BACKGROUND. GAS and GBS infections continue to be among the most common bacterial infections causing severe clinical conditions including immune pathologies and death of the patients. The aim of this investigation was to prepare and preliminarily evaluate recombinant vaccine candidates against GAS and GBS.
MATERIAL AND METHODS. To generate recombinant vaccines against GAS and GBS we selected and analyzed several bacterial genes encoding for potential virulence factors. Regions encoding for immunogenic domains were assembled in silico as chimeric molecules, which were synthesized and cloned in E.coli expression vector systems. Two protein constructs of this kind: Su4 against GBS (Bac, CspA, ScpB, ScaAB, SspB1) and Sa1(ScpA-SpeA) against GAS were generated and tested for immunogenicity and protection against streptococcal infection in mice model. Vaccines were introduced subcutaneously, intranasally, or intravaginally. Recombinant proteins encoding for separate GAS or GBS epitopes were used as control. IgG level was determined by ELISA. Bacteria for protection study were introduced intranasally at a dose of 10x8 CFU/mouse.
RESULTS. Recombinant proteins Su4 and Sa1 have been isolated, purified, and used for immunization of mice. Both chimeric proteins were able to generate a specific IgG response against streptococci and their individual components. Su4 was shown as protective against model GBS infection in mice independently of the mode of vaccine delivery. Sa1 vaccine efficacy is presently under evaluation.
CONCLUSION. A study of the immunogenicity and protective efficacy of the polyepitope recombinant chimeric proteins revealed that immunization induced a systemic IgG response specific to GBS and GAS infection. GBS vaccine Su4 demonstrated protective activity.