Stromal cells are targets for delivery of vaccine mRNA and can be leveraged for stable retention of foreign nucleic acid 2711

Abstract Description Following vaccination, antigen is transported through the lymphatics to the draining lymph node either passively or via migratory cells that traffic antigens from the site of injection. Our prior work outlined a process by which lymphatic endothelial cells (LECs) of the lymph node capture and archive protein antigens for six or more weeks after vaccination or viral infection. Antigen archiving results in a positive effect on cellular immune memory and enhanced protection against pathogenic re-challenge. To address whether LECs also may participate in vaccine retention and immune responses following mRNA vaccination, we used an mRNA-encoded Cre recombinase “vaccine” to activate a fluorescent reporter system in-vivo. Out of all measured cell types, stromal and hematopoietic, LECs were converted most efficiently (∼70% produce fluorescent reporter). To better address whether the protein-stable environment in archiving LECs can be leveraged for RNA retention, we designed a protein-DNA/RNA hybrid molecule biosensor compatible with single cell sequencing platforms. We found that lymph node LECs acquire and retain these protein-oligo conjugates with high efficiency relative to other cell types and maintain the biosensor in an RNA stable environment. We predict that maintaining RNA based vaccines within LECs for extended periods could, like in the case of protein antigen archiving, improve immune memory. Funding Sources NIH T32 GM136444 Topic Categories Vaccines and Immunotherapy (VAC)