Bacterial Vaccines with Regulated Delayed Attenuation

Over the past 200 years since the moment of E. Jenner’s discovery, vaccination continues to be the leading strategy for protection against infectious diseases, but commercially available live attenuated and inactivated vaccines have a number of serious drawbacks. Bacterial strains should be completely attenuated in live vaccines, while maintaining a high degree of immunogenicity. However, the majority of attenuation methods currently used makes potential vaccine strains more susceptible to the action of various host defenses, reducing the ability to persist in the body of the vaccinated individual in quantities and for periods sufficient for formation of long-term and intense immunity. Inactivation of microorganisms underlying the production of killed vaccines, applying various reagents and /or physical factors, can disrupt the native conformation of antigenic epitopes located on bacterial cell surface, which leads to a decrease in immunogenicity. This review examines a promising biotechnological platform for the development of vaccines based on the methodology of regulated delayed gene expression and repression of genes, which was developed to resolve the above-mentioned contradictions.