Insights into leghorn male hepatocellular cells response to fowl adenovirus serotype 4 infection by transcriptome analysis

Fowl adenovirus serotype 4 (FAdV-4), a member of the Aviadenovirus genus of the Adenoviridae family, causes hepatitis-hydropericardium syndrome (HHS) in chickens. It causes mortality of up to 80% in 3-6-week-old broilers, posing a substantial threat to the poultry industry. However, the specific host responses to the virus are not well understood. To better understand the interactions between the host and FAdV-4 and to explore the pathogenesis of this virus, a high-throughput RNA-seq technology was utilized with leghorn male hepatocellular (LMH) cells at 12, 24, and 48 h after FAdV-4 infection. We identified a total of 7000 differentially expressed genes (DEGs), which were enriched in a variety of biological processes and pathways using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Several immune related pathways, including Toll-like receptor (TLR) signaling pathway and cytokine-cytokine receptor interaction pathway, were activated after the FAdV-4 infection. The transcriptional data were validated by quantitative real-time PCR. The expression profiles of 10 genes involved in FAdV-4-infected chicken livers, including TLR2A, TLR3, TLR5, MyD88, IL12B, IL15, IL18, CCL20, TNFRSF21, and CD30, were consistent with RNA-seq profiles. By transfecting small interfering RNA into LMH cells, our results confirmed that MyD88 mediated FAdV-4-induced inflammation. To our knowledge, this was the first study to use transcriptome analysis to investigate host responses to FAdV-4 infection. These findings provide insights into the mechanisms of FAdV-4 pathogenesis and host-FAdV-4 interaction.