Interleukin-21 regulates expression of the immediate-early lytic cycle genes and proteins in Epstein-Barr Virus infected B cells.

The switch between the latent and the lytic cycle of Epstein-Barr Virus (EBV) infection is characterized by the induction of viral transcriptional activators Zta and Rta. CD4(+) T cell-derived cytokines are likely to regulate expression of these proteins in EBV-infected B cells. Here we show that interleukin-21 decreases constitutive expression of Rta and its target EA-D in EBV-infected B cell lines during the first 3 days of culture. In some cell lines this is followed by a strong increase in the expression of Zta, Rta, and EA-D during prolonged culture. Additionally, we provide evidence that IL-21-mediated JAK/STAT signals regulate increase in the Zta expression.