Effects of activated serum factor on the induction of Epstein-Barr virus antigens and cell differentiation

EBV interferes with the sensitivity of Burkitt lymphoma Akata cells to etoposide

Burkitt lymphoma (BL) commonly exhibits Epstein-Barr virus (EBV) positivity associated with latent chronic infection. Models of acute EBV infection have been associated with cellular resistance to apoptosis. However, the effect of latent long-term EBV infection on apoptosis induced by drugs is not well defined. To determine this, we have studied the response of the Akata EBV+ cell line (type I latency) to etoposide, before and after downregulating EBV gene expression. We observed that downregulating EBV nuclear antigen-1 (EBNA-1) expression with siRNAs reverted cellular sensitivity to etoposide. In accordance with this finding, Akata EBV+ cells showed increased sensitivity to etoposide, when compared to the Akata EBV- cells. We also observed that Akata EBV+ cells presented increased apoptosis levels and decreased Bcl-xL mRNA and protein levels, when compared to the Akata EBV- cells. In addition, Akata EBV+ cells contained less endoplasmic reticulum (ER) than EBV- cells. Finally, downregulation of EBV with EBNA-1 siRNAs caused an increase in the expression of Bcl-xL indicating that EBV is responsible for the differences found between the Akata EBV+ and EBV- cell lines.

Chemically purified serum factor can induce both Epstein-Barr virus antigen synthesis and cell differentiation

The effects of purified Epstein-Barr virus-inducing serum factor (EIF) on the lymphoblastoid cell line Raji latently infected with Epstein-Barr virus were studied. Activated serum factor was capable of both: cooperating with n-butyrate and/or TPA in inducing synthesis of EBV antigens and triggering cell differentiation towards plasma cell as determined by electron microscopy. It seems therefore that the same serum component was involved in the induction of both phenomena.