Drissi Touzani Charifa, Fellahi Siham, Gaboun Fatima, Fassi Fihri Ouafaa, Baschieri Selene, Mentag Rachid, El Houadfi Mohammed
Unité de Pathologie Aviaire, Département de Pathologie et Santé Publique Vétérinaire, IAV Hassan II, BP 6202, Rabat-Instituts, 10000, Rabat, Morocco.
Unité de Biotechnologie, CRRA-Rabat, Institut National de la Recherche Agronomique INRA, Avenue Mohamed Belarbi Alaoui, Rabat-Instituts, B.P 6356, 10101, Rabat, Morocco.
Arch Virol. 2019 Feb;164(2):381-390. doi: 10.1007/s00705-018-4076-3. Epub 2018 Oct 26.
Very virulent infectious bursal disease virus (vvIBDV), the cause of significant economic losses in many poultry-producing areas, has been present in Morocco since 1991. In spite of the introduction of vaccination, disease outbreaks are frequently observed. To ascertain if vaccines failure may be due to the emergence of new strains, the aim of this study was to perform for the first time the molecular characterization of vvIBDV strains circulating in Morocco by focusing on the hypervariable region (HVR) of the VP2 protein, which is frequently used for molecular epidemiology and phylogenetic studies. Field samples of haemorrhagic bursae of Fabricius were collected for molecular characterization in different parts of the country during 2016-2017 from 48 chicken flocks showing symptoms of disease. In a phylogenetic tree, nucleotide sequences containing the VP2 HVR of 13 samples that were positive for vvIBDV formed a common branch with those of vvIBDV references strains published in GenBank, but they clearly grouped into a distinct subcluster. An alignment of the deduced amino acid sequences, in addition to confirming the presence of the "signature" typical of the vvIBDV HVR, also revealed the presence of substitutions in hydrophilic loops that are known to be involved in the elicitation of neutralizing antibodies. One of these substitutions is unique to the Moroccan isolates. These results represent the first molecular characterization of vvIBDV isolates in Morocco and may indicate that one of the causes of vaccine ineffectiveness is antigenic drift.
超强毒传染性法氏囊病病毒（vvIBDV）在许多家禽养殖地区造成了重大经济损失，自1991年以来一直在摩洛哥存在。尽管引入了疫苗接种，但仍经常观察到疾病暴发。为了确定疫苗失效是否可能是由于新毒株的出现，本研究的目的是首次通过聚焦于VP2蛋白的高变区（HVR）对在摩洛哥流行的vvIBDV毒株进行分子特征分析，该区域常用于分子流行病学和系统发育研究。2016 - 2017年期间，从该国不同地区48个表现出疾病症状的鸡群中采集了法氏囊出血的田间样本用于分子特征分析。在系统发育树中，13个vvIBDV阳性样本中包含VP2 HVR的核苷酸序列与GenBank中公布的vvIBDV参考毒株的序列形成一个共同分支，但它们明显聚为一个独特的亚簇。推导的氨基酸序列比对，除了证实存在vvIBDV HVR典型的“特征”外，还揭示了已知参与中和抗体诱导的亲水性环中存在替代。这些替代之一是摩洛哥分离株所特有的。这些结果代表了摩洛哥vvIBDV分离株的首次分子特征分析，可能表明疫苗无效的原因之一是抗原漂移。
