Synthesis and delivery of short, noncoding RNA by B lymphocytes.

Evolutionarily conserved short (20-30 nucleotides) noncoding RNAs (microRNAs) are powerful regulators of gene expression in a variety of physiological and pathological processes. As such, means to efficiently modulate microRNA function constitute an important therapeutic opportunity. Here we demonstrate that primary B lymphocytes can be genetically programmed with nonviral plasmid DNA for the biogenesis and delivery of antisense sequences (anti-microRNA) against microRNA-150 (miR-150). Within 18 h of transfection with an anti-miR-150 construct, primary B lymphocytes secrete ∼3,000 copies of anti-miR-150 molecules per cell. Anti-miR-150 molecules released by B lymphocytes were internalized by CD8 T lymphocytes during cross-priming in vitro and in vivo, resulting in marked down-regulation of endogenous miR-150. However, such internalization was not observed in the absence of cross-priming. These results suggest that shuttling anti-miR-150 molecules from B lymphocytes to T cells requires the activation of receiver T cells via the antigen receptor. Finally, anti-miR-150 synthesized in B cells were secreted both as free and extracellular vesicle-associated fractions, but only extracellular vesicle-associated anti-miR-150 were apparently taken up by CD8 T cells. Collectively, these data indicate that primary B lymphocytes represent an efficient platform for the synthesis and delivery of short, noncoding RNA, paving the way for an approach to immunogenomic therapies.