Project Number: 8042-32000-008-20-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2016
End Date: Aug 31, 2018
The current project has two objectives: (1) evaluate efficacy of two ARS novel anti-tick antigens, when used individually or in mixture, against blacklegged ticks (Ixodes scapularis) infesting mice; and (2) determine how the anti-tick vaccine may block tick blood feeding and other physiological processes that lead to tick mortality.
This work will be conducted by the research team at Department of Veterinary Medicine, University of Maryland. Laboratory animals (mice) will be purchased from commercial sources and maintained and used for this project at their laboratory following protocols approved by the university’s Institutional Animal Use and Care Committee (IAUCC). (1) Anti-tick antigen efficacy tests. Forty laboratory mice will be randomly assigned into one of four experimental groups (control, antigen-1, antigen-2, and mixture of antigens 1 and 2) with 10 animals in each group. Mice will be housed in individual spaces to facility handling, tick infestation, and sample collection. A small volume of the injectable anti-tick antigen formulation, or the adjuvant only formulation (control), will be administrated to individual mice through subcutaneous injection. Each mouse will be infested with 30 nymphs of the blacklegged tick at three days post-vaccination by releasing ticks on the back of the animal in a holding chamber. Tick attachment will be examined at 6, 12 and 24 h post-infestation. Unattached ticks will be removed from experiments at 24 h post-infestation. Tick attachment rate will be recorded for each animal. Animals will be monitored daily for 8 days to collect and record ticks (live, dead, fed or unfed) dropped from each animal. A final examination of each animal will be performed on day 9 to remove any still attached ticks and record the status of each tick (live or dead). The attachment rate, percentage of blood fed, and percent mortality will be calculated for each experimental group. The experiment will be repeated two times so each treatment group will have a minimum of three replicates. The mean attachment rate, blood feeding rate, and mortality will be calculated for each treatment group. Control efficacy of antigen-1, antigen-2, and the mixture formulations will be calculated by comparing with the control group following an established formula. (2) Effects of host vaccination on tick blood feeding activity. An electric feeding monitor will be used to record blood feeding activities of an attached tick. A mouse with attached ticks chosen from one of the experiment group will be restrained in a holding tube. A fine silver electrode (150 µm in diameter) will be attached to the back of the tick and a similar silver wire electrode will attached to mouse skin next to tick attachment site. Electrode wires will be connected to the feeding monitor that amplifies and records the signals through a computer-based data acquisition and analysis system. The system records minute voltage changes associated with blood ingestion, salivation, and other activities during blood feeding. Recordings will be conducted to collect data from at least 5 ticks from each of the four experimental groups. Different waveforms will be compared among ticks feeding on animals in different experimental groups, and effects of anti-tick vaccination on tick blood feeding activity will be determined.