Location: Cattle Fever Tick Research Unit
Project Number: 3094-32000-042-038-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 15, 2019
End Date: Apr 30, 2022
Objective:
Demonstrate a novel and economical method of antigen delivery that can be used to immunoprotect cattle and white-tailed deer (WTD) from cattle fever tick infestation. A segment is being added which we anticipate will offer CFT researchers and the CFTEP new information on CFT seasonal habitat change, which will expand the understanding of the impacts of microclimate on tick survivorship and reproduction.
Approach:
Each of 3 antigen formulations produced by ARS scientists at Ames, IA using their bacterial antigen expression system will be tested including: 1) a hybrid polypeptide with leukotoxoid + Rm86Texas epitopes, 2) leukotoxoid + Rm aquaporin 1 epitopes, and 3) leukotoxoid + Rm86Texas + Rm aquaporin epitopes. There will be six bovines or deer per group, along with a 4th non-immunized control group. The cattle portion of the project will be conducted at the USDA, ARS, Cattle Fever Tick Laboratory, Moore Field, Edinburg, TX. The WTD portion will be performed at the Winnie Carter Wildlife Center in College Station, Texas.
In the experiment, the antigen formulations will be administered by sub-cutaneous injection. The dynamics of the specific immune response to each treatment group for both cattle and deer will be measured by ELISA testing at various collection intervals. Cattle will then be challenged through artificial infestation in a controlled stall trial setting with cattle fever ticks provided by the ARS from its laboratory colony, to assess treatment efficacy following standard protocols. Blood samples will also be collected for “in-vitro” capillary feeding tests with cattle fever ticks to be conducted at the same facility. In the second set of trials conducted in College Station, the same experimental design will be conducted with WTD, except that the deer will not subsequently be infested with fever ticks. Following vaccination, the WTD blood samples will be collected to assess the immune response by ELISA. Additional WTD blood samples will be collected and shipped to the Cattle Fever Tick Research Laboratory for capillary feeding tests to cattle fever ticks.
Multiple studies have shown a linear relationship between antibody titers and vaccine efficacy. Proving the concept that immunization through injectable delivery of the antigen immunoprotects susceptible hosts against fever tick infestation will initiate discussions with the USDA, ARS Office of Technology Transfer for guidance and instructions in identifying commercial partners interested in developing the technology for registration and use by the Cattle Fever Tick Eradication Program.
Process.
• 24 beef cattle (6 animals per group) will be used in the protocol
o Group 1 - Control
o Group 2 - hybrid polypeptide with leukotoxoid + Rm86Texas epitopes
o Group 3 - leukotoxoid + Rm aquaporin 1 epitopes
o Group 4 - leukotoxoid + Rm86Texas + Rm aquaporin epitopes
• Collect pre-immune sera from all animals
• Immunize animals at days 0, 21, 35 and 60 with 2ml of the antigen
• Collect Blood samples at days: 0(pre), 14, 21, 35, 49, 60, 74 and 90
• Evaluate specific IgG titers in all groups by means of ELISA assays at the Texas Veterinary Medical Diagnostic Laboratory (TVMDL)
