MicroRNAs Regulate the Expression of Genes Related to the Innate Immune and Inflammatory Response in Rabbits Infected with Lagovirus europaeus GI.1 and GI.2 Genotypes

MicroRNAs (miR) are a group of small, non-coding RNAs of 17-25 nucleotides that regulate gene expression at the post-transcriptional level. Dysregulation of miRNA expression or function may contribute to abnormal gene expression and signaling pathways, leading to disease pathology. <i>Lagovirus europaeus</i> (<i>L. europaeus</i>) causes severe disease in rabbits called rabbit hemorrhagic disease (RHD). The symptoms of liver, lung, kidney, and spleen degeneration observed during RHD are similar to those of acute liver failure (ALF) and multi-organ failure (MOF) in humans. In this study, we assessed the expression of miRs and their target genes involved in the innate immune and inflammatory response. Also, we assessed their potential impact on pathways in <i>L. europaeus</i> infection-two genotypes (GI.1 and GI.2)-in the liver, lungs, kidneys, and spleen. The expression of miRs and target genes was determined using quantitative real-time PCR (qPCR). We assessed the expression of miR-155 (<i>MyD88</i>, <i>TAB2</i>, <i>p65</i>, <i>NLRP3</i>), miR-146a (<i>IRAK1</i>, <i>TRAF6</i>), miR-223 (<i>TLR4</i>, <i>IKKα</i>, <i>NLRP3</i>), and miR-125b (<i>MyD88</i>). We also examined biomarkers of inflammation: <i>IL-1β</i>, <i>IL-6</i>, <i>TNF-α</i>, and <i>IL-18</i> in four tissues at the mRNA level. Our study shows that the main regulators of the innate immune and inflammatory response in <i>L. europaeus</i>/GI.1 and GI.2 infection, as well as RHD, are miR-155, miR-223, and miR-146a. During infection with <i>L. europaeus</i>/RHD, miR-155 has both pro- and anti-inflammatory effects in the liver and anti-inflammatory effects in the kidneys and spleen; miR-146a has anti-inflammatory effects in the liver, lungs and kidneys; miR-223 has anti-inflammatory effects in all tissues; however, miR-125b has anti-inflammatory effects only in the liver. In each case, such an effect may be a determinant of the pathogenesis of RHD. Our research shows that miRs may regulate three innate immune and inflammatory response pathways in <i>L. europaeus</i> infection. However, the result of this regulation may be influenced by the tissue microenvironment. Our research shows that infection of rabbits with <i>L. europaeus</i>/GI.1 and GI.2 genotypes causes an overexpression of two critical acute phase cytokines: <i>IL-6</i> in all examined tissues and <i>TNF-α</i> (in the liver, lungs, and spleen). <i>IL-1β</i> was highly expressed only in the lungs after <i>L. europaeus</i> infection. These facts indicate a strong and rapid involvement of the local innate immune and inflammatory response in <i>L. europaeus</i> infection-two genotypes (GI.1 and GI.2)-and in the pathogenesis of RHD. Profile of biomarkers of inflammation in rabbits infected with <i>L. europaeus</i>/GI.1 and GI.2 genotypes are similar regarding the nature of changes but are different for individual tissues. Therefore, we propose three inflammation profiles for <i>L. europaeus</i> infection for both GI.1 and GI.2 genotypes (pulmonary, renal, liver, and spleen).