MicroRNA transcriptome analysis in chicken kidneys in response to differing virulent infectious bronchitis virus infections.

Infectious bronchitis virus (IBV) can cause a highly contagious and acute respiratory disease in poultry. MicroRNAs (miRNAs) have emerged as a class of crucial regulators for gene expression and are involved in the regulation of virus defence and immunological processes. To understand miRNA regulation in chickens in response to IBV infection, high-throughput sequencing was performed to compare the small RNA libraries from the kidneys of chicken infected with SCK2, SCDY2 and LDT3-A. By comparing these data to healthy chickens, a total of 58 differentially expressed (DE) miRNAs were identified. The DE miRNAs were further classified into five miRNA expression patterns (up or down regulation compared to control). Using Gene Ontology (GO) enrichment prediction, the DE miRNAs were shown to be mostly associated with metabolic processes, catalytic activities, gene expression, binding activities and immune responses. Seven highly expressed miRNAs (gga-miR-30d, gga-miR-1454, gga-miR-7b, gga-miR-215-5p, gga-miR-1a-3p, gga-miR-3538 and gga-miR-2954) were selected for miRNA-mRNA conjoint analysis. Furthermore, the miRNAs inversely correlated with the corresponding target gene mRNAs. These seven miRNAs were considered to play an important role in IBV-host interactions and the differing virulence of IBV strains. This is the first demonstration that infection with different virulent IBVs elicits different expression of miRNAs in chicken kidneys; this expression also seems to be associated with the virulence of IBV. These results are significant for the study of immune responses to infection with different virulent IBVs mediated by miRNAs as well as the interaction between the chicken host and IBV.