Protective mAbs and Cross-Reactive mAbs Raised by Immunization with Engineered Marburg Virus GPs

Abstract

The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel “wing” feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV.

Neglected filoviruses

“…Several serological or nucleic-acid based RESTVspecific diagnostic systems have been described (Kalter et al 1995;Ksiazek et al 1999;Niikura et al 2001;Ikegami et al 2002bIkegami et al , 2003aOu et al 2011). RESTV-specific monoclonal or polyclonal murine, rabbit or crab-eating macaque antibodies (Ou et al 2011;Holtsberg et al 2015;Keck et al 2015;Wang et al 2015), RESTV cross-reactive murine antibodies (Fusco et al 2015;Wang et al 2015;Furuyama et al 2016), RESTV cross-reactive murine scFvs and IgNAR Vs raised against inactivated EBOV particles (Goodchild et al 2011) are available.…”

Generation and characterization of protective antibodies to Marburg virus

“…The identification of neutralizing mAbs to MARV has been problematic, with neutralizers reported in the literature limited to vesicular stomatitis virus (VSV)-expressed Ravn 17 or Uganda 18 glycoprotein, although Kajihara et al was able to demonstrate an inhibitory mechanism specific to viral budding. 19 In this study, we utilized two separate assays to evaluate neutralization of MARV.…”

“…Standard mouse models, using C57BL/6 or BALB/c, could only be utilized with a mouse-adapted Ravn 17,20 or mouse-adapted Ci67 18 , as previously done by others. These antibodies bind to Ci67 with some cross reactivity to Angola or Musoke, but are not cross reactive to Ravn.…”

“…Fusco et al demonstrated post-exposure prophylactic protection using 500 mg of antibody administered 1 hr after 1000 PFU challenge with mouse-adapted Ravn. 21 Flyak et al used a similar approach to our experimental design, but with i.m. administration of a 100 mg of antibody, with multi-dose regimen beginning 24-hr pre-exposure followed by 24 hr post-exposure against 1000 PFU mouse-adapted Ci67 strain.…”

“…The first utilization of a monoclonal antibody (mAb) therapy for MARV was recently reported by Fusco et al; they found two mAbs that bind to GP, which were able to provide protection, but to a mouse-adapted Ravn strain of Marburg virus (RAVV). 17 In this study, we present the generation, isolation and characterization of a series of macaque, high-affinity single-chain variable fragments (scFvs) targeting MARV GP, as well as the protection in a mouse model obtained by these antibodies in the scFv-Fc format.…”