Laboratory of Epidemiology and Veterinary Microbiology LR0020, Institut Pasteur of Tunis, Tunis El Manar University, Tunis Belvedere 1002, Tunisia.
Veterinary Practice El Intilaka, Canal Street 20, 2097 Ben Arous, Tunisia.
Poult Sci. 2021 Feb;100(2):496-506. doi: 10.1016/j.psj.2020.11.035. Epub 2020 Nov 28.
Infectious bursal disease (IBD), an acute, highly contagious, and immunosuppressive avian disease, is caused by infectious bursal disease virus (IBDV) and constitutes one of the main threats to the poultry industry, worldwide. This study was performed to isolate and characterize IBDV isolates circulating in Tunisia. Eleven collected bird samples were identified using an SYBR Green-based one-step real-time reverse transcriptase polymerase chain reaction. The full-length genome sequencing of 7 of the 11 IBDV isolates has been realized. VP2 gene data showed limited sequence variations for all the 7 tested samples. The few nucleotide changes were silent and the deduced amino acid sequences were identical with the exception of a unique and characteristic nonsilent mutation (C) detected for the TN37/19 isolate, with a change of amino acid (L) to (F) at position 401. In addition, the serine-rich heptapeptide SWSASGS, characteristic of virulent IBDV, as well the amino acid residues, conserved in most very virulent IBDV (vvIBDV) strains, were detected in all the Tunisian tested isolates. Nucleotide sequences of VP5 gene revealed the presence of 5 substitutions leading to changes in the amino acid sequences of the virus. Two of these mutations were unique and characteristic of the Tunisian isolates. Besides, the alternative AUG start codon, characteristic of vvIBDV, was observed in all obtained VP5 gene sequences. The Tunisian protein sequences of VP1 showed E242 and the TDN triplet at positions 145, 146, and 147, a motif specific of vvIBDV. Phylogenetic analyses of the 5 genes confirmed the sequence alignment results and showed that the Tunisian strains are closely related to the very virulent Algerian IBDV strains.
传染性法氏囊病（IBD）是一种急性、高度传染性和免疫抑制性的禽类疾病，由传染性法氏囊病病毒（IBDV）引起，是全球家禽业的主要威胁之一。本研究旨在分离和鉴定突尼斯流行的 IBDV 分离株。使用基于 SYBR Green 的一步实时逆转录聚合酶链反应鉴定了 11 个采集的鸟类样本。对 11 个 IBDV 分离株中的 7 个进行了全长基因组测序。所有 7 个测试样本的 VP2 基因数据显示出有限的序列变异。少数核苷酸变化是沉默的，推导的氨基酸序列是相同的，除了 TN37/19 分离株检测到一个独特的特征性非沉默突变（C），导致 401 位氨基酸（L）到（F）的变化。此外，在所有测试的突尼斯分离株中都检测到了富含丝氨酸的七肽 SWSASGS，这是强毒 IBDV 的特征，以及大多数非常强毒 IBDV（vvIBDV）株中保守的氨基酸残基。VP5 基因的核苷酸序列显示存在 5 个导致病毒氨基酸序列变化的取代。其中两个突变是突尼斯分离株所特有的。此外，所有获得的 VP5 基因序列都观察到了 vvIBDV 特征的替代 AUG 起始密码子。突尼斯 VP1 蛋白序列在位置 145、146 和 147 处显示 E242 和 TDN 三联体，这是 vvIBDV 的特征基序。5 个基因的系统进化分析证实了序列比对结果，表明突尼斯株与非常强毒的阿尔及利亚 IBDV 株密切相关。
