Biology subjects

Cannac, F.

Publications and source records attributed to Cannac, F..

6 recordsLinked to original sources

bioRxiv2026

Protective near-germline antibodies to malaria elicited by RTS,S/AS01E vaccination in African infants

Malaria is a leading cause of childhood mortality, yet infant immune responses to vaccination remain poorly understood. Here, we characterize 88 monoclonal antibodies (mAbs) directed against the Plasmodium falciparum circumsporozoite protein cloned from African infants immunized with the RTS,S/AS01E malaria vaccine, identifying potent antiparasitic mAbs exhibiting molecular features resembling those observed in adults and minimal somatic hypermutation. Importantly, germline-reverted variants of four mAbs inducing sterile protection in vivo maintained high binding affinity and Fab-dependent parasite killing. Structural analyses revealed that a few amino acid replacements drive homotypic helical assemblies, fine-tuning parasite inhibition and protective efficacy. Thus, despite maturational constraints of early life, infants can generate potent antimalarial antibodies in a near-germline configuration, informing next-generation vaccine development for this vulnerable group.

immunology↗

bioRxiv2026

Consensus native-like hepatitis C virus E1E2 engages broadly neutralizing antibody precursors

A major goal for hepatitis C virus (HCV) vaccine development is to elicit broadly neutralizing antibodies (bNAbs) against the E1E2 glycoprotein complex located on the viral surface. Inducing HCV bNAbs requires engagement of their germline B cell precursors. HCV glycoproteins usually do not bind and activate inferred germline precursors of bNAbs (igl-bNAbs), possibly because most circulating strains contain non-conserved isolate-specific residues, even in bNAb epitopes. Here, we generated stabilized native-like soluble E1E2 (sE1E2) antigens based on a consensus sequence of HCV (HepCon) to limit the exposure of antigenically rare residues. The antigenicity and glycosylation profiles show that HepCon sE1E2 resembles a native-like E1E2 heterodimer. HepCon sE1E2 induced cross-reactive neutralizing antibody responses as a soluble protein immunogen and as membrane-anchored mRNA-delivered immunogen in animals. Importantly, HepCon sE1E2 engages multiple igl-bNAbs against two major epitopes: antigenic region 3 (AR3), which is targeted by igl-bNAbs derived from the widely expressed human VH1-69 B cell gene, and antigenic region 4 (AR4), which is only present on native-like E1E2. Nanoparticles with HepCon sE1E2 efficiently activated B cell lines expressing AR3 and AR4 igl-bNAb B cell receptors in vitro. Finally, using HepCon sE1E2 we elucidated the atomic contacts of an AR3 igl-bNAb by cryo-electron microscopy. Thus, HepCon sE1E2 is a promising candidate for germline-targeting vaccination strategies.

immunology↗

bioRxiv2026

Membrane controlled Mechanoregulation in PIEZO1 Interactions

PIEZO channels are mechanosensitive membrane proteins whose activation is governed by the surrounding lipid environment. However, the direct mechanistic contribution of native membrane composition to the molecular interactions remains unclear. In this study, a systematic comparison is made between PIEZO1 reconstituted in detergent micelles and in cell membrane-derived nanodiscs, which preserve the native lipid composition. Initial characterization employing a combination of atomic force microscopy and coarse-grained molecular dynamics simulations unveils distinct physical signatures of PIEZO1 in these two environments. Single-molecule force spectroscopy measurements demonstrate that interaction between the extracellular domain of PIEZO1 and a specific antibody exhibits unique mechanical responses strongly influenced by the surrounding membrane. In nanodiscs, PIEZO1 exhibits reversible, elastic-like behavior with preserved structural integrity and consistent adhesion forces even when modulated by Yoda1 (agonist) and Dooku1 (antagonist). Conversely, micelles induce a plastic response with altered mechanosensitivity and functional stability. Based on these findings, we propose a possible membrane-mediated force transmission pathway and quantify a simplified interaction energy landscape. Collectively, our findings offer the initial direct evidence of how the native lipid environment mechanistically governs PIEZO1 interactions, establishing native membranes as critical determinants for mechanotransduction.

biophysics↗

bioRxiv2026

Structural basis for conserved and distinct antigen recognition by a lineage of malaria-protective antibodies

Monoclonal antibodies (mAbs) targeting the Plasmodium falciparum circumsporozoite protein (PfCSP) have demonstrated substantial promise in preventing malaria infection and disease. PfCSP is characterized by a central region composed of repetitive NANP motifs, which serve as major targets for protective antibodies. Several potent mAbs targeting this region exhibit homotypic Fab-Fab interactions, which enhance antigen binding and contribute to their neutralization potency. Among these, mAb 399, encoded by the IGHV3-49/IGKV2D-29 (VH3-49/VK2D-29) germline lineages, forms head-to-head inter-Fab contacts mediated primarily by germline-encoded residues. In this study, we determined high-resolution X-ray crystal and cryo-EM structures of two additional Fabs, derived from the same germline lineages, 7160 and 7118, in complex with PfCSP-derived peptides. Both Fabs bound the NANP6 repeats with high affinity (KD 5-10 nM). Fab 7160 formed similar inter-Fab homotypic interactions to Fab 399 upon binding to an extended repeat peptide (NANP), indicating a conserved mode of recognition. In contrast, Fab 7118, which features a longer CDRH3, does not form homotypic contacts. Instead, Fab 7118 induced a bend in the peptide and adopted a distinct binding mode, which prevents inter-Fab interactions. A cryo-EM structure of Fab 7118 in complex with a recombinant shortened PfCSP construct (rsCSP) further revealed potential disruptions at inter-Fab contact sites. These findings highlight the structural versatility of VH3-49/VK2D-29-derived antibodies and demonstrate that CDR loop variations within a shared antibody lineage can modulate antibody conformation, homotypic Fab-Fab interactions, and epitope engagement. Our study provides mechanistic insights into the diverse strategies by which CSP-specific antibodies can achieve high-avidity binding and protective immunity.

microbiology↗

bioRxiv2021

Polyclonal antibody responses to HIV Env immunogens resolved using cryoEM

In BriefHerein, we evaluated the immunogenicity of several BG505 SOSIP-based HIV Env immunogens in the rhesus macaque animal model using a combination of serology and biophysical approaches. We applied electron cryo-microscopy for high-resolution mapping of elicited polyclonal antibody responses, which provided detailed insights into the binding modes of the most common classes of antibodies elicited by BG505 SOSIP immunogens as well as the critical differences in immunogenicity that can occur as a consequence of engineered stabilizing mutations and partial glycan occupancy at different sites. SummaryEngineered ectodomain trimer immunogens based on BG505 envelope glycoprotein are widely utilized as components of HIV vaccine development platforms. In this study, we used rhesus macaques to evaluate the immunogenicity of several stabilized BG505 SOSIP constructs both as free trimers and presented on a nanoparticle. We applied a cryoEM-based method for high-resolution mapping of polyclonal antibody responses elicited in immunized animals (cryoEMPEM). Mutational analysis coupled with neutralization assays were used to probe the neutralization potential at each epitope. We demonstrate that cryoEMPEM data can be used for rapid, high-resolution analysis of polyclonal antibody responses without the need for monoclonal antibody isolation. This approach allowed to resolve structurally distinct classes of antibodies that bind overlapping sites. In addition to comprehensive mapping of commonly targeted neutralizing and non-neutralizing epitopes in BG505 SOSIP immunogens, our analysis revealed that epitopes comprising engineered stabilizing mutations and of partially occupied glycosylation sites can be immunogenic. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

immunology↗

bioRxiv2019

Cryo-EM structure of the Hedgehog release protein Dispatched

The Hedgehog signaling pathway controls embryonic development and adult tissue homeostasis in multicellular organisms. In Drosophila melanogaster, the pathway is primed by secretion of a dually lipid-modified morphogen, Hedgehog (Hh), a process dependent on a membrane-integral protein Dispatched. Although Dispatched is a critical component of the pathway, the structural basis of its activity has so far not been described. Here, we describe a cryo-EM structure of the Drosophila melanogaster Dispatched at 3.2 [A] resolution. The ectodomains of Dispatched adopt an open conformation suggestive of a receptor-chaperone role. A 3D reconstruction of Dispatched bound to Hh confirms the ability of Dispatched to bind Hh but using a unique mode distinct from those previously observed in structures of Hh complexes. The structure may represent the state of the complex that precedes shedding of Hh from the surface of the morphogen-releasing cell.

biochemistry↗