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Kumar D, Budachetri K, Rikihisa Y, Karim S. Analysis of Amblyomma americanum microRNAs in response to Ehrlichia chaffeensis infection and their potential role in vectorial capacity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.03.592465. [PMID: 38765993 PMCID: PMC11100627 DOI: 10.1101/2024.05.03.592465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Background MicroRNAs (miRNAs) represent a subset of small noncoding RNAs and carry tremendous potential for regulating gene expression at the post-transcriptional level. They play pivotal roles in distinct cellular mechanisms including inhibition of bacterial, parasitic, and viral infections via immune response pathways. Intriguingly, pathogens have developed strategies to manipulate the host's miRNA profile, fostering environments conducive to successful infection. Therefore, changes in an arthropod host's miRNA profile in response to pathogen invasion could be critical in understanding host-pathogen dynamics. Additionally, this area of study could provide insights into discovering new targets for disease control and prevention. The main objective of the present study is to investigate the functional role of differentially expressed miRNAs upon Ehrlichia chaffeensis, a tick-borne pathogen, infection in tick vector, Amblyomma americanum. Methods Small RNA libraries from uninfected and E. chaffeensis-infected Am. americanum midgut and salivary gland tissues were prepared using the Illumina Truseq kit. Small RNA sequencing data was analyzed using miRDeep2 and sRNAtoolbox to identify novel and known miRNAs. The differentially expressed miRNAs were validated using a quantitative PCR assay. Furthermore, a miRNA inhibitor approach was used to determine the functional role of selected miRNA candidates. Results The sequencing of small RNA libraries generated >147 million raw reads in all four libraries and identified a total of >250 miRNAs across the four libraries. We identified 23 and 14 differentially expressed miRNAs in salivary glands, and midgut tissues infected with E. chaffeensis, respectively. Three differentially expressed miRNAs (miR-87, miR-750, and miR-275) were further characterized to determine their roles in pathogen infection. Inhibition of target miRNAs significantly decreased the E. chaffeensis load in tick tissues, which warrants more in-depth mechanistic studies. Conclusions The current study identified known and novel miRNAs and suggests that interfering with these miRNAs may impact the vectorial capacity of ticks to harbor Ehrlichia. This study identified several new miRNAs for future analysis of their functions in tick biology and tick-pathogen interaction studies.
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Affiliation(s)
- Deepak Kumar
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406, USA
| | - Khemraj Budachetri
- Laboratory of Molecular, Cellular, and Environmental Rickettsiology, Department of Veterinary Biosciences, College of Veterinary Medicine, Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States
| | - Yasuko Rikihisa
- Laboratory of Molecular, Cellular, and Environmental Rickettsiology, Department of Veterinary Biosciences, College of Veterinary Medicine, Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States
| | - Shahid Karim
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406, USA
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Adegoke A, Ribeiro JMC, Smith R, Karim S. Tick innate immune responses to hematophagy and Ehrlichia infection at single-cell resolution. Front Immunol 2024; 14:1305976. [PMID: 38274813 PMCID: PMC10808623 DOI: 10.3389/fimmu.2023.1305976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 12/22/2023] [Indexed: 01/27/2024] Open
Abstract
Introduction Ticks rely on robust cellular and humoral responses to control microbial infection. However, several aspects of the tick's innate immune system remain uncharacterized, most notably that of the immune cells (called hemocytes), which are known to play a significant role in cellular and humoral responses. Despite the importance of hemocytes in regulating microbial infection, our understanding of their basic biology and molecular mechanisms remains limited. Therefore, we believe that a more detailed understanding of the role of hemocytes in the interactions between ticks and tick-borne microbes is crucial to illuminating their function in vector competence and to help identify novel targets for developing new strategies to block tick-borne pathogen transmission. Methods This study examined hemocytes from the lone star tick (Amblyomma americanum) at the transcriptomic level using the 10X genomics single-cell RNA sequencing platform to analyze hemocyte populations from unfed, partially blood-fed, and Ehrlichia chaffeensis-infected ticks. The functional role of differentially expressed hemocyte markers in hemocyte proliferation and Ehrlichia dissemination was determined using an RNA interference approach. Results and discussion Our data exhibit the identification of fourteen distinct hemocyte populations. Our results uncover seven distinct lineages present in uninfected and Ehrlichia-infected hemocyte clusters. The functional characterization of hemocytin, cystatin, fibronectin, and lipocalin demonstrate their role in hemocyte population changes, proliferation, and Ehrlichia dissemination. Conclusion Our results uncover the tick immune responses to Ehrlichia infection and hematophagy at a single-cell resolution. This work opens a new field of tick innate immunobiology to understand the role of hemocytes, particularly in response to prolonged blood-feeding (hematophagy), and tick-microbial interactions.
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Affiliation(s)
- Abdulsalam Adegoke
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Jose M. C. Ribeiro
- Vector Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, United States
| | - Ryan C. Smith
- Department of Plant Pathology, Entomology, and Microbiology, Iowa State University, Ames, IA, United States
| | - Shahid Karim
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
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Adegoke A, Hanson J, Smith R, Karim S. Ehrlichia chaffeensis co-opts phagocytic hemocytes for systemic dissemination in the Lone Star tick, Amblyomma americanum. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.17.553720. [PMID: 37645829 PMCID: PMC10462121 DOI: 10.1101/2023.08.17.553720] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Hematophagous arthropods can acquire and transmit several pathogens of medical importance. In ticks, the innate immune system is crucial in the outcome between vector-pathogen interaction and overall vector competence. However, the specific immune response(s) elicited by the immune cells known as hemocytes remains largely undefined in Ehrlichi a chaffeensis and its competent tick vector, Amblyomma americanum . Here, we show that granulocytes, professional phagocytic cells, are integral in eliciting immune responses against commensal and pathogen infection. The chemical depletion of granulocytes led to decreased phagocytic efficiency of tissues-associated hemocytes. We demonstrate E. chaffeensis can infect circulating hemocytes, and both cell-free plasma and hemocytes from E. chaffeensis- infected ticks can establish Ehrlichia infection in recipient ticks. Lastly, we provide evidence to show granulocytes play a dual role in E. chaffeensis infection. Depleting granulocytic hemocytes increased Ehrlichia load in the salivary gland and midgut tissues. In contrast, granulocyte depletion led to a reduced systemic load of Ehrlichia . This study has identified multiple roles for granulocytic hemocytes in the control and systemic dissemination of E. chaffeensis infection.
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Guizzo MG, Budachetri K, Adegoke A, Ribeiro JMC, Karim S. Rickettsia parkeri infection modulates the sialome and ovariome of the Gulf coast tick, Amblyomma maculatum. Front Microbiol 2022; 13:1023980. [PMID: 36439862 PMCID: PMC9684213 DOI: 10.3389/fmicb.2022.1023980] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Accepted: 10/06/2022] [Indexed: 07/21/2023] Open
Abstract
The Gulf Coast tick, Amblyomma maculatum, is a vector of several tick-borne pathogens, including Rickettsia parkeri. The ability of R. parkeri to persist within the tick population through transovarial and transstadial transmission, without apparently harming the ticks, contributes to the pathogen's perpetuation in the tick population. Previous studies have shown that the R. parkeri load in A. maculatum is regulated by the tick tissues' oxidant/antioxidant balance and the non-pathogenic tick microbiome. To obtain further insights into the interaction between tick and pathogen, we performed a bulk RNA-Seq for differential transcriptomic analysis of ovaries and salivary glands from R. parkeri-infected and uninfected ticks over the feeding course on a host. The most differentially expressed functional category was of bacterial origin, exhibiting a massive overexpression of bacterial transcripts in response to the R. parkeri infection. Candidatus Midichloria mitochondrii and bacteria from the genus Rickettsia were mainly responsible for the overexpression of bacterial transcripts. Host genes were also modulated in R. parkeri-infected tick organs. A similar number of host transcripts from all analyzed functional categories was negatively and positively modulated, revealing a global alteration of the A. maculatum transcriptome in response to pathogen infection. R. parkeri infection led to an increase in salivary transcripts involved in blood feeding success as well as a decrease in ovarian immune transcripts. We hypothesize that these transcriptional alterations facilitate pathogen persistence and transmission within tick population.
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Affiliation(s)
- Melina Garcia Guizzo
- Vector Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, United States
| | - Khemraj Budachetri
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Abdulsalam Adegoke
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Jose M. C. Ribeiro
- Vector Biology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, United States
| | - Shahid Karim
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
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Martins LA, Palmisano G, Cortez M, Kawahara R, de Freitas Balanco JM, Fujita A, Alonso BI, Barros-Battesti DM, Braz GRC, Tirloni L, Esteves E, Daffre S, Fogaça AC. The intracellular bacterium Rickettsia rickettsii exerts an inhibitory effect on the apoptosis of tick cells. Parasit Vectors 2020; 13:603. [PMID: 33261663 PMCID: PMC7706286 DOI: 10.1186/s13071-020-04477-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 11/05/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Rickettsia rickettsii is a tick-borne obligate intracellular bacterium that causes Rocky Mountain spotted fever, a life-threatening illness. To obtain an insight into the vector-pathogen interactions, we assessed the effects of infection with R. rickettsii on the proteome cells of the tick embryonic cell line BME26. METHODS The proteome of BME26 cells was determined by label-free high-performance liquid chromatography coupled with tandem mass spectrometry analysis. Also evaluated were the effects of infection on the activity of caspase-3, assessed by the hydrolysis of a synthetic fluorogenic substrate in enzymatic assays, and on the exposition of phosphatidyserine, evaluated by live-cell fluorescence microscopy after labeling with annexin-V. Finally, the effects of activation or inhibition of caspase-3 activity on the growth of R. rickettsii in BME26 cells was determined. RESULTS Tick proteins of different functional classes were modulated in a time-dependent manner by R. rickettsii infection. Regarding proteins involved in apoptosis, certain negative regulators were downregulated at the initial phase of the infection (6 h) but upregulated in the middle of the exponential phase of the bacterial growth (48 h). Microorganisms are known to be able to inhibit apoptosis of the host cell to ensure their survival and proliferation. We therefore evaluated the effects of infection on classic features of apoptotic cells and observed DNA fragmentation exclusively in noninfected cells. Moreover, both caspase-3 activity and phosphatidylserine exposition were lower in infected than in noninfected cells. Importantly, while the activation of caspase-3 exerted a detrimental effect on rickettsial proliferation, its inhibition increased bacterial growth. CONCLUSIONS Taken together, these results show that R. rickettsii modulates the proteome and exerts an inhibitory effect on apoptosis in tick cellsthat seems to be important to ensure cell colonization.
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Affiliation(s)
- Larissa Almeida Martins
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.,Rocky Mountain Laboratories, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Hamilton, USA
| | - Giuseppe Palmisano
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Mauro Cortez
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Rebeca Kawahara
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.,Department of Molecular Sciences, Macquarie University, Sydney, NSW, Australia
| | | | - André Fujita
- Department of Computational Science, Institute of Mathematics and Statistics, University of São Paulo, São Paulo, SP, Brazil
| | - Beatriz Iglesias Alonso
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | | | - Gloria Regina Cardoso Braz
- Department of Biochemistry, Institute of Chemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Lucas Tirloni
- Rocky Mountain Laboratories, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Hamilton, MT, USA
| | - Eliane Esteves
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Sirlei Daffre
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Andréa Cristina Fogaça
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
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An Entry-Triggering Protein of Ehrlichia Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis. mBio 2020; 11:mBio.00895-20. [PMID: 32723916 PMCID: PMC7387794 DOI: 10.1128/mbio.00895-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The incidence of tick-borne diseases has risen dramatically in the past two decades and continues to rise. Discovered in 1986 and designated a nationally notifiable disease in 1998 by the Centers for Disease Control and Prevention, human monocytic ehrlichiosis, which is caused by the bacterium Ehrlichia chaffeensis, is one of the most prevalent, life-threatening, emerging tick-borne zoonoses in the United States. We investigated the role of the E. chaffeensis protein EtpE in transmission of the bacterium from tick to human cells and in vaccinated dogs with EtpE to assess the efficacy of vaccination against E. chaffeensis-infected tick challenge. Our results help fill gaps in our understanding of E. chaffeensis-derived protective antigens that could be used in a candidate vaccine for immunization of humans to counter tick-transmitted ehrlichiosis. Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes human monocytic ehrlichiosis, an emerging disease transmitted by the Lone Star tick, Amblyomma americanum. E. chaffeensis outer membrane protein entry triggering protein of Ehrlichia (EtpE) is necessary for bacterial entry into human cells. We investigated the role of EtpE in transmission of the bacteria from tick to human cells and whether or not vaccination with EtpE can prevent transmission of ehrlichiae from ticks to mammals. An antiserum against the recombinant C terminus of EtpE (rEtpE-C), which binds a mammalian cell-surface receptor and triggers bacterial entry, significantly inhibited E. chaffeensis transmission from infected tick cells to human monocytes in culture. Each of five specific-pathogen-free dogs were vaccinated with rEtpE-C along with an immunostimulating complex or were sham vaccinated with the complex alone. Dogs vaccinated with rEtpE-C developed high antibody titers against rEtpE-C and produced interferon-γ-secreting cells, as assessed with the ELISpot assay. All 10 dogs were challenged with A. americanum adult ticks infected as nymphs by syringe inoculation with E. chaffeensis. Upon challenge, both the vaccinated and control dogs became infected by day 1 post-tick attachment, but the majority of rEtpE-C-vaccinated dogs rapidly cleared the infection from the bloodstream as soon as day 7, whereas most of sham-vaccinated dogs remained infected at day 35. Peripheral blood leukocytes from vaccinated dogs had significantly elevated interferon-γ mRNA levels and secreted significantly elevated interferon-γ soon after tick attachment. Thus, the EtpE-C vaccine represents the first ehrlichial protein vaccine demonstrated to reduce bacterial infection in mammals upon challenge with infected ticks.
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Jaworski DC, Cheng C, Nair ADS, Ganta RR. Amblyomma americanum ticks infected with in vitro cultured wild-type and mutants of Ehrlichia chaffeensis are competent to produce infection in naïve deer and dogs. Ticks Tick Borne Dis 2016; 8:60-64. [PMID: 27729288 DOI: 10.1016/j.ttbdis.2016.09.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 09/25/2016] [Accepted: 09/25/2016] [Indexed: 11/30/2022]
Abstract
Monocytic ehrlichiosis in people caused by the intracellular bacterium, Ehrlichia chaffeensis, is an emerging infectious disease transmitted by the lone star tick, Amblyomma americanum. Tick transmission disease models for ehrlichiosis require at least two hosts and two tick blood feeding episodes to recapitulate the natural transmission cycle. One blood feeding is necessary for the tick to acquire the infection from an infected host and the next feeding is needed to transmit the bacterium to a naïve host. We have developed a model for E. chaffeensis transmission that eliminates the entire tick acquisition stage while still producing high numbers of infected ticks that are also able to transmit infections to naïve hosts. Fully engorged A. americanum nymphs were ventrally needle-infected, possibly into the midgut, and following molting, the unfed adult ticks were used to infect naive deer and dogs. We have also described using the ticks infected by this method the transmission of both wild-type and transposon mutants of E. chaffeensis to its primary reservoir host, white tailed deer and to another known host, dog. The infection progression and IgG antibody responses in deer were similar to those observed with transmission feeding of ticks acquiring infection by natural blood feeding. The pathogen infections acquired by natural tick transmission and by feeding needle-infected ticks on animals were also similar to intravenous infections in causing persistent infections. Needle-infected ticks having the ability to transmit pathogens will be a valuable resource to substantially simplify the process of generating infected ticks and to study infection systems in vertebrate hosts where interference of other pathogens could be avoided.
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Affiliation(s)
- Deborah C Jaworski
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States; Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, United States.
| | - Chuanmin Cheng
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States
| | - Arathy D S Nair
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States
| | - Roman R Ganta
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States
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Cheng C, Nair ADS, Jaworski DC, Ganta RR. Mutations in Ehrlichia chaffeensis Causing Polar Effects in Gene Expression and Differential Host Specificities. PLoS One 2015; 10:e0132657. [PMID: 26186429 PMCID: PMC4505860 DOI: 10.1371/journal.pone.0132657] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 06/18/2015] [Indexed: 12/20/2022] Open
Abstract
Ehrlichia chaffeensis, a tick-borne rickettsial, is responsible for human monocytic ehrlichiosis. In this study, we assessed E. chaffeensis insertion mutations impacting the transcription of genes near the insertion sites. We presented evidence that the mutations within the E. chaffeensis genome at four genomic locations cause polar effects in altering gene expressions. We also reported mutations causing attenuated growth in deer (the pathogen’s reservoir host) and in dog (an incidental host), but not in its tick vector, Amblyomma americanum. This is the first study documenting insertion mutations in E. chaffeensis that cause polar effects in altering gene expression from the genes located upstream and downstream to insertion sites and the differential requirements of functionally active genes of the pathogen for its persistence in vertebrate and tick hosts. This study is important in furthering our knowledge on E. chaffeensis pathogenesis.
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Affiliation(s)
- Chuanmin Cheng
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States of America
| | - Arathy D. S. Nair
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States of America
| | - Deborah C. Jaworski
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States of America
- Department of Entomology and Plant Pathology, Oklahoma State University, Noble Research Center, Stillwater, OK 74074, United States of America
| | - Roman R. Ganta
- Center of Excellence for Vector-Borne Diseases, Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, United States of America
- * E-mail:
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Browning R, Karim S. RNA interference-mediated depletion of N-ethylmaleimide sensitive fusion protein and synaptosomal associated protein of 25 kDa results in the inhibition of blood feeding of the Gulf Coast tick, Amblyomma maculatum. INSECT MOLECULAR BIOLOGY 2013; 22:245-57. [PMID: 23437815 PMCID: PMC3644323 DOI: 10.1111/imb.12017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The signalling pathways in tick salivary glands that control 'sialo-secretome' secretion at the tick-host interface remain elusive; however, this complex process is essential for successful feeding and manipulation of the host haemostatic response. Exocytosis of the sialo-secretome in the salivary glands requires a core of soluble N-ethylmaleimide-sensitive fusion (NSF) attachment proteins (SNAPs) and receptor proteins (SNAREs). SNAREs have been identified as the key components in regulating the sialo-secretome in the salivary gland cells. In this study, we utilized RNA interference to investigate the functional role of two Amblyomma maculatum SNARE complex proteins, AmNSF and AmSNAP-25, in the tick salivary glands during extended blood feeding on the vertebrate host. Knock-down of AmNSF and AmSNAP-25 resulted in death, impaired feeding on the host, lack of engorgement and inhibited oviposition in ticks. Depletion also led to important morphological changes in the collapse of the Golgi apparatus in the salivary gland cells. Our results imply a functional significance of AmNSF and AMSNAP-25 in prolonged tick feeding, and survival on the host. Further characterization of the factors that regulate exocytosis may lead to novel approaches to prevent tick-borne diseases.
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Affiliation(s)
| | - Shahid Karim
- Corresponding author: Shahid Karim, 118 College Drive #5018, Hattiesburg, MS 39406, , Phone: 601.266.6232, Fax: 601.266.5797
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Villarreal AM, Adamson SW, Browning RE, Khem Raj B, Sajid MS, Karim S. Molecular characterization and functional significance of the Vti family of SNARE proteins in tick salivary glands. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:483-93. [PMID: 23499931 PMCID: PMC3633690 DOI: 10.1016/j.ibmb.2013.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 02/25/2013] [Accepted: 03/04/2013] [Indexed: 05/12/2023]
Abstract
Exocytosis involves membrane fusion between secretory vesicles and the plasma membrane. The Soluble N-ethylmaleimide-sensitive factor attachment proteins (SNAPs) and their receptor proteins (SNAREs) interact to fuse vesicles with the membrane and trigger the release of their sialosecretome out of the tick salivary gland cells. In this study, we examined the functional significance of the Vti family of SNARE proteins of blood-feeding Amblyomma maculatum and Amblyomma americanum. Vti1A and Vti1B have been implicated in multiple functional roles in vesicle transport. QRT-PCR studies demonstrated that the highest transcriptional expression of vti1a and vti1b genes occurs in unfed salivary glands, suggesting that elevated secretory vesicle formation occurs prior to feeding but continues at low rates after blood feeding commences. Vti1A and Vti1B localize to the secretory vesicles in unfed tick salivary glands in immunofluorescence microscopy studies. Knockdown of vti1a and vti1b by RNA interference resulted in a significant decrease in the engorged tick weight compared to the control during prolonged blood-feeding on the host. RNA interference of vti1a or vti1b impaired oviposition and none of the ticks produced eggs masses. Surprisingly, the double knockdown did not produce a strong phenotype and ticks fed normally on the host and produced egg masses, suggesting a compensatory mechanism exists within the secretory system which may have been activated in the double knockdown. These results suggest an important functional role of the Vti family of SNARE proteins in tick blood feeding and ultimately oviposition. Understanding the basic functions of the Vti family of SNARE proteins in salivary glands may lead to better ways to prevent tick attachment and transmission of tick-borne diseases.
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Affiliation(s)
| | | | | | | | | | - Shahid Karim
- Corresponding author: Shahid Karim, 118 College Drive #5018, Hattiesburg, MS 39406 Phone: 601.266.6232 Fax: 601.266.5797
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Drolia R, Von Ohlen T, Chapes SK. Ehrlichia chaffeensis replication sites in adult Drosophila melanogaster. Int J Med Microbiol 2013; 303:40-9. [PMID: 23306065 DOI: 10.1016/j.ijmm.2012.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 10/22/2012] [Accepted: 12/02/2012] [Indexed: 10/27/2022] Open
Abstract
Ehrlichia chaffeensis is a Gram-negative, obligate intracellular bacterium which causes the tick-borne disease human monocytic ehrlichiosis. In vertebrates, E. chaffeensis replicates in monocytes and macrophages. However, no clear cell or tissue tropism has been defined in arthropods. Our group identified two host genes that control E. chaffeensis replication and infection in vivo in Drosophila, Uridine cytidine kinase and separation anxiety. Using the UAS-GAL4 RNAi system, we generated F1 flies (UAS-gene of interestRNAi x tissue-GAL4 flies) that have Uck2 or san silenced in ubiquitous or tissue-specific fashion. When Uck2 or san were suppressed in the hemocytes or in the fat body, E. chaffeensis replicated poorly and caused significantly less severe infections. Silencing of these genes in the eyes, wings, or the salivary glands did not impact fly susceptibility or bacterial replication. Our data suggest that in Drosophila, E. chaffeensis replicates within the hemocytes, the insect homolog of mammalian macrophages, and in the fat body, the liver homolog of mammals.
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Affiliation(s)
- Rishi Drolia
- Division of Biology, Kansas State University, Manhattan, KS 66506, USA
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