Anti-tick vaccine candidate subolesin is important for blood feeding and innate immune gene expression in soft ticks

Subolesin is a conserved molecule in both hard and soft ticks and is considered as an effective candidate molecule for the development of anti-tick vaccine. Previous studies have reported the role of subolesin in blood feeding, reproduction, development, and gene expression in hard ticks. However, studies addressing the role of subolesin in soft ticks are limited. In this study, we report that subolesin is not only important in soft tick Ornithodoros turicata americanus blood feeding but also in the regulation of innate immune gene expression in these ticks. We identified and characterized several putative innate immune genes including Toll, Lysozyme precursor (Lp), fibrinogen-domain containing protein (FDP), cystatin and ML-domain containing protein (MLD) in O. turicata americanus ticks. Quantitative real-time polymerase chain reaction analysis revealed the expression of these genes in both O. turicata americanus salivary glands and midgut and in all developmental stages of these soft ticks. Significantly increased expression of fdp was noted in salivary glands and midgut upon O. turicata americanus blood feeding. Furthermore, RNAi-mediated knockdown of O. turicata americanus subolesin expression affected blood feeding and innate immune gene expression in these ticks. Significant downregulation of toll, lp, fdp, cystatin, and mld transcripts was evident in sub-dsRNA-treated ticks when compared to the levels noted in mock-dsRNA-treated control. Collectively, our study not only reports identification and characterization of various innate immune genes in O. turicata americanus ticks but also provides evidence on the role of subolesin in blood feeding and innate immune gene expression in these medically important ticks. Soft ticks belonging to Ornithodoros genus such as O. turicata are important vectors for human relapsing fever agent. Tick-borne relapsing fever is a neglected disease. Therefore, studies that address molecular aspects of the vector biology of these soft ticks are important. In this study, we identified and partially sequenced several innate immune genes in O. turicata americanus ticks. Studies with hard ticks have shown that subolesin plays an important role in tick feeding, reproduction, and regulation of gene expression. However, studies deciphering the role of subolesin in soft ticks are limited. In this study, we report that O. turicata americanus subolesin not only plays a role in blood feeding but also regulates innate immune gene expression in these ticks.

Automated summary

This study reports the role of subolesin in blood feeding and innate immune gene expression in soft ticks. The researchers identified and characterized several innate immune genes in Ornithodoros turicata americanus ticks, and found that the knockdown of subolesin expression affected blood feeding and innate immune gene expression in these ticks.