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Tick histamine release factor is critical for Ixodes scapularis engorgement and transmission of the lyme disease agent.

Dai J, Narasimhan S, Zhang L, Liu L, Wang P, Fikrig E - PLoS Pathog. (2010)

Bottom Line: Silencing tHRF by RNA interference (RNAi) significantly impaired tick feeding and decreased B. burgdorferi burden in mice.Interfering with tHRF by actively immunizing mice with recombinant tHRF, or passively transferring tHRF antiserum, also markedly reduced the efficiency of tick feeding and B. burgdorferi burden in mice.Recombinant tHRF was able to bind to host basophils and stimulate histamine release.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.

ABSTRACT
Ticks are distributed worldwide and affect human and animal health by transmitting diverse infectious agents. Effective vaccines against most tick-borne pathogens are not currently available. In this study, we characterized a tick histamine release factor (tHRF) from Ixodes scapularis and addressed the vaccine potential of this antigen in the context of tick engorgement and B. burgdorferi transmission. Results from western blotting and quantitative Reverse Transcription-PCR showed that tHRF is secreted in tick saliva, and upregulated in Borrelia burgdorferi-infected ticks. Further, the expression of tHRF was coincident with the rapid feeding phase of the tick, suggesting a role for tHRF in tick engorgement and concomitantly, for efficient B. burgdorferi transmission. Silencing tHRF by RNA interference (RNAi) significantly impaired tick feeding and decreased B. burgdorferi burden in mice. Interfering with tHRF by actively immunizing mice with recombinant tHRF, or passively transferring tHRF antiserum, also markedly reduced the efficiency of tick feeding and B. burgdorferi burden in mice. Recombinant tHRF was able to bind to host basophils and stimulate histamine release. Therefore, we speculate that tHRF might function in vivo to modulate vascular permeability and increase blood flow to the tick bite-site, facilitating tick engorgement. These findings suggest that blocking tHRF might offer a viable strategy to complement ongoing efforts to develop vaccines to block tick feeding and transmission of tick-borne pathogens.

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Tick histamine release factor (tHRF) was up-regulated in B. burgdorferi- infected ticks.(A) The expression of tHRF in B. burgdorferi-infected or uninfected ticks during I. scapularis feeding. Results are expressed as the mean ± the SEM (*p<0.05; **p<0.01). (B) tHRF-antiserum recognizes recombinant tHRF generated in Escherichia coli (tHRF E.coli) or Drosophila S2 cells (tHRF DES). (C–D) The up-regulation of tHRF protein in B. burgdorferi-infected ticks. (*p<0.05) (E) The detection of tHRF in adult tick saliva (Saliva), nymphal tick salivary glands (S.G.), midgut (M.G.) and whole ticks (Tick).
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ppat-1001205-g001: Tick histamine release factor (tHRF) was up-regulated in B. burgdorferi- infected ticks.(A) The expression of tHRF in B. burgdorferi-infected or uninfected ticks during I. scapularis feeding. Results are expressed as the mean ± the SEM (*p<0.05; **p<0.01). (B) tHRF-antiserum recognizes recombinant tHRF generated in Escherichia coli (tHRF E.coli) or Drosophila S2 cells (tHRF DES). (C–D) The up-regulation of tHRF protein in B. burgdorferi-infected ticks. (*p<0.05) (E) The detection of tHRF in adult tick saliva (Saliva), nymphal tick salivary glands (S.G.), midgut (M.G.) and whole ticks (Tick).

Mentions: To identify tick proteins that may be utilized by B. burgdorferi to facilitate transmission, 2-dimensional fluorescence difference gel electrophoresis (DIGE) was performed using extracts from B. burgdorferi-infected, and uninfected, I. scapularis salivary glands. Seventeen differentially expressed proteins (5-fold or more expression levels in Borrelia-infected salivary glands) were selected for mass spectrometric analysis, and 4 I. scapularis proteins were unambiguously identified with significant MASCOT scores (p<0.05) of 79 (Table S1). In this study, we characterize one of the most highly induced proteins, named tHRF because it shares high homology with a murine histamine release factor (57.1% similarity and 40.1% identity at amino acid level). tHRF mRNA levels were induced during I. scapularis engorgement, and significantly higher in B. burgdorferi-infected, than in uninfected, ticks (p<0.01). Immunoblots using tHRF antiserum further demonstrated a ∼2.5 fold up-regulation of tHRF in B. burgdorferi-infected ticks (Figure 1, A, C–D). tHRF was present in tick saliva, as well as in the salivary glands and midgut, indicating that it is a secreted protein (Figure 1E).


Tick histamine release factor is critical for Ixodes scapularis engorgement and transmission of the lyme disease agent.

Dai J, Narasimhan S, Zhang L, Liu L, Wang P, Fikrig E - PLoS Pathog. (2010)

Tick histamine release factor (tHRF) was up-regulated in B. burgdorferi- infected ticks.(A) The expression of tHRF in B. burgdorferi-infected or uninfected ticks during I. scapularis feeding. Results are expressed as the mean ± the SEM (*p<0.05; **p<0.01). (B) tHRF-antiserum recognizes recombinant tHRF generated in Escherichia coli (tHRF E.coli) or Drosophila S2 cells (tHRF DES). (C–D) The up-regulation of tHRF protein in B. burgdorferi-infected ticks. (*p<0.05) (E) The detection of tHRF in adult tick saliva (Saliva), nymphal tick salivary glands (S.G.), midgut (M.G.) and whole ticks (Tick).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2991271&req=5

ppat-1001205-g001: Tick histamine release factor (tHRF) was up-regulated in B. burgdorferi- infected ticks.(A) The expression of tHRF in B. burgdorferi-infected or uninfected ticks during I. scapularis feeding. Results are expressed as the mean ± the SEM (*p<0.05; **p<0.01). (B) tHRF-antiserum recognizes recombinant tHRF generated in Escherichia coli (tHRF E.coli) or Drosophila S2 cells (tHRF DES). (C–D) The up-regulation of tHRF protein in B. burgdorferi-infected ticks. (*p<0.05) (E) The detection of tHRF in adult tick saliva (Saliva), nymphal tick salivary glands (S.G.), midgut (M.G.) and whole ticks (Tick).
Mentions: To identify tick proteins that may be utilized by B. burgdorferi to facilitate transmission, 2-dimensional fluorescence difference gel electrophoresis (DIGE) was performed using extracts from B. burgdorferi-infected, and uninfected, I. scapularis salivary glands. Seventeen differentially expressed proteins (5-fold or more expression levels in Borrelia-infected salivary glands) were selected for mass spectrometric analysis, and 4 I. scapularis proteins were unambiguously identified with significant MASCOT scores (p<0.05) of 79 (Table S1). In this study, we characterize one of the most highly induced proteins, named tHRF because it shares high homology with a murine histamine release factor (57.1% similarity and 40.1% identity at amino acid level). tHRF mRNA levels were induced during I. scapularis engorgement, and significantly higher in B. burgdorferi-infected, than in uninfected, ticks (p<0.01). Immunoblots using tHRF antiserum further demonstrated a ∼2.5 fold up-regulation of tHRF in B. burgdorferi-infected ticks (Figure 1, A, C–D). tHRF was present in tick saliva, as well as in the salivary glands and midgut, indicating that it is a secreted protein (Figure 1E).

Bottom Line: Silencing tHRF by RNA interference (RNAi) significantly impaired tick feeding and decreased B. burgdorferi burden in mice.Interfering with tHRF by actively immunizing mice with recombinant tHRF, or passively transferring tHRF antiserum, also markedly reduced the efficiency of tick feeding and B. burgdorferi burden in mice.Recombinant tHRF was able to bind to host basophils and stimulate histamine release.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.

ABSTRACT
Ticks are distributed worldwide and affect human and animal health by transmitting diverse infectious agents. Effective vaccines against most tick-borne pathogens are not currently available. In this study, we characterized a tick histamine release factor (tHRF) from Ixodes scapularis and addressed the vaccine potential of this antigen in the context of tick engorgement and B. burgdorferi transmission. Results from western blotting and quantitative Reverse Transcription-PCR showed that tHRF is secreted in tick saliva, and upregulated in Borrelia burgdorferi-infected ticks. Further, the expression of tHRF was coincident with the rapid feeding phase of the tick, suggesting a role for tHRF in tick engorgement and concomitantly, for efficient B. burgdorferi transmission. Silencing tHRF by RNA interference (RNAi) significantly impaired tick feeding and decreased B. burgdorferi burden in mice. Interfering with tHRF by actively immunizing mice with recombinant tHRF, or passively transferring tHRF antiserum, also markedly reduced the efficiency of tick feeding and B. burgdorferi burden in mice. Recombinant tHRF was able to bind to host basophils and stimulate histamine release. Therefore, we speculate that tHRF might function in vivo to modulate vascular permeability and increase blood flow to the tick bite-site, facilitating tick engorgement. These findings suggest that blocking tHRF might offer a viable strategy to complement ongoing efforts to develop vaccines to block tick feeding and transmission of tick-borne pathogens.

Show MeSH
Related in: MedlinePlus