Skip to main content
ARS Home » Research » Publications at this Location » Publication #302126
Title: Expression of bovine genes associated with a local and systemic immune response to infestation by the Lone Star tick, Amblyomma americanum

Author
item BRANNON, JAIME - Texas A&M University
item RIGGS, PENNY - Texas A&M University
item Olafson, Pia
item IVANOV, IVAN - Texas A&M University
item HOLMAN, PATRICIA - Texas A&M University

Submitted to: Ticks and Tick Borne Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2014
Publication Date: 9/12/2014
Citation: Brannon, J.L., Riggs, P.K., Olafson, P.U., Ivanov, I., Holman, P.J. 2014. Expression of bovine genes associated with a local and systemic immune response to infestation by the Lone Star tick, Amblyomma americanum. Ticks and Tick Borne Diseases. 5:676-688.

Interpretive Summary: The Lone Star tick, Amblyomma americanum, causes considerable production losses to the Southern U.S. cattle industry due to reduced weight, infertility, secondary infections at bite wounds, damaged hides, and potentially death, as these ticks tend to infest livestock in large numbers. Chemical residues in food products and the environment have led to public concerns and a focus on developing alternative tick controls such as selective breeding programs and anti-tick vaccines. To do so, knowledge regarding bovine host immune mechanisms elicited by ticks is needed. In this study, seven calves were phenotyped as susceptible, moderately resistant, and highly resistant to adult A. americanum. Tick bite-site biopsies and blood leukocytes were collected at multiple time points throughout three successive tick infestations, and molecular tools were used to study temporal variations in gene expression as a result of tick infestation. Four bovine immune system genes displayed increased expression in bovine tick bite-site biopsies, suggesting that Th2 differentiation may be important for the localized bovine response to A. americanum ticks. Further, up-regulation of two immune system genes in blood leukocytes from tick-infested calves suggested 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.

Technical Abstract: The Lone Star tick, Amblyomma americanum, causes considerable production losses to the Southern U.S. cattle industry due to reduced weight, infertility, secondary infections at bite wounds, damaged hides, and potentially death, as these ticks tend to infest livestock in large numbers. Chemical residues in food products and the environment have led to public concerns and a focus on developing alternative tick controls such as selective breeding programs and anti-tick vaccines. To do so, knowledge regarding bovine host immune mechanisms elicited by ticks is needed. In this study, seven calves were phenotyped as susceptible, moderately resistant, and highly resistant to adult A. americanum. Tick bite-site biopsies and blood leukocytes were collected at multiple time points throughout three successive tick infestations. Microarrays compared gene expression in tick bite-site biopsies over three time points for each phenotype. Gene-specific qRT-PCR assays evaluated 11 candidate genes in tick bite-site biopsies, and six in blood leukocytes. Regression curve estimates were calculated from expression values generated by qRT-PCR in tick bite-sites, and correlations between several candidate genes were identified. IGHG1, IL6, IL1a, and IL1RN showed increased expression in bovine tick bite-site biopsies, suggesting that Th2 differentiation may be important for the local bovine response to A. americanum ticks. Strong correlations in expression for IL1a and IL1b, for IL1a and IL1RN, and for IL1a 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.