Viral Nanoparticles: Cancer Vaccines and Immune Modulators.

In the last decades, viruses have gained great interest in the field of immuno-oncology (I-O) for their ability of interacting both with the immune system and the tumour microenvironment. Those pathogens have naturally evolved and been evolutionary to specifically infect hosts, replicate, deliver their genome, and spread. These properties, initially considered a disadvantage, have been investigated and edited to turn viruses into precious allies for molecular biology serving as gene therapy vectors, adjuvants for the immune system, drug cargos, and, lately, anticancer therapeutics. As anticancer drug, one interesting option is viral engineering. Modification of either the viral genome or the outer shell of viruses can change infectivity and tissue targeting and add new functions to the viral particle. Remarkably, in the field of cancer virotherapy, scientists realized that a specific viral genomic depletion would turn the normal tropism of viruses to conditionally replicate in cancer cells only. This category of viruses, named 'Oncolytic viruses', have been investigated and used for cancer treatment in the past decades resulting in the approval of the first oncolytic virus, a herpes simplex virus expressing a stimulating factor, named T-Vec, in 2015. As such, oncolytic viruses achieved positive outcome but still are not able to completely eradicate the disease. This has brought the scientific community to edit those agents, adding to their ability to directly lysate cancer cells, few modifications to mainly boost their interaction with the immune system. Viruses experienced then a renaissance not only as infecting agent but as nanoparticle and cancer vaccines too. These strategies bring new life to the concept of using viruses as viral particles for therapeutic applications.