Neutrophil recruitment during Leishmania infection: The role of sand fly salivary proteins

FARE Award Winner

Authors

• AB Guimaraes-Costa
• X Wen
• A Carvalho
• C Meneses
• J Brzostowski
• J Valenzuela
• F Oliveira

Abstract

Leishmania infection begins when an infected sand fly bites a vertebrate host inoculating parasites into the skin. Neutrophils are the first cells recruited to the site of the bite, exacerbating the infection. Here we investigate the effect of sand fly saliva on neutrophil recruitment. We purified bone marrow neutrophils from C57BL/6 mice or from peripheral blood of healthy human donors. Chemotaxis driven by sand fly saliva of vectors of visceral (Lutzomyia longipalpis) or cutaneous (Phlebotomus duboscqi) disease was measured by modified Boyden chamber assay. Both mouse and human neutrophils migrated towards saliva glands of the vectors P. duboscqi and L. longipalpis in a dose-dependent manner. Proteinase K treatment of saliva completely abrogated neutrophil recruitment, suggesting a protein as the chemotactic factor. To unearth the identity of the chemotactic factor from the saliva, plasmids coding for the 20 most abundant salivary proteins from P. duboscqi were injected in the ears of C57BL/6 mice. Neutrophil recruitment was analyzed by flow cytometry staining at 2, 6, 12 and 24 hours post injection. We have identified 3 different salivary proteins with neutrophil recruitment activity. Our next step is to perform the in vitro and in vivo chemotaxis assays with the recombinant proteins. We plan to validate the role of the salivary chemotactic factor in vivo and test if its neutralization can alter Leishmania infection. We put forward the hypothesis that blockage of this protein activity will disrupt neutrophil migration early in the Leishmania infection possibly altering the disease outcome.

Scientific Focus Area: Immunology

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