Isolation of a Field Marek’s Disease Virus with Acute Oncogenicity from Tibetan Chickens in China and Sequence Analysis of Oncogenic Genes

Abstract

A field Marek’s disease virus (MDV), named as BY strain, was firstly isolated from Tibetan chickens in Sichuan province, China, by method of co-cultivation of the lymphocytes with duck embryo fibroblasts (DEF). Analysis of the oncogenic genes showed that there were 2 copies of 132-bp repeated sequence in long terminal repeat of the BY strain, The nucleotide and amino acid sequence identities of Meq gene of BY strain with other prevalent MDV strains in China were 97.6-100.0% and 98.8-100.0%, respectively, and some point mutations assumed to be relevant to the oncogenecity of MDV also existed in the Meq gene of BY strain. The result of animal challenge test on specific-pathogen-free (SPF) chickens showed lymphomas may occur in a variety of organs as early as 18 days post challenge, and the rate of tumor occurrences and mortalities reached to 73.33% and 66.67% in HVT immunized chickens, respectively. In conclusion, an MDV strain charac-terized of acute oncogenicity was isolated from Tibetan chickens in China, though there were no obvious difference between the oncogenic genes of this strain and other virulent MDV strains isolated in China in recent years.

Pathotyping of recent Indian field isolates of Marek's disease virus serotype 1

“…Primary cell cultures were prepared from the 10/12-day-old embryonated duck/chicken eggs according to the protocol of supplemental assay methods (2005), Centre for Veterinary Biologicals, USDA. Lymphocytes that were positive for 132 bp repeats in PCR were collected aseptically from the blood samples by using ficoll-plaque assay and co-cultivated with duck embryo fibroblasts (DEF) as described by Tian et al (2012). The co-cultivated monolayers were observed every day for five to seven days.…”