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.
The subtype of avian leukosis virus (ALV) was mainly determined by the gp85 glycoprotein. A subtype J ALV strain SCDY1 associated with hemangioma was isolated from grandparent breeding chicken and the highly antigenic region of its gp85 gene was amplified and expressed in Rosetta Escherichia coli using the pET-32a(+)vector. The fusion protein, which was expressed at a high level, was similar antigenically to the native gp85 protein as determined by Western blot assay using polyclonal antibodies against ALV-J strain. The fusion protein was also purified. This research lays a foundation for using this recombinant protein for development of indirect enzyme-linked immunosorbent assay (ELISA) for serum antibody detection or for production of monoclonal antibodies against prevalent ALV-J.
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