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Abstract
The role of exosomes in cellular communication is one of highly specific cell signaling and transport involved in various cellular processes. In order to better understand the role of basally excreted exosomes in relation to intracellular microRNA (miR) signaling during influenza A virus (IAV) infection, a miR screening panel was used to identify and evaluate exosomal-associated miRNA expression patterns across mock and IAV-infected cells. Expression of miRs was also evaluated intracellularly via use of a novel P19 protein-based staining technique. P19 is a 19 kDa protein that binds double-stranded 21-25 base miRNAs with high affinity in a size dependent, but sequence independent, fashion making it a pan-miR marker of cellular processes. Additionally, basally-derived miRs were evaluated for their potential to regulate signaling via their addition to undifferentiated immortalized (Calu-3) or primary (human or swine) bronchoepithelial cells where basally secreted exosomes were examined from the recipient cell population. The presence of exosome-associated miRs in fetal bovine serum (FBS) was also evaluated in relation to their effects on influenza infection studies as well as cell growth characteristics. Our studies indicated that in the case of certain miRs, exosomes not only acted as carriers for the miR, but that the miR itself was vital to propagating a cellular signal that can affect not only cell growth, but cellular responses during influenza infection.