Streptococcus pneumoniae (the pneumococcus) is a Gram-positive human pathogen that causes a number of diseases such as pneumonia, otitis media, bacteraemia, and meningitis. The increasing rate by which the pneumococcus acquires resistance to the widely used antibiotics and the limitations of currently licensed vaccines have made pneumococcal diseases a major health problem. Search for more effective vaccines is ongoing and many pneumococcal proteins associated with virulence are now considered good candidates for new vaccine formulas. This study reports that intranasal immunization of mice with a live attenuated strain of the pneumococcus containing a deletion in the gene encoding for the High Temperature Requirement A (HtrA) protein, one of the major virulence factors in the pneumococcus, induces a cross-protection from pneumococcal infection. Mucosal and serum antibody levels were significantly increased in mice immunized with the HtrA mutant. Data presented here, together with other published reports, suggest that nasal immunization with live attenuated pneumococcal strains is a safe and effective strategy for the prevention of pneumococcal infections.
Key words: S. pneumoniae, HtrA protein, live attenuated vaccines, pneumococcal infection
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