Antiviral RNA interference in disease vector (Asian longhorned) ticks

Area of Science:

• Virology
• Immunology
• Entomology

Background:

• Ticks are significant vectors for viral diseases, yet their antiviral mechanisms remain poorly understood compared to mosquitoes.
• The Asian longhorned tick (Haemaphysalis longicornis) is an emerging vector of concern for human and animal pathogens.

Purpose of the Study:

• To investigate the antiviral responses in ticks, specifically focusing on the RNA interference (RNAi) pathway.
• To explore the role of viral suppressors of RNAi (VSRs) in tick-borne virus replication within the vector.

Main Methods:

• Asian longhorned ticks were exposed to various viruses (SFTSV, NoV, SINV) via blood feeding or injection.
• Virus-derived small interfering RNAs (vsiRNAs) production was analyzed in response to viral infection.
• Knockdown of tick Dicer2-like protein and expression of viral suppressors of RNAi (VSRs) were experimentally manipulated.

Main Results:

• Ticks produced predominantly 22-nucleotide virus-derived siRNAs (vsiRNAs) upon infection with SFTSV, NoV, or SINV.
• A mutant virus lacking a VSR replicated less efficiently, while VSR expression enhanced viral accumulation.
• Knockdown of tick Dicer2-like protein led to increased viral accumulation, suggesting an antiviral role.

Conclusions:

• This study provides the first in vivo evidence of an antiviral RNAi response in ticks.
• The findings establish a new model for tick-borne virus research and highlight the importance of the RNAi pathway in tick antiviral defense.
• Identifying viral non-structural proteins as potential VSRs is crucial for understanding virus-host interactions and controlling tick-borne diseases.