Gene expression and the development of live enteric vaccines.

Rationally attenuated live Salmonella vaccines provide good protection against homologous challenge and can act as carriers of heterologous antigens. However, the optimum expression system for each heterologous antigen will need to be established individually. This will ensure that the antigen in question is produced at appropriate levels, in the correctly folded conformation, within or at the surface of the carrier cell, and can therefore elicit the optimal immune response.