title: Pleiotropic effects of cell wall amidase LytA on Streptococcus pneumoniae sensitivity to the host immune response.
abstract: The complement system is a key component of the host immune response for the recognition and clearance of Streptococcus pneumoniae. In this study, we demonstrate that the amidase LytA, the main pneumococcal autolysin, inhibits complement-mediated immunity independently of effects on pneumolysin by a complex process of impaired complement activation, increased binding of complement regulators, and direct degradation of complement C3. The use of human sera depleted of either C1q or factor B confirmed that LytA prevented activation of both the classical and alternative pathways, whereas pneumolysin inhibited only the classical pathway. LytA prevented binding of C1q and the acute-phase protein C-reactive protein to S. pneumoniae, thereby reducing activation of the classical pathway on the bacterial surface. In addition, LytA increased recruitment of the complement downregulators C4BP and factor H to the pneumococcal cell wall and directly cleaved C3b and iC3b to generate degradation products. As a consequence, C3b deposition and phagocytosis increased in the absence of LytA and were markedly enhanced for the lytA ply double mutant, confirming that a combination of LytA and Ply is essential for the establishment of pneumococcal pneumonia and sepsis in a murine model of infection. These data demonstrate that LytA has pleiotropic effects on complement activation, a finding which, in combination with the effects of pneumolysin on complement to assist with pneumococcal complement evasion, confirms a major role of both proteins for the full virulence of the microorganism during septicemia.
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain Spanish Pneumococcal Reference Laboratory, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), Madrid, Spain.
authors.forename: Elisa
authors.initials: E
authors.lastname: Ramos-Sevillano
authors.affiliation: Department of Immunology, Hospital Universitario de la Princesa, Instituto Investigación Sanitaria Princesa (IIS-IP), Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Urzainqui
authors.affiliation: Department of Analytical Chemistry, School of Chemistry, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Campuzano
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Moscoso
authors.affiliation: Confocal Microscopy Facility, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: González-Camacho
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain.
authors.forename: Mirian
authors.initials: M
authors.lastname: Domenech
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain CIBER de Enfermedades Raras (CIBERER), Madrid, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Rodríguez de Córdoba
authors.affiliation: Department of Immunology, Hospital Universitario de la Princesa, Instituto Investigación Sanitaria Princesa (IIS-IP), Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Sánchez-Madrid
authors.affiliation: Centre for Inflammation and Tissue Repair, University College London, London, United Kingdom.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Brown
authors.affiliation: Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain.
authors.forename: Ernesto
authors.initials: E
authors.lastname: García
authors.affiliation: CIBER de Enfermedades Respiratorias (CIBERES), Madrid, Spain Spanish Pneumococcal Reference Laboratory, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), Madrid, Spain jyuste@isciii.es.
authors.forename: Jose
authors.initials: J
authors.lastname: Yuste
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000276:immunology; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002473:Cell Wall / Q000201:enzymology / Q000276:immunology*; D003167:Complement Activation / Q000276:immunology*; D003176:Complement C3 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D017242:Complement Factor H / Q000276:immunology; D006649:Histocompatibility Antigens / Q000276:immunology; D054884:Host-Pathogen Interactions / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics / Q000378:metabolism*; D010587:Phagocytosis / Q000276:immunology; D010767:Phosphorylcholine / Q000378:metabolism; D011008:Pneumococcal Infections / Q000276:immunology* / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000276:immunology; D018805:Sepsis / Q000276:immunology / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000276:immunology*; D013301:Streptolysins / Q000235:genetics / Q000276:immunology
chemical_list: D001426:Bacterial Proteins; C489166:C4bp protein, mouse; D003176:Complement C3; D006649:Histocompatibility Antigens; D011135:Polysaccharides, Bacterial; C110344:SpsA protein, Streptococcus pneumoniae; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae; D010767:Phosphorylcholine; D017242:Complement Factor H; D009238:N-Acetylmuramoyl-L-alanine Amidase