Analysis of vIL8 mRNA expression among different Marek's disease virus strains

Marek's disease(MD) is a lymphoproliferative disorder of chickens caused by Marek's disease virus(MDV).MDV encodes a virokine,vIL8,within the terminal repeat region of the viral genome.To examine the vIL8 expression in relation to MDV virulence,SPF chickens were inoculated intra-abdominally with different reference strains of MDV-1,including CVI988/Rispens(avirulent),GA(virulent) and RB1B(very virulent),respectively.RNA was extracted from the spleens at 4,7 and 10 days post infection,MDV vIL8 and MDV gB were detected by semi-quantitative RT-PCR with chicken β-actin as internal reference.The relative quantities of vIL8(or gB) gene were determined by integrated optical density.The results showed that mRNA expression of vIL8 and gB varied among virus strains after infection,the more virulent the strain,the higher level of vIL8 mRNA expression.The vIL8 mRNA level was much higher than gB mRNA level throughout the experiment.These results suggested that the expression level of vIL8 may be one of virulent factors related with the MDV virulence.