Adoptive cellular immunotherapy for virus-associated cancers: a new paradigm in personalized medicine.

Persistent viral infections are associated with the majority of human cancers where infectious agents have been recognized as the primary etiological agent. These viruses contribute to the malignant transformation of human cells either through the expression of oncogenic proteins or chronic inflammation. In spite of the high prevalence of these viral infections in humans, only a small proportion of these individuals who may have an underlying immune defect develop malignant disease. Furthermore, many of these viruses have evolved unique mechanisms to avoid the host immune system to successfully establish latent infection with limited gene expression. Technological advances in delineating the role of cellular immune responses in the control of viral infections and ability to rapidly expand these effector cells in vitro have provided an important platform for the development of novel immunotherapeutic strategies to treat virus-associated cancers. While autologous T cell therapies have provided promising results, development of 'off-the-shelf' third-party allogeneic virus-specific T cell therapies have emerged as powerful tools to treat many of the virus-associated diseases. It is anticipated that adoptive T cell therapy in combination with newly emerging immune checkpoint inhibitors and therapeutic vaccines will provide opportunities to successfully treat advanced metastatic virus-associated cancers which are currently not amenable to standard therapeutic strategies.