The effect of lysosomal-associated membrane protein-1-targeting of Epstein–Barr virus nuclear antigen 1 (EBNA1) on immune response and tumor growth in preclinical studies.

Abstract

74 Background: Epstein-Barr virus (EBV) is an oncogenic γ-herpes virus that infects > 90% of the global population. EBV is the primary cause of infectious mononucleosis and is associated with several epithelial and lymphoid malignancies, including nasopharyngeal carcinoma, gastric carcinoma, non-Hodgkin’s and Hodgkin’s lymphoma. Of these, nasopharyngeal carcinoma is particularly prevalent in East and Southeast Asia and is highly metastatic. Current treatment strategies for nasopharyngeal carcinoma are limited to radiation and chemotherapy, demonstrating a need for new, targeted therapies. Most nasopharyngeal carcinomas express EBNA1, a DNA-binding protein involved in maintenance of the episomal virus genome that is required for EBV latency and associated transformation. Targeting EBNA1 allows for an immunotherapeutic approach, by exploiting the potential of the immune system to recognize tumor cells through their expression of this viral antigen. Methods: We designed a DNA vaccine encoding EBNA1 using the UNITE (UNiversal Intracellular Targeted Expression) platform. The UNITE platform is based in part on lysosomal targeting technology which results in enhanced antigen presentation and a balanced T cell response. Results: We report that the EBNA1-UNITE vaccine induced IFNγ-producing effector memory (EM) CD4+ T and CD8+ T cells with complete rejection of EBNA1-expressing tumors observed in 50% of mice. Mice rejecting tumors were protected from rechallenge with CT26-EBNA1, demonstrating that antigen-specific memory was induced in these animals. Tumor microenvironment (TME) analysis showed vaccine-induced mobilization of effector cells, including tumor infiltration of IL-12-producing type 1 dendritic cells, iNOS-producing M1 macrophages, activated EM CD4+T, and CD8+TNFα+T cells. Furthermore, increased PD-1+CD8+T cells in the TME suggests that a combination strategy with PD-1/PD-L1 blockade may be beneficial in a therapeutic setting. Conclusions: This pre-clinical data suggests that the EBNA1-UNITE vaccine has the potential to be used as an immunotherapeutic agent against EBV-associated cancers.