EBV-specific, HLA-E-restricted cytotoxic T cells in EBV+LDs

Epstein-Barr virus (EBV) is a highly prevalent herpesvirus that infects over 90% of the adult human population worldwide. In some EBV-infected humans, EBV leads to the development of malignant EBV+ lymphoproliferative diseases (LDs). There is currently no licensed EBV vaccine available that could prevent this process. EBV encodes for the BZLF1 protein that is highly expressed during the development of distinct EBV+ LDs. This is of special interest, as most EBV-infected individuals are able to mount potent immune responses such as BZLF1-specific and HLA-E-restricted CD8+ T cells against this protein. In our pre- study analysis, we could already demonstrate that these specific T cell responses can control EBV. The main hypothesis of our study is thus to reveal, whether these BZLF1-specific and HLA-E-restricted CD8+ T cell responses can prevent the development of EBV+ LDs. In our planned study, we aim to evaluate, whether the induction or transfer of BZLF1-specific and HLA-E-restricted CD8+ T cell responses are a suitable prevention strategy and treatment option for EBV+ LDs. We aim to first isolate BZLF1-specific and HLA-E- restricted CD8+ T cell clones and their ability to control EBV will subsequently be tested in cell culture models that measure the destruction of EBV+ lymphoma cells. Finally, the most potent CD8+ T cell clones will then be tested on their ability to prevent the development of EBV+ LDs in vivo using a humanized mouse model. This project is a cooperation between Hannes Vietzen, PhD (Center for Virology, Medical University of Vienna) and the host institution, the Viral Immunology Research Unit, Institute of Experimental Immunology, University of Zurich, led by Prof. Dr. Christian Münz.

The Epstein-Barr virus (EBV) is widespread worldwide and is one of the most common viral infections in humans. In most people, an infection goes unnoticed or causes only mild symptoms, but in certain situations, EBV can have serious consequences. People with weakened immune systems, such as those who have undergone organ or stem cell transplants, are particularly at risk. In these individuals, EBV can promote the development of lymphomas, a form of blood cancer that can quickly become life-threatening. To date, there is no approved vaccine or reliable preventive treatment for these diseases, making the development of new strategies urgently needed. In this project, we investigated whether specialized immune cells, so-called "non-classical" CD8+ T cells, can recognize and kill EBV-infected cells before they develop into lymphomas. These T cells respond to a specific piece of the virus, called the SQAPLPCVL peptide, which is presented to the T cells on specialized molecules known as HLA-E molecules. Our studies show that these T cells are present in sufficient numbers in healthy individuals and can effectively control the virus. In contrast, patients with EBV-associated lymphomas rarely have these cells, and they are often dysfunctional, which likely contributes to disease development. We pursued several approaches to examine the potential of these T cells: Laboratory tests: The specialized CD8+ T cells are isolated from blood samples and tested for their ability to specifically kill EBV-infected cells. Animal models: In humanized mice, whose immune system mimics that of humans, we investigate whether these T cells can stop viral replication and prevent the development of lymphomas. Innovative therapies: We also explore whether artificially engineered killer cells (so-called NK cells) can be equipped with the same T-cell receptors to target EBV-positive cancer cells. The project is carried out in close collaboration between the Institute of Experimental Immunology at the University of Zurich and the Center for Virology at the Medical University of Vienna, combining cutting-edge methods from immunology, cell biology, and gene therapy. In the long term, it aims to develop new strategies to prevent or treat EBV-associated lymphomas-both in healthy individuals and in patients after transplantation. The insights gained could be crucial for the future development of vaccines, the optimization of T-cell-based therapies, and the creation of new immunotherapies against EBV-associated diseases. In this way, the project makes an important contribution to protecting people from a common viral infection and its potentially life-threatening consequences, and it could significantly improve the lives of many patients.