title: Expression of bovine genes associated with local and systemic immune response to infestation with the Lone Star tick, Amblyomma americanum.
abstract: The Lone Star tick, Amblyomma americanum Linnaeus 1758 (Acari; Ixodidae), causes considerable production losses to the southern U.S. cattle industry due to reduced weight, infertility, secondary infections at bite wound sites, damaged hides, and potentially death, as these ticks tend to infest livestock in large numbers. Increasing environmental concerns, along with the potential for chemical residue in food products, have led to more emphasis on alternative tick control strategies, such as selective breeding practices and anti-tick vaccines. To enable progress toward these goals, a better understanding of bovine host immune mechanisms elicited by ticks is needed. In this study, 7 calves were phenotyped as susceptible, moderately resistant, or highly resistant to adult A. americanum ticks. Tick bite-site biopsies and blood leukocytes were collected at multiple time points throughout 3 successive tick infestations. Gene expression at tick bite-site biopsies was assessed by microarray analysis over 3 time points for each phenotype group. Quantitative reverse transcriptase-PCR expression analysis evaluated 11 candidate genes in tick bite-site biopsies, and 6 in blood leukocytes. Regression curve estimates calculated from the expression values generated by qRT-PCR in tick bite-sites identified correlations between several candidate genes. Increased expression of IGHG1, IL6, IL1α, and IL1RN in bovine tick bite-site biopsies suggests that Th2 differentiation may be important for the local bovine response to A. americanum ticks. Strong correlations in expression for IL1α and IL1β, for IL1α and IL1RN, and for IL1α and TLR4 were found in biopsies from the tick-resistant phenotypes. The up-regulation of IL12 and IL23 in blood leukocytes from Lone Star tick-infested calves of all phenotypes suggests a possible systemic recruitment of memory T cells. This study provides novel insight concerning the bovine immune response to Lone Star ticks and a basis for future investigations to characterize the importance of these factors for tick-resistance in cattle.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, 4467 TAMU, Texas A&M University, College Station, TX 77843-4467, United States.
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Brannan
authors.affiliation: Department of Animal Science, 2471 TAMU, Texas A&M University, College Station, TX 77843-2471, United States.
authors.forename: Penny K
authors.initials: PK
authors.lastname: Riggs
authors.affiliation: USDA-ARS, Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, TX 78028, United States.
authors.forename: Pia U
authors.initials: PU
authors.lastname: Olafson
authors.affiliation: Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, 4466 TAMU, Texas A&M University, College Station, TX 77843-4467, United States.
authors.forename: Ivan
authors.initials: I
authors.lastname: Ivanov
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, 4467 TAMU, Texas A&M University, College Station, TX 77843-4467, United States. Electronic address: PHOLMAN@cvm.tamu.edu.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Holman
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics* / Q000276:immunology / Q000469:parasitology; D005260:Female; D026863:Ixodidae / Q000502:physiology*; D008297:Male; D011506:Proteins / Q000235:genetics / Q000276:immunology*; D013984:Tick Infestations / Q000235:genetics / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*
chemical_list: D011506:Proteins
keywords: Amblyomma americanum; Bovine; Gene expression; Immune response; Quantitative reverse transcriptase-PCR (qRT-PCR); Tick-resistance