Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
PLoS One. 2011 Jan 25;6(1):e16164. doi: 10.1371/journal.pone.0016164.
Individuals infected with the 2009 pandemic virus A(H1N1) developed serological response which can be measured by hemagglutination-inhibition (HI) and microneutralization (microNT) assays.
METHODOLOGY/PRINCIPAL FINDINGS: MicroNT and HI assays for specific antibody to the 2009 pandemic virus were conducted in serum samples collected at the end of the first epidemic wave from various groups of Thai people: laboratory confirmed cases, blood donors and health care workers (HCW) in Bangkok and neighboring province, general population in the North and the South, as well as archival sera collected at pre- and post-vaccination from vaccinees who received influenza vaccine of the 2006 season. This study demonstrated that goose erythrocytes yielded comparable HI antibody titer as compared to turkey erythrocytes. In contrast to the standard protocol, our investigation found out the necessity to eliminate nonspecific inhibitor present in the test sera by receptor destroying enzyme (RDE) prior to performing microNT assay. The investigation in pre-pandemic serum samples showed that HI antibody was more specific to the 2009 pandemic virus than NT antibody. Based on data from pre-pandemic sera together with those from the laboratory confirmed cases, HI antibody titers ≥ 40 for adults and ≥ 20 for children could be used as the cut-off level to differentiate between the individuals with or without past infection by the 2009 pandemic virus.
CONCLUSIONS/SIGNIFICANCE: Based on the cut-off criteria, the infection rates of 7 and 12.8% were estimated in blood donors and HCW, respectively after the first wave of the 2009 influenza pandemic. Among general population, the infection rate of 58.6% was found in children versus 3.1% in adults.
感染 2009 年大流行病毒 A(H1N1)的个体产生的血清学反应可以通过血凝抑制（HI）和微量中和（microNT）测定来衡量。
方法/主要发现：在曼谷和邻近省份的实验室确诊病例、献血者和医护人员（HCW）、北部和南部的普通人群以及接受 2006 年流感疫苗接种的疫苗接种者在大流行前和接种后收集的档案血清中，对 2009 年大流行病毒的特异性抗体进行了 microNT 和 HI 测定。本研究表明，鹅红细胞产生的 HI 抗体滴度与火鸡红细胞相当。与标准方案不同，我们的研究发现，在进行 microNT 测定之前，需要通过受体破坏酶（RDE）消除测试血清中存在的非特异性抑制剂。在大流行前血清样本的研究表明，HI 抗体比 NT 抗体更特异于 2009 年大流行病毒。基于大流行前血清数据以及实验室确诊病例的数据，成人 HI 抗体滴度≥40，儿童 HI 抗体滴度≥20 可作为区分个体是否曾感染 2009 年大流行病毒的临界值。
结论/意义：根据临界值标准，在 2009 年流感大流行第一波后，献血者和 HCW 的感染率分别估计为 7%和 12.8%。在普通人群中，儿童的感染率为 58.6%，而成年人的感染率为 3.1%。
