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Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria.

ABSTRACT: BACKGROUND:Avian Infectious Bronchitis Virus (IBV) is a highly contagious disease that imposes a huge economic burden on the global poultry industry. IBV contains numerous serotypes and variants with incomplete tenuous cross immunological protection. The failure of currently used vaccines to protect against diverse, circulating IBV strains that are specific to a given region poses a major problem for the poultry industry. Thus, there is an urgent need to conduct studies aimed at genotyping field IB viruses. In this study, we have determined the molecular characteristics of circulating IBV by sequencing the S1 gene of viral isolates from affected previously vaccinated broiler flocks suffering from the disease. RESULTS:Ten isolates propagated in embryonated eggs showed an ability to induce typical IBV lesions after three successive viral passages. We performed a nested RT-PCR assay that targeted the hypervariable region 3 (HVR-3) of the S1 gene, and identified the isolates as IBV through sequence analysis. The IBV isolates showed sequence similarity between the Syrian isolates that vary from 96.20 to 100%, and those being closer to the Variant-2 strain IS/1494/06 (EU780077.2) with 97.5 to 99.4% similarities. However, less nucleotide identity was found with sequences belonging to the used vaccine strains such as H120, Mass5, and 4/91. CONCLUSIONS:This study showed the presence of the Variant-2 strain circulating in Syrian broiler flocks showing signs of IBV disease. Currently, there is no commercial effective vaccine which protects birds against the Variant-2 strain. Continuous monitoring procedures should be taken to control and limit the spread of the IBV Variant-2 strain. This research emphasizes both the importance of epidemiological monitoring in intensive poultry farming for novel pathogens and the use of local isolates as future vaccine targets.

SUBMITTER: Al-Jallad T

PROVIDER: S-EPMC7678145 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria.

Al-Jallad Tamara T Kassouha Morshed M Salhab Mohamad M Alomar Anouar A Al-Masalma Mouhamad M Abdelaziz Fahim F

BMC veterinary research 20201119 1

<h4>Background</h4>Avian Infectious Bronchitis Virus (IBV) is a highly contagious disease that imposes a huge economic burden on the global poultry industry. IBV contains numerous serotypes and variants with incomplete tenuous cross immunological protection. The failure of currently used vaccines to protect against diverse, circulating IBV strains that are specific to a given region poses a major problem for the poultry industry. Thus, there is an urgent need to conduct studies aimed at genotypi ...[more]

PMID: 33213457

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Project description: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.

Dataset Information

Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria.

Publications

Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria.

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