Immunization with a Combination of Three Pneumococcal Proteins Confers Additive and Broad Protection against Streptococcus pneumoniae Infections in Mice

Abstract

Pneumococcal polysaccharide-based vaccines are effective in preventing pneumococcus infection; however, some drawbacks preclude their widespread use in developing and undeveloped countries. Here, we evaluated the protective effects of ATP-dependent caseinolytic protease (ClpP), pneumolysin mutant (⌬A146 Ply), putative lipoate-protein ligase (Lpl), or combinations thereof against pneumococcal infections in mice. Vaccinated mice were intraperitoneally and/or intranasally challenged with different pneumococcal strains. In intraperitoneal challenge models with pneumococcal strain D39 (serotype 2), the most striking protection was obtained with the combination of the three antigens. Similarly, with the intranasal challenge models, (i) additive clearance of bacteria in lungs was observed for the combination of the three antigens and (ii) a combination vaccine conferred complete protection against intranasal infections of three of the four most common pneumococcal strains (serotypes 14, 19F, and 23F) and 80% protection for pneumococcal strain 6B. Even so, immunity to this combination could confer protection against pneumococcal infection with a mixture of four serotypes. Our results showed that the combination vaccine was as effective as the currently used vaccines (PCV7 and PPV23). These results indicate that system immunization with the combination of pneumococcal antigens could provide an additive and broad protection against Streptococcus pneumoniae in pneumonia and sepsis infection models.Streptococcus pneumoniae (pneumococcus) commonly colonizes the upper respiratory tract asymptomatically and was estimated, in 2005, to kill 1.6 million people every year, most of whom were children aged Ͻ5 years in developing and undeveloped countries (36). As far as we know, 91 capsular polysaccharide serotypes have been identified in S. pneumoniae (33); among these, serotypes 23F, 19F, 14, and 6B are the four most epidemic strains worldwide (2,5,15,17,25,26,29). Moreover, and of recent concern, the widespread use of antibiotics, leading to the development of antibiotic resistance or multidrug resistance against S. pneumoniae, is increasing (9,12,26).Heptavalent protein-polysaccharide conjugate vaccine (PCV7) and 23-valent pneumococcal polysaccharide vaccine (PPV23) are the two vaccines currently being used against S. pneumoniae. Both of these vaccines are polysaccharide-based formulations and effective in preventing invasive pneumococcal infections; however, some drawbacks, such as high cost, the limited polysaccharides covered, poor immunogenicity in the very young and the very old, and serotype replacement (22,24,26,36), limit their wider use.Alternatively, in an attempt to overcome the disadvantages of polysaccharide-based vaccines, a number of studies have been focusing on the screening and evaluation of proteinbased vaccine candidates. Pneumococcal protein vaccine candidates, such as nontoxic pneumolysin derivates, pneumococcal surface proteins (PspA and PspC), pneumococcal surface adhesin (PsaA), and ATP-dependent caseino...

Mucosal Immunization with Recombinant Fusion Protein DnaJ-ΔA146Ply Enhances Cross-Protective Immunity against Streptococcus pneumoniae Infection in Mice via Interleukin 17A

“…Serum passive transfer studies have revealed the protective property of antigen-specific IgG in controlling pneumococcal diseases (26,34). Also, it is well known that IgA is an important immunoglobulin with anti-inflammatory properties (45).…”

“…The ⌬A146Ply (full-length wild-type Ply with a deletion of A146) gene was constructed by using site-directed mutagenesis by overlap extension in our previous study (30). It was then cloned, expressed, and purified as described in the previous studies (26,30). The full-length DnaJ gene was PCR amplified from the TIGR4 strain using two pairs of primers: F-DnaJ-N plus RDnaJ-N and F-DnaJ-C plus R-DnaJ-C (Table 1).…”

“…In previous studies, pneumococcal carriage was shown to induce production of anti-Ply antibodies (23,24). Several Ply variants have been used as potential vaccine candidates and also as carriers for glycoconjugated vaccines in animal models (25)(26)(27)(28); of them, ⌬A146Ply (Ply with a single deletion of A146) was one of the most remarkable variants with minimal toxicity. Hence, we wanted to evaluate whether ⌬A146Ply has mucosal adjuvant capacity like its wild type.…”

Induction of the pneumococcal vncRS operon by lactoferrin is essential for pneumonia

“…Mice were immunized according to the protocol described in a previous study [44], with slight modifications. Briefly, separate formulations of the His 6 -tagged VncS antigen and the commercially available synthetic Pep27 peptide (ProSci Inc, USA) were prepared using aluminum hydroxide (Alum) as an adjuvant, in the ratio 1:10.…”

A Novel Protein, RafX, Is Important for Common Cell Wall Polysaccharide Biosynthesis in Streptococcus pneumoniae: Implications for Bacterial Virulence

“…The sequences of the primers used are listed in Table S2 in the supplemental material. The rafX and lgt genes were deleted from the chromosome of S. pneumoniae by insertion-deletion mutagenesis, which was performed essentially according to an established protocol (25). For example, upstream and downstream fragments of the rafX gene were PCR amplified with primers rafX UP P1-2 and rafX DW P3-4, respectively.…”