Heterologous boost vaccines for bacillus Calmette–Guérin prime immunization against tuberculosis

The current tuberculosis (TB) epidemic continues to call for the development of effective vaccination strategies. The initial TB vaccine research effort mostly focused on the search for a vaccine that might be better than, and thus could replace, the current bacillus Calmette-Guérin (BCG) vaccine. It has increasingly been realized that BCG or an improved BCG will continue to be used as a prime TB vaccine and there is a need to develop effective boost vaccines that could enhance and prolong the protective immunity of BCG prime immunization. Mounting experimental evidence suggests that recombinant vaccines, including both recombinant protein and genetic vector vaccines, are effective in boosting immune activation and protection by BCG vaccination. This review will discuss recent advances and the authors' views in the development of there boost vaccines.