Biology subjects

Reuther, P.

Publications and source records attributed to Reuther, P..

4 recordsLinked to original sources

bioRxiv2026

MHC-II acts as a fusion-triggering receptor for bat influenza virus

Influenza A virus hemagglutinin is a prototypical class I viral fusion protein that binds sialylated glycans and is activated by low pH in endosomes. In contrast, bat-derived IAV subtypes H17N10 and H18N11 use major histocompatibility complex class II (MHC-II) as an entry receptor, but how this receptor contributes to membrane fusion remains unknown. We find that MHC-II-dependent hemagglutinin subtypes H17, H18, and H19 possess an increased negative net charge relative to canonical HAs. Using cryo-electron tomography, we demonstrate that H18N11 morphology remains stable and H18 is in prefusion conformation at strongly acidic pH. Remarkably, H18 undergoes fusion-relevant conformational changes only when both MHC-II binding and low pH are present. By reconstitution of H18N11 fusion with liposomes and purified MHC-II, we show that receptor engagement is required to trigger the fusion activity of H18. These findings identify MHC-II as a receptor that directly triggers membrane fusion and reveal a previously unrecognized receptor-dependent mechanism of influenza virus entry. SignificanceBat-derived influenza A viruses (IAV) challenged established paradigms because they use major histocompatibility complex class II (MHC-II) molecules instead of sialylated glycans for cell entry. Recent studies suggest that MHC-II usage extends beyond bats, with avian, swine, and human strains showing dual receptor specificity. However, how MHC-II contributes to membrane fusion has remained unclear. We show that, unlike conventional HAs that are activated by acidity alone, the H18 fusion protein requires receptor engagement and low pH to undergo fusion-relevant conformational changes leading to membrane fusion. Hence, we reveal a novel receptor-dependent mechanism of membrane fusion for the MHC-II dependent entry of H18N11.

microbiology↗

bioRxiv2024

Single influenza A viruses induce nanoscale cellular reprogramming at the virus-cell interface

Viruses, as nanoscale entities with limited proteomes, must efficiently infect target cells using their available resources. During infection, individual virions induce specific cellular signaling within the virus-cell interface, a nanoscale patch of the plasma membrane in contact with the virus. However, virus-induced receptor recruitment and cellular activation are transient processes that occur within minutes and at the nanoscale level. Hence, the temporal and spatial kinetics of such early events often remain poorly understood due to technical limitations. To address this challenge, we developed a novel protocol to covalently immobilize unmodified influenza A viruses on glass surfaces before exposing them to live epithelial cells. This approach extends the observation time for virus-plasma membrane interaction while preserving the viruses native state for uncompromised cell interaction. Using single-molecule super-resolution microscopy, we investigated virus-receptor interaction showing that viral receptors are not immobilized by the virus but rather slowed down, which leads to a specific local receptor accumulation and turnover. We further followed the dynamics of clathrin-mediated endocytosis at the single-virus level and demonstrate the recruitment of adaptor protein 2 (AP-2), previously thought to be uninvolved in influenza A virus infection. Finally, we examined the nanoscale organization of the actin cytoskeleton at the virus-binding site, showing a local and dynamic response of the cellular actin cortex to the infecting virus. Our findings provide novel insights into the fundamental process of virus-cell interaction and demonstrate the versatility and potential impact of our approach on virus-cell biology.

microbiology↗

bioRxiv2024

The bat Influenza A virus subtype H18N11 induces nanoscale MHCII clustering upon host cell attachment

Prior to the discovery of the bat influenza A virus (IAV) subtypes H17N10 and H18N11, it was believed that all IAVs bind via the viral hemagglutinin (HA) to sialic acid residues to mediate attachment and subsequent viral entry. Both HA subtypes, H17 and H18, however, do not bind to sialic acids but instead engage a proteinaceous receptor: major histocompatibility complex class II (MHCII). The mechanistic details of this hitherto unknown protein-mediated entry are not understood. Since conventional IAVs require attachment to clusters of sialylated glycans to overcome the low affinity of the HA-sialic acid interaction, we hypothesized that bat HA would likewise interact with multiple MHCII molecules. Here, we used photoactivated localization microscopy (PALM) on fixed and live cells expressing MHCII fused to appropriate fluorescent reporters. We show that bat IAV particles attach to pre-existing MHCII clusters present on susceptible cells and that the local HA-MHCII interaction results in an increased cluster size. To measure the impact of viral attachment on the dynamics of MHCII, we utilized an experimental setup designated "inverse infection" where intact viral particles were immobilized on coverslips before live MHCII-expressing cells were seeded on top. Recording the trajectories of single MHCII molecules, this approach revealed that the mobility of MHCII was indeed slowed down in viral proximity leading to a local enrichment of MHCII molecules beneath the viral particle. Taken together, these data suggest that attachment of viral particles leads to clustering of MHCII, a process similar to the MHCII dynamics observed during the formation of an immunological synapse.

microbiology↗

bioRxiv2020

Opposing effects of T cell receptor signal strength on CD4 T cells responding to acute versus chronic viral infection

A hallmark of the adaptive immune response is the ability of CD4 T cells to differentiate into a variety of pathogen appropriate and specialized effector subsets. A long-standing question in CD4 T cell biology is whether the strength of TCR signals can instruct one Th cell fate over another. The contribution of TCR signal strength to the development of Th1 and T follicular helper (Tfh) cells has been particularly difficult to resolve, with conflicting results reported in a variety of models. Although cumulative TCR signal strength can be modulated by the infection specific environment, whether or not TCR signal strength plays a dominant role in Th1 versus Tfh cell fate decisions across distinct infectious contexts is not known. Here we characterized the differentiation of CD4 TCR transgenic T cells responding to a panel of recombinant wild type or altered peptide ligand lymphocytic choriomeningitis viruses (LCMV) derived from acute and chronic parental strains. We found that while TCR signal strength positively regulates T cell expansion in both infection settings, it exerts opposite and hierarchical effects on the balance of Th1 and Tfh cells generated in response to acute versus persistent infection. The observation that weakly activated T cells, which comprise up to fifty percent of an endogenous CD4 T cell response, support the development of Th1 effectors highlights the possibility that they may resist functional inactivation during chronic infection. We anticipate that the panel of variant ligands and recombinant viruses described herein will be a valuable tool for immunologists investigating a wide range of CD4 T cell responses. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=192 SRC="FIGDIR/small/236497v2_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1fdb592org.highwire.dtl.DTLVardef@19bc5e3org.highwire.dtl.DTLVardef@1dcf03forg.highwire.dtl.DTLVardef@20f27f_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIdentification of a wide panel of altered peptide ligands for the LCMV-derived GP61 peptide C_LIO_LIGeneration of LCMV variant strains to examine the impact of TCR signal strength on CD4 T cells responding during acute and chronic viral infection C_LIO_LIThe relationship between TCR signal strength and Th1 differentiation shifts according to the infection context: TCR signal strength correlates positively with Th1 generation during acute infection but negatively during chronic infection. C_LI

immunology↗