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Wulff JP, Temeyer KB, Tidwell JP, Schlechte KG, Lohmeyer KH, Pietrantonio PV. Periviscerokinin (Cap 2b; CAPA) receptor silencing in females of Rhipicephalus microplus reduces survival, weight and reproductive output. Parasit Vectors 2022; 15:359. [PMID: 36203198 PMCID: PMC9535995 DOI: 10.1186/s13071-022-05457-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/24/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The cattle fever tick, Rhipicephalus (Boophilus) microplus, is a vector of pathogens causative of babesiosis and anaplasmosis, both highly lethal bovine diseases that affect cattle worldwide. In Ecdysozoa, neuropeptides and their G-protein-coupled receptors play a critical integrative role in the regulation of all physiological processes. However, the physiological activity of many neuropeptides is still unknown in ticks. Periviscerokinins (CAP2b/PVKs) are neuropeptides associated with myotropic and diuretic activities in insects. These peptides have been identified only in a few tick species, such as Ixodes ricinus, Ixodes scapularis and R. microplus, and their cognate receptor only characterized for the last two. METHODS Expression of the periviscerokinin receptor (Rhimi-CAP2bR) was investigated throughout the developmental stages of R. microplus and silenced by RNA interference (RNAi) in the females. In a first experiment, three double-stranded (ds) RNAs, named ds680-805, ds956-1109 and ds1102-1200, respectively, were tested in vivo. All three caused phenotypic effects, but only the last one was chosen for subsequent experiments. Resulting RNAi phenotypic variables were compared to those of negative controls, both non-injected and dsRNA beta-lactamase-injected ticks, and to positive controls injected with beta-actin dsRNA. Rhimi-CAP2bR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues. RESULTS Rhimi-CAP2bR transcript expression was detected throughout all developmental stages. Rhimi-CAP2bR silencing was associated with increased female mortality, decreased weight of surviving females and of egg masses, a delayed egg incubation period and decreased egg hatching (P < 0.05). CONCLUSIONS CAP2b/PVKs appear to be associated with the regulation of female feeding, reproduction and survival. Since the Rhimi-CAP2bR loss of function was detrimental to females, the discovery of antagonistic molecules of the CAP2b/PVK signaling system should cause similar effects. Our results point to this signaling system as a promising target for tick control.
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Affiliation(s)
- Juan P. Wulff
- Department of Entomology, Texas A&M University, College Station, TX 77843-2475 USA
| | - Kevin B. Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
| | - Jason P. Tidwell
- Cattle Fever Tick Research Laboratory, United States Department of Agriculture–Agricultural Research Service, 22675 N. Moorefield Rd. Building 6419, Edinburg, TX 78541-5033 USA
| | - Kristie G. Schlechte
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
| | - Kimberly H. Lohmeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
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Wulff JP, Temeyer KB, Tidwell JP, Schlechte KG, Xiong C, Lohmeyer KH, Pietrantonio PV. Pyrokinin receptor silencing in females of the southern cattle tick Rhipicephalus (Boophilus) microplus is associated with a reproductive fitness cost. Parasit Vectors 2022; 15:252. [PMID: 35818078 PMCID: PMC9272880 DOI: 10.1186/s13071-022-05349-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/28/2022] [Indexed: 12/12/2022] Open
Abstract
Background Rhipicephalusmicroplus is the vector of deadly cattle pathogens, especially Babesia spp., for which a recombinant vaccine is not available. Therefore, disease control depends on tick vector control. However, R.microplus populations worldwide have developed resistance to available acaricides, prompting the search for novel acaricide targets. G protein-coupled receptors (GPCRs) are involved in the regulation of many physiological processes and have been suggested as druggable targets for the control of arthropod vectors. Arthropod-specific signaling systems of small neuropeptides are being investigated for this purpose. The pyrokinin receptor (PKR) is a GPCR previously characterized in ticks. Myotropic activity of pyrokinins in feeding-related tissues of Rhipicephalussanguineus and Ixodesscapularis was recently reported. Methods The R.microplus pyrokinin receptor (Rhimi-PKR) was silenced through RNA interference (RNAi) in female ticks. To optimize RNAi, a dual-luciferase assay was applied to determine the silencing efficiency of two Rhimi-PKR double-stranded RNAs (dsRNA) prior to injecting dsRNA in ticks to be placed on cattle. Phenotypic variables of female ticks obtained at the endpoint of the RNAi experiment were compared to those of control female ticks (non-injected and beta-lactamase dsRNA-injected). Rhimi-PKR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues. Results The Rhimi-PKR transcript was expressed in all developmental stages. Rhimi-PKR silencing was confirmed in whole ticks 4 days after injection, and in the tick carcass, ovary and synganglion 6 days after injection. Rhimi-PKR silencing was associated with an increased mortality and decreased weight of both surviving females and egg masses (P < 0.05). Delays in repletion, pre-oviposition and incubation periods were observed (P < 0.05). Conclusions Rhimi-PKR silencing negatively affected female reproductive fitness. The PKR appears to be directly or indirectly associated with the regulation of female feeding and/or reproductive output in R.microplus. Antagonists of the pyrokinin signaling system could be explored for tick control. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05349-w.
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Affiliation(s)
- Juan P Wulff
- Department of Entomology, Texas A&M University, College Station, TX, 77843-2475, USA
| | - Kevin B Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Jason P Tidwell
- Cattle Fever Tick Research Laboratory, USDA-ARS, 22675 N. Moorefield Rd. Building 6419, Edinburg, TX, 78541-5033, USA
| | - Kristie G Schlechte
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Caixing Xiong
- Department of Entomology, Texas A&M University, College Station, TX, 77843-2475, USA
| | - Kimberly H Lohmeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Patricia V Pietrantonio
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA.
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Temeyer KB, Schlechte KG, Olafson PU, Drolet BS, Tidwell JP, Osbrink WLA, Showler AT, Gross AD, Pérez de León AA. Association of Salivary Cholinesterase With Arthropod Vectors of Disease. J Med Entomol 2020; 57:1679-1685. [PMID: 32459332 DOI: 10.1093/jme/tjaa096] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Indexed: 06/11/2023]
Abstract
Acetylcholinesterase (AChE) was previously reported to be present in saliva of the southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini), with proposed potential functions to 1) reduce acetylcholine toxicity during rapid engorgement, 2) modulate host immune responses, and 3) to influence pathogen transmission and establishment in the host. Potential modulation of host immune responses might include participation in salivary-assisted transmission and establishment of pathogens in the host as has been reported for a number of arthropod vector-borne diseases. If the hypothesis that tick salivary AChE may alter host immune responses is correct, we reasoned that similar cholinesterase activities might be present in saliva of additional arthropod vectors. Here, we report the presence of AChE-like activity in the saliva of southern cattle ticks, Rhipicephalus (Boophilus) microplus; the lone star tick, Amblyomma americanum (Linnaeus); Asian tiger mosquitoes, Aedes albopictus (Skuse); sand flies, Phlebotomus papatasi (Scopoli); and biting midges, Culicoides sonorensis Wirth and Jones. Salivary AChE-like activity was not detected for horn flies Haematobia irritans (L.), stable flies Stomoxys calcitrans (L.), and house flies Musca domestica L. Salivary cholinesterase (ChE) activities of arthropod vectors of disease-causing agents exhibited various Michaelis-Menten KM values that were each lower than the KM value of bovine serum AChE. A lower KM value is indicative of higher affinity for substrate and is consistent with a hypothesized role in localized depletion of host tissue acetylcholine potentially modulating host immune responses at the arthropod bite site that may favor ectoparasite blood-feeding and alter host defensive responses against pathogen transmission and establishment.
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Affiliation(s)
- Kevin B Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX
| | - Kristie G Schlechte
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX
| | - Pia U Olafson
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX
| | - Barbara S Drolet
- Arthropod-Borne Animal Diseases Research Unit, Center for Grain and Animal Health Research, USDA-ARS, Manhattan, KS
| | - Jason P Tidwell
- Cattle Fever Tick Research Laboratory, USDA-ARS, Edinburg, TX
| | - Weste L A Osbrink
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX
| | - Allan T Showler
- Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX
| | - Aaron D Gross
- Molecular Physiology and Toxicology Laboratory, Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA
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Arafa WM, Klafke GM, Tidwell JP, de León AAP, Esteve-Gassent M. Detection of single nucleotide polymorphism in the para-sodium channel gene of Rhipicephalus annulatus populations from Egypt resistant to deltamethrin. Ticks Tick Borne Dis 2020; 11:101488. [PMID: 32723654 DOI: 10.1016/j.ttbdis.2020.101488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Revised: 05/25/2020] [Accepted: 06/01/2020] [Indexed: 02/07/2023]
Abstract
Rhipicephalus annulatus field populations collected from small cattle farms in Beni-Suef province in Egypt were evaluated for deltamethrin resistance by toxicological in vitro bioassays (adult immersion test-AIT and larval packet test-LPT). Moreover, a quantitative PCR high resolution melting (PCR-HRM) technique was used to detect nucleotide substitutions in the voltage-gated sodium channel (Na-channel) gene. By the in vitro bioassays, the examined ticks were phenotypically categorized as deltamethrin susceptible (populations El-Wasta - A, and El-Hakamna - C) or resistant (populations El-Wasta - B, El-Hakamna - D, EL-Halabia - E, and Kom-abokhalad - F). Based on LPT findings, the phenotypic resistant populations were found to have a resistance ratio between 6.5 - 10.8. The PCR-HRM genotyping of the ticks showed variable melting curves among the populations in domain II of the Na-channel gene. Analysis of the curves showed the presence of wild type, mutant homozygous, and mutant heterozygous tick individuals. By sequencing the PCR amplified fragments, the C190A mutation was the only detected nucleotide polymorphism of domain II among the phenotypically resistant populations, which was present in 39.5 % (34/86) of the ticks tested. On the other hand, the phenotypically susceptible populations A and C did not show C190A mutant homozygous (RR) individuals. Meanwhile, in domain III all of the examined populations revealed melting curves like the wild type. Furthermore, the sequence analysis of these populations confirmed the absence of SNPs in domain III. The C190A single point mutation was detected for the first time in domain II of the Na-channel gene of deltamethrin-resistant R. annulatus in Egypt using PCR-HRM. Screening for efficacy of chemical compounds used by farmers to control ticks on cattle should be considered as part of animal health programs to manage the emerging resistance to acaricides in R. annulatus populations.
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Affiliation(s)
- Waleed M Arafa
- Department of Parasitology, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, 62512, Egypt.
| | - Guilherme M Klafke
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA; Centro de Pesquisa em Saúde Animal - IPVDF, Secretaria da Agricultura, Pecuária e Desenvolvimento Rural, Estrada do Conde, 6000, Eldorado do Sul, RS, 92990-000, Brazil
| | - Jason P Tidwell
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA
| | - Adalberto A Pérez de León
- United States Department of Agriculture, Agricultural Research Service, Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA
| | - Maria Esteve-Gassent
- Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843-4467, USA
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Klafke GM, Moreno HC, Tidwell JP, Miller RJ, Thomas DB, Feria-Arroyo TP, Pérez de León AA. Partial characterization of the voltage-gated sodium channel gene and molecular detection of permethrin resistance in Rhipicephalus annulatus (Say, 1821). Ticks Tick Borne Dis 2019; 11:101368. [PMID: 31917128 DOI: 10.1016/j.ttbdis.2019.101368] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 12/17/2019] [Accepted: 12/23/2019] [Indexed: 12/18/2022]
Abstract
The cattle tick, Rhipicephalus annulatus (Say) is a vector of bovine babesiosis and responsible for direct and indirect losses to cattle producing areas located in temperate and subtropical dry regions. Resistance against pyrethroids has been reported for this species in Asia and Africa, but never before in North America. An outbreak strain, Rio Lado, collected close to the border between Mexico and the United States, in Maverick County, Texas, showed low level of resistance to permethrin, a pyrethroid pesticide. We used genomic material from different strains of cattle ticks collected within the Permanent Quarantine Zone (Rio Lado, Vega and Klein Grass strains) to partially characterize the coding gene of the voltage-gated sodium channel (Na-channel), target-site of pyrethroid pesticides, and search for putative mutations associated with resistance using quantitative PCR high resolution melt (HRM) analysis. The two amplified fragments, corresponding to domains II and III of the Na-channel, were 100 % identical to its ortholog in Rhipicephalus microplus (Canestrini). No nucleotide polymorphisms in the Na-channel gene were observed in the pyrethroid-resistant Rio Lado strain, when compared to the susceptible strains Klein Grass and Vega. This study reports the first case of pyrethroid resistance in R. annulatus collected in the United States. Also, we provide new genomic data for this species of tick that allows for the development of a new method to screen for mutations associated with pyrethroid resistance.
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Affiliation(s)
- Guilherme M Klafke
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA; Centro de Pesquisa em Saúde Animal - IPVDF, Secretaria da Agricultura, Pecuária e Desenvolvimento Rural, Estrada do Conde, 6000. Eldorado do Sul, RS, 92990-000, Brazil.
| | - Hannah C Moreno
- Department of Biology, The University of Texas Rio Grande Valley, 1201 W. University Dr. Science Building 4.635, Edinburg, TX, 78539, USA
| | - Jason P Tidwell
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA
| | - Robert J Miller
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA
| | - Donald B Thomas
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd. MAB 6419, Edinburg, TX, 78541, USA
| | - Teresa P Feria-Arroyo
- Department of Biology, The University of Texas Rio Grande Valley, 1201 W. University Dr. Science Building 4.635, Edinburg, TX, 78539, USA
| | - Adalberto A Pérez de León
- United States Department of Agriculture, Agricultural Research Service, Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA.
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Klafke GM, Miller RJ, Tidwell JP, Thomas DB, Sanchez D, Feria Arroyo TP, Pérez de León AA. High-resolution melt (HRM) analysis for detection of SNPs associated with pyrethroid resistance in the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). Int J Parasitol Drugs Drug Resist 2019; 9:100-111. [PMID: 30889438 PMCID: PMC6423475 DOI: 10.1016/j.ijpddr.2019.03.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 02/27/2019] [Accepted: 03/04/2019] [Indexed: 01/30/2023]
Abstract
The southern cattle fever tick, Rhipicephalus (Boophilus) microplus, is the most economically important ectoparasite of cattle worldwide. A limitation for sustainable control and eradication is the emergence of acaricide resistance among tick populations. Molecular diagnostic tools offer the opportunity to detect resistance rapidly, which can be complemented with confirmatory bioassays with larvae and adult ticks that are more resource and time consuming to generate. Synthetic pyrethroid resistance is one of the most prevalent and well-studied forms of resistance in arthropods, being linked with target site alterations in the sodium ion channel gene. Here, we report research on a novel molecular method to detect mutations in the para-sodium channel gene of R. microplus associated with acaricide resistance that is based on quantitative PCR high-resolution melt (HRM) analysis. Genomic DNA fragments of domains II and III of the para-sodium channel gene were amplified by real-time PCR in the presence of EVA®Green dye to test resistant and susceptible reference ticks from the U.S., Brazil, and Mexico. Larval packet tests with discriminating doses and a modified lethal time analysis were performed to confirm resistance to permethrin, cypermethrin, deltamethrin, and flumethrin in laboratory strains. Tick specimens collected from cattle that were inspected at the United States Port-of-Entry at the Texas-Mexico border were also genotyped. Previously described mutations associated with pyrethroid resistance (T170C, C190A, G184C, and T2134A) were successfully detected by qPCR-HRM in different genotypes and confirmed by sequencing. A novel non-synonymous SNP located at domain III (C2136A) and the G215T mutation in domain II, previously described only in Asian R. microplus and R. australis, were also detected with the HRM and confirmed by sequencing. This technique could be adapted for high-throughput screening, detection, and discovery of allele-specific mutations in cattle tick outbreak populations to inform eradication strategies in the USA. This knowledge could also be applied to integrated control programs in other parts of the world where R. microplus is endemic and where similar SNPs have been identified associated with pyrethroid resistance. This study highlights the existence of several mutations in the para-sodium channel gene in different combinations in field populations of R. microplus from Mexico. Molecular detection of acaricide resistance in Rhipicephalus (Boophilus) microplus is needed. Mutations associated with pyrethroid resistance can be detected with PCR. A quantitative PCR with high-resolution melt (qPCR-HRM) analysis was developed. The qPCR-HRM was successful in detecting pyrethroid resistance in R. microplus.
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Affiliation(s)
- Guilherme M Klafke
- Instituto de Pesquisas Veterinárias Desidério Finamor, Secretaria da Agricultura, Pecuária e Irrigação, Estrada do Conde 6000, Eldorado do Sul, RS, 92990-000, Brazil; United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd, MAB 6419, Edinburg, TX, 78541, USA.
| | - Robert J Miller
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd, MAB 6419, Edinburg, TX, 78541, USA
| | - Jason P Tidwell
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd, MAB 6419, Edinburg, TX, 78541, USA
| | - Donald B Thomas
- United States Department of Agriculture, Agricultural Research Service, Cattle Fever Tick Research Laboratory, 22675 North Moorefield Rd, MAB 6419, Edinburg, TX, 78541, USA
| | - Daniela Sanchez
- Department of Biology, The University of Texas Rio Grande Valley, 1201 W. University Dr. Science Building 4.635, Edinburg, TX, 78539, USA
| | - Teresa P Feria Arroyo
- Department of Biology, The University of Texas Rio Grande Valley, 1201 W. University Dr. Science Building 4.635, Edinburg, TX, 78539, USA
| | - Adalberto A Pérez de León
- United States Department of Agriculture, Agricultural Research Service, Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA.
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Brake DK, Wikel SK, Tidwell JP, Pérez de León AA. Rhipicephalus microplus salivary gland molecules induce differential CD86 expression in murine macrophages. Parasit Vectors 2010; 3:103. [PMID: 21054882 PMCID: PMC2993695 DOI: 10.1186/1756-3305-3-103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 11/05/2010] [Indexed: 01/01/2023] Open
Abstract
Background Tick parasitism is a major impediment for cattle production in many parts of the world. The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an obligate hematophagous parasite of domestic and wild animals that serves as vector of infectious agents lethal to cattle. Tick saliva contains molecules evolved to modulate host innate and adaptive immune responses which facilitates blood feeding and pathogen transmission. Tick feeding promotes CD4 T cell polarization to a Th2 profile usually accompanied by down-regulation of Th1 cytokines through as yet undefined mechanisms. Co-stimulatory molecules on antigen presenting cells are central to development of T cell responses including Th1 and Th2 responses. Tick induced changes to antigen presenting cell signal transduction pathways are largely unknown. Here we document the ability of R. microplus salivary gland extracts (SGE) to effect differential CD86 expression. Results We examined changes in co-stimulatory molecule expression in murine RAW 264.7 cells in response to R. microplus SGE exposure in the presence of the toll-like receptor 4 (TLR4) ligand, LPS. After 24 hrs, CD86, but not CD80, was preferentially up-regulated on mouse macrophage RAW 264.7 cells when treated with SGE and then LPS, but not SGE alone. CD80 and CD40 expression was increased with LPS, but the addition of SGE did not alter expression. Higher concentrations of SGE were less effective at increasing CD86 RNA expression. The addition of mitogen or extracellular kinase (MEK) inhibitor, PD98059, significantly reduced the ability for SGE to induce CD86 expression, indicating activation of MEK is necessary for SGE induced up-regulation. Conclusions Molecules in SGE of R. microplus have a concentration-dependent effect on differential up-regulation of CD86 in a macrophage cell line activated by the TLR4 ligand, LPS. This CD86 up-regulation is at least partially dependent on the ERK1/2 pathway and may serve to promote Th2 polarization of the immune response.
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Affiliation(s)
- Danett K Brake
- USDA-ARS Knipling-Bushland U,S, Livestock Insects Research Laboratory, 2700 Fredericksberg Rd, Kerrville, TX 78028, USA.
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