Anchoring of TLR agonists in the plasma membrane of B cells for enhanced cellular vaccines. (VAC10P.962)

B cells are a unique lymphocyte subset that can integrate adaptive and innate receptor signaling. B cells can serve as cellular vaccines if appropriately activated (e.g., by TLR ligands) and loaded with antigen. However, activation can also lead to changes in homing receptor expression that abrogate their ability to traffic efficiently to lymphoid organs. To overcome this issue, we present a strategy to provide sustained TLR stimulation to B cells using brief (15 min pulse) exposure to lipid-tailed CpG oligonucleotides (lipoCpGs), which results in stable insertion of the TLR ligand in the plasma membranes of primary murine B cells. LipoCpG internalization was studied by flow cytometry and confocal microscopy, revealing that nearly 100% of lipoCpG was surface-localized for at least 2 h. LipoCpG-pulsed B cells exhibited sustained activation for 3 days in vitro as determined by expression of MHC I, MHC II, CD86 and CD69; expression was equivalent to levels on B cells continuously incubated with soluble CpG. Pulsed B cells did not significantly activate unpulsed B cells in a mixed coculture, indicating that inserted lipoCpG acts in an autocrine fashion. Finally, LipoCpG-pulsed B cells incubated with ovalbumin drove proliferation of OT-I CD8+ T cells in vitro. These data suggest that inserted lipoCpG provides strong activation signaling, potentially enabling rapid cell priming and prolonged in situ activation, facilitating development of B cell-based immunotherapies.