Novel findings on the role of ficolins and colectins in the innate response against Leishmania braziliensis

•Initiator proteins of the lectin pathway bind “in vitro” to promastigotes forms of L. braziliensis parasites.•The incubation of L. braziliensis with either normal human serum or the recombinant proteins leads to deposition of CL-11, ficolin-1, ficolin-2 and ficolin-3 on parasite surface.•The findings suggest the involvement of the lectin complement pathway in the first steps of host defense against L. braziliensis infection. Leishmania (Viannia) braziliensis is the main agent of mucocutaneous Leishmaniasis, a neglected tropical disease that affects thousands of people in Brazil. It has been shown that complement plays a critical role at early stages of Leishmania infection and that is involved in the invasion of macrophages by the promastigotes. Ficolins and collectins are soluble pattern recognition and triggering molecules of the lectin complement pathway. We investigated here whether lectin pathway activators ficolin-1, ficolin-2, ficolin-3 and CL-11 bind to live L. braziliensis promastigotes in vitro. Promastigote forms in the stationary growth phase were incubated with normal human serum (NHS) or recombinant ficolins 1, 2 and 3, MBL and CL-11, and protein binding was evaluated by confocal microscopy and flow cytometry. Ficolins 1, 2 and 3, MBL and CL-11 were able to bind to the surface of live promastigotes after incubation with either NHS or recombinant proteins. A partial inhibition by N-acetyl-d-glucosamine characterizing the participation of acetylated groups in the deposition of ficolins and CL-11 to glycoconjugates on the surface of L. braziliensis was observed. These evidences highlight a role for the lectin pathway in the innate response to L. braziliensis. [Display omitted]