The ability of pneumococcal conjugate vaccine (PCV) to decrease transmission by blocking the acquisition of colonization has been attributed to herd immunity. We describe the role of mucosal IgG to capsular polysaccharide (CPS) in mediating protection from carriage, translating our findings from a murine model to humans. We used a flow-cytometric assay to quantify antibody-mediated agglutination demonstrating that hyperimmune sera generated against an unencapsulated mutant was poorly agglutinating. Passive immunization with this antiserum was ineffective to block acquisition of colonization compared to agglutinating antisera raised against the encapsulated parent strain. In the human challenge model samples were collected from PCV and control vaccinated adults. In PCV-vaccinated subjects IgG levels to CPS were increased in serum and nasal wash (NW). IgG to the inoculated strain CPS dropped in NW samples after inoculation suggesting its sequestration by colonizing pneumococci. In post-vaccination NW samples pneumococci were heavily agglutinated compared to pre-vaccination samples in subjects protected against carriage. Our results indicate that pneumococcal agglutination mediated by CPS specific antibodies is a key mechanism of protection against acquisition of carriage. Capsule may be the only vaccine target that can elicit strong agglutinating antibody responses, leading to protection against carriage acquisition and generation of herd immunity.

In a search for the genetic basis for the structural difference between the related Streptococcus pneumoniae capsular serotypes 15B and 15C and for the reported reversible switching between these serotypes, the corresponding capsular polysaccharide synthesis (cps) loci were investigated by keeping in mind that at the structural level, the capsules differ only in O acetylation. The cps locus of a serotype 15B strain was identified, partially PCR amplified with primers based on the related serotype 14 sequence, and sequenced. Sequence analysis revealed, among other open reading frames, an intact open reading frame (designated cps15bM) whose product, at the protein level, exhibited characteristics of previously identified acetyltransferases. Genetic analysis of the corresponding region in a serotype15C strain indicated that the same gene was present but had a premature stop in translation. Closer analysis indicated that the serotype 15B gene contained a short tandem TA repeat consisting of eight TA units. In serotype 15C, this gene contained nine TA units that resulted in a frameshift and a truncated product. Genetic analysis of 17 serotype 15B and 15C clinical isolates revealed a perfect correlation between the serotype and the length of the short tandem repeat in the putative O-acetyltransferase gene. The number of TA repeating units varied between seven and nine in the various isolates. Together, the data strongly suggest that the structural difference between serotypes 15B and 15C is based on variation in the short tandem TA repeat in the O-acetyltransferase gene and that the transition between serotypes is due to slipped-strand mispairing with deletion or insertion of TA units in the cps15bM gene.The human pathogen Streptococcus pneumoniae (pneumococcus) is a major cause of respiratory tract infections, bacteremia, and meningitis, particularly in young children and the elderly (32, 35). One of the prime virulence determinants of this bacterium is the polysaccharide capsule (CPS). This structure is thought to protect the bacterium against harmful environmental conditions and exhibits antiphagocytic properties (8). The CPS is composed of saccharide repeating units that are polymerized into a polysaccharide chain. Thus far, 90 different capsule serotypes have been identified. The diversity is based on variation in the carbohydrate structure of the oligosaccharide units or the attached side groups (18).The genes encoding the enzymes involved in CPS biosynthesis are clustered on the bacterial genome in the capsular polysaccharide synthesis (cps) locus. The cps locus is typically flanked by the genes dexB and aliA. At this time, the cps loci of 16 different serotypes have been sequenced (3, 12, 13, 16, 20, 23, 24, 26-29, 33, 34, 42, 50). Nearly all loci have the same genetic organization (38). The first four genes of the loci are conserved in almost all serotypes, and it has been demonstrated that three of these genes encode enzymes involved in the regulation of capsule production (5,7,30,54). The central parts of ...

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractThe present work reports the use of non-living non-recombinant bacteria as a delivery system for mucosal vaccination. Antigens are bound to the cell-wall of pretreated Lactococcus lactis, designated as Gram-positive enhancer matrix (GEM), by means of a peptidoglycan binding domain. The influence of the GEM particles on the antigen-specific serum antibody response was studied. Following nasal immunization with the GEM-based vaccines, antibody responses were induced at systemic and local levels. Furthermore, different GEM-based vaccines could be used consecutively in the same mice without adverse effects or loss of activity. Taken together, the results evidence the adjuvant properties of the GEM particles and indicate that GEM-based vaccines can be used repeatedly and are particularly suitable for nasal immunization purposes.

Streptococcus pneumoniae is an important human bacterial pathogen, causing such infections as pneumonia, meningitis, septicemia, and otitis media. Current capsular polysaccharide-based conjugate vaccines protect against a fraction of the over 90 serotypes known, whereas vaccines based on conserved pneumococcal proteins are considered promising broad-range alternatives. The pneumococcal genome encodes two conserved proteins of an as yet unknown function, SP1298 and SP2205, classified as DHH (Asp-His-His) subfamily 1 proteins. Here we examined their contribution to pneumococcal pathogenesis using single and double knockout mutants in three different strains: D39, TIGR4, and BHN100. Mutants lacking both SP1298 and SP2205 were severely impaired in adherence to human epithelial Detroit 562 cells. Importantly, the attenuated phenotypes were restored upon genetic complementation of the deleted genes. Single and mixed mouse models of colonization, otitis media, pneumonia, and bacteremia showed that bacterial loads in the nasopharynx, middle ears, lungs, and blood of mice infected with the mutants were significantly reduced from those of wild-type-infected mice, with an apparent additive effect upon deletion of both genes. Minor strain-specific phenotypes were observed, i.e., deletion of SP1298 affected host-cell adherence in BHN100 only, and deletion of SP2205 significantly attenuated virulence in lungs and blood in D39 and BHN100 but not TIGR4. Finally, subcutaneous vaccination with a combination of both DHH subfamily 1 proteins conferred protection to nasopharynx, lungs, and blood of mice infected with TIGR4. We conclude that SP1298 and SP2205 play a significant role at several stages of pneumococcal infection, and importantly, these proteins are potential candidates for a multicomponent protein vaccine.Streptococcus pneumoniae is a Gram-positive bacterium causing serious invasive diseases, such as pneumonia, septicemia, and meningitis. In addition, this human pathogen is the causative agent of less serious but highly prevalent mucosal infections, such as otitis media (OM) and sinusitis. Young children under the age of 2 years, the elderly, and immunocompromised individuals account for the majority of pneumococcal morbidity and mortality observed worldwide (10). One of the main virulence factors of the pneumococcus is its polysaccharide capsule, of which over 90 serotypes distinct in biochemical structure have been identified to date. The polysaccharide capsule contributes to protection against phagocytosis, enabling the pneumococcus to evade the immune system of the host (23, 24). Current pneumococcal vaccines, such as Pneumovax 23 (23-valent; Merck), Synflorix (10-valent; GlaxoSmithKline, United Kingdom), and Prevnar (7-and 13-valent; Pfizer) target this polysaccharide capsule. While these vaccines do provide good immune protection, it is restricted to the serotypes included in the vaccine. As a result, serotype replacement is already occurring, and the need for a serotype-independent vaccine is urgent (17,38).