title: Preferential protection of Borrelia burgdorferi sensu stricto by a Salp15 homologue in Ixodes ricinus saliva.
abstract: BACKGROUND
  Ixodes ticks are the main vectors for Borrelia burgdorferi sensu lato. In the United States, B. burgdorferi is the sole causative agent of Lyme borreliosis and is transmitted by Ixodes scapularis. In Europe, 3 Borrelia species-B. burgdorferi, B. garinii, and B. afzelii-are prevalent, which are transmitted by Ixodes ricinus. The I. scapularis salivary protein Salp15 has been shown to bind to B. burgdorferi outer surface protein (Osp) C, protecting the spirochete from antibody-mediated killing.
  
  
  RESULTS
  We recently identified a Salp15 homologue in I. ricinus, Salp15 Iric-1. Here, we have demonstrated, by solid-phase overlays, enzyme-linked immunosorbent assay, and surface plasmon resonance, that Salp15 Iric-1 binds to B. burgdorferi OspC. Importantly, this binding protected the spirochete from antibody-mediated killing in vitro and in vivo; immune mice rechallenged with B. burgdorferi preincubated with Salp15 Iric-1 displayed significantly higher Borrelia numbers and more severe carditis, compared with control mice. Furthermore, Salp15 Iric-1 was capable of binding to OspC from B. garinii and B. afzelii, but these Borrelia species were not protected from antibody-mediated killing.
  
  
  CONCLUSIONS
  Salp15 Iric-1 interacts with all European Borrelia species but differentially protects B. burgdorferi from antibody-mediated killing, putatively giving this Borrelia species a survival advantage in nature.
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. j.w.hovius@amc.uva.nl
authors.forename: J W
authors.initials: JW
authors.lastname: Hovius
authors.forename: T J
authors.initials: TJ
authors.lastname: Schuijt
authors.forename: K A
authors.initials: KA
authors.lastname: de Groot
authors.forename: J J T H
authors.initials: JJ
authors.lastname: Roelofs
authors.forename: G A
authors.initials: GA
authors.lastname: Oei
authors.forename: J A
authors.initials: JA
authors.lastname: Marquart
authors.forename: R
authors.initials: R
authors.lastname: de Beer
authors.forename: C
authors.initials: C
authors.lastname: van 't Veer
authors.forename: T
authors.initials: T
authors.lastname: van der Poll
authors.forename: N
authors.initials: N
authors.lastname: Ramamoorthi
authors.forename: E
authors.initials: E
authors.lastname: Fikrig
authors.forename: A P
authors.initials: AP
authors.lastname: van Dam