Abstract: Objective To investigate whether BZLF1 and BILF1 can inhibit the expression of major histocompatibility complex(MHC)molecules in Raji cells during Epstein-Barr virus (EBV) lytic cycle. Methods Reactivation was triggered by treating Raji cells with TPA and NaB. As the marker protein during EBV lytic state, the BZLF1 protein expression was detected by Western blot. The expression of BZLF1 and BILF1 at transcription level was analyzed by RT-qPCR in EBV reactivation. The expression of MHC class Ⅱ and MHC class Ⅰ molecules was analyzed by flow cytometry. After BZLF1 and BILF1 over-expression or gene silencing via siRNA in Raji cells by electroporation, the expression of MHC class Ⅱ and MHC class Ⅰ molecules was detected by flow cytometry and Western blot respectively. Results EBV reactivation can be triggered with TPA and NaB. The BZLF1 and BILF1 gene expression was observed by inducing EBV reactivation in Raji cells. The levels of MHC class Ⅱ and MHC class Ⅰ molecules were down regulated by inducing EBV reactivation or ectopic expression of BZLF1 and BILF1 (P＜0.05). Expression of MHC class Ⅱ and MHC class Ⅰ molecules was restored by specific siRNA. Conclusions BZLF1 and BILF1 down regulate the expression of MHC class Ⅱ and MHC class Ⅰ molecules in EBV reactivation respectively.

Key words: BZLF1, BILF1, major histocompatibility complex Ⅱ, major histocompatibility complex Ⅰ