title: Additive inhibition of complement deposition by pneumolysin and PspA facilitates Streptococcus pneumoniae septicemia.
abstract: Streptococcus pneumoniae is a common cause of septicemia in the immunocompetent host. To establish infection, S. pneumoniae has to overcome host innate immune responses, one component of which is the complement system. Using isogenic bacterial mutant strains and complement-deficient immune naive mice, we show that the S. pneumoniae virulence factor pneumolysin prevents complement deposition on S. pneumoniae, mainly through effects on the classical pathway. In addition, using a double pspA-/ply- mutant strain we demonstrate that pneumolysin and the S. pneumoniae surface protein PspA act in concert to affect both classical and alternative complement pathway activity. As a result, the virulence of the pspA-/ply- strain in models of both systemic and pulmonary infection is greatly attenuated in wild-type mice but not complement deficient mice. The sensitivity of the pspA-/ply- strain to complement was exploited to demonstrate that although early innate immunity to S. pneumoniae during pulmonary infection is partially complement-dependent, the main effect of complement is to prevent spread of S. pneumoniae from the lungs to the blood. These data suggest that inhibition of complement deposition on S. pneumoniae by pneumolysin and PspA is essential for S. pneumoniae to successfully cause septicemia. Targeting mechanisms of complement inhibition could be an effective therapeutic strategy for patients with septicemia due to S. pneumoniae or other bacterial pathogens.
authors: Centre for Respiratory Research, Department of Medicine, Royal Free and University College Medical School, Rayne Institute, London, United Kingdom.
authors: Jose
authors: J
authors: Yuste
authors: Marina
authors: M
authors: Botto
authors: James C
authors: JC
authors: Paton
authors: David W
authors: DW
authors: Holden
authors: Jeremy S
authors: JS
authors: Brown
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology / Q000502:physiology*; D015922:Complement C1q / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D003176:Complement C3 / Q000172:deficiency / Q000378:metabolism / Q000502:physiology; D011415:Complement Factor B / Q000172:deficiency / Q000235:genetics; D003169:Complement Inactivator Proteins / Q000172:deficiency / Q000494:pharmacology / Q000502:physiology*; D003171:Complement Pathway, Classical / Q000235:genetics / Q000276:immunology; D003165:Complement System Proteins / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D004357:Drug Synergism; D006360:Heat-Shock Proteins / Q000172:deficiency / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011008:Pneumococcal Infections / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D018805:Sepsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013301:Streptolysins / Q000172:deficiency / Q000494:pharmacology / Q000502:physiology*; D037521:Virulence Factors / Q000172:deficiency / Q000494:pharmacology / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D003176:Complement C3; D003169:Complement Inactivator Proteins; D006360:Heat-Shock Proteins; D013301:Streptolysins; D037521:Virulence Factors; C069816:phage shock protein, Bacteria; C032290:plY protein, Streptococcus pneumoniae; D015922:Complement C1q; D003165:Complement System Proteins; D011415:Complement Factor B