Protective activity of mixtures of pneumococcal antigens in infection caused by <i>Streptococcus pneumoniae</i> serotype 3

Introduction. Pneumococcal diseases remain relevant for the whole world. On the one hand, this is due to the high prevalence of pneumococcus and the other hand, the growth of antibiotic-resistant strains and the constant change of clinically significant serotypes of the pathogen.The aim of the research was to study of the protective activity of a mixture of pneumococcal antigens.Material and methods. we used preparations of a capsular polysaccharide (CPS) obtained from Streptococcus pneumoniae serotype 3; protein-containing fraction (PCF) obtained from an aqueous extract of cells of S. pneumoniae serotype 6B; recombinant pneumolysin (rPly). Mice were immunized intraperitoneally twice with an interval of 14 days with mixtures of bacterial antigens: CPS + PCF; CPS + rPly; PCF + rPly. To assess the protective activity of the studied drugs after double immunization animals were infected intraperitoneally with S. pneumoniae serotype 3. To study the effect of mixtures of bacterial preparations on the infectious process in the lungs immunized mice were infected with S. pneumoniae serotype 3. The humoral immune response was studied with IgG using the method of ELISA.Results. The CPS + rPly mixture protected mice from intraperitoneal infection with S. pneumoniae serotype 3 regardless of the infecting dose. Immunization with CPS + PCF or CPS + rPly mixtures influenced a significant decrease the number of seeded bacterial cells from lungs during the entire observation period (72 h) compared to the control. Administration of mixtures of bacterial antigens of CPS + PCF, CPS + rPly or PCF + rPly to animals led to a significant increase of the level of antibodies to all antigens, however, the highest levels of IgG were determined to PCF and rPly.Conclusion. The results obtained suggest that different antigenic drugs in mixtures affect different mechanisms of immunity activation.