CD21-independent Epstein-Barr virus entry into NK cells

Abstract

Purpose: Extranodal NK/T-cell lymphoma is an aggressive malignant disease which is associated with Epstein-Barr virus. Although several lines of evidence point at EBV as a key player in the pathogenesis of ENKTCL, the viral mechanism of entry into NK/T cells remains uncertain. Therefore, this study was conducted to identify the entry mechanism of EBV into NK/T cells. Methods: NKL cells were used as EBV-negative NK cell lymphoma cell line and Raji cells were used as EBV-positive B cell lymphoma cell line which is not producible for viral particle. Viral supernatant was obtained from B95-8 cell line and exosomes were isolated by serial centrifugation from Raji cell culture supernatant. Viral gene was detected by RT-PCR/PCR. Results: Viral mRNAs were detected in Raji-derived exosomes, and also in NKL cells co-cultured with Raji-derived exosomes. To evaluate the effect of Raji-derived exosomes on the EBV infection, viral supernatant which was obtained from B95-8 cells, treated to NKL cells after Raji-derived exosomes. Although Raji-derived exosomes transferred viral mRNAs, viral entry was not detected in NKL cells. The CD21 receptor intensity was increased after that NKL cells were co-cultured with Raji cells. To demonstrate the effect of CD21 trogocytosis on the infection, EBV treated to NKL cells which were co-cultured with Raji cells. Although CD21 trogocytosis has occurred, viral genes were not detected in NKL cells. Interestingly, viral DNA was found in all EBV treated NKL groups and primary NK cells. Conclusions: CD21 mRNA transfer via EBV-positive B cell-derived exosomes and CD21 receptor trogocytosis from EBV-positive B cells are not key factors of viral entry mechanism to NK cells. EBV enters NKL cells without any interactions with EBV-positive B cells.