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A tick gut protein with fibronectin III domains aids Borrelia burgdorferi congregation to the gut during transmission.

Narasimhan S, Coumou J, Schuijt TJ, Boder E, Hovius JW, Fikrig E - PLoS Pathog. (2014)

Bottom Line: Immunization against Ixofin3D and RNA interference-mediated reduction in expression of Ixofin3D resulted in decreased spirochete burden in tick salivary glands and in the murine host.Microscopic examination showed decreased aggregation of spirochetes on the gut epithelium concomitant with reduced expression of Ixofin3D.Our observations suggest that the interaction between Borrelia and Ixofin3D facilitates spirochete congregation to the gut during transmission, and provides a "molecular exit" direction for spirochete egress from the gut.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America.

ABSTRACT
Borrelia burgdorferi transmission to the vertebrate host commences with growth of the spirochete in the tick gut and migration from the gut to the salivary glands. This complex process, involving intimate interactions of the spirochete with the gut epithelium, is pivotal to transmission. We utilized a yeast surface display library of tick gut proteins to perform a global screen for tick gut proteins that might interact with Borrelia membrane proteins. A putative fibronectin type III domain-containing tick gut protein (Ixofin3D) was most frequently identified from this screen and prioritized for further analysis. Immunization against Ixofin3D and RNA interference-mediated reduction in expression of Ixofin3D resulted in decreased spirochete burden in tick salivary glands and in the murine host. Microscopic examination showed decreased aggregation of spirochetes on the gut epithelium concomitant with reduced expression of Ixofin3D. Our observations suggest that the interaction between Borrelia and Ixofin3D facilitates spirochete congregation to the gut during transmission, and provides a "molecular exit" direction for spirochete egress from the gut.

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RNA interference-mediated decrease in Ixofin3D results in decreased B. burgdorferi burden in the salivary glands and in murine skin.Double-stranded ixofin3D (ds ixofin3D) or ds gfp was injected through the anal pore 3 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of ticks fed to repletion. Each data point represents one tick; B. qRT-PCR assessment of ixofin3D expression; and C. Borrelia burden in tick guts and salivary glands. Each data point in B and C represents a pool of 3 guts or salivary glands; and D. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. Each data point represents one mouse. Error bars represent mean ± SEM and mean values significantly different in a two-tailed non-parametric Mann-Whitney test (p<0.05) indicated by an asterisk. A representative of 3 experiments is shown.
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ppat-1004278-g006: RNA interference-mediated decrease in Ixofin3D results in decreased B. burgdorferi burden in the salivary glands and in murine skin.Double-stranded ixofin3D (ds ixofin3D) or ds gfp was injected through the anal pore 3 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of ticks fed to repletion. Each data point represents one tick; B. qRT-PCR assessment of ixofin3D expression; and C. Borrelia burden in tick guts and salivary glands. Each data point in B and C represents a pool of 3 guts or salivary glands; and D. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. Each data point represents one mouse. Error bars represent mean ± SEM and mean values significantly different in a two-tailed non-parametric Mann-Whitney test (p<0.05) indicated by an asterisk. A representative of 3 experiments is shown.

Mentions: To circumvent the possibility that antibodies against partial Ixofin3D might not efficiently abrogate Ixofin3D function in vivo, and to clarify the role of Ixofin3D in Borrelia transmission, we decreased the expression of Ixofin3D by RNA interference (RNAi) as described earlier [23]. Four to five double stranded (ds) ixofin3D RNA-injected nymphs or ds gfp RNA-injected were allowed to engorge on each mouse (8 mice/group). Nymphs injected with ds ixofin3D RNA engorged comparably to control nymphs injected with ds gfp RNA (Fig. 6A) despite a significant decrease in the expression of ixofin3D RNA in the guts as seen by qRT-PCR (Fig. 6B). While Borrelia burden in the guts was comparable in ds gfp and ds ixofin3D-injected nymphs (Fig. 6C), Borrelia burden in the salivary glands of fed ds ixofin3D-injected nymphs when compared to that in the salivary glands of ds gfp RNA-injected nymphs was significantly decreased (Fig. 6C). Borrelia burden in the skin of mice fed upon by ds ixofin3D RNA-injected nymphs (experimental group) at 7 and 14 days post tick feeding was significantly decreased when compared to that in the skin of mice that were fed upon by ds gfp RNA-injected nymphs (Fig. 6D).


A tick gut protein with fibronectin III domains aids Borrelia burgdorferi congregation to the gut during transmission.

Narasimhan S, Coumou J, Schuijt TJ, Boder E, Hovius JW, Fikrig E - PLoS Pathog. (2014)

RNA interference-mediated decrease in Ixofin3D results in decreased B. burgdorferi burden in the salivary glands and in murine skin.Double-stranded ixofin3D (ds ixofin3D) or ds gfp was injected through the anal pore 3 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of ticks fed to repletion. Each data point represents one tick; B. qRT-PCR assessment of ixofin3D expression; and C. Borrelia burden in tick guts and salivary glands. Each data point in B and C represents a pool of 3 guts or salivary glands; and D. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. Each data point represents one mouse. Error bars represent mean ± SEM and mean values significantly different in a two-tailed non-parametric Mann-Whitney test (p<0.05) indicated by an asterisk. A representative of 3 experiments is shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4125277&req=5

ppat-1004278-g006: RNA interference-mediated decrease in Ixofin3D results in decreased B. burgdorferi burden in the salivary glands and in murine skin.Double-stranded ixofin3D (ds ixofin3D) or ds gfp was injected through the anal pore 3 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of ticks fed to repletion. Each data point represents one tick; B. qRT-PCR assessment of ixofin3D expression; and C. Borrelia burden in tick guts and salivary glands. Each data point in B and C represents a pool of 3 guts or salivary glands; and D. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. Each data point represents one mouse. Error bars represent mean ± SEM and mean values significantly different in a two-tailed non-parametric Mann-Whitney test (p<0.05) indicated by an asterisk. A representative of 3 experiments is shown.
Mentions: To circumvent the possibility that antibodies against partial Ixofin3D might not efficiently abrogate Ixofin3D function in vivo, and to clarify the role of Ixofin3D in Borrelia transmission, we decreased the expression of Ixofin3D by RNA interference (RNAi) as described earlier [23]. Four to five double stranded (ds) ixofin3D RNA-injected nymphs or ds gfp RNA-injected were allowed to engorge on each mouse (8 mice/group). Nymphs injected with ds ixofin3D RNA engorged comparably to control nymphs injected with ds gfp RNA (Fig. 6A) despite a significant decrease in the expression of ixofin3D RNA in the guts as seen by qRT-PCR (Fig. 6B). While Borrelia burden in the guts was comparable in ds gfp and ds ixofin3D-injected nymphs (Fig. 6C), Borrelia burden in the salivary glands of fed ds ixofin3D-injected nymphs when compared to that in the salivary glands of ds gfp RNA-injected nymphs was significantly decreased (Fig. 6C). Borrelia burden in the skin of mice fed upon by ds ixofin3D RNA-injected nymphs (experimental group) at 7 and 14 days post tick feeding was significantly decreased when compared to that in the skin of mice that were fed upon by ds gfp RNA-injected nymphs (Fig. 6D).

Bottom Line: Immunization against Ixofin3D and RNA interference-mediated reduction in expression of Ixofin3D resulted in decreased spirochete burden in tick salivary glands and in the murine host.Microscopic examination showed decreased aggregation of spirochetes on the gut epithelium concomitant with reduced expression of Ixofin3D.Our observations suggest that the interaction between Borrelia and Ixofin3D facilitates spirochete congregation to the gut during transmission, and provides a "molecular exit" direction for spirochete egress from the gut.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America.

ABSTRACT
Borrelia burgdorferi transmission to the vertebrate host commences with growth of the spirochete in the tick gut and migration from the gut to the salivary glands. This complex process, involving intimate interactions of the spirochete with the gut epithelium, is pivotal to transmission. We utilized a yeast surface display library of tick gut proteins to perform a global screen for tick gut proteins that might interact with Borrelia membrane proteins. A putative fibronectin type III domain-containing tick gut protein (Ixofin3D) was most frequently identified from this screen and prioritized for further analysis. Immunization against Ixofin3D and RNA interference-mediated reduction in expression of Ixofin3D resulted in decreased spirochete burden in tick salivary glands and in the murine host. Microscopic examination showed decreased aggregation of spirochetes on the gut epithelium concomitant with reduced expression of Ixofin3D. Our observations suggest that the interaction between Borrelia and Ixofin3D facilitates spirochete congregation to the gut during transmission, and provides a "molecular exit" direction for spirochete egress from the gut.

Show MeSH
Related in: MedlinePlus