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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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Impact of passive and active immunization against Ixofin3D-PF on B. burgdorferi burden in ticks and in murine skin.A–C: Rabbit anti-rIxofin3D-PF serum or rabbit anti-Ovalbumin serum was passively transferred into each mouse 24 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of repleted ticks; B. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; C. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. D–F: Mice actively immunized with rIxofin3D-PF or Ovalbumin and challenged with B. burgdorferi-infected ticks (4–5 ticks/mouse). D. Engorgement weights of repleted ticks; E. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; F. qPCR assessment of Borrelia burden in mice skin at 7 and 14 days post-tick feeding. Each data point in A and D represents one tick. Each data point in B and E represents a pool of 2–3 guts or salivary glands. Each data point in C and F 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 three experiments is shown.
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ppat-1004278-g005: Impact of passive and active immunization against Ixofin3D-PF on B. burgdorferi burden in ticks and in murine skin.A–C: Rabbit anti-rIxofin3D-PF serum or rabbit anti-Ovalbumin serum was passively transferred into each mouse 24 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of repleted ticks; B. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; C. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. D–F: Mice actively immunized with rIxofin3D-PF or Ovalbumin and challenged with B. burgdorferi-infected ticks (4–5 ticks/mouse). D. Engorgement weights of repleted ticks; E. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; F. qPCR assessment of Borrelia burden in mice skin at 7 and 14 days post-tick feeding. Each data point in A and D represents one tick. Each data point in B and E represents a pool of 2–3 guts or salivary glands. Each data point in C and F 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 three experiments is shown.

Mentions: To determine the role of Ixofin3D in spirochete transmission, we passively transferred purified rabbit IgG against rIxofin3D-PF into eight C3H/HeN mice and challenged these mice with Borrelia-infected I. scapularis nymphs. Control mice received purified rabbit IgG against ovalbumin (Ova). Ticks fed to repletion and engorged comparably on both control and experimental mice (Fig. 5A). Guts and salivary glands were dissected from engorged nymphs and Borrelia burden assessed by qRT-PCR. While the spirochete burden in the guts were comparable in both groups, Borrelia burden in the salivary glands was reduced in nymphs that fed on mice that received anti-rIxofin3D-PF antibodies (Fig. 5B) when compared to that in salivary glands of nymphs fed on mice that received anti-Ovalbumin antibodies, however, the decrease was not statistically significant. Borrelia burden in the skin of mice that received anti-rIxofin3D-PF antibodies (Fig. 5C) was also reduced at 7 days post tick feeding when compared to that in the skin of mice that received anti-Ovalbumin antibodies, however, the decrease was not statistically significant.


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)

Impact of passive and active immunization against Ixofin3D-PF on B. burgdorferi burden in ticks and in murine skin.A–C: Rabbit anti-rIxofin3D-PF serum or rabbit anti-Ovalbumin serum was passively transferred into each mouse 24 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of repleted ticks; B. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; C. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. D–F: Mice actively immunized with rIxofin3D-PF or Ovalbumin and challenged with B. burgdorferi-infected ticks (4–5 ticks/mouse). D. Engorgement weights of repleted ticks; E. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; F. qPCR assessment of Borrelia burden in mice skin at 7 and 14 days post-tick feeding. Each data point in A and D represents one tick. Each data point in B and E represents a pool of 2–3 guts or salivary glands. Each data point in C and F 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 three experiments is shown.
© Copyright Policy
Related In: Results  -  Collection

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

ppat-1004278-g005: Impact of passive and active immunization against Ixofin3D-PF on B. burgdorferi burden in ticks and in murine skin.A–C: Rabbit anti-rIxofin3D-PF serum or rabbit anti-Ovalbumin serum was passively transferred into each mouse 24 h prior to B. burgdorferi-infected tick challenge (4–5 ticks/mouse). A. Engorgement weights of repleted ticks; B. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; C. qPCR assessment of Borrelia burden in murine skin at 7 and 14 days post-tick feeding. D–F: Mice actively immunized with rIxofin3D-PF or Ovalbumin and challenged with B. burgdorferi-infected ticks (4–5 ticks/mouse). D. Engorgement weights of repleted ticks; E. qRT-PCR assessment of Borrelia burden in tick guts and salivary glands; F. qPCR assessment of Borrelia burden in mice skin at 7 and 14 days post-tick feeding. Each data point in A and D represents one tick. Each data point in B and E represents a pool of 2–3 guts or salivary glands. Each data point in C and F 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 three experiments is shown.
Mentions: To determine the role of Ixofin3D in spirochete transmission, we passively transferred purified rabbit IgG against rIxofin3D-PF into eight C3H/HeN mice and challenged these mice with Borrelia-infected I. scapularis nymphs. Control mice received purified rabbit IgG against ovalbumin (Ova). Ticks fed to repletion and engorged comparably on both control and experimental mice (Fig. 5A). Guts and salivary glands were dissected from engorged nymphs and Borrelia burden assessed by qRT-PCR. While the spirochete burden in the guts were comparable in both groups, Borrelia burden in the salivary glands was reduced in nymphs that fed on mice that received anti-rIxofin3D-PF antibodies (Fig. 5B) when compared to that in salivary glands of nymphs fed on mice that received anti-Ovalbumin antibodies, however, the decrease was not statistically significant. Borrelia burden in the skin of mice that received anti-rIxofin3D-PF antibodies (Fig. 5C) was also reduced at 7 days post tick feeding when compared to that in the skin of mice that received anti-Ovalbumin antibodies, however, the decrease was not statistically significant.

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