In situ treatment with a TLR9 agonist virus-like particle to promote immune responses against oral epithelial dysplasia progression

Leukoplakia, a common type of oral dysplasia, is simply defined as a white patch in the mouth or other mucosal surface. Oral dysplasia is the most common premalignancy in the oral cavity and yet it is insufficiently researched and thus both diagnosing and treating oral dysplasia are still problematic issues. This study focuses on the immune signature of oral dysplasia and explores whether stimulating the immune system with an immune therapy, vidutolimod (± immune checkpoint blockade (ICB)), can prevent the progression of oral dysplasia or even cause regression. Vidutolimod, a virus-like particle encapsulating G10, is believed to activate plasmacytoid dendritic cells (pDCs) through the activation of the Toll-like receptor 9 (TLR9). To investigate this, an established murine model for inducing oral cancer was used to study oral dysplasia development and response to in situ injection of vidutolimod at the premalignant phase. The effect of treatment was analyzed histologically and immunologically. ELISA revealed significantly elevated levels of IFN-γ, IL-12, and TNF-α in the sera of mice after 24 h of one treatment with vidutolimod + ICB as well as increased levels of proliferating T cells and pDCs in draining lymph nodes 72 h after the third and final treatment, thus indicating the immune-boosting effect of this therapy. Vidutolimod + ICB caused a significant decrease in Ki-67 expression by epithelial cells in the lesion area compared to untreated mice, implicating that this treatment regime may prevent lesion progression.