Transcriptome analysis of the innate immune system of Hyalomma asiaticum

Ticks are considered to be the second most important vectors of human infectious diseases. The innate immune system is the key factor that affects its vector competence. Hyalomma asiaticum is the primary vector of Crimean-Congo hemorrhagic fever virus (CCHFV). However, the immune system of H. asiaticum remains virtually unknown. Here, a high throughput full-length mRNA sequencing method was adopted to define the immunotranscriptome of H. asiaticum infected with the fungal pathogen Beauveria bassiana and gram-negative bacterium Enterobacter cloacae. The analysis yielded 22,300 isoforms with an average length of 3233 bps. In total, 68 potential immunity-related genes were identified based on similarity to the homologs known to be involved in immunity. These included most members of the Toll and JAK/STAT signaling pathways, but not the IMD signaling pathway. Moreover, two copies of Dicer-2 and five copies of Argonaute-2 were detected. These genes are postulated to be involved in the RNA interference (RNAi) pathway, which is an important defense against RNA viruses. Overall, this study provides the foundation for understanding the immune response of H. asiaticum to CCHFV.