Vaccination against Epstein–Barr Latent Membrane Protein 1 Protects against an Epstein–Barr Virus-Associated B Cell Model of Lymphoma

SIMPLE SUMMARY: The Epstein–Barr virus is a human herpesvirus that infects the majority of the human population. Initially, infection can cause mild symptoms in infants and children, but can also cause short-lived infectious mononucleosis in teenage and young adults. But, in a small minority of older patients, persistent expression of virus antigens can cause B cell transformation to a cancer. Patients with Epstein–Barr virus-positive B cell lymphoma are often more resistant to treatment with standard chemotherapy. One difficulty in developing new methods of treatment is that Epstein–Barr only infects human cells, and there are no mouse B cell models of the disease. Our goal was to develop a mouse model of disease, in order to study the potential for effective vaccination against an Epstein–Barr virus antigen. We were successful in generating a mouse B cell line expressing latent membrane protein 1, and could show that vaccination protected mice against B cell tumors that expressed latent membrane protein 1. This system will allow us to further study the potential for vaccination in patients with cancer, to help the immune system recognize and eliminate tumor cells. ABSTRACT: In this study, we demonstrate that expression of viral latent membrane protein 1 (LMP1) in a mouse B cell line renders the animals responsive to protection from a 38C13-LMP1 tumor challenge with a novel vaccine. The Epstein–Barr virus (EBV) preferentially infects circulating B lymphocytes, has oncogenic potential, and is associated with a wide variety of B cell lymphomas. EBV is ectotrophic to human cells, and currently there are no B cell animal models of EBV-associated lymphoma that can be used to investigate vaccine immunotherapy. Since most EBV-infected human tumor cells express latent membrane protein 1 (LMP1) on their surface, this viral antigen was tested as a potential target for an anticancer vaccine in a mouse model. Here, we describe a new mouse model of LMP1-expressing B cell lymphoma produced with plasmid transduction of 38C13 into mouse B cells. The expression of LMP-1 was confirmed with a western blot analysis and immunocytochemistry. We then designed a novel LMP1 vaccine, by fusing viral antigen LMP1 surface loop epitopes to the surface of a viral antigen carrier, the Tobacco Mosaic virus (TMV). Vaccinated mice produced high titer antibodies against the TMV-LMP1 vaccine; however, cellular responses were at the baseline, as measured with IFNγ ELISpot. Despite this, the vaccine showed significant protection from a 38C13-LMP1 tumor challenge. To provide additional immune targets, we compared TMV-LMP1 peptide immunization with DNA immunization with the full-length LMP1 gene. Anti-LMP1 antibodies were significantly higher in TMV-LMP1-vaccinated mice compared to the DNA-immunized mice, but, as predicted, DNA-vaccinated mice had improved cellular responses using IFNγ ELISpot. Surprisingly, the TMV-LMP1 vaccine provided protection from a 38C13-LMP1 tumor challenge, while the DNA vaccine did not. Thus, we demonstrated that LMP1 expression in a mouse B cell line is responsive to antibody immunotherapy that may be applied to EBV-associated disease.