Ir-LBP, an ixodes ricinus tick salivary LTB4-binding lipocalin, interferes with host neutrophil function.
BACKGROUND
During their blood meal, ticks secrete a wide variety of proteins that can interfere with their host's defense mechanisms. Among these proteins, lipocalins play a major role in the modulation of the inflammatory response.


RESULTS
We previously identified 14 new lipocalin genes in the tick Ixodes ricinus. One of them codes for a protein that specifically binds leukotriene B4 with a very high affinity (Kd: +/-1 nM), similar to that of the neutrophil transmembrane receptor BLT1. By in silico approaches, we modeled the 3D structure of the protein and the binding of LTB4 into the ligand pocket. This protein, called Ir-LBP, inhibits neutrophil chemotaxis in vitro and delays LTB4-induced apoptosis. Ir-LBP also inhibits the host inflammatory response in vivo by decreasing the number and activation of neutrophils located at the tick bite site. Thus, Ir-LBP participates in the tick's ability to interfere with proper neutrophil function in inflammation.


CONCLUSIONS
These elements suggest that Ir-LBP is a "scavenger" of LTB4, which, in combination with other factors, such as histamine-binding proteins or proteins inhibiting the classical or alternative complement pathways, permits the tick to properly manage its blood meal. Moreover, with regard to its properties, Ir-LBP could possibly be used as a therapeutic tool for illnesses associated with an increased LTB4 production.
Beaufays
Jérôme
J
Laboratory for Molecular Biology of Ectoparasites, IBMM, Université Libre de Bruxelles, Gosselies, Belgium.
Adam
Benoît
B
Menten-Dedoyart
Catherine
C
Fievez
Laurence
L
Grosjean
Amélie
A
Decrem
Yves
Y
Prévôt
Pierre-Paul
PP
Santini
Sébastien
S
Brasseur
Robert
R
Brossard
Michel
M
Vanhaeverbeek
Michel
M
Bureau
Fabrice
F
Heinen
Ernst
E
Lins
Laurence
L
Vanhamme
Luc
L
Godfroid
Edmond
E
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D003198:Computer Simulation; D005260:Female; D006790:Host-Parasite Interactions / Q000235:genetics / Q000276:immunology*; D018884:Ixodes / Q000276:immunology / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism*; D054834:Lipocalins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018375:Neutrophil Activation / Q000502:physiology; D009504:Neutrophils / Q000502:physiology*; D011485:Protein Binding; D011817:Rabbits; D018102:Receptors, Leukotriene B4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012471:Salivary Proteins and Peptides / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013984:Tick Infestations / Q000276:immunology
D054834:Lipocalins; D018102:Receptors, Leukotriene B4; D012471:Salivary Proteins and Peptides; D007975:Leukotriene B4