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.
View: Text | PDF
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

×

Figure 4

Options: View larger image (or click on image) Download as PowerPoint
Measurement of viable B. burgdorferi and ospC gene expression in feeding...
Measurement of viable B. burgdorferi and ospC gene expression in feeding ticks exposed to OspC F(ab)2. (a) Assessment of viable B. burgdorferi as measured by quantitative PCR of flaB mRNA in feeding tick gut. B. burgdorferi–infected nymphs were treated with NRS-F(ab)2 or OspC-F(ab)2 (NRS-Fab or OspC-Fab, respectively) were analyzed at 48 or 96 hours after the onset of feeding. Equal amounts of cDNA, converted from total RNA from each group of ticks, were subjected to quantitative PCR. Known quantities of B. burgdorferi DNA and pCR 2.1 plasmid carrying the tick β-actin gene were used to prepare standard PCR curves. Amounts of tick β-actin were determined in each samples and use to normalize the quantities of spirochete DNA between the samples. Differences in flaB RNA amounts between NRS-Fab and OspC-Fab groups of tick at 48 or 96 hours were not significant (n = 3). (b) Measurement of ospC transcripts in feeding tick gut by quantitative PCR as described above. NRS-Fab and OspC-Fab nymphs were analyzed at 48 or 96 hours after the onset of the feeding. The amounts of flaB and ospC transcripts were measured in each samples and data shown are the quantities of ospC cDNA relative to flaB cDNA in normalized tick samples. Differences in ospC cDNA amounts between NRS-Fab and OspC-Fab groups of tick at 48 or 96 hours were not significant (n = 3).