A cocktail of protective antibodies subverts the dense glycan shield of Lassa virus

Abstract

Developing potent therapeutics and effective vaccines are the ultimate goals in controlling infectious diseases. Lassa virus (LASV), the causative pathogen of Lassa fever (LF), infects hundreds of thousands annually, but effective antivirals or vaccines against LASV infection are still lacking. Furthermore, neutralizing antibodies against LASV are rare. Here, we describe biochemical analyses and high-resolution cryo-electron microscopy structures of a therapeutic cocktail of three broadly protective antibodies that target the LASV glycoprotein complex (GPC), previously identified from survivors of multiple LASV infections. Structural and mechanistic analyses reveal compatible neutralizing epitopes and complementary neutralization mechanisms that offer high potency, broad range, and resistance to escape. These antibodies either circumvent or exploit specific glycans comprising the extensive glycan shield of GPC. Further, they require mammalian glycosylation, native GPC cleavage, and proper GPC trimerization. These findings guided engineering of a next-generation GPC antigen suitable for future neutralizing antibody and vaccine discovery. Together, these results explain protective mechanisms of rare, broad, and potent antibodies and identify a strategy for the rational design of therapeutic modalities against LF and related infectious diseases.

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

“…In addition to the approved and previously authorized mAbs and those directed against SARS-CoV-2, many other mAbs have been or are under development against existing and emerging diseases (see [58][59][60][61] for some examples). Historically, therapeutic mAbs were derived from immunized mice or rats and engineered as chimeric or humanized mAbs to reduce the immunogenicity due the "foreignness" of rodent mAbs in humans.…”

Defining bottlenecks and opportunities for Lassa virus neutralization by structural profiling of vaccine-induced polyclonal antibody responses

“…This highly potent broadly neutralizing antibody (bNAb) directly blocks matriglycan binding and has been shown to require the native cleavage site to engage with GPC. 29 Therefore, to generate a trimeric GPC immunogen that presents all currently known bNAb epitopes, we reverted the RRRR site of GPCysR4 to the native RRLL sequence.…”

“…27,28 Since then, methods have been described to stabilize the trimeric conformation of prefusion GPC in the absence of a trimer-stabilizing mAb. [29][30][31] We previously demonstrated that prefusion GPC trimers are stabilized by genetic fusion to the trimeric scaffold I53-50A. 30,31 These fusion proteins, known as GPC-I53-50A, have not only proven to be a useful reagent for characterizing and isolating GPC-specific antibodies but also were able to induce NAb responses in rabbits.…”

“…39 Nevertheless, numerous potent NAbs have been isolated from convalescent individuals and the mechanism of action for several of these NAbs has been elucidated. 15,[27][28][29]31,40,41 Cocktails of isolated NAbs have shown great promise as therapeutics in animal models. For example, Arevirumab-3, a cocktail of NAbs 8.9F, 37.2D and 12.1F, shows protection in non-human primates after LASV challenge.…”

Deep mutational scanning reveals functional constraints and antigenic variability of Lassa virus glycoprotein complex

“…28 Some of these antibodies are being developed as antibody cocktails and there is evidence that they can protect from lethal Lassa virus infection. [29][30][31][32] In addition, vaccines that elicit antibodies against GPC are also being developed. [33][34][35][36][37] However, the high variability of GPC (up to ~8% amino-acid divergence among lineages) raises the specter of antibody and vaccine escape, a problem that has been observed for other viruses-including most recently SARS-CoV-2.…”