CD8+ T Cells Primed by Antigenic Peptide-Pulsed B Cells or Dendritic Cells Generate Similar Anti-Tumor Response.

Background: Peptide-loaded antigen-presenting cell (APC)-based vaccines have been under investigation as a therapeutic approach for treating cancer. However, in general they have demonstrated limited efficacy in clinical trials. Dendritic cells (DCs) have been the primary choice for APC-based vaccines given their ability to cross-present antigens. B cells have been less studied as APCs for vaccines. Here we compare the phenotype and anti-tumor activity of activated T cells that result from peptide-specific priming using either B cells or DCs. Methods: B cells and DCs were isolated from C57Bl/6 mice, and either treated or not treated with lipopolysaccharide (LPS) for maturation, and then either loaded or not loaded with SIINFEKL peptide to prime CD8+ T cells from OT-1 mice. Activated T cells were then analyzed for their phenotype and anti-tumor efficacy. Results: We report that both immature B cells and immature DCs were similarly capable of activating antigen-specific CD8+ T cells. However, LPS-matured DCs generated a stronger CD8+ T cell activation profile in vitro compared to LPS-matured B cells. Immature B cells, mature DCs and immature DCs all generated a similar anti-tumor response upon adoptive transfer of primed CD8+ T cells to tumor-bearing mice. Conclusions: Collectively, our data suggests that B cells and DCs are each capable of priming CD8+ T cells and generating anti-tumor responses. Given that B cells are relatively easier to culture and expand compared to DCs, our study suggests that, following further validation, B cells could be further investigated as APCs for peptide-based human cancer vaccines.