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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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Related in: MedlinePlus

Silencing tHRF impairs tick feeding and B. burgdorferi transmission.(A) tHRF and SSRB (another tick gene, as a control) were silenced efficiently and specifically in nympal tick salivary gland by micro-injection of dsRNA. Results are expressed as the mean ± the SEM. (B) The weight of B. burgdorferi-infected ticks after feeding on naive mice. (C) The B. burgdorferi burden in whole ticks at 72 h post tick-engorgement. Spirochete burden in (D) murine skin at day 7, (E) joints and (F) heart at day 21 post-infection. (G) The weight of uninfected ticks after feeding on naive mice. Horizontal lines and bars represent the mean values ± the SEM. * p<0.05 and ** p<0.01 when compared with MOCK controls. Results are pooled from 3 independent experiments.
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ppat-1001205-g002: Silencing tHRF impairs tick feeding and B. burgdorferi transmission.(A) tHRF and SSRB (another tick gene, as a control) were silenced efficiently and specifically in nympal tick salivary gland by micro-injection of dsRNA. Results are expressed as the mean ± the SEM. (B) The weight of B. burgdorferi-infected ticks after feeding on naive mice. (C) The B. burgdorferi burden in whole ticks at 72 h post tick-engorgement. Spirochete burden in (D) murine skin at day 7, (E) joints and (F) heart at day 21 post-infection. (G) The weight of uninfected ticks after feeding on naive mice. Horizontal lines and bars represent the mean values ± the SEM. * p<0.05 and ** p<0.01 when compared with MOCK controls. Results are pooled from 3 independent experiments.

Mentions: To analyze the potential role of tHRF in tick feeding, and also during B. burgdorferi transmission, tHRF-deficient I. scapularis nymphs were generated by RNA interference (RNAi). Buffer-injected (MOCK), SSRB (another tick gene- Single Sequence Receptor Beta- found in our 2DIGE list, used as a control) or tHRF double-stranded RNA (dsRNA)-injected B. burgdorferi-infected nymphs were allowed to engorge on mice. The silencing of tHRF and SSRB were confirmed by quantitative RT-PCR (Figure 2A). After 3 days, the weighs of tHRF-deficient ticks were significantly lower than control ticks (Figure 2B). Q-PCR revealed a decrease in spirochete levels in tHRF-deficient ticks, as well as in the skin of mice that were fed upon by tHRF-deficient ticks (Figure 2, C and D). At 3 weeks, when spirochetes have disseminated to diverse organs, the B. burgdorferi burden in the heart and joints was also lower in mice infected by tHRF-deficient ticks, compared to that in mice infected with control ticks (Figure 2, E and F).


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)

Silencing tHRF impairs tick feeding and B. burgdorferi transmission.(A) tHRF and SSRB (another tick gene, as a control) were silenced efficiently and specifically in nympal tick salivary gland by micro-injection of dsRNA. Results are expressed as the mean ± the SEM. (B) The weight of B. burgdorferi-infected ticks after feeding on naive mice. (C) The B. burgdorferi burden in whole ticks at 72 h post tick-engorgement. Spirochete burden in (D) murine skin at day 7, (E) joints and (F) heart at day 21 post-infection. (G) The weight of uninfected ticks after feeding on naive mice. Horizontal lines and bars represent the mean values ± the SEM. * p<0.05 and ** p<0.01 when compared with MOCK controls. Results are pooled from 3 independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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

ppat-1001205-g002: Silencing tHRF impairs tick feeding and B. burgdorferi transmission.(A) tHRF and SSRB (another tick gene, as a control) were silenced efficiently and specifically in nympal tick salivary gland by micro-injection of dsRNA. Results are expressed as the mean ± the SEM. (B) The weight of B. burgdorferi-infected ticks after feeding on naive mice. (C) The B. burgdorferi burden in whole ticks at 72 h post tick-engorgement. Spirochete burden in (D) murine skin at day 7, (E) joints and (F) heart at day 21 post-infection. (G) The weight of uninfected ticks after feeding on naive mice. Horizontal lines and bars represent the mean values ± the SEM. * p<0.05 and ** p<0.01 when compared with MOCK controls. Results are pooled from 3 independent experiments.
Mentions: To analyze the potential role of tHRF in tick feeding, and also during B. burgdorferi transmission, tHRF-deficient I. scapularis nymphs were generated by RNA interference (RNAi). Buffer-injected (MOCK), SSRB (another tick gene- Single Sequence Receptor Beta- found in our 2DIGE list, used as a control) or tHRF double-stranded RNA (dsRNA)-injected B. burgdorferi-infected nymphs were allowed to engorge on mice. The silencing of tHRF and SSRB were confirmed by quantitative RT-PCR (Figure 2A). After 3 days, the weighs of tHRF-deficient ticks were significantly lower than control ticks (Figure 2B). Q-PCR revealed a decrease in spirochete levels in tHRF-deficient ticks, as well as in the skin of mice that were fed upon by tHRF-deficient ticks (Figure 2, C and D). At 3 weeks, when spirochetes have disseminated to diverse organs, the B. burgdorferi burden in the heart and joints was also lower in mice infected by tHRF-deficient ticks, compared to that in mice infected with control ticks (Figure 2, E and F).

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