The Meq Genes of Nigerian Marek’s Disease Virus (MDV) Field Isolates Contain Mutations Common to Both European and US High Virulence Strains
Date
2024-12-31
Journal Title
Journal ISSN
Volume Title
Publisher
Viruses
Abstract
Background: Marek’s disease (MD) is a pathology affecting chickens caused by Marek’s disease virus (MDV), an acute transforming alphaherpesvirus of the genus Mardivirus. MD is characterized by paralysis, immune suppression, and the rapid formation of T-cell (primarily CD4+) lymphomas. Over the last 50 years, losses due to MDV infection have been controlled worldwide through vaccination; however, these live-attenuated vaccines are non-sterilizing and potentially contributed to the virulence evolution of MDV field strains. Mutations common to field strains that can overcome vaccine protection were identified in the C-terminal proline-rich repeats of the oncoprotein Meq (Marek’s EcoRI-Q-encoded protein). These mutations in meq have been found to be distinct to their region of origin, with high virulence strains obtained in Europe differing from those having evolved in the US. The present work reports on meq mutations identified in MDV field strains in Nigeria, arising at farms employing different vaccination practices. Materials and Methods: DNA was isolated from FTA cards obtained at 12 farms affected by increased MD in the Plateau State, Nigeria. These sequences included partial whole genomes as well as targeted sequences of the meq oncogenes from these strains. Several of the meq genes were cloned for expression and their localization ability to interact with the chicken NF-IL3 protein, a putative Meq dimerization partner, were assessed. Results: Sequence analysis of the meq genes from these Nigerian field strains revealed an RB1B-like lineage co-circulating with a European Polen5-like lineage, as well as recombinants harboring a combination of these mutations. In a number of these isolates, Meq mutations accumulated in both N-terminal and C-terminal domains. Discussion: Our data, suggest a direct effect of the vaccine strategy on the selection of Meq mutations. Moreover, we posit the evolution of the next higher level of virulence MDVs, a very virulent plus plus pathotype (vv++).
Description
This article was originally published in Viruses. The version of record is available at: https://doi.org/10.3390/v17010056.
© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
This research was featured in UDaily on 3/26/2025 at: https://www.udel.edu/udaily/2025/march/mareks-disease-chickens-nigeria-research-mark-parcells/
Keywords
Marek’s disease, Marek’s disease virus, meq oncogene, virulence, virulence evolution
Citation
Patria, Joseph N., Luka Jwander, Ifeoma Mbachu, Levi Parcells, Brian Ladman, Jakob Trimpert, Benedikt B. Kaufer, Phaedra Tavlarides-Hontz, and Mark S. Parcells. 2025. "The Meq Genes of Nigerian Marek’s Disease Virus (MDV) Field Isolates Contain Mutations Common to Both European and US High Virulence Strains" Viruses 17, no. 1: 56. https://doi.org/10.3390/v17010056