ABSTRACT
In this chapter, the authors describe some recent developments in vaccine design, using recombinant DNA technology to express antigens in heterologous systems. They discuss various approaches they have taken to analyze protective antigens and optimize their expression. The authors describe an experimental approach that has made important contributions toward replacing traditional bacterial vaccines. The use of Salmonella strains carrying tetanus toxin fragment C is the only example of the use of this carrier system to protect against an infection of humans. The use of the nirB promoter to regulate the expression of antigens inside mammalian cells represents a significant advance in the use of salmonellae as carriers of foreign antigens. The attenuated salmonella carrier system offers an attractive route for the delivery of foreign antigens to the host immune system. It has the considerable advantage that it can be administered orally.
