A “Trojan horse” bispecific-antibody strategy for broad protection against ebolaviruses

Abstract

There is an urgent need for monoclonal antibody (mAb) therapies that broadly protect against Ebola virus and other filoviruses. The conserved, essential interaction between the filovirus glycoprotein, GP, and its entry receptor Niemann-Pick C1 (NPC1) provides an attractive target for such mAbs but is shielded by multiple mechanisms, including physical sequestration in late endosomes. Here, we describe a bispecific-antibody strategy to target this interaction, in which mAbs specific for NPC1 or the GP receptor–binding site are coupled to a mAb against a conserved, surface-exposed GP epitope. Bispecific antibodies, but not parent mAbs, neutralized all known ebolaviruses by coopting viral particles themselves for endosomal delivery and conferred postexposure protection against multiple ebolaviruses in mice. Such “Trojan horse” bispecific antibodies have potential as broad antifilovirus immunotherapeutics.

Antibodies from a Human Survivor Define Sites of Vulnerability for Broad Protection against Ebolaviruses

“…Recombinant vesicular stomatitis Indiana viruses (rVSV) expressing eGFP in the first position, and encoding representative GP proteins from EBOV/Mayinga (EBOV/H.sap-tc/COD/76/Yambuku-Mayinga), EBOV/Makona (EBOV/H.sap-rec/LBR/14/Makona-L2014), BDBV (BDBV/H.sap/UGA/07/But-811250), SUDV/Boneface (SUDV/C.por-lab/SSD/76/Boneface), RESTV (RESTV/M.fastc/USA/89/Phi89-AZ-1435), and LLOV (LLOV/M.sch-wt/ESP/03/Asturias-Bat86), in place of VSV G have been described previously (Ng et al, 2014; Wec et al, 2016; Wong et al, 2010). VSV pseudotypes bearing eGFP and GP proteins from TAFV (TAFV/H.sap-tc/CIV/94/CDC807212) and MARV (MARV/H.sap-tc/KEN/80/Mt.…”

“…Frei et al (2016) combined known EBOV and SUDV GP-specific neutralizing antibodies (NAbs) KZ52 and a humanized variant of 16F6, respectively, to generate bispecific antibodies that protected against both viruses in mice. More recently, bispecific antibodies combining two broadly reactive but non-neutralizing mAbs targeting virus:host receptor interactions were shown to neutralize all known ebolaviruses through a “Trojan horse” mechanism and to protect mice challenged with EBOV or SUDV (Wec et al, 2016). The presence of cross-reactive and cross-neutralizing antibodies in natural antibody repertoires following monospecific ebolavirus infection or immunization has also been noted (Bornholdt et al, 2016b; Macneil et al, 2011; Natesan et al, 2016), and antibody discovery efforts have yielded cross-neutralizing mAbs with increased protective breadth (Flyak et al, 2016; Furuyama et al, 2016; Howell et al, 2016; Keck et al, 2015).…”

Systematic Analysis of Monoclonal Antibodies against Ebola Virus GP Defines Features that Contribute to Protection

“…Recombinant vesicular stomatitis virus (VSV) expressing both eGFP and recombinant surface GP (rVSV-EBOV) in place of VSV G was described previously (Wec et al, 2016; Wong et al, 2010). For neutralization assays, Vero cells were seeded at 6.0 × 10 4 cells/well and cultured overnight in Eagle’s minimal essential medium (EMEM) supplemented with 10% fetal bovine serum (FBS) and 100 I.U./ml penicillin and 100 μg/ml streptomycin at 37 °C and 5% CO 2 .…”

Principles of Broad and Potent Antiviral Human Antibodies: Insights for Vaccine Design

“…Based on this canonical mode of interaction with an aromatic residue and the capacity of MR72 to bind to Ebola GP, a bispecific antibody comprising the Marburg MR72 Fab and another antibody (to NPC1 receptor or to Ebola GP glycan cap) was used to deliver a construct to the cell endosome. In that cell compartment, the Marburg antibody could recognize the RBD in the cleaved Ebola GP (which is protected by the viral glycan cap prior to cleavage) and neutralize Ebola virus (Wec et al, 2016). Even more remarkable, a three-way structural mimicry for this interaction using these principles has now been described.…”