OspC facilitates Borrelia burgdorferi invasion of Ixodes scapularis salivary glands
Utpal Pal, … , Michael V. Norgard, Erol Fikrig
Utpal Pal, … , Michael V. Norgard, Erol Fikrig
Published January 15, 2004
Citation Information: J Clin Invest. 2004;113(2):220-230. https://doi.org/10.1172/JCI19894.
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Article Infectious disease

OspC facilitates Borrelia burgdorferi invasion of Ixodes scapularis salivary glands

Abstract

Outer surface protein C (OspC) is a differentially expressed major surface lipoprotein of Borrelia burgdorferi. ospC is swiftly upregulated when spirochetes leave the Ixodes scapularis tick gut, migrate to the salivary gland, and exit the arthropod vector. Here we show that OspC strongly binds to the tick salivary gland, suggesting a role for OspC in spirochete adherence to this tissue. In vivo studies using a murine model of Lyme borreliosis showed that while OspC F(ab)2 fragments did not influence either the viability of spirochetes or ospC gene expression, they did interfere with B. burgdorferi invasion of tick salivary glands. We then generated ospC knockout spirochetes in an infectious clone of B. burgdorferi and examined them within the vector. OspC-deficient or wild-type spirochetes persisted equally within the gut of unfed ticks and multiplied during the tick engorgement; however, unlike wild-type B. burgdorferi, the mutants were unable to invade salivary glands. Salivary gland colonization of OspC-deficient spirochetes was completely restored when this mutant was complemented in trans with a plasmid harboring the wild-type ospC gene. These studies conclusively demonstrate the importance of OspC in the invasion of tick salivary glands by B. burgdorferi, a critical step in the transmission of spirochetes from the arthropod vector to the mammalian host.

Authors

Utpal Pal, Xiaofeng Yang, Manchuan Chen, Linda K. Bockenstedt, John F. Anderson, Richard A. Flavell, Michael V. Norgard, Erol Fikrig

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Binding of OspC F(ab)2 fragments to B. burgdorferi N40. (a) Binding of a...
Binding of OspC F(ab)2 fragments to B. burgdorferi N40. (a) Binding of anti-OspC sera (black bars), normal rabbit sera (white bars), IgG, or F(ab)2 by ELISA. B. burgdorferi N40 lysates were immobilized onto microtiter wells (10 μg/ml) and probed with a 1:100 dilution of sera (OspC sera) or normal rabbit sera (NRS), or 8 μg/ml of purified IgGs (OspC IgG or NRS IgG) or 8 μg/ml of purified F(ab)2 fragments (OspC-Fab or NRS-Fab). Binding was detected using anti–rabbit F(ab)2 fragment–specific goat IgG conjugated to horseradish peroxidase. Data represent the OD450 at 15 minutes (mean ± SEM, n = 3; differences between values of wells treated with OspC or NRS Ab were at least P < 0.001). (b) OspC F(ab)2 fragments directly bind to the surface of intact B. burgdorferi. Unfixed B. burgdorferi were immobilized onto glass slides and incubated in the presence of F(ab)2 fragments prepared from normal rabbit sera (NRS-Fab) or anti-OspC sera (anti–OspC-Fab). Binding was detected using anti–rabbit F(ab)2 fragment–specific goat IgG labeled with FITC. Images were obtained using a 40× objective lens on a Zeiss LSM 510 confocal microscope (n = 3).