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Molecular detection and phylogenetic analysis of Marek's disease virus oncogenes from vaccinated flocks in southern India reveals circulation of very virulent MDV genotype
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  • Kannaki Ramasamy,
  • E. Priyanka,
  • Y. Nishitha,
  • S. Vamshi Krishna,
  • Santosh Haunshi,
  • Madhuri Subbiah
Kannaki Ramasamy
Directorate of Poultry Research
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E. Priyanka
Directorate of Poultry Research
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Y. Nishitha
Sri PV Narasimha Rao Telangana State Veterinary University
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S. Vamshi Krishna
Sri PV Narasimha Rao Telangana State Veterinary University
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Santosh Haunshi
Directorate of Poultry Research
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Madhuri Subbiah
National Institute of Animal Biotechnology
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Abstract

Marek’s disease (MD) is a re-emerging viral disease of chicken and a serious economic threat to poultry industry worldwide. Continuous surveillance with molecular investigation is mandatory to monitor the emergence of virulent MDV strains and to devise any appropriate vaccination strategy and implement bio-security programs. In the present study, we investigated the cases of MD outbreaks in vaccinated poultry flocks. The MD outbreak was confirmed through necropsy (majorily visceral tumors), histopathology and viral gene specific PCR. The pathotypes of the field MDV strains were assessed by molecular analysis of three oncogenes -Meq, pp38 and vIL-8. The Meq sequence of the field strains analyzed in this study lacked the 59 aa unique to mild strains indicating that they are virulent strains. Mutation at position 71 and presence of five proline rich repeats in the transactivation domain, both associated with virulence were observed in these strains, however, the signature sequences specific to very virulent plus strains were absent. Phylogenetic analysis of Meq gene sequences revealed clustering of the field strains with North Indian strains and with a very virulent plus ATE 2539 strain from Hungary. Analyses of pp38 protein at positions 107 and 109 and vIL-8 protein at positions 4 and 31 showed signatures of virulence. Sequence and phylogenetic analysis of oncogenes from field MDVs from vaccinated flock indicated these strains possessing molecular features of very virulent strains. Our data shows here that Meq, vIL-8 and pp38 genes can be used as markers for molecular analysis to decipher the pathotype of MDV strains. Our present study suggests evolution of virulent MDV induced by vaccination.

Peer review status:ACCEPTED

27 May 2021Submitted to Transboundary and Emerging Diseases
01 Jun 2021Submission Checks Completed
01 Jun 2021Assigned to Editor
06 Jun 2021Reviewer(s) Assigned
25 Jun 2021Review(s) Completed, Editorial Evaluation Pending
05 Jul 2021Editorial Decision: Revise Major
18 Jul 20211st Revision Received
18 Jul 2021Assigned to Editor
18 Jul 2021Submission Checks Completed
21 Jul 2021Reviewer(s) Assigned
31 Jul 2021Review(s) Completed, Editorial Evaluation Pending
11 Aug 2021Editorial Decision: Revise Minor
12 Aug 20212nd Revision Received
12 Aug 2021Assigned to Editor
12 Aug 2021Submission Checks Completed
16 Aug 2021Review(s) Completed, Editorial Evaluation Pending
16 Aug 2021Editorial Decision: Accept