Arthropod exosomal glycine-rich protein as a potential vaccine candidate effectively reduces tick blood-feeding and pathogen transmission.

During blood feeding, Ixodidae ticks secrete cement proteins, including glycine-rich proteins (GRPs), that facilitate attachment to the vertebrate host. However, the molecular mechanisms underlying exosomal GRP secretion at the feeding site and their roles in tick-pathogen interactions remain poorly understood. Here, we analyzed the Ixodes scapularis genome to identify salivary exosomal components involved in modulation of the tick-host skin interface. We identify an arthropod exosomal GRP ( XM_002400035 ) that promotes transmission of Langat virus (LGTV), a tick-borne flavivirus, from ticks to vertebrate hosts. XM_002400035 was consistently upregulated in LGTV-infected I. scapularis ticks, tick-derived cells, and in tick exosomes. RNAi-mediated silencing of this exosomal GRP reduced viral loads, impaired tick blood-feeding efficiency, decreased tick body size and weights, and diminished LGTV acquisition and transmission. Similarly, active immunization of mice with recombinant GRP disrupted tick feeding, reduced tick fitness, and significantly impaired LGTV transmission from infected ticks to naive recipient hosts. Mechanistically, the exosomal GRP modulated host skin chemokine CXCL-12 levels at the feeding site. Together, these findings establish a dual role for a tick exosomal GRP in blood feeding and pathogen transmission and identify this tick exosomal GRP as a potential target for exosome-based transmission-blocking vaccines. More broadly, this work highlights arthropod exosomes as active mediators of flavivirus transmission and suggests new strategies for preventing and controlling tick-borne diseases.