Delivery route, MyD88 signaling and cross-priming events determine the anti-tumor efficacy of an Adenovirus based melanoma vaccine

Adenovirus (Ad)-based vaccines are considered for cancer immunotherapy, yet, detailed knowledge on their mechanism of action and optimal delivery route for anti-tumor efficacy is lacking. Here, we compared the anti-tumor efficacy of an Ad-based melanoma vaccine after intradermal, intravenous, intranasal or intraperitoneal delivery in the B16F10 melanoma model. The intradermal route induced superior systemic anti-melanoma immunity which was MyD88 signaling-dependent. Predominant transduction of non-professional antigen-presenting cells at the dermal vaccination sites and draining lymph nodes, suggested a role for cross-presentation, which was confirmed in vitro. We conclude that the dermis provides an optimal route of entry for Ad-based vaccines for high-efficacy systemic anti-tumor immunization and that this immunization likely involves cross-priming events in the draining lymph nodes.