B cells require licensing by dendritic cells to serve as primary antigen-presenting cells for plasmid DNA

ABSTRACT

DNA vaccines have been an attractive approach for treating cancer patients, however have demonstrated modest immunogenicity in human clinical trials. Dendritic cells (DCs) are known to cross-present DNA-encoded antigens expressed in bystander cells. However, we have previously reported that B cells, and not DCs, serve as primary antigen-presenting cells (APCs) following passive uptake of plasmid DNA. Here we sought to understand the requirements for B cells to present DNA-encoded antigens, to ultimately increase the immunogenicity of plasmid DNA vaccines. Using ovalbumin-specific OT-1 CD8+ T cells and isolated APC populations, we demonstrated that following passive uptake of plasmid DNA, B cells but not DC, can translate the encoded antigen. However, CD8 T cells were only activated by B cells when they were co-cultured with DCs. We found that a cell-cell contact is required between B cells and DCs. Using MHCI KO and re-purification studies, we demonstrated that B cells were the primary APCs and DCs serve to license this function. We further identified that the gene expression profiles of B cells that have been licensed by DCs, compared to the B cells that have not, are vastly different and have signatures similar to B cells activated with a TLR7/8 agonist. Our data demonstrate that B cells transcribe and translate antigens encoded by plasmid DNA following passive uptake, however require licensing by live DC to present antigen to CD8 T cells. Further study of the role of B cells as APCs will be important to improve the immunological efficacy of DNA vaccines.

KEYWORDS:

• Antigen presentation
• B cell
• dendritic cell
• DNA vaccine
• plasmid DNA

Acknowledgments

We thank the University of Wisconsin Flow Cytometry Core Facility, UW Biotechnology Center, UW Carbone Cancer Center Microscopy Center, and the NIH Tetramer Facility (Emory University, Atlanta, GA) for their support.

Disclosure statement

Douglas G. McNeel has ownership interest, has received research support, and serves as consultant to Madison Vaccines, Inc. which has licensed intellectual property related to this content. IR has no relevant potential conflicts of interest.

Authors’ contributions

IR wrote the manuscript, performed all experiments, and carried out data analysis. DGM oversaw the experimental design and is responsible for the overall content as the guarantor. Both authors contributed to the writing and approval of the final manuscript.

Availability of data and material

The data generated and/or analyzed during this study are available from the corresponding author on reasonable request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/2162402X.2023.2212550.

Additional information

Funding

This work was supported by the National Institutes of Health (P30 CA014520) and the Department of Defense Prostate Cancer Research Program (W81XWH-17-1-0247).