Abdelwhab E M, Grund Christian, Aly Mona M, Beer Martin, Harder Timm C, Hafez Hafez M
A Institute of Poultry Diseases, Free University of Berlin, Koenigsweg 63-14163 Berlin, Germany.
B National Laboratory for Veterinary Quality Control on Poultry Production (NLQP), Animal Health Research Institute, P.O. Box 246, Dokki, Giza-12618, Egypt.
Avian Dis. 2016 Jun;60(2):496-9. doi: 10.1637/11207-060115-ResNote.
Serologic tests are a valuable tool for retrospective surveillance of avian influenza viruses (AIV) and monitoring of postvaccination host immune response. Yet collection of serum samples, particularly in adult breeder chickens, is laborious, intrusive to birds, and may pose a serious risk to the biosecurity of a flock. In this study we compared the level of AIV-specific antibody titers in eggs and serum samples obtained from broiler breeder chickens vaccinated at 6, 12, and 18 wk of age with H5N2-inactivated vaccine. Nucleocapsid protein-specific ELISA and hemagglutination inhibition test (HI) against homologous as well as heterologous antigens were used. The eggs and sera were collected at 22, 30, 45, and 50 wk of age (i.e., 4, 12, 27, and 32 wk after the third and final immunization, respectively). Using ELISA, the number of positive egg yolk samples decreased over time after vaccination, from 97% to 47%, while the seropositivity rate of serum samples was 97%-100% during the whole investigation period. No antibody titers were detected in egg white. By HI, antibody titers in serum samples were higher than in egg yolk samples. Compared to the homologous H5N2 antigen, significantly lower HI titers were obtained by using a heterologous H5N1 virus of clade 2.2.1.2. In addition, no HI titers were detected in egg yolk and/or serum samples tested against the antigen of an Egyptian H5N1 antigenic drift variant of clade 2.2.1.1. This study indicates that egg yolk may be used to monitor the postvaccination immune status of broiler breeder chickens and retrospective serosurveillance-by HI when a matching antigen is available as well as by ELISA-particularly for up to 12 wk postvaccination.
血清学检测是回顾性监测禽流感病毒（AIV）和监测疫苗接种后宿主免疫反应的重要工具。然而，采集血清样本，尤其是成年种鸡的血清样本，既费力又会对鸡造成侵扰，还可能对鸡群的生物安全构成严重风险。在本研究中，我们比较了从6、12和18周龄接种H5N2灭活疫苗的肉种鸡获得的鸡蛋和血清样本中AIV特异性抗体滴度水平。使用了针对同源和异源抗原的核衣壳蛋白特异性ELISA和血凝抑制试验（HI）。在22、30、45和50周龄（即分别在第三次也是最后一次免疫后的4、12、27和32周）采集鸡蛋和血清。使用ELISA检测，接种疫苗后，阳性蛋黄样本数量随时间减少，从97%降至47%，而在整个调查期间血清样本的血清阳性率为97%-100%。蛋清中未检测到抗体滴度。通过HI检测，血清样本中的抗体滴度高于蛋黄样本。与同源H5N2抗原相比，使用2.2.1.2分支的异源H5N1病毒获得的HI滴度显著较低。此外，针对2.2.1.1分支的埃及H5N1抗原漂移变体的抗原检测的蛋黄和/或血清样本中未检测到HI滴度。本研究表明，当有匹配抗原时，蛋黄可用于监测肉种鸡接种疫苗后的免疫状态以及通过HI进行回顾性血清监测，也可通过ELISA进行监测，特别是在接种疫苗后的12周内。
