title: Riemerella anatipestifer extracellular protease S blocks complement activation via the classical and lectin pathways.
abstract: Riemerella anatipestifer (RA) is the causative agent of infectious serositis in ducklings and other avian species. It is difficult to control the disease due to its 21 serotypes, poor cross-protection, and bacterial resistance to antimicrobial agents. The complement system is an important component of the innate immune system. However, bacterial pathogens exploit several strategies to evade detection by the complement system. Here, we purified and identified a 59-kDa RA extracellular protease S (EcpS) consisting of a gelatinase. In this study, we aimed to determine how EcpS interferes with complement activation and whether it could block complement-dependent neutrophil function. We found that EcpS potently blocked RA phagocytosis and killing by duck neutrophils. Furthermore, EcpS inhibited the opsonization of bacteria by complement 3b. EcpS specifically blocked complement 3b and complement 4b deposition via the classical and lectin pathways, whereas the alternative pathway was not affected. In summary, we show that RA can survive the bactericidal activity of the duck complement system. These results indicate that RA has evolved mechanisms to evade the duck complement system that may increase the efficiency by which this pathogen can gain access and colonize the inner tissues where it may cause severe infections.
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Mengnan
authors.initials: M
authors.lastname: Fan
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Sihuai
authors.initials: S
authors.lastname: Chen
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Ludan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Junxuan
authors.initials: J
authors.lastname: Bi
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Jiasun
authors.initials: J
authors.lastname: Peng
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Xinyan
authors.initials: X
authors.lastname: Huang
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Huan
authors.initials: H
authors.lastname: Li
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Sheng
authors.initials: S
authors.lastname: Jiang
authors.affiliation: a Rongchang Campus, Southwest University , Chongqing , People's Republic of China.
authors.forename: Jixiang
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology; D003167:Complement Activation / Q000187:drug effects*; D003165:Complement System Proteins / Q000378:metabolism*; D004372:Ducks; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D045826:Flavobacteriaceae Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary; D011201:Poultry Diseases / Q000382:microbiology; D060494:Riemerella / Q000201:enzymology*; D044967:Serum
chemical_list: D001426:Bacterial Proteins; D003165:Complement System Proteins; D010450:Endopeptidases; C019061:protease S
keywords: EcpS; Riemerella anatipestifer; complement; immune evasion