Factors influencing the immune response to foreign antigen expressed in recombinant BCG vaccines

A wide range of recombinant BCG vaccine candidates containing foreign viral, bacterial, parasite or immunomodulatory genetic material have been developed and evaluated, primarily in animal models, for immune response to the foreign antigen. This review considers some of the factors that may influence the immunogenicity of these vaccines. The influence of levels and timing of expression of the foreign antigen and the use of targeting sequences are considered in the first section. Genetic and functional stability of rBCG is reviewed in the second section. In the last section, the influence of dose and route of immunization, strain of BCG and the animal model used are discussed.