title: Serologic assay for avian-origin influenza A (H7N9) virus in adults of Shanghai, Guangzhou and Yunnan, China.
abstract: OBJECTIVE
  To investigate serologic status for novel avian influenza A (H7N9) virus in different areas in China, we examined serum samples collected in winter of 2011 from adult population of Shanghai (eastern China), Guangzhou (southern China) and Yunnan (southwest China) for the antibody responses to this virus.
  
  
  METHODS
  A total of 900 stored serum samples of adult outpatients (300 samples for each area) were subjected to anti-hemagglutinin (HA) antibodies assay using enzyme-linked immunosorbent assay (ELISA) and neutralizing antibodies assay using H7N9 pseudotyped particles (H7N9pp) and authentic H7N9 virus based neutralization test.
  
  
  RESULTS
  Anti-H7 antibodies were detected in 164, 186 and 123 samples from three areas above, respectively. Among anti-H7 positive sera, 20, 42 and 13 samples had neutralizing titers of ≥10 when 8×10(2) focus-forming units (FFU) of H7N9 pseudotyped particles (pp) were adopted in neutralizing assay, respectively. When neutralizing antibodies were assayed using classic microneutralization (MN) test, MN titers of ≥10 were found in 7 samples from Guangzhou, but none from Shanghai and Yunnan.
  
  
  CONCLUSIONS
  Low levels of protective immunity pre-existed in some general adult population of the three areas, and pre-existing immunity against H7N9 in Guangzhou appears stronger than that in Shanghai and Yunnan.
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Wenbo
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Haoran
authors.initials: H
authors.lastname: Peng
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Tao
authors.affiliation: Microbiology Laboratory, Center for Disease Control and Prevention of Xuhui District, Shanghai, China.
authors.forename: Xuetao
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Hailin
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: National Institute for Viral Disease Control and Prevention, China CDC, Beijing, China. Electronic address: euy-tokyo@umin.ac.jp.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China. Electronic address: pnzhao@163.com.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai, China. Electronic address: qizt@smmu.edu.cn.
authors.forename: Zhongtian
authors.initials: Z
authors.lastname: Qi
mesh_terms: D000328:Adult; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D002681:China; D002947:Cities; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D064766:Influenza A Virus, H7N9 Subtype / Q000145:classification*; D007251:Influenza, Human / Q000175:diagnosis* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D010045:Outpatients; D012698:Serologic Tests; D012703:Serotyping; D055815:Young Adult
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D007074:Immunoglobulin G
keywords: H7N9; Influenza; Neutralizing antibody; Pre-existing immunity; Serology