Evaluation the immuno-protective effect of an infectious clone of meq-deleted Marek’s disease virus

Abstract:

Abstract:[Objective] To evaluate the immuno-protective effect of GX0101Δmeq-BAC containing an infectious meq-null Marek’s disease virus genome. [Method] One-day-old SPF birds were reared separately in isolators with positive filtered air. On day 1 of age, chickens immunized with 10μg of GX0101Δmeq-BAC suspended in PBS, challenge infection with 500PFU very virulent rMD5 was performed at day 5 and 12 post-immunization separately. During 90 days after challenge, all bird were recorded and checked for necropsy. The samples of heart and liver were collected for histo-sections. [Results] The protective index of the two vaccines used was 87 and 33 for CVI988/Rispens and GX0101Δmeq-BAC, respectively, after challenged with the very virulent virus rMd5 at day 5 post-immunization. When challenged with rMd5 at day 12 post-immunization, the protection index of GX0101Δmeq-BAC increased to 53%. [Conclusion] Except that GX0101Δmeq-BAC can confer protection against very virulent Marek’s disease virus, a delay in the development of Marek’s disease could be observed in some chickens vaccinated with GX0101Δmeq-BAC. On the other hand, compared with CVI988/Rispens, the reconstruction of GX0101Δmeq-BAC in the body is a prerequisite for access to protection. Therefore, there is a blank period after immunization, which provides a chance for infection with the wild Marek’s disease virus.