NCT07479537

Acquired Tick Resistance in Naturally Exposed Participants

The Uninfected Ixodes Scapularis Human Tick Challenge Model - Acquired Tick Resistance in Naturally Exposed Participants

• Status: Active Not Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 24 (actual)
• Sponsor: Academisch Medisch Centrum - Universiteit van Amsterdam (AMC-UvA) · Academic / Other
• Sex: All
• Age: 18 Years – 70 Years
• Healthy volunteers: Accepted

Summary

Tick-borne diseases are increasing worldwide, and there are currently few effective ways to prevent them. One promising new strategy is to develop a vaccine that targets the tick itself ("anti-tick vaccine") to block the transmission of multiple pathogens. Some animals naturally develop resistance to ticks after repeated tick bites. There are indications that a similar form of acquired tick resistance (ATR) may also occur in humans who have been heavily exposed to ticks. This study investigates whether humans can naturally develop tick resistance and how this affects tick feeding. The investigators will compare people with a long history of tick bites and self-reported signs of tick resistance to people who are tick-naïve. The investigators will also include a small group of volunteers who previously participated in an experimental human tick challenge to evaluate what their reaction on tickbites is 1-2 years after their initial exposures.

Detailed description

Study Objectives Primary Objective To determine whether humans develop naturally acquired tick resistance by measuring tick feeding success, specifically the weight of ticks after feeding. Secondary Objectives To measure additional tick feeding parameters (tick mortality, attachment rate, duration of feeding, and molting). To assess clinical skin reactions such as itch and redness. To study immune responses (antibodies and immune cells) against tick saliva proteins in all groups. To identify tick salivary antigens that may be useful for future anti-tick vaccine development. Study Design Single-center, open-label human experimental tick challenge study. Three groups: ATR group: 11 adults with extensive prior tick exposure and self-reported signs of tick resistance. Control group: 11 adults with no significant tick exposure. Follow-up challenge group: Up to 4 adults previously challenged in the "TICK ME" study. Outcome measures Primary Outcome Measure Post-feeding tick weight Secondary Outcome Measures Tick mortality, attachment rate, days attached, and molting success Clinical skin responses (itch, redness) Immune responses to tick salivary proteins Skin biopsy analyses

Conditions

• Tick Bites
• Tick Resistance

Interventions

Type	Name	Description
OTHER	Tick challenge	uninfected ixodes scapularis ticks will be placed underneath a closed dressing

Timeline

• Start date: 2025-08-14
• Primary completion: 2026-04-01
• Completion: 2026-06-01
• First posted: 2026-03-18
• Last updated: 2026-03-18

Locations

1 site across 1 country: Netherlands