Adenovirus 14p1 induced changes in miRNA expression increases lung immunopathogenesis

Adenovirus is a frequent cause of mild, usually self-limited infections in infants and young children. Severe infections occur in immunocompromised patients but are rarely observed in healthy, immunocompetent adults. However, there have been outbreaks around the world of infections with different adenoviral (Ad) serotypes that have resulted in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) in some of those infected. Ad14p1, the predominant circulating strain of Ad14 worldwide is one such serotype. The explanations for the severity of illness caused by Ad14p1 infection in immunocompetent patients is unknown. Previously, we have shown that A549 cells infected with Ad14 repress macrophage pro29 inflammatory responses whereas cells infected with Ad14p1 fail to repress macrophages and, instead, can increase pro-inflammatory responses. Micro-RNAs (miRNA) are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Adenoviral infection has been shown to modulate host miRNA expression, and we hypothesized that differences in miRNA expression between Ad14 and Ad14p1 infected cells might impact pathogenesis. A549 cells were infected with either Ad14 or Ad14p1 and total RNA samples were collected at 6, 12, 24, 36 and 48 post infection for miRNA sequencing. Cluster analysis revealed that there were 3 temporal changes in miRNA expression profiles following infection. Differential expression analysis showed 8-23 differentially expressed miRNA between Ad14 and Ad14p1 from 6 to 36hpi. However, at 48hpi there were 98 differentially expressed miRNAs in Ad14p1 infected cells compared to those infected by Ad14. Pathway enrichment analysis showed that the differentially expressed miRNA might explain the increased pathogenesis of Ad14p1caused by strain-related loss of modulation of cytokine expression. Overall, the data suggest a role for viral regulation of host miRNA expression in pathogenesis by regulating host inflammatory responses through the delivery of deregulated miRNAs by virally infected cell corpses to macrophages. Author SummaryAcute respiratory distress syndrome (ARDS) is a severe inflammatory disease in the lungs, and both the onset and resolution of ARDS appears to be regulated primarily by alveolar macrophages. Emergent strains of human adenovirus (Ad) can induce ARDS in healthy immunocompetent people, whereas most, common Ad infections go unnoticed or causes minimal symptoms. Why emergent strains of Ad, such as Ad14p1, are more likely to induce acute lung injury (ALI) and ARDS is unknown. Cells that die from wild type Ad14 infection have been shown to repress alveolar macrophage inflammatory responses, whereas cells dying from Ad14p1 infection enhance inflammatory responses of alveolar macrophages. Here, we explored whether virus induced changes in the expression of cellular small regulatory RNAs could explain the differential effects of virally infected cells on alveolar macrophage inflammatory responses. The data show that there are differences in small RNA expression between Ad14 and Ad14p1 infected cells at late times after infection, when Ad14p1 infected cells lose expression of the small RNAs that repress pro-inflammatory cellular signaling pathways in macrophages. Our study provides insights into a mechanism that could drive the increased pathogenesis of some outbreak strains of adenovirus.