MicroRNAs (miRNAs) repress the expression levels of genes by binding to mRNA transcripts, acting as master regulators of cellular processes. Differential expression of miRNAs has been linked to virus-associated diseases involving members of the Hepacivirus, Herpesvirus, and Retrovirus families. In contrast, limited biological and molecular information has been reported on the potential role of cellular miRNAs in the life cycle of influenza A viruses (infA). In this study, we hypothesize that elucidating the miRNA expression signatures induced by low-pathogenicity swine-origin infA (S-OIV) pandemic H1N1 (2009) and highly pathogenic avian-origin infA (A-OIV) H7N7 (2003) infections could reveal temporal and strain-specific miRNA fingerprints during the viral life cycle, shedding important insights into the potential role of cellular miRNAs in host-infA interactions. Using a microfluidic microarray platform, we profiled cellular miRNA expression in human A549 cells infected with S- and A-OIVs at multiple time points during the viral life cycle, including global gene expression profiling during S-OIV infection. Using target prediction and pathway enrichment analyses, we identified the key cellular pathways associated with the differentially expressed miRNAs and predicted mRNA targets during infA infection, including the immune system, cell proliferation, apoptosis, cell cycle, and DNA replication and repair. By identifying the specific and dynamic molecular phenotypic changes (microRNAome) triggered by S- and A-OIV infection in human cells, we provide experimental evidence demonstrating a series of temporal and strain-specific host molecular responses involving different combinatorial contributions of multiple cellular miRNAs. Our results also identify novel potential exosomal miRNA biomarkers associated with pandemic S-OIV and deadly A-OIV-host infection.
