Revealing the Specificity of Human H1 Influenza A Viruses to Complex N-Glycans

Influenza virus infection remains a threat to human health since viral hemagglutinins are constantly drifting, escaping infection and vaccine-induced antibody responses. Viral hemag-glutinins from different viruses display variability in glycan recognition. In this context, recent H3N2 viruses have specificity for alpha 2,6 sialylated branched N-glycans with at least three N- acetyllactosamine units (tri-LacNAc). In this work, we combined glycan arrays and tissue binding analyses with nuclear magnetic resonance experiments to characterize the glycan specificity of a family of H1 variants, including the one responsible for the 2009 pandemic outbreak. We also analyzed one engineered H6N1 mutant to understand if the preference for tri-LacNAc motifs could be a general trend in human-type receptor-adapted viruses. In addition, we developed a new NMR approach to perform competition experiments between glycans with similar compositions and different lengths. Our results point out that pandemic H1 viruses differ from previous seasonal H1 viruses by a strict preference for a minimum of di-LacNAc structural motifs.R.P.d.V. is a recipient of an ERC Starting grant from the European Commission (802780) and a Beijerinck Premium of the Royal Dutch Academy of Sciences. The glycan array setup was supported by the Netherlands Organization for Scientific Research (NWO, TOP-PUNT 718.015.003 to G.-J.P.H.B.). Dr. Lin Liu (CCRC) and Dr. Margreet A . Wolfert (Utrecht University) developed, printed, and validated the glycan microarray. We would like to thank Nikoloz Nemanichvili for technical assistance. A.C. acknowledges funding from Agencia Estatal de Investigacion "Spanish Ministry of Science and Innovation" (MICINN) project PID2019-105237GB-I00. J.P.C. acknowledges funding by the Spanish MICINN, grant no. RTI2018-095588-B-I00 (co-funded by the European Regional Development Fund/European Social Fund, "Invest-ing in your future"). JJB also tha n k s funding by the European Research Council (RECGLYCANMR, Advanced grant no. 788143), the Agencia Estatal de Investigacion (Spain) for grants RTI2018-094751-B-C21 and C22 and PDI2021-1237810B-C21 and C22, and CIBERES, an initiative of the Instituto de Salud Carlos III (ISCIII), Madrid, Spain. The NMR spectra were acquired at the NMR service of CIBMargarita Salas and in the NMR faci l i t y of the UCM. We also acknowledge Prof. Robert Woods group for sending us the coordinates of a glycan-hemagglut i n i n model

Revealing the Specificity of Human H1 Influenza A Viruses to Complex N-Glycans

Influenza virus infection remains a threat to human health since viral hemagglutinins are constantly drifting, escaping infection and vaccine-induced antibody responses. Viral hemagglutinins from different viruses display variability in glycan recognition. In this context, recent H3N2 viruses have specificity for α2,6 sialylated branched N-glycans with at least three N-acetyllactosamine units (tri-LacNAc). In this work, we combined glycan arrays and tissue binding analyses with nuclear magnetic resonance experiments to characterize the glycan specificity of a family of H1 variants, including the one responsible for the 2009 pandemic outbreak. We also analyzed one engineered H6N1 mutant to understand if the preference for tri-LacNAc motifs could be a general trend in human-type receptor-adapted viruses. In addition, we developed a new NMR approach to perform competition experiments between glycans with similar compositions and different lengths. Our results point out that pandemic H1 viruses differ from previous seasonal H1 viruses by a strict preference for a minimum of di-LacNAc structural motifs

In Silico-Aided Design of a Glycan Ligand of Sialoadhesin for in Vivo Targeting of Macrophages

Cell-specific delivery of therapeutic agents using ligand targeting is gaining interest because of its potential for increased efficacy and reduced side effects. The challenge is to develop a suitable ligand for a cell-surface receptor that is selectively expressed on the desired cell. Sialoadhesin (Sn, Siglec-1, CD169), a sialic acid-binding immunoglobulin-like lectin (Siglec) expressed on subsets of resident and inflammatory macrophages, is an attractive target for the development of a ligand-targeted delivery system. Here we report the development of a high-affinity and selective ligand for Sn that is an analogue of the natural ligand and is capable of targeting liposomal nanoparticles to Sn-expressing cells in vivo. An efficient in silico screen of a library of ∼8400 carboxylic acids was the key to identifying novel 9-<i>N</i>-acyl-substituted <i>N</i>-acetylneuramic acid (Neu5Ac) substituents as potential lead compounds. A small panel of targets were selected from the screen and synthesized to evaluate their affinities and selectivities. The most potent of these Sn ligands, 9-<i>N</i>-(4<i>H</i>-thieno­[3,2-<i>c</i>]­chromene-2-carbamoyl)-Neu5Acα2–3Galβ1–4GlcNAc (^TCCNeu5Ac), was conjugated to lipids for display on a liposomal nanoparticle for evaluation of targeted delivery to cells. The ^TCCNeu5Ac liposomes were found to target liposomes selectively to cells expressing either murine or human Sn in vitro, and when administered to mice, they exhibited in vivo targeting to Sn-positive macrophages

The virulence factor LecB varies in clinical isolates: consequences for ligand binding and drug discovery

International audienc

Glycan-Targeted Virus-like Nanoparticles for Photodynamic Therapy

Virus-like particles (VLPs) have proven to be versatile platforms for chemical and genetic functionalization for a variety of purposes in biomedicine, catalysis, and materials science. We describe here the simultaneous modification of the bacteriophage Qβ VLP with a metalloporphyrin derivative for photodynamic therapy and a glycan ligand for specific targeting of cells bearing the CD22 receptor. This application benefits from the presence of the targeting function and the delivery of a high local concentration of singlet oxygen-generating payload

Targeted delivery of lipid antigen to macrophages via the CD169/sialoadhesin endocytic pathway induces robust invariant natural killer T cell activation

Invariant natural killer T (iNKT) cells induce a protective immune response triggered by foreign glycolipid antigens bound to CD1d on antigen-presenting cells (APCs). A limitation of using glycolipid antigens to stimulate immune responses in human patients has been the inability to target them to the most effective APCs. Recent studies have implicated phagocytic CD169(+) macrophages as major APCs in lymph nodes for priming iNKT cells in mice immunized with glycolipid antigen in particulate form. CD169 is known as sialoadhesin (Sn), a macrophage-specific adhesion and endocytic receptor of the siglec family that recognizes sialic acid containing glycans as ligands. We have recently developed liposomes decorated with glycan ligands for CD169/Sn suitable for targeted delivery to macrophages via CD169/Sn-mediated endocytosis. Here we show that targeted delivery of a lipid antigen to CD169(+) macrophages in vivo results in robust iNKT cell activation in liver and spleen using nanogram amounts of antigen. Activation of iNKT cells is abrogated in Cd169(−/−) mice and is macrophage-dependent, demonstrating that targeting CD169(+) macrophages is sufficient for systemic activation of iNKT cells. When pulsed with targeted liposomes, human monocyte–derived dendritic cells expressing CD169/Sn activated human iNKT cells, demonstrating the conservation of the CD169/Sn endocytic pathway capable of presenting lipid antigens to iNKT cells

Sn-targeted liposomes bind to IFN-α stimulated bone marrow derived macrophages (BMM)s.

<p>(<b>A</b>) Mature macrophages differentiated from wild type mouse bone marrow cells were stimulated with IFN-α or left untreated before staining with anti-Sn, anti-F4/80 antibodies (<i>filled gray</i>) and Sn-targeted liposomes (<i>filled gray</i>). Cells were thoroughly washed prior to FACS analysis. Isotype antibody or naked liposome stained cells were used as negative controls (<i>black lines</i>). (<b>B</b>) BMMs derived from wild type or Sn^−/− mice were stained with fluorescent naked (blue lines) or Sn-targeted (<i>filled red</i>) liposomes prior to FACS analysis. Unstained cells (<i>black lines</i>) were used as a negative control. Data are representative of 3 independent experiments.</p

A structural explanation for the low effectiveness of the seasonal influenza H3N2 vaccine.

The effectiveness of the annual influenza vaccine has declined in recent years, especially for the H3N2 component, and is a concern for global public health. A major cause for this lack in effectiveness has been attributed to the egg-based vaccine production process. Substitutions on the hemagglutinin glycoprotein (HA) often arise during virus passaging that change its antigenicity and hence vaccine effectiveness. Here, we characterize the effect of a prevalent substitution, L194P, in egg-passaged H3N2 viruses. X-ray structural analysis reveals that this substitution surprisingly increases the mobility of the 190-helix and neighboring regions in antigenic site B, which forms one side of the receptor binding site (RBS) and is immunodominant in recent human H3N2 viruses. Importantly, the L194P substitution decreases binding and neutralization by an RBS-targeted broadly neutralizing antibody by three orders of magnitude and significantly changes the HA antigenicity as measured by binding of human serum antibodies. The receptor binding mode and specificity are also altered to adapt to avian receptors during egg passaging. Overall, these findings help explain the low effectiveness of the seasonal vaccine against H3N2 viruses, and suggest that alternative approaches should be accelerated for producing influenza vaccines as well as isolating clinical isolates

Synthesis of the 3′-^BPCNeuAc-pegylated lipids.

<p>The sialic acid ligand with an ethylamine linker was coupled to an NHS-activated pegylated lipid.</p

Highly Pathogenic Influenza A(H5Nx) Viruses with Altered H5 Receptor-Binding Specificity

Emergence and intercontinental spread of highly pathogenic avian influenza A(H5Nx) virus clade 2.3.4.4 is unprecedented. H5N8 and H5N2 viruses have caused major economic losses in the poultry industry in Europe and North America, and lethal human infections with H5N6 virus have occurred in Asia. Knowledge of the evolution of receptor-binding specificity of these viruses, which might affect host range, is urgently needed. We report that emergence of these viruses is accompanied by a change in receptor-binding specificity. In contrast to ancestral clade 2.3.4 H5 proteins, novel clade 2.3.4.4 H5 proteins bind to fucosylated sialosides because of substitutions K222Q and S227R, which are unique for highly pathogenic influenza virus H5 proteins. North American clade 2.3.4.4 virus isolates have retained only the K222Q substitution but still bind fucosylated sialosides. Altered receptor-binding specificity of virus clade 2.3.4.4 H5 proteins might have contributed to emergence and spread of H5Nx viruses