Open in a separate window FIG. A recent report of the World Health Organization Melanocyte stimulating hormone release inhibiting factor concluded that the impact of pneumococcal disease worldwide is similar to that of tuberculosis (25). It has been emphasized that the development of an improved pneumococcal vaccine is among the three vaccine priorities of industrialized countries (5). The 23-valent pneumococcal-polysaccharide vaccine provides only limited protection in young children, immunocompromised individuals, and elderly people (3, 6, 8, 14). Although the new polysaccharide-protein conjugate vaccine appears to be efficient in these poor responder groups, it will not protect against the capsular types of pneumococcal strains not included in the formulation. A promising approach in overcoming this problem is the use of third-generation vaccines composed of species-specific pneumococcal protein(s), which may elicit long-lasting, broadly protective T-cell-dependent immunity. One of these proteins currently considered as a vaccine candidate is the 37-kDa protein PsaA (pneumococcal surface adhesin A). This protein was first identified by Russell et al. (19) using monoclonal antibodies (MAbs) and has attracted a great deal of interest in recent years. Soon after the protein was identified, the gene was cloned and sequenced (23). Although the two first pneumococcal sequences reported from strains R36A and D39 showed high heterogeneity (1), PCR-restriction fragment length polymorphism analysis showed that is highly conserved among the serotypes included in the 23-valent polysaccharide vaccine (22). In the same study (22), the authors sequenced a serotype 6B strain and concluded that the sequences from D39 and the serotype 6B strain most likely represented the prototype sequences. More recently, Novak et al. reported that the gene from a serotype 4 strain was 99.6% identical to the gene from strain D39 and 99.9% identical to the gene from the serotype 6B strain (17). Morrison and coworkers confirmed the presence of in all of the 90 serotypes by PCR analysis (16). The specificity of the assay was proven by the lack of a similar signal when analyzing heterologous bacterial species (= 30) and genera (= 14), including the viridans group streptococci. This Rabbit Polyclonal to CYSLTR1 finding suggests that the PCR assay might be successfully used for the detection of pneumococci and diagnosis of pneumococcal diseases (16). The possible involvement of PsaA in the pathogenesis of pneumococcal disease was indicated by immunization studies performed with purified PsaA (24) and confirmed by insertion-duplication mutagenesis analysis of the gene (1). Recently, Briles et al. (2) observed that immunization with PsaA reduces the carriage of pneumococci, suggesting that PsaA may be useful for the elicitation of herd immunity in humans. During the search for protein antigens that could elicit protective immune responses against from the unencapsulated pneumococcal strain R6 and from one serotype 3 clinical isolate. Moreover, the gene has also been identified and sequenced in three viridans group streptococcal species: and showed positive hybridization with a probe. The demonstration of PsaA in heterologous organisms suggests that the effectiveness of this antigen as a useful diagnostic marker should be reconsidered. MATERIALS AND METHODS Bacterial strains. The unencapsulated strain R6 was kindly provided by A. Tomasz (Rockefeller University, New York, N.Y.), and strain 746/96 was provided by J. A. Melanocyte stimulating hormone release inhibiting factor Sez-Nieto (Centro Nacional de Microbiologa, Madrid, Spain). Eleven strains of of serotypes 3, 4, 6, 9, 14, 15, 19, and 23 were taken from our laboratory collection. The other strains were NCTC 12261, NCTC 11427, NCTC 10713, NCTC 7863, NCDO 573, NCDO 597, and NCTC 10449. The strains used were Melanocyte stimulating hormone release inhibiting factor N 462, ATCC 10618, ATCC 10555, ATCC 14685, and C-11. We also used ATCC 25922. In addition, we.