Immunization with Recombinant Pneumolysin Induces the Production of Antibodies and Protects Mice in a Model of Systemic Infection Caused by Streptococcus pneumoniae

Immunogenic and protective activity of recombinant pneumolysin was studied in experiments on male BALB/c mice. The mice were immunized intraperitoneally with recombinant pneumolysin sorbed on Al(OH)3 (200 μg per mouse). In 2 weeks after immunization, the isotypes of antibodies to recombinant pneumolysin in the serum of immunized mice were determined by ELISA. The animals were infected with Streptococcus pneumoniae serotype 3. Immunization with recombinant pneumolysin induced the production of anti-pneumolysin antibodies, mainly of IgG1 subisotype. On day 21 after intraperitoneal infection with S. pneumoniae serotype 3 in a dose of 106 microbial cells, the survival rate of animals immunized with recombinant pneumolysin in a dose of 25 μg/mouse was 67% vs. 0% in the control (p<0.001). Recombinant pneumolysin could be considered as a promising protective antigen for inclusion in the serotype-independent vaccine against S. pneumoniae.