Most neutralizing human monoclonal antibodies target novel epitopes requiring both Lassa virus glycoprotein subunits

Abstract

Lassa fever is a severe multisystem disease that often has haemorrhagic manifestations. The epitopes of the Lassa virus (LASV) surface glycoproteins recognized by naturally infected human hosts have not been identified or characterized. Here we have cloned 113 human monoclonal antibodies (mAbs) specific for LASV glycoproteins from memory B cells of Lassa fever survivors from West Africa. One-half bind the GP2 fusion subunit, one-fourth recognize the GP1 receptor-binding subunit and the remaining fourth are specific for the assembled glycoprotein complex, requiring both GP1 and GP2 subunits for recognition. Notably, of the 16 mAbs that neutralize LASV, 13 require the assembled glycoprotein complex for binding, while the remaining 3 require GP1 only. Compared with non-neutralizing mAbs, neutralizing mAbs have higher binding affinities and greater divergence from germline progenitors. Some mAbs potently neutralize all four LASV lineages. These insights from LASV human mAb characterization will guide strategies for immunotherapeutic development and vaccine design.

Convergent immunological solutions to Argentine hemorrhagic fever virus neutralization

“…As a result, the identification of nAbs targeting other neutralizing epitopes is an important consideration for developing synergetic, noncompeting combinations of therapeutic anti-JUNV mAbs. Indeed, Robinson et al (36) reported a range of neutralizing epitopes among human mAbs raised upon infection by Lassa virus (LASV), a more distantly related Old World arenavirus. Of the 16 identified anti-LASV nAbs, 13 require the assembled GPC for binding, whereas 3 require only the GP1 (36).…”

“…Indeed, Robinson et al (36) reported a range of neutralizing epitopes among human mAbs raised upon infection by Lassa virus (LASV), a more distantly related Old World arenavirus. Of the 16 identified anti-LASV nAbs, 13 require the assembled GPC for binding, whereas 3 require only the GP1 (36). Thus, emerging techniques in mAb generation, such as the isolation of antigen-specific B cells (37) against an intact prefusion GPC spike antigen, may reveal antibodies capable of targeting alternative non-RBS epitopes on the JUNV glycoprotein surface.…”

Mutational Analysis of Lassa Virus Glycoprotein Highlights Regions Required for Alpha-Dystroglycan Utilization

“…Trichloroacetic acid (TCA)-precipitated pseudotyped particles were fractionated as described for biotinylated material. Protein was detected with specific antibodies directed against LASV GP2 (22.5D), kindly provided by James Robinson (Tulane University), and against VSV matrix (23H12; courtesy of Douglas Lyles; Kerafast) (56,57). Alpha-dystroglycan was detected with IIH6 monoclonal antibody (EMD Millipore).…”

Treatment of Lassa virus infection in outbred guinea pigs with first-in-class human monoclonal antibodies

“…Since 2008, the Viral Hemorrhagic Fever Consortium (http://www.VHFC.org) has concentrated efforts at characterizing protective or pathogenic roles of B cells in LF directly from human patients (Robinson et al, 2016). This work has resulted in the derivation of the largest known collection of fully human monoclonal antibodies (huMAbs) from convalescent West African LF patients.…”

“…A panel of 125 independently derived LASV glycoprotein-specific huMAbs were extensively characterized for binding, epitope grouping, and neutralization potential in vitro (Robinson et al, 2016). Eleven huMAbs consistently registered greater than 50% neutralization in a lentiviral entry assay system pseudotyped with the LASV (Josiah strain, Clade IV) GPC, a lymphocytic choriomeningitis virus (LCMV) backbone pseudotyped with LASV GPC, or in a live LASV plaque reduction neutralization test (PRNT) (Robinson et al, 2016).…”