Novel anti-Siglec-1 monoclonal antibodies offer cross-protection against Ebola virus and HIV-1
D Perez-Zsolt1, I Erkizia1, M Pino1, M García-Gallo2, MT Martin2, S Benet1, MT Fernández-Figueras3,4,5, D Guerrero6, V Urrea1, L Kremer2, J Martinez-Picado1,7,8,*, N Izquierdo-Useros1,*
1IrsiCaixa, Badalona, Spain; 2CNB/CSIC, Madrid, Spain; 3HUGC, Barcelona, Spain; 4UIC, Barcelona, Spain; 5IGTP, Badalona, Spain; 6HUGTiP, Badalona, Spain; 7UVic-UCC, Vic, Spain, 8ICREA, Barcelona, Spain.
*Senior and corresponding authors
Several filoviruses cause outbreaks of hemorrhagic fever, but developing therapies only tackle Zaire Ebola virus. Dendritic cells (DCs) are primary targets of this infection in vivo, but factors governing viral entry into these cells are not fully understood. DCs express the sialic acid-binding Ig-like lectin 1 (Siglec-1), which mediates HIV-1 uptake via recognition of viral membrane gangliosides. Since filoviruses also incorporate gangliosides on their membranes, here we studied the role of Siglec-1 during filoviral entry into DCs.
Ebola virus-like particles (EboVLP) were incubated with DCs and myeloid cells from lymphoid tissues. Capture and fusion of EboVLP were assessed by flow cytometry and compared to HIV-1. Endocytosis of viral particles was determined by confocal and electron microscopy. Novel anti-Siglec-1 monoclonal antibodies (mAbs) were developed immunizing mice with human Siglec-1 and characterized by surface plasmon resonance. Statistical significance was assessed with paired and one-sample t tests.
Activating immune signals such as lipopolysaccharide or interferon-α, which are present throughout the course of filovirus infection, up-regulated Siglec-1 expression on DCs. Moreover, on activated DCs, Siglec-1 inhibition blocked EboVLP uptake (P<0.0001) and fusion (P≤0.0004). Captured EboVLP accumulated in the same Siglec-1+ virus-containing compartment as HIV-1. Finally, we generated a set of novel anti-Siglec-1 mAbs with affinities below the nanomolar range that halted Ebola viral uptake and fusion on activated DCs or myeloid cells from lymphoid tissues. Importantly, these mAbs also offered cross-protection against other ganglioside-containing viruses like HIV-1.
Thus, we identified a role for Siglec-1 in Ebola virus fusion. As all filoviruses rely on gangliosides for viral particle formation, targeting Siglec-1 with novel mAbs may protect against distinct emerging outbreaks.
Funding: Spanish Secretariat of R+D+I grant SAF2016-80033-R.