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Streptococcus pneumoniae Facteurs de virulence

Streptococcus pneumoniae Facteurs de virulence

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Streptococcus pneumoniae Facteurs de virulence

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  1. Streptococcus pneumoniaeFacteurs de virulence Pierre MOINE CHU de Bicêtre

  2. Host-pathogen interactions: Redefining the basic Concepts of virulence and pathogenicity [Cassadeval & Pirofski, Infect Immun 1999] Virulence « The relative capacity of a microbe to cause damage In host » Virulence factor « A component of a pathogen that damages the host »

  3. Large scale identification of virulence genes from Streptococcus pneumoniae[Polissi A, Infect Immun 1998] • 126 Virulence genes • Class I "known virulence factors": LytA, IgA1 protease, NanA, Hyl, Cbp • Class II "métabolic pathways": purine biosynthesis, phosphate assimilation, synthesis of glutamine, anaerobic metabolism • Class III "ATP dependent proteases" • Class IV "ABC transporters" • Class V "DNA recombination/repair" • Class VI "unknown functions": n = 63

  4. Large scale identification of virulence genes from Streptococcus pneumoniae[Polissi A, Infect Immun 1998] • Processus multifactoriel • Adaptation bactérienne à l'environnement hôte (infection, croissance, survie) • Gènes identifiés chez S pneumoniae déjà identifiés chez d'autres pathogènes (V cholerae, S typhimurium, S aureus, P aeruginosa) • Spécificité de site: modèle de pneumonie (LytA, Hyl, NanA) vs modèle de septicémie (ip)

  5. Ply pneumolysin LytA autolysin PspA surface protein NanA neuraminidase Hyl hyaluronidase CbpA surface protein i.p. challenge 5 x 103 cfu Berry AM, Infect Immun 2000

  6. Ply pneumolysin LytA autolysin PspA surface protein NanA neuraminidase Hyl hyaluronidase CbpA surface protein i.p. challenge 8 x 106 cfu Berry AM, Infect Immun 2000

  7. Ply pneumolysin LytA autolysin PspA surface protein NanA neuraminidase Hyl hyaluronidase CbpA surface protein i.p. challenge 105 cfu Berry AM, Infect Immun 2000

  8. Differences in virulence for mice among S pneumoniae strains of capsular types 2, 3, 4, 5, and 6 are not attributable to differences in pneumolysin production Capsular Strains Mean survival Cytoplasmic hemolytic Type DL100 time (days) pneumolysin titers 2 D39 1.1 8800 3 WU2 0.9 1900 3 A66.1 1.1 1600 3 EF10197 1.2 3100 4 EF3296 3.5 4900 4 L81905 2.3 4900 4 BG9739 2.4 7000 6A DBL6A 6.7 2820 6A EF6796 5.3 2300 6B BG9163 6.8 3900 6B BG7322 5.7 2300 [Benton, Infect Immun 1997]

  9. Relationship between virulence in mice and susceptibility to penicillin for 122 clinical S. pneumoniae strains of various serotypes. [Azoulay Dupuis, AAC 2000]

  10. Relationship between virulence in mice and susceptibility to penicillin within 3 groups of S pneumoniae serotypes [Azoulay-Dupuis, AAC 2000] Serotypes V+S V+R V-S V-I V-R 1, 3, 4 (n=16) 83% - 17% - - 6 (n=32) 34% - 38% 12% 16% 9, 14, 19, 23 (n=50) - - 44% 24% 32% V+ virulent; V- avirulent; S penicillin susceptible; I intermediate or R resistant

  11. Complex Relationship between acquisition of b-lactam resistance and loss of virulence in Streptococcus pneumoniae [Rieux et al., JID 2001] Strain Construction Penicillin LD50 MIC (mg/l)log10cfu/mouse 15986 DNA donor 8 6.8±0.1 23477 Recipient 0.03 2.0±0.6 23.2b 23477x pbp2b allele 0.06 5.7±1.0 23.2x 23477x pbpX allele 0.06 4.4±0.2 23.2b.2x 23.2bx pbp X allele 0.125 6.0±0.6 After 1 i.p. passage in mice 23.2b 1.9±0.2 23.2x 4.1±0.6 23.2b.2x 1.9±0.1

  12. Variants pneumococciques Transparent Opaque Autolyse + 0 Colonisation nasopharyngée ++ 0 Adhérence récepteurs glycoconjugués Cel nasopharyngées GlcNAcb1-3Gal ++ 0 Cel pulmonaires repos GlcNAcb1-3Gal + + Cel pulmonaires repos GlcNAcb1-4Gal + + Cel pulmonaires activées GlcNAc ++ 0 Adhérence aux PAF récepteurs ++ 0 Adhérence cellulaire Pulmonaires repos + + Pulmonaires activées + 0 Endothéliales repos + + Endothéliales activées ++ 0 Virulence Infection ip 0 ++ Opsonisation-phagocytose ++ ± Ac téichoique/polysaccharide capsulaire +++ / + + / +++

  13. Variants pneumococciques Transparent Opaque Ply (pneumolysine) + + LytA (autolysine CBP) +++ + PsPA (protéine de surface CBP) + +++ CbpA (protéine de surface) +++ + SpxB Pyruvate oxydase (H2O2) +++ + EF-Ts + +++ PpmA (« proteinase maturation protein ») +++ + [Weiser, Infect Immun 1996; Rosenow, Mol Microbiol 1997; Kim, J Infect Dis 1998; Overweg, Infect Immun 2000]

  14. Role of TNFa in pathogenesis of pneumococcal pneumoniae in mice[Takashima et al. Infect Immun 1997] Survival rate (%) Control anti-TNFa antibody Time after infection (day)

  15. Role of TNF-a in the host response of mice bacteremia caused by pneumolysin-deficient S. pneumoniae [Benton, Infect Immun 1998] Log TNF-a pg/ml Log CFU/ml blood 10 5 4 8 3 2 6 1 4 0 0 10 20 30 40 50 Time (hr) 0 10 20 30 40 50 Time (hr) D 39 + anti-TNF-a D 39 PLN PLN + anti-TNF-a

  16. Targeted disruption of the p50 subunit of NF-kB leads to multifocal defects in immune responses[Sha et al., 1995] Increased susceptibility to S. pneumoniae

  17. Infected mice/control uninfected mice NF-kB ratio P4241 Mix "P4241" R6 P15986 8 7 i.t. challenge 105 cfu of S. pneumoniae per mouse 6 5 4 3 2 1 1 4 6 24 Time after infection (hrs) Amory-Rivier et al, CCM 2000

  18. TNF-a pg/ml 1250 P4241 R6 P15986 1000 750 500 250 0 2 4 6 12 24 Time after infection (hrs) Amory-Rivier et al, CCM 2000

  19. Lung TNF-a 12500 10000 P30606: 107 cfu/mouse 7500 P23477: 107 cfu/mouse P26772: 107 cfu/mouse 5000 P15986: 107 cfu/mouse 2500 P4241: 105 cfu/mouse 0 0 2 4 6 12 24 48 Time post infection (hrs)

  20. Conclusion - Virulence et facteurs de virulence du germe Processus multifactoriel Variations intra-souches Site dépendant « Effet inoculum » Effets additifs synergiques Résistance à la pénicilline Multiples inconnus - Hôte: polymorphisme génétique humain

  21. S. pneumoniae TIGR4 genome R6 D39 Comparative genome hybridizations Science 2001