Aliyu Hayatuddeen Bako, Hair-Bejo Mohd, Omar Abdul Rahman, Ideris Aini
Department of Veterinary Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Malaysia.
Avian Unit, Veterinary Teaching Hospital, Ahmadu Bello University, Zaria, Nigeria.
Front Vet Sci. 2021 Apr 20;8:643976. doi: 10.3389/fvets.2021.643976. eCollection 2021.
Vaccination is an essential component in controlling infectious bursal disease (IBD), however, there is a lack of information on the genetic characteristics of a recent infectious bursal disease virus (IBDV) that was isolated from IBD vaccinated commercial flocks in Malaysia. The present study investigated 11 IBDV isolates that were isolated from commercial poultry farms. The isolates were detected using reverse transcription-polymerase chain reaction (RT-PCR) targeting the hypervariable region (HVR) of VP2. Based on the HVR sequences, five isolates (IBS536/2017, IBS624/2017, UPM766/2018, UPM1056/2018, and UPM1432/2019) were selected for whole-genome sequencing using the MiSeq platform. The nucleotide and amino acid (aa) sequences were compared with the previously characterized IBDV strains. Deduced aa sequences of VP2HVR revealed seven isolates with 94-99% aa identity to very virulent strains (genogroup 3), two isolates with 97-100% aa identity to variant strains (genogroup 2), and two strains with 100% identity to the vaccine strain (genogroup 1) of IBDV. The phylogenetic analysis also showed that the isolates formed clusters with the respective genogroups. The characteristic motifs 222T, 249K, 286I, and 318D are typical of the variant strain and were observed for UPM1219/2019 and UPM1432/2019. In comparison, very virulent residues such as 222A, 249Q, 286T, and 318G were found for the vvIBDV, except for the UPM1056/2018 strain with a A222T substitution. In addition, the isolate has aa substitutions such as D213N, G254D, S315T, S317R, and A321E that are not commonly found in previously reported vvIBDV strains. Unlike the other vvIBDVs characterized in this study, UPM766/2018 lacks the MLSL aa residues in VP5. The aa tripeptides 145/146/147 (TDN) of VP1 were conserved for the vvIBDV, while a different motif, NED, was observed for the Malaysian variant strain. The phylogenetic tree showed that the IBDV variant clustered with the American and Chinese variant viruses and are highly comparable to the novel Chinese variants, with 99.9% identity. Based on the sequences and phylogenetic analyses, this is the first identification of an IBDV variant being reported in Malaysia. Further research is required to determine the pathogenicity of the IBDV variant and the protective efficacy of the current IBD vaccines being used against the virus.
疫苗接种是控制传染性法氏囊病（IBD）的重要组成部分，然而，关于最近从马来西亚接种IBD疫苗的商业鸡群中分离出的传染性法氏囊病病毒（IBDV）的基因特征，目前缺乏相关信息。本研究对从商业家禽养殖场分离出的11株IBDV进行了调查。使用针对VP2高变区（HVR）的逆转录-聚合酶链反应（RT-PCR）检测这些分离株。基于HVR序列，选择了5株分离株（IBS536/2017、IBS624/2017、UPM766/2018、UPM1056/2018和UPM1432/2019），使用MiSeq平台进行全基因组测序。将核苷酸和氨基酸（aa）序列与先前鉴定的IBDV毒株进行比较。推导的VP2HVR氨基酸序列显示，7株分离株与超强毒株（基因群3）的氨基酸同一性为94-99%，2株分离株与变异毒株（基因群2）的氨基酸同一性为97-100%，2株毒株与IBDV疫苗株（基因群1）的同一性为100%。系统发育分析还表明，这些分离株与各自的基因群形成了聚类。特征基序222T、249K、286I和318D是变异毒株的典型特征，在UPM1219/2019和UPM1432/2019中观察到。相比之下，除了具有A222T替换的UPM1056/2018毒株外，超强毒IBDV中发现了如222A、249Q、286T和318G等超强毒残基。此外，该分离株具有如D213N、G254D、S315T、S317R和A321E等氨基酸替换，这些替换在先前报道的超强毒IBDV毒株中并不常见。与本研究中鉴定的其他超强毒IBDV不同，UPM766/2018在VP5中缺乏MLSL氨基酸残基。VP1的氨基酸三联体145/146/147（TDN）在超强毒IBDV中是保守的，而在马来西亚变异毒株中观察到了不同的基序NED。系统发育树显示，IBDV变异株与美国和中国的变异病毒聚类，与新型中国变异株高度相似，同一性为99.9%。基于序列和系统发育分析，这是首次在马来西亚报道IBDV变异株。需要进一步研究以确定IBDV变异株的致病性以及当前使用的IBD疫苗对该病毒的保护效力。
