Li Yan, Wang Jinjin, Chen Longfei, Wang Qun, Zhou Meng, Zhao Hui, Chi Zengna, Wang Yixin, Chang Shuang, Zhao Peng
College of Veterinary Medicine, Shandong Agricultural University, Tai'an, China.
Front Vet Sci. 2022 Jul 6;9:930887. doi: 10.3389/fvets.2022.930887. eCollection 2022.
Live attenuated vaccines have been extensively used to prevent infectious disease in poultry flocks. Freedom from exogenous virus is a high priority for any veterinary vaccines. Recently, attenuated Newcastle disease virus (NDV) vaccines were detected to be contaminated with chicken infectious anemia virus (CIAV) in a routine screening for exogenous viruses. To investigate the possible source of the contamination, we conducted virological tests on a specific-pathogen-free (SPF) layer breeder flock that provide the raw materials for vaccines in this manufacturer. Firstly, CIAV antibodies in serum and egg yolks samples of the SPF laying hens were detected by ELISA assays. The results showed that CIAV antibodies in serum and egg yolks were 62% positive and 57% positive, respectively. Then, DNA was extracted from the NDV vaccines and SPF chicken embryonated eggs, and detected by molecular virology assays. The results showed that three assays for pathogens in embryonated eggs had similar positive rates (35.8%). And the sequences of CIAV from SPF embryos and NDV vaccines consisted of 2,298 nucleotides (nt) with 100% homology. The new full-length genome of CIAV was designated SDSPF2020 (Genbank accession number: MW660821). Data showed SDSPF2020 had the sequence similarities of 95.8-99.6% with reference strains, and shared the highest homology with the Chinese strain HLJ15125. These results strongly suggested that exogenous CIAV contamination is most likely caused by wild virus infection in SPF flocks and vertical transmission to chicken embryos. Collectively, this study illustrated that vertical transmission of CIAV from a SPF layer breeder flock to embryos was a non-neglible way for exogenous virus contamination in vaccine production.
减毒活疫苗已被广泛用于预防家禽群中的传染病。对于任何兽用疫苗而言，避免外源病毒污染都是重中之重。最近，在对外源病毒的常规筛查中，发现减毒新城疫病毒（NDV）疫苗被鸡传染性贫血病毒（CIAV）污染。为了调查污染的可能来源，我们对为本制造商提供疫苗原材料的无特定病原体（SPF）蛋种鸡群进行了病毒学检测。首先，通过ELISA检测法检测了SPF蛋鸡血清和蛋黄样本中的CIAV抗体。结果显示，血清和蛋黄中的CIAV抗体阳性率分别为62%和57%。然后，从NDV疫苗和SPF鸡胚中提取DNA，并通过分子病毒学检测法进行检测。结果显示，对胚蛋中病原体的三种检测方法的阳性率相似（35.8%）。并且，来自SPF胚和NDV疫苗的CIAV序列由2298个核苷酸（nt）组成，同源性为100%。CIAV的新全长基因组被命名为SDSPF2020（Genbank登录号：MW660821）。数据显示，SDSPF2020与参考毒株的序列相似性为95.8 - 99.6%，与中国毒株HLJ15125的同源性最高。这些结果有力地表明，外源CIAV污染很可能是由SPF鸡群中的野生病毒感染以及向鸡胚的垂直传播所致。总体而言，本研究表明，CIAV从SPF蛋种鸡群向胚蛋的垂直传播是疫苗生产中外源病毒污染的一个不可忽视的途径。
