The Putative Proteinase Maturation Protein A of Streptococcus pneumoniae Is a Conserved Surface Protein with Potential To Elicit Protective Immune Responses

Abstract

Surface-exposed proteins often play an important role in the interaction between pathogenic bacteria and their host. We isolated a pool of hydrophobic, surface-associated proteins of Streptococcus pneumoniae. The opsonophagocytic activity of hyperimmune serum raised against this protein fraction was high and species specific. Moreover, the opsonophagocytic activity was independent of the capsular type and chromosomal genotype of the pneumococcus. Since the opsonophagocytic activity is presumed to correlate with in vivo protection, these data indicate that the protein fraction has the potential to elicit species-specific immune protection with cross-protection against various pneumococcal strains. Individual proteins in the extract were purified by two-dimensional gel electrophoresis. Antibodies raised against three distinct proteins contributed to the opsonophagocytic activity of the serum. The proteins were identified by mass spectrometry and Nterminal amino acid sequencing. Two proteins were the previously characterized pneumococcal surface protein A and oligopeptide-binding lipoprotein AmiA. The third protein was the recently identified putative proteinase maturation protein A (PpmA), which showed homology to members of the family of peptidyl-prolyl cis/trans isomerases. Immunoelectron microscopy demonstrated that PpmA was associated with the pneumococcal surface. In addition, PpmA was shown to elicit species-specific opsonophagocytic antibodies that were crossreactive with various pneumococcal strains. This antibody cross-reactivity was in line with the limited sequence variation of ppmA. The importance of PpmA in pneumococcal pathogenesis was demonstrated in a mouse pneumonia model. Pneumococcal ppmA-deficient mutants showed reduced virulence. The properties of PpmA reported here indicate its potential for inclusion in multicomponent protein vaccines.Streptococcus pneumoniae is an important human pathogen which causes meningitis, otitis media, sepsis, and pneumonia. The precise molecular mechanisms by which the pneumococcus invades and damages host tissues are not fully understood. For many years, the polysaccharide capsule has been recognized as the major virulence factor and consequently was considered an important vaccine candidate (for reviews see references 5 and 34). The use of a 23-valent vaccine containing capsular polysaccharides from pneumococci commonly causing disease has had limited effect in reducing the morbidity and mortality associated with this organism (1,16,19,41). The current pneumococcal vaccine strategy focuses on the use of conjugates, in which a limited number of capsular polysaccharides are linked to a carrier protein. The proteins in the conjugate vaccines cause a switch in the immune response to polysaccharides from T-cell independent to T-cell dependent. This results in an increase in the antibody response and the generation of memory T lymphocytes. Conjugate vaccines are more immunogenic in young children than polysaccharide vaccines (15,18). Although the results of early trial...

The Lactococcus lactis CodY Regulon

“…In the genome of S. pneumoniae R6, highly conserved copies of the CodY-box were found upstream of genes (putatively) involved in nitrogen metabolism and especially of those concerned with the biosynthesis of BCAAs. Most interestingly, the CodY-box is present upstream of ppmA and rgg, two genes that are known to be involved in virulence of this human pathogen (59,60). In contrast to B. subtilis, a CodY-box is present in the upstream region of S. pneumoniae R6 codY, which suggests that transcription of codY of the latter organism, like that of L. lactis, is auto-regulated.…”

Versatility of pneumococcal surface proteins

“…Involvement in virulence has been suggested for PpmA. Overweg et al (2000) demonstrated that mutation of ppmA of strain D39 increased the survival rate of mice. SlrA knockout mutants have been shown to be less efficient in the nasopharyngeal colonization of mice, and this has been attributed to the decreased ability of the knockout mutants to adhere to nonprofessional cells (Hermans et al, 2005).…”

Analysis of the Transcriptome of Group A Streptococcus in Mouse Soft Tissue Infection

“…Seven of the 16 GAS-specific antibodies were reactive in situ with several GAS antigens demonstrating high levels of immunoreactivity or abundance ( Figure 5; Supplementary 27 a significant note, given that PrtM-immunized mice are protected against S. pneumoniae infection. 46 Despite limited detection of malE RNA transcripts (M5005_Spy1058; ranked 561st); a surprisingly high degree of immunoreactivity was observed for the solute-binding surface lipoprotein Figure 3. Analysis of variance revealed a significant strain effect in the in vivo microarray expression data.…”