Genetic variability of the Avian leukosis virus subgroup J gp85 gene in layer flocks in Lower Egypt

Vet World Vol.13 June-2020 Article-8

Research Article

Veterinary World, 13(6): 1065-1072

https://doi.org/10.14202/vetworld.2020.1065-1072

Nahed Yehia¹, Hemat S. El-Sayed², Sabry E. Omar², and Fatma Amer¹

1. Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Agriculture Research Center, Giza 12618, Egypt.
2. Department of Poultry Diseases, Benha Provincial Laboratory, Animal Health Research Institute, Agriculture Research Center, Giza 12618, Egypt.

Background and Aim: This study aimed to determine the prevalence of layer flock tumor disease in Lower Egypt during the period of 2018- 2019 and to undertake molecular characterization and determine the genetic diversity of all identified viruses.

Materials and Methods: Forty samples were collected from layer chicken located in six governorates of Lower Egypt during the period of 2018-2019. Samples were taken from tumors in different organs. Tumor tissues were identified by histopathological sectioning and then further confirmed by a reverse-transcription polymerase chain reaction. Finally, genetic evolution of Avian leukosis virus (ALV-J) gp85 gene was studied.

Results: All the study samples were negative for Marek's disease virus, reticuloendotheliosis virus, ALV (A,B,C and D) and 20 samples were positive for ALV-J in backyard in six governrates. Sequencing of ALV-J gp85 gene was performed for six representative samples (one from each governorate), and they were found to be genetically related to prototype virus HPRS-1003 (identity percentage: 91.2-91.8%), but they were from a different group that was similar to the AF88-USA strain (first detected in 2000) with specific mutations, and they differed from a strain that was previously isolated in Egypt in 2005, forming two different subgroups (I and II) that had mutations in the hr1domain (V128F, R136A) and hr2 domain (S197G, E202K).

Conclusion: The ALV-J virus was the main cause of neoplastic disease in layer chickens from Lower Egypt in the period of 2018-2019. We found that the genetic evolution of ALV-J gp85 gene was related to prototype virus HPRS-1003 but in a different group with a specific mutation. Further studies are needed to evaluate the antigenicity and pathogenicity of recently detected ALV-J strains. Keywords: Avian leukosis (J), gp85 gene, Marek's disease, reticuloendotheliosis virus, tumor viruses.

Keywords: Avian leukosis (J), gp85 gene, Marek's disease, reticuloendotheliosis virus, tumor viruses.

How to cite this article: Yehia N, El-Sayed HS, Omar SE, Amer F (2020) Genetic variability of the Avian leukosis virus subgroup J gp85 gene in layer flocks in Lower Egypt, Veterinary World, 13(6): 1065-1072.

Received: 10-02-2020 Accepted: 15-04-2020 Published online: 12-06-2020

Corresponding author: Nahed Yehia E-mail: nahedyehia@yahoo.com

DOI: 10.14202/vetworld.2020.1065-1072

Copyright: Yehia, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.