Norouzian H, Farjanikish G, Hosseini H
Acta Virol. 2017;61(2):191-196. doi: 10.4149/av_2017_02_09.
Infectious bursal disease (IBD) virus causes a highly contagious immunosuppressive disease in chickens. A total number of 12 pooled bursal samples were collected during 2014-2015 from broiler farms in different regions of Iran. Typical macroscopical and histopathological lesions of the bursa of Fabricius were found similar to reports by other researchers. A 474-bp part of hypervariable region of VP2 (hvVP2) was sequenced and analyzed. Ten isolates had the characteristic amino acid residues of very virulent IBD (vvIBD) viruses and the other two were identified as attenuated (vaccine) strains. The vvIBD isolates had a unique G to S mutation at position 254, compared to other Iranian vvIBD isolates. Two attenuated isolates had the mutation 253Q, not found in D78 strain, creating virulent variant of vaccine strains. Degree of similarity among the studied vvIBD isolates was relatively high (97.6-100%), proposing a common ancestor for them. However, they were partly different from previous Iranian and neighbor countries' isolates (96.2-97.3% similarity to Shiraz isolate and 95.7-96.7% to Iraq and Turkey isolates). In phylogenetic analysis, the studied vvIBD isolates classified as a separate subgroup in the group of isolates from Iran and neighbor countries. More studies on genetic and antigenic characteristics of these isolates as well as probable modifications in their pathogenicity are needed to evaluate the significance of the mentioned differences.
传染性法氏囊病（IBD）病毒可在鸡群中引发一种高度传染性的免疫抑制疾病。2014年至2015年期间，从伊朗不同地区的肉鸡养殖场共采集了12份法氏囊混合样本。法氏囊典型的宏观和组织病理学病变与其他研究人员的报告相似。对VP2高变区（hvVP2）的474个碱基对部分进行了测序和分析。10株分离株具有超强毒力传染性法氏囊病（vvIBD）病毒的特征性氨基酸残基，另外两株被鉴定为弱毒（疫苗）株。与其他伊朗vvIBD分离株相比，vvIBD分离株在254位有一个独特的G到S突变。两株弱毒分离株有253Q突变，这在D78株中未发现，产生了疫苗株的强毒变体。所研究的vvIBD分离株之间的相似程度相对较高（97.6 - 100%），表明它们有一个共同的祖先。然而，它们与先前的伊朗及邻国分离株部分不同（与设拉子分离株的相似性为96.2 - 97.3%，与伊拉克和土耳其分离株的相似性为95.7 - 96.7%）。在系统发育分析中，所研究的vvIBD分离株在来自伊朗和邻国的分离株组中被归类为一个单独的亚组。需要对这些分离株的遗传和抗原特性以及其致病性可能的变化进行更多研究，以评估上述差异的意义。
