Hepatic transcriptional profiling of mRNA and microRNA in pigs infected with Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae is a gram-negative bacterium that causes porcine pleuropneumonia, which is a widespread, highly contagious, and often fatal respiratory disease in swine. In this experiment pigs were inoculated with A. pleuropneumoniae serotype 5b. Liver samples from three non-inoculated pigs and three experimental inoculated pigs were used to characterize the expression profiles of mRNA and microRNA genes using DNA microarrays and Illumina GA deep sequencing, respectively. The microarray analysis identified a large number of genes, which significantly differed in expression in infected versus non-infected animals. MicroRNAs are short single stranded RNA molecules that regulate gene expression by sequence specific binding to the 3´ untranslated region (3´UTR) of target mRNAs. The deep sequencing analysis determined the identity and abundance of nearly 400 microRNAs, of which a portion was found to significantly differ in expression between the infected and non-infected animals. Target genes for differentially expressed microRNAs were predicted using microCosm Targets, which is based on the miRanda algorithm. Comparison on the two gene lists showed many common genes, which may suggest a causative relationship between changes in microRNA expression and target gene expression. The expression profiles of mRNA and smallRNA in liver from three experimentally infected pigs were compared with the profiles three non-infected contol pigs.