title: Chlamydia psittaci infection increases mortality of avian influenza virus H9N2 by suppressing host immune response.
abstract: Avian influenza virus subtype H9N2 (H9N2) and Chlamydia psittaci (C. psittaci) are frequently isolated in chickens with respiratory disease. However, their roles in co-infection remain unclear. We tested the hypothesis that C. psittaci enhances H9N2 infection through suppression of host immunity. Thus, 10-day-old SPF chickens were inoculated intra-tracheally with a high or low virulence C. psittaci strain, and were simultaneously vaccinated against Newcastle disease virus (NDV). Significant decreases in body weight, NDV antibodies and immune organ indices occurred in birds with the virulent C. psittaci infection, while the ratio of CD4+/CD8+ T cells increased significantly compared to that of the lower virulence strain. A second group of birds were inoculated with C. psittaci and H9N2 simultaneously (C. psittaci+H9N2), C. psittaci 3 days prior to H9N2 (C. psittaci/H9N2), or 3 days after H9N2 (H9N2/C. psittaci), C. psittaci or H9N2 alone. Survival rates were 65%, 80% and 90% in the C. psittaci/H9N2, C. psittaci+H9N2 and H9N2/C. psittaci groups, respectively and respiratory clinical signs, lower expression of pro-inflammatory cytokines and higher pathogen loads were found in both C. psittaci/H9N2 and C. psittaci+H9N2 groups. Hence, virulent C. psittaci infection suppresses immune response by inhibiting humoral responses and altering Th1/Th2 balance, increasing mortality in H9N2 infected birds.
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chu
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Tianyuan
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Er
authors.initials: E
authors.lastname: Han
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhao
authors.affiliation: Faculty of Veterinary Medicine, University of Agriculture, Faisalabad 38040, Pakistan.
authors.forename: Ahrar
authors.initials: A
authors.lastname: Khan
authors.affiliation: Key Lab of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.|Shandong Binzhou Animal Science and Veterinary Medicine Academy, Binzhou 256600, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: He
authors.affiliation: Unit of Cellular Biology &Microbial Infection, CNRS UMR3691, Institut Pasteur, 75015 Paris, France.
authors.forename: Yongzheng
authors.initials: Y
authors.lastname: Wu
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis; D001717:Birds; D001835:Body Weight; D002691:Chlamydophila psittaci / Q000302:isolation & purification* / Q000472:pathogenicity; D060085:Coinfection / Q000276:immunology*; D053127:Influenza A Virus, H9N2 Subtype / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000150:complications / Q000276:immunology / Q000401:mortality* / Q000821:virology; D008168:Lung / Q000382:microbiology / Q000821:virology; D009522:Newcastle disease virus / Q000276:immunology / Q000302:isolation & purification; D009956:Psittacosis / Q000150:complications*; D013154:Spleen / Q000276:immunology / Q000473:pathology; D013950:Thymus Gland / Q000276:immunology / Q000473:pathology; D014774:Virulence
chemical_list: D000914:Antibodies, Viral