Natural Pattern-Recognition-Receptor Agonists As Adjuvants For In Situ Vaccination Lymphoma Immunotherapy.

123Background: In patients with low-grade lymphoma, in situ vaccination has yielded both partial and complete remissions in clinical trials. Though clinical responses have been observed with multiple pattern recognition receptor agonists (PRRa), the optimal immune stimulant is unknown. We hypothesize that natural PRRa, such as the attenuated pathogens or subunits found in common prophylactic vaccines, could target multiple PRR in a physiologically relevant context and lead to a more robust activation of dendritic cells (DCs) versus synthetic PRRa. Methods: 20 vaccines, including BCG, Typhim Vi, MMR-II, etc. were screened in vitro, where DC phenotype and function were evaluated by flow cytometry. Flt3L-mobilized DC ability to phagocytose, process, present, and cross-present soluble protein or tumor derived antigen, were assessed using CRISPR gene-edited, β2m(-/-) GFP-lymphoma cells and a novel GFP-specific (‘JEDI’) CD8 T cell system. Vaccine mechanism of immune activation was elucidated using a library of ...