of subunit vaccines that could be produced at very low costs and widely distributed ensuring vaccination coverage. Subunit vaccines often demand the use of adjuvants to reach proper immunogenicity. Several bacterial toxins have been used as mucosal and systemic adjuvants and a potential molecule for this purpose is the PirA-like toxin (ToxA) from V. parahaemolyticus , which was deemed highly immunogenic in some species. In this study a protein named ToxAentero was expressed in tobacco plants to initiate the development of accessible vaccines against enteric diseases. ToxAentero is based on ToxA, as adjuvant carrier, and epitopes from ETEC, V. cholerae , V. parahaemolyticus , and S. typhimurium . The production yields reached up to 5.46 µg g − 1 fresh leaf tissue. The plant-made ToxAentero was found immunogenic in mice immunized by oral or subcutaneous routes in terms of the induction of IgG (sera) and IgA (feces) humoral responses against most of the target epitopes from the enteric pathogens. This study opens the path for the development of a promising oral plant-based multiepitopic vaccine candidate in the fight against enteric diseases. Key message A multiepitopic protein targeting several enteric pathogens, was expressed in plants and characterized in mice; revealing that it is immunogenic and thus is proposed as an attractive vaccine candidate.