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Vaccination is a key element in prophylaxis of infectious diseases. Effective vaccines based on polysaccharide capsules were developed for a number of microorganisms. Effectiveness of polysaccharides as antigens, however, is low in the main risk groups - infants and patients with immunedeficiency conditions. Use of polysaccharide antigens conjugated with protein carriers as vaccines became a principal step forward. Though use of carriers became a breakthrough for vaccine effectiveness increase, mechanisms of interaction of proteins and carbohydrate components of the vaccines in T-cell immune response induction and immunological memory remains studied incompletely. Lack of theoretical base complicates execution of directed engineering of conjugated vaccines with the goal of expansion of their nomenclature and effectiveness increase. Despite significant volume of new information in the field of interaction of various antigens, and significant expansion of spectrum of potential carriers, including of non-protein nature, the number of pathogens, for which conjugated vaccines are introduced into clinical practice, remains insignificant. Information regarding problems and perspectives of use of carriers for conjugated polysaccharide vaccines is summarized in the review.

For many decades, live vaccines remain the most effective means for prophylaxis of bacterial infections. Until recently, the main source of vaccine strains were empirically selected bacteria, virulence of which was attenuated due to natural mutations. Despite effectiveness of such vaccines against a number of infections, use of attenuated strains for many pathogens either does not induce sufficient protection, or is unsafe. Traditional technologies of vaccine creation frequently have low effectiveness with the lack of pronounced «protective» antigens in the pathogen. Methods of rational construction of live vaccines have received development in the recent years, based on methodology of synthetic biology. Contribution of synthetic biology into creation of vaccines is not limited to use of means of bioinformatics and construction of optimized DNA fragments, but also includes coordinated adjustments to various components of the bacterial genome, creation of vector strains, inclusion of altered immunogens and immune system activators into them, search and design of immunogens in silico and much more. Methodologies of synthetic biology allow to combine various engineering ideas and building blocks, obtained during creation and modification of various prophylaxis, therapeutic and bioengineering systems for production of microorganisms with qualitatively novel and programmable properties, and in perspective - rapidly create vaccines «on demand».