Pneumococcal Surface Protein A Inhibits Complement Activation by Streptococcus pneumoniae

ABSTRACT Pneumococcal surface protein A (PspA) is a surface-exposed protein virulence factor for Streptococcus pneumoniae. In this study, no significant depletion of serum complement was observed for the serum of mice infected with pneumococci that express PspA. In contrast, in mice infected with an isogenic strain of pneumococci lacking PspA, significant activation of serum complement was detected within 30 min after infection. Also, the PspA-deficient strain but not the PspA-expressing strain was cleared from the blood within 6 h. The contribution of PspA to pneumococcal virulence was further investigated by using mice deficient for C5, C3, or factor B. In mice deficient for C3 or factor B, PspA-negative pneumococci became fully virulent. In contrast, in C5-deficient mice as in wild-type mice, PspA-deficient pneumococci were avirulent. These in vivo data suggest that, in nonimmune mice infected with pneumococci, PspA interferes with complement-dependent host defense mechanisms mediated by factor B. Immunoblots of pneumococci opsonized in vitro suggested that more C3b was deposited on PspA-negative than on PspA-positive pneumococci. This was observed with and without anticapsular antibody. Furthermore, processing of the α chain of C3b was reduced in the presence of PspA. We propose that PspA exerts its virulence function by interfering with deposition of C3b onto pneumococci and/or by inhibiting formation of a fully functional alternative pathway C3 convertase. By blocking recruitment of the alternative pathway, PspA reduces the amount of C3b deposited onto pneumococci, thereby reducing the effectiveness of complement receptor-mediated pathways of clearance.

Download Full-text

Both Innate Immunity and Type 1 Humoral Immunity to Streptococcus pneumoniae Are Mediated by MyD88 but Differ in Their Relative Levels of Dependence on Toll-Like Receptor 2

Infection and Immunity ◽

10.1128/iai.73.1.298-307.2005 ◽

2005 ◽

Vol 73 (1) ◽

pp. 298-307 ◽

Cited By ~ 74

Author(s):

Abdul Q. Khan ◽

Quanyi Chen ◽

Zheng-Qi Wu ◽

James C. Paton ◽

Clifford M. Snapper

Keyword(s):

Streptococcus Pneumoniae ◽

Humoral Immunity ◽

Protein A ◽

Surface Protein ◽

Lethal Challenge ◽

Humoral Immune ◽

Extracellular Bacterium

ABSTRACT Little is known regarding the role of Toll-like receptors (TLRs) in regulating protein- and polysaccharide-specific immunoglobulin (Ig) isotype production in response to an in vivo challenge with an extracellular bacterium. In this report we demonstrate that MyD88−/−, but not TLR2−/−, mice are markedly defective in their induction of multiple splenic proinflammatory cytokine- and chemokine-specific mRNAs after intraperitoneal (i.p.) challenge with heat-killed Streptococcus pneumoniae capsular type 14 (S. pneumoniae type 14). This is correlated with analogous responses in splenic cytokine protein release in vitro following addition of S. pneumoniae type 14. Consistent with these data, naïve MyD88−/−, but not TLR2−/−, mice are more sensitive to killing following i.p. challenge with live S. pneumoniae type 14, relative to responses in wild-type mice. However, prior immunization of MyD88−/− mice with heat-killed S. pneumoniae type 14 protects against an otherwise-lethal challenge with live S. pneumoniae type 14. Surprisingly, both MyD88−/− and TLR2−/− mice exhibit striking and equivalent defects in elicitation of type 1 IgG isotypes (IgG3, IgG2b, and IgG2a), but not the type 2 IgG isotype, IgG1, specific for several protein and polysaccharide antigens, in response to i.p. challenge with heat-killed S. pneumoniae type 14. Of note, the type 1 IgG isotype titers specific for pneumococcal surface protein A are reduced in MyD88−/− mice but not TLR2−/− mice. These data suggest that distinct TLRs may differentially regulate innate versus adaptive humoral immunity to intact S. pneumoniae and are the first to implicate a role for TLR2 in shaping an in vivo type 1 IgG humoral immune response to a gram-positive extracellular bacterium.

Download Full-text

Pertussis Toxin Improves Immune Responses to a Combined Pneumococcal Antigen and Leads to Enhanced Protection against Streptococcus pneumoniae

Clinical and Vaccine Immunology ◽

10.1128/cvi.00134-14 ◽

2014 ◽

Vol 21 (7) ◽

pp. 972-981 ◽

Cited By ~ 3

Author(s):

Carolina Salcedo-Rivillas ◽

Anne-Sophie Debrie ◽

Eliane Namie Miyaji ◽

Jorge M. C. Ferreira ◽

Isaías Raw ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Pertussis Toxin ◽

Protein A ◽

Passive Immunization ◽

Surface Protein ◽

Interleukin 17 ◽

Adjuvant Activity ◽

Content Type

ABSTRACTPneumococcal surface protein A (PspA) is a candidate antigen for the composition of protein-based vaccines againstStreptococcus pneumoniae. While searching for efficient adjuvants for PspA-based vaccines, our group has described the potential of combining PspA with the whole-cell pertussis vaccine (wP). When given to mice through the nasal route, a formulation composed of PspA from clade 5 (PspA5) and wP (PspA5-wP) induced high levels of antibodies and protection against challenges with different pneumococcal strains. PspA5-wP also induced the secretion of interleukin 17 (IL-17) by splenocytes and the infiltration of leukocytes in the lungs after challenge. Here, we show that protection against a pneumococcal invasive challenge was completely abrogated in μMT−/−mice, which are deficient in the maturation of B cells, illustrating the importance of antibodies in the survival elicited by the PspA5-wP vaccine. Moreover, passive immunization showed that IgG purified from the sera of mice immunized with PspA5-wP conferred significant protection to naive mice, whereas the respective F(ab′)2did not. Additionally,in vivodepletion of complement abolished protection against the pneumococcal challenge. The combination of PspA5 with wild-type or mutantBordetella pertussisstrains or with purified components showed that the pertussis toxin (PT)-containing formulations induced the highest levels of antibodies and protection. This suggests that the adjuvant activity of wP in the PspA5 model is mediated at least in part by PT. The sera from mice immunized with such formulations displayed high IgG binding and induction of complement deposition on the pneumococcal surfacein vitro, which is consistent with thein vivoresults.

Download Full-text

DNA vaccines expressing pneumococcal surface protein A (PspA) elicit protection levels comparable to recombinant protein

Journal of Medical Microbiology ◽

10.1099/jmm.0.46217-0 ◽

2006 ◽

Vol 55 (4) ◽

pp. 375-378 ◽

Cited By ~ 14

Author(s):

Daniela M. Ferreira ◽

Eliane N. Miyaji ◽

Maria Leonor S. Oliveira ◽

Michelle Darrieux ◽

Ana Paula M. Arêas ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Recombinant Protein ◽

Dna Vaccines ◽

Protein A ◽

Surface Protein ◽

Humoral Response ◽

Cost Effective ◽

Promising Candidate ◽

Pneumococcal Surface Protein A ◽

Antibody Levels

Pneumococcal surface protein A (PspA) is a promising candidate for the development of cost-effective vaccines against Streptococcus pneumoniae. In the present study, BALB/c mice were immunized with DNA vaccine vectors expressing the N-terminal region of PspA. Animals immunized with a vector expressing secreted PspA developed higher levels of antibody than mice immunized with the vector expressing the antigen in the cytosol. However, both immunogens elicited similar levels of protection against intraperitoneal challenge. Furthermore, immunization with exactly the same fragment in the form of a recombinant protein, with aluminium hydroxide as an adjuvant, elicited even higher antibody levels, but this increased humoral response did not correlate with enhanced protection. These results show that DNA vaccines expressing PspA are able to elicit protection levels comparable to recombinant protein, even though total anti-PspA IgG response is considerably lower.

Download Full-text