Phenotypic knock-out of the latent membrane protein 1 of Epstein–Barr virus by an intracellular single-chain antibody

Abstract

Epstein–Barr virus (EBV) causes lymphoproliferative diseases in immunocompromised patients and is associated with endemic Burkitt lymphoma, nasopharyngeal carcinoma and some cases of Hodgkin disease. The latent membrane protein 1 (LMP1) of EBV is a transmembrane protein that is essential for the transformation of B lymphocytes. LMP1-mediated up-regulation of Bcl-2 is thought to be an important element in this process. As an approach to explore novel treatments for EBV-associated lymphomas, we constructed a single-chain antibody (sFv) directed against LMP1 to achieve functional inhibition of this oncoprotein in EBV-transformed B lymphocytes. We demonstrated that intracellular expression of an endoplasmic reticulum (ER)-targeted form of this sFv markedly reduced LMP1 protein levels. We also observed a decrease in intracellular level of this protein which correlated with a marked reduction of Bcl-2 expression in EBV-transformed B lymphocytes. We further demonstrated that anti-LMP1 sFv-mediated reduction of Bcl-2 correlated with increased sensitivity of these cells to drug-induced cell death. Therefore, these data suggest that an anti-LMP1 sFv used in combination with conventional chemotherapy may be useful for gene therapy of EBV-associated lymphomas in immunocompromised patients.