Influenza A virus (IAV) infections cause ailment in birdsand a number of mammalian species including human population worldwide and haveinordinate impact on human health and prosperity. They are the major causativeagents of acute viral infections of the respiratory tract which may causeseverity from asymptomatic infection to primary viral pneumonia and death. Thisvirus genome consists of 8 fragments of negative-sense single-stranded RNAwhich encodes for 11 major proteins (1). In the 20th century, threenovel strains of influenza virus arose that caused the 1918, 1957, and 1968pandemics which lead to high mortality rates (2). Themain antigenic elements of influenza A viruses are the hem-agglutinin (H) andneuraminidase (N) trans-membrane glycoproteins.
On the basis of theantigenicity of these glycoproteins, influenza A viruses are further dividedinto 16 H (H1 to H16) and 9 N (N1 to N9) subtypes. Currently, H1N1 and H3N2subtypes are the main isolates circulating in the human population (3, 4). In human, influenza A virusinfection promotes the massive release of inflammatory cytokines andchemokines which lead to pulmonary edema, pneumonia, alveolar hemorrhage (5). MicroRNAs are small non-coding RNAs (~22?nt), which modulatecellular gene expression by interrupting the mRNA translation. Recent findingsreport that several host cellular microRNAs (cell associated or cell free) areinvolved in influenza A virus infection and disease progression in humans.
Forexample, miR- 323, miR-491, and miR-654 bind to the PBI gene and inhibit thereplication of the H1N1 influenza A virus (6). While miR-155 gets up-regulateduring IAV infection and promotes type I interferon (IFN) signaling whichresults in activation of host antiviral innate immune response in macrophages(7). Since miRNAs are associated in several cellularprocesses from developmental biology to disease pathology, they are supposed tobe potent modulators of a range of biological processes.Circulating miRNAs have been reported to exhibit typicalexpression patterns in context to a number of different pathologicalconditions, including cardiovascular, cerebrovascular, systemic inflammatorydiseases, cancer, infectious diseases and metabolicdisorders such as type 2diabetes and obesity (8, 9).
Thus, this modulation in expression level of differentcirculating miRNAs due to influenza virus infection can be quantified ordetected in circulation by different techniques which proposed them aspotential biomarkers for various diseases.