{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:21:14Z","timestamp":1772252474798,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2020,4,21]],"date-time":"2020-04-21T00:00:00Z","timestamp":1587427200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["31272542"],"award-info":[{"award-number":["31272542"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>In a pilot study, simultaneous infection with Chlamydia psittaci (C. psittaci) and H9N2 virus induced 20% mortality and severe avian airsacculitis, shedding light on animal models of poultry respiratory diseases. However, the pathogenesis is still unclear. In the current study, we hypothesized that C. psittaci infection execrates macrophage function and facilitates H9N2 infection. To explore the potential mechanism, we studied the effect of C. psittaci and H9N2 on the functions of HD11 cells in vitro by simultaneous infection of C. psittaci and H9N2. At the same time, we used infection with C. psittaci or H9N2 alone as the control groups. The results showed that coinfection with C. psittaci and H9N2 could significantly aggravate the mortality of HD11 cells compared to C. psittaci or H9N2 infection alone. In addition, coinfection with C. psittaci and H9N2 did not induce high C. psittaci loads compared to C. psittaci infection alone at 12- and 24-hours post-inoculation (hpi), but coinfection with C. psittaci and H9N2 could increase the loads of H9N2 compared to H9N2 alone in HD11 cells at 12 hpi. More importantly, inducible nitric oxide synthase (iNOS) expression levels, enzyme activity, nitric oxide (NO) production, and phagocytosis were reduced significantly in the group with C. psittaci and H9N2 coinfection compared to those of H9N2 or C. psittaci alone at 24 hpi. Finally, C. psittaci infection induced robust expressions of type Th2 cytokines interleukin (IL)-4 and IL-10, while interferon gamma (IFN-\u03b3) and tumor necrosis factor-\u03b1 (TNF-\u03b1) displayed a significant decrease compared to H9N2 infection alone at 24 hpi. All the above data indicate that C. psittaci infection can facilitate H9N2 invasion and to aggravate severe avian airsacculitis by impairing macrophage functions.<\/jats:p>","DOI":"10.3390\/ani10040722","type":"journal-article","created":{"date-parts":[[2020,4,22]],"date-time":"2020-04-22T04:15:13Z","timestamp":1587528913000},"page":"722","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Chlamydia psittaci Triggers the Invasion of H9N2 Avian Influenza Virus by Impairing the Functions of Chicken Macrophages"],"prefix":"10.3390","volume":"10","author":[{"given":"Jun","family":"Chu","sequence":"first","affiliation":[{"name":"College of Life Science and Engineering, Foshan University, Foshan 528000, Guangdong, China"},{"name":"Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Services, Beijing 100097, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yongxia","family":"Guo","sequence":"additional","affiliation":[{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guanlong","family":"Xu","sequence":"additional","affiliation":[{"name":"National Reference Lab for Animal Brucellosis, China Institute of Veterinary Drug Control, Beijing 100082, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qiang","family":"Zhang","sequence":"additional","affiliation":[{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zonghui","family":"Zuo","sequence":"additional","affiliation":[{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qiang","family":"Li","sequence":"additional","affiliation":[{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yihui","family":"Wang","sequence":"additional","affiliation":[{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1223-9639","authenticated-orcid":false,"given":"Cheng","family":"He","sequence":"additional","affiliation":[{"name":"College of Life Science and Engineering, Foshan University, Foshan 528000, Guangdong, China"},{"name":"Key Lab of Animal Epidemiology and Zoonosis of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1093\/femspd\/ftu007","article-title":"Chlamydia psittaci: Update on an underestimated zoonotic agent","volume":"73","author":"Knittler","year":"2015","journal-title":"Pathog. Dis."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1093\/infdis\/88.2.109","article-title":"Human carrier of the psittacosis virus","volume":"88","author":"Meyer","year":"1951","journal-title":"J. Infect. Dis."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1016\/j.vetmic.2008.09.046","article-title":"Chlamydophila psittaci infections in birds: A review with emphasis on zoonotic consequences","volume":"135","author":"Harkinezhad","year":"2009","journal-title":"Vet. Microbiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"382","DOI":"10.1089\/vbz.2012.1131","article-title":"Prevalence and genotype distribution of Chlamydia psittaci in feral Canada geese (Branta canadensis) in Belgium","volume":"13","author":"Dickx","year":"2013","journal-title":"Vector Borne Zoonotic Dis."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1099\/jmm.0.070003-0","article-title":"Chlamydia psittaci exposure in pet birds","volume":"63","author":"Cong","year":"2014","journal-title":"J. Med. Microbiol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1211","DOI":"10.1099\/jmm.0.059287-0","article-title":"Seroprevalence of Chlamydia psittaci infection in market-sold adult chickens, ducks and pigeons in north-western China","volume":"62","author":"Cong","year":"2013","journal-title":"J. Med. Microbiol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1111\/zph.12161","article-title":"Epidemiology of Chlamydia psittaci Infection in Racing Pigeons and Pigeon Fanciers in Beijing, China","volume":"62","author":"Ling","year":"2015","journal-title":"Zoonoses Public Health"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1089\/vbz.2017.2214","article-title":"Epidemiological Investigation and Genotype of Chlamydia Exposure in Pigeons in Three Provinces in Northern China","volume":"18","author":"Wang","year":"2018","journal-title":"Vector Borne Zoonotic Dis."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1556\/avet.2013.038","article-title":"Mixed infection by fowlpox virus and Chlamydophila psittaci in a commercial laying hen flock","volume":"62","author":"Karpinska","year":"2014","journal-title":"Acta Vet. Hung."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1017\/S0043933916000179","article-title":"Emerging threat of H9N2 viruses in poultry of Pakistan and vaccination strategy","volume":"72","author":"Umar","year":"2016","journal-title":"Worlds Poult. Sci. J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1007\/s13238-014-0111-7","article-title":"H9N2 influenza virus in China: A cause of concern","volume":"6","author":"Sun","year":"2015","journal-title":"Protein Cell"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1246","DOI":"10.3201\/eid2407.172059","article-title":"Avian Influenza A Virus Infection among Workers at Live Poultry Markets, China, 2013\u20132016","volume":"24","author":"Ma","year":"2018","journal-title":"Emerg Infect. Dis."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1515\/jvetres-2017-0035","article-title":"Pathological Alterations in Respiratory System During Co-infection with Low Pathogenic Avian Influenza Virus (H9N2) and Escherichia Coli in Broiler Chickens","volume":"61","author":"Jaleel","year":"2017","journal-title":"J. Vet. Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1016\/j.jviromet.2018.06.011","article-title":"Viral interference between low pathogenic avian influenza H9N2 and avian infectious bronchitis viruses in vitro and in ovo","volume":"259","author":"Aouini","year":"2018","journal-title":"J. Virol. Methods"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"29421","DOI":"10.1038\/srep29421","article-title":"Chlamydia psittaci infection increases mortality of avian influenza virus H9N2 by suppressing host immune response","volume":"6","author":"Chu","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"13997","DOI":"10.1038\/s41598-017-14519-1","article-title":"Co-infection of Chlamydia psittaci with H9N2, ORT and Aspergillus fumigatus contributes to severe pneumonia and high mortality in SPF chickens","volume":"7","author":"Chu","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"654","DOI":"10.1093\/infdis\/jir333","article-title":"Chlamydia psittaci genetic variants differ in virulence by modulation of host immunity","volume":"204","author":"Miyairi","year":"2011","journal-title":"J. Infect. Dis."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2092","DOI":"10.4049\/jimmunol.181.3.2092","article-title":"Type I IFNs enhance susceptibility to Chlamydia muridarum lung infection by enhancing apoptosis of local macrophages","volume":"181","author":"Qiu","year":"2008","journal-title":"J. Immunol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"342","DOI":"10.1016\/j.vetmic.2009.09.032","article-title":"Biology and intracellular pathogenesis of high or low virulent Chlamydophila psittaci strains in chicken macrophages","volume":"141","author":"Beeckman","year":"2010","journal-title":"Vet. Microbiol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"13","DOI":"10.12703\/P6-13","article-title":"The M1 and M2 paradigm of macrophage activation: Time for reassessment","volume":"6","author":"Martinez","year":"2014","journal-title":"F1000Prime Rep."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Pan, Q., Liu, A., Zhang, F., Ling, Y., Ou, C., Hou, N., and He, C. (2012). Co-infection of broilers with Ornithobacterium rhinotracheale and H9N2 avian influenza virus. BMC Vet. Res., 8.","DOI":"10.1186\/1746-6148-8-104"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1016\/j.virol.2012.08.037","article-title":"Characterization of cellular furin content as a potential factor determining the susceptibility of cultured human and animal cells to coronavirus infectious bronchitis virus infection","volume":"433","author":"Tay","year":"2012","journal-title":"Virology"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1186\/1297-9716-42-64","article-title":"Induction of inflammatory cytokines and Toll-like receptors in chickens infected with avian H9N2 influenza virus","volume":"42","author":"Nang","year":"2011","journal-title":"Vet. Res."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1006\/meth.2001.1262","article-title":"Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method","volume":"25","author":"Livak","year":"2001","journal-title":"Methods"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"275","DOI":"10.1001\/jama.2012.194139","article-title":"Bacterial coinfection in influenza: A grand rounds review","volume":"309","author":"Chertow","year":"2013","journal-title":"JAMA"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Getie, S., Wondimeneh, Y., Getnet, G., Workineh, M., Worku, L., Kassu, A., and Moges, B. (2015). Prevalence and clinical correlates of Schistosoma mansoni co-infection among malaria infected patients, Northwest Ethiopia. BMC Res. Notes, 8.","DOI":"10.1186\/s13104-015-1468-2"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1637\/0005-2086-47.s3.817","article-title":"Evaluation of pathogenic potential of avian influenza virus serotype H9N2 in chickens","volume":"47","author":"Bano","year":"2003","journal-title":"Avian Dis."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"680","DOI":"10.1637\/10109-030112-Reg.1","article-title":"Co-infection of Ornithobacterium rhinotracheale with Streptococcus zooepidemicus in chickens","volume":"56","author":"Pan","year":"2012","journal-title":"Avian Dis."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1524","DOI":"10.1093\/ps\/76.11.1524","article-title":"Nitric oxide synthase activity and mRNA expression in chicken macrophages","volume":"76","author":"Hussain","year":"1997","journal-title":"Poult. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"805","DOI":"10.1016\/S1074-7613(00)00078-9","article-title":"Inhibition of Th1 differentiation by IL-6 is mediated by SOCS1","volume":"13","author":"Diehl","year":"2000","journal-title":"Immunity"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1615\/CritRevEukarGeneExpr.v20.i2.10","article-title":"Tumor necrosis factor-alpha signaling in macrophages","volume":"20","author":"Parameswaran","year":"2010","journal-title":"Crit. Rev. Eukaryot. Gene Expr."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3164","DOI":"10.1128\/IAI.73.5.3164-3165.2005","article-title":"Tumor necrosis factor alpha plays a role in the acceleration of atherosclerosis by Chlamydia pneumoniae in mice","volume":"73","author":"Campbell","year":"2005","journal-title":"Infect. Immun."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1010","DOI":"10.4049\/jimmunol.162.2.1010","article-title":"IL-10 gene knockout mice show enhanced Th1-like protective immunity and absent granuloma formation following Chlamydia trachomatis lung infection","volume":"162","author":"Yang","year":"1999","journal-title":"J. Immunol."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/10\/4\/722\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T14:26:45Z","timestamp":1760365605000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/10\/4\/722"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,4,21]]},"references-count":33,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2020,4]]}},"alternative-id":["ani10040722"],"URL":"https:\/\/doi.org\/10.3390\/ani10040722","relation":{"has-preprint":[{"id-type":"doi","id":"10.20944\/preprints202003.0203.v1","asserted-by":"object"}]},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,4,21]]}}}