Immune response and protective efficacy of S9 ribosomal protein of Streptococcus pneumoniae in a model of sepsis

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Vaccination is the most promising strategy to reduce the incidence of pneumococcal infection. Although there are vaccines available, all of them are based on polysaccharide antigens (conjugated or not). In addition to their high cost, those vaccines do not cover all serotypes. To overcome these hindrances, we evaluated the immunogenicity and the protective efficacy of the S9 ribosomal protein of Streptococcus pneumoniae with the aim of developing a protein-based vaccine in the future. The gene encoding the S9 ribosomal protein was cloned in pET21-a expression vector, and the recombinant S9 protein was used to immunize mice. Significantly higher levels of anti-S9 immunoglobulin G were achieved (with predominance of immunoglobulin G1) in comparison with the control. Antibodies elicited against S. pneumoniae protein extract in rabbit recognized the recombinant S9 protein by Western blot, thus demonstrating its immunogenicity. Moreover, mice immunized with recombinant S9 protein and challenged with a virulent strain of S. pneumoniae presented a significant reduction of bacteremia after 24 h of infection as compared with the control. However, in the S9-immunized mice the onset of death was insignificantly delayed, but all of them died by the fourth day postinfection.

Keywords: immunogenicity; immunogénicité; protéine ribosomique; recombinant vaccine; ribosomal protein; streptococcus; streptocoque; vaccin recombinant

Document Type: Research Article


Affiliations: 1: Research and Development Center, Ezequiel Dias Foundation (Funed), Belo Horizonte, MG, Brazil. 2: Otavio Magalhães Institute Ezequiel Dias Foundation (Funed), Belo Horizonte, MG, Brazil.

Publication date: September 20, 2012

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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