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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Endemic Poultry Viral Diseases Research » Research » Publications at this Location » Publication #359603
Research Project: Genetic and Biological Determinants of Avian Herpesviruses Pathogenicity, Transmission, and Evolution to Inform the Development of Effective Control Strategies

Location: Endemic Poultry Viral Diseases Research

Title: Identification of Marek’s disease virus genes associated with virulence of US strains

Author
item Dunn, John
item BLACK PYRKOSZ, ALEXIS - Michigan State University
item STEEP, ALEC - Michigan State University
item Cheng, Hans

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2019
Publication Date: 6/11/2019
Citation: Dunn, J.R., Black Pyrkosz, A., Steep, A., Cheng, H.H. 2019. Identification of Marek’s disease virus genes associated with virulence of US strains. Journal of General Virology. 100(7):1132-1139. https://doi.org/10.1099/jgv.0.001288.
DOI: https://doi.org/10.1099/jgv.0.001288

Interpretive Summary: Marek’s disease virus (MDV) is the most well-cited example of a virus that is thought to have evolved due to vaccines. In this study, we characterized 70 MDV genomes with known virulence and identified changes that showed association with virulence. Our results revealed a number of MDV genes as would be expected for a complex trait. Interestingly, high virulence isolates from the same farms persisted over years despite eradication attempts, which has implications on control efforts. Once validated, these genetic changes may provide an alternative to live bird testing for evaluating virulence of new MDV field strains.

Technical Abstract: Marek’s disease virus (MDV) is the most well-cited example of vaccine-driven virulence evolution. MDV induces a lymphoproliferative disease in chickens, which is currently controlled by widespread vaccination of flocks. Unfortunately, Marek’s disease (MD) vaccines, while effective in preventing tumors, do not prevent viral replication and mutation, which has been hypothesized as the major driving force for increased MDV virulence of field strains during the past 40 years in US commercial flocks. To limit future virulence increases, there is interest in characterizing MDV strain genomes collected over the years and associating genetic variations with variation in virulence. In this study, we characterized 70 MDV genomes with known virulence by complete or targeted DNA sequencing, and identified genetic variants that showed association with virulence. Our results revealed a number of MDV genes as would be expected for a complex trait. In addition, phylogenetic analysis revealed a clear separation of strains that varied by virulence. Interestingly, high virulence isolates from the same farms persisted over years despite eradication attempts, which has implications on control efforts. Given the growing ability to bioengineer the MDV genome, it should be feasible to experimentally test whether these individual variants influence virulence markers alone or combinations. Once validated, these markers may provide an alternative to live bird testing for evaluating virulence of new MDV field strains.