Ticks and tick-borne diseases (TBDs) are increasing in severity and importance. Human incidence of TBDs is on the rise, most likely caused by the wider spread of tick vectors. Whereas acaricides are the mainstay for preventing TBDs, rapid resistance development, food chain contamination, and environmental concerns limit their usefulness. Anti-tick vaccination might serve as a helpful alternative. A potential target antigen has been found in AAS19 (Amblyomma americanum tick saliva serine protease inhibitor). Its functional domain is highly conserved across all ixodid tick species. AAS19, expressed in most tick tissues, is injected into the host by the tick and is highly immunogenic. RNAi silencing AAS19 in ticks resulted in smaller blood meals and caused morphologic deformities in the ticks.
It was postulated that since AAS19 is injected into the host during feeding, it could serve to booster the initial AAS19 immunization, which would be particularly valuable in wildlife immunization programs for which administering vaccine boosters are impractical. In trials, ticks feeding on rabbits immunized with AAS19 obtained blood meals that were 50% smaller than controls. During a second feeding on immunized rabbits, ticks were smaller and most failed to lay eggs. Although more research is needed, AAS19 could become a component of an anti-tick vaccine in the future.
This capsule is part of the One Health Initiative.
