Engagement of CD40 antigen with soluble CD40 ligand up-regulates peptide transporter expression and restores endogenous processing function in Burkitt's lymphoma cells.

Cells from the EBV-associated tumor, Burkitt's lymphoma (BL), are known to be highly inefficient at endogenous processing of class I-restricted CTL epitopes due to a consistent loss of peptide transporters (TAP) and MHC expression. We investigated the potential of CD40 engagement to up-regulate the expression of class I-processing genes and to enhance the immunogenicity of these malignant cells toward EBV-specific CTLs. Here we show that engagement of CD40 Ag with soluble CD40 ligand (CD40L) up-regulates TAP-1 and HLA class I expression on BL cells. More importantly, analysis of the Ag-processing function, using a recombinant vaccinia virus to transiently express the EBV nuclear Ags, revealed that CD40L-treated BL cells consistently processed endogenously synthesized viral Ags for recognition by HLA class I-restricted, virus-specific CTLs. These findings raise the possibility that CD40L treatment of tumor cells might be exploited in immunotherapeutic protocols.