Virus-based cancer vaccines are nowadays considered an interesting approach in the field of cancer immunotherapy, despite the observation that the majority of the immune responses they elicit are against the virus and not against the tumor. In contrast, targeting tumor associated antigens is effective, however the identification of these antigens remains challenging. Here, we describe ExtraCRAd, a multi-vaccination strategy focused on an oncolytic virus artificially wrapped with tumor cancer membranes carrying tumor antigens. We demonstrate that ExtraCRAd displays increased infectivity and oncolytic effect in vitro and in vivo. We show that this nanoparticle platform controls the growth of aggressive melanoma and lung tumors in vivo both in preventive and therapeutic setting, creating a highly specific anti-cancer immune response. In conclusion, ExtraCRAd might serve as the next generation of personalized cancer vaccines with enhanced features over standard vaccination regimens, representing an alternative way to target cancer.

The effects of cancer immunotherapy are based on activating and utilizing the immune system to fight cancer cells. In this thesis, a form of immunotherapy, specifically oncolytic adenoviruses, were studied. Immunotherapies are costly to produce and different oncolytic viruses are used in relatively high concentrations and amounts when cancer patients are treated. Thus we wanted to optimize adenovirus vector design, enhance the delivery of adenoviruses to the tumor as well as define and show the immunological response to the adenovirus vector we have developed. It was shown, the physical and functional titers of the produced vectors were relatively stable. However, production was negatively affected if very large constructs (such as antibodies) were inserted or more than five mutations were made to the virus genome. Adenoviruses are attractive vectors for example due to their good safety profile and high production concentrations. When oncolytic virotherapy was originally conceptualized, it was believed that the lytic effect of the virus was driving the benefits for patients. Later, it was shown that other signaling events, such as danger- and pathogen-associated molecular pattern signaling, also play important roles, maybe even more so than virus-induced lysis of cancer cells. Therefore, pattern recognition receptor (PRR) signaling during an oncolytic adnovirus called TILT-123 infection was studied. TILT-123 induced alarmin release through PRRs (such as AIM2) that trigged the activation of immunostimulating signaling cascades, leading to immune-cell activation and tumor clearance. The knowledge of which signaling cascades are activated during infection can be used to further enhance effects of TILT-123 and be extended to enhance the efficacy of other virotherapeutics as well. Most humans have naturally encountered adenovirus and thus many have immune memory towards it. Therefore, when adenovirus vectors are administered intravenously, the pre-existing immunity among other virus clearing reactions, leads to unwanted clearance of the virions from the blood, before the vectors can reach their target. Consequently, we hypothesized that if a mixture of both TILT-123 and tumor infiltrating lymphocytes also known as TILs are administered intravenously a higher efficacymay be achieved. Indeed, TILT-123 did bind to the surface of T cells. When administered simultaneously, the treatment led to a positive tumor-clearing effect in vivo. Unfortunately, some cancer types are still hard to treat. For example, ovarian cancers are often diagnosed at late stages when the tumor size and metastases may hinder effective treatment of the disease. Furthermore, the tumor microenvironment in ovarian cancers is often immunosuppressive. To solve these issues, the effects of TILT-123 on ovarian cancer was studied. It was shown that TILT-123 can be employed to treat ovarian cancer. TILT-123 treatment modified the immunosuppressive microenvironment and enabled a more successful combinatorial treatment with T cell therapy.