Serotype-independent protective activity of recombinant pneumolysin in a model of systemic infection caused by Streptococcus pneumoniae serotypes 4 and 6B

Background. The development of a pneumococcal vaccine with serotype-independent activity is relevant for the whole world, as this is due to the high prevalence of Streptococcus pneumoniae (S. pneumoniae), the constant change of pathogen serotypes and the growth of antibiotic-resistant strains. In previous experiments, we revealed a protective effect of immunization with recombinant pneumolysin (rPly) in a model of systemic infection caused by S. pneumoniae serotype 3.Aim. Study of serotype-independent protective activity of rPly.Materials and methods. Strains of S. pneumoniae serotypes 4 and 6B were used. Mice were immunized intraperi-toneally two or three times with an interval of 14 days with rPly. To assess the protective activity of rPly, animals after double or triple immunization were infected intraperitoneally with S. pneumoniae .Results. rPly at a triple immunization in a dose of 25 μg protected mice from intraperitoneal infection with S. pneu- moniae serotype 4, the efficiency index increased by 2 times compared with the control. with a double immunization, rPly protected mice from intraperitoneal infection with S. pneumoniae serotype 6B, efficiency index increased by 6.61 times compared with the control.Conclusion. rPly protects animals from infection with different serotypes of S. pneumoniae, which allows us to consider it a promising drug for the development of pneumococcal vaccines with serotype-independent activity.