Isolation and characterization of a non-pathogenic Marek’s disease virus with a naturally inserted REV LTR sequence

Abstract:

Abstract:［Objective］Marek’s disease virus (MDV)，GD06 strain，was isolated from healthy Three-Yellow chickens without MD vaccine．In this study，we characterized GD06 strain/［Methods］Meq gene and repeat short region of GD06 strain were amplified and analyzed，and the serotype was determined by indirect immunofluorescence assay．The growth characteristics of GD06 stain were evaluated in Specific Pathogen Free (SPF) chickens and chicken embryo fibroblasts．The pathogenicity of GD06 strain was assessed by challenge test using SPF chickens.［Results］GD06 strain was MDV-1 serotype with a naturally inserted reticuloendotheliosis virus long terminal repeat sequence．Similar to the vaccinated strains CVI988/Rispens and 814，the Meq gene of strain GD06 contained a 59-aa insertion in the proline-rich domain compared with very virulent strain Md5．On 96，120，144，168 and 192 hours post infection，the virus titers of GD06 were higher than that of CVI988/Rispens in vitro (P＜0.05)，and the viremia levels in GD06-infected group were significantly higher than that of CVI988/Rispens group on 21 and 42 days post inoculation (P＜0.05)．The result of challenge test demonstrated that GD06 remained nonpathogenic for chickens and induced little immunosuppressive effects.［Conclusion］GD06 is an MDV-1 non-pathogenic strain naturally integrated with reticuloendotheliosis virus and long terminal repeat sequence．