bioRxiv Science⌕ Search

Biology subjects

Esperante, S.

Publications and source records attributed to Esperante, S..

2 recordsLinked to original sources
bioRxiv2025

Unraveling the Dual Immunomodulatory and Immunogenic Roles of the Central Conserved Cysteine-Rich Region in Respiratory Syncytial Virus G Protein

Respiratory syncytial virus (RSV) causes severe respiratory disease in infants and high-risk adults, in part by subverting host immunity. The RSV G glycoproteins central conserved cysteine-rich domain (CCD) contains a CX3C motif implicated in immune modulation, but the relationship between CCD redox state, structure and function is unresolved. We recombinantly expressed a CCD peptide (Gpep, residues 149-196) and combined structural and biophysical characterizations with cellular immunology and human serology to define how redox-dependent conformations govern immunogenicity and immunomodulation. Reduced Gpep is compact and rapidly folds via a dominant intermediate into an oxidized, extended monomer; at higher concentrations intermolecular disulfide isomerization produces covalent oligomers. Functionally, monomeric Gpep potently suppresses innate and adaptive activation inhibiting LPS- or UV-inactivated RSV-induced maturation of mouse bone marrow-derived dendritic cells, reducing antigen-specific CD4+ T cell proliferation and IFN-{gamma} production, and attenuating multiple human neutrophil responses (chemotaxis, CD11b upregulation, ROS, MPO release and NET formation), without cytotoxicity. Oligomerized Gpep lacks these suppressive activities. To link molecular mechanism and human exposure, analysis of sera from an ambulatory pediatric cohort (0-72 months) showed a progressive transient increase in the anti-F/anti-G IgG ratio with repeated early RSV exposures, maturating into a functional 2 to 3 ratio. This serologic shift is consistent with previously reported enrichment of F-directed neutralizing immunity. We propose a redox-dependent immune-evasion model in which soluble, monomeric G mediates transient immunosuppression that is removed by disulfide-driven oligomerization, which may occur in membrane-bound G. This may impact therapeutic strategies that commonly favor F-focused responses. ImportanceRespiratory syncytial virus (RSV) remains a leading cause of severe respiratory disease in young children and high-risk adults. This study identifies a chemical switch in a small conserved region of the RSV attachment protein that changes its shape and immune activity: when the region is present as a soluble, single chain, it transiently suppresses key innate and adaptive immune cells, but this activity is lost upon disulfide-mediated oligomerization. We also show that repetitive RSV exposures in early life bias the antibody response, initially boosting antibody responses toward the Fusion protein, rather than this conserved central region. Together, these results may uncover a mechanism by which RSV shapes the host immune response explaining the features of antibody development in children. Understanding this redox-dependent balance between immune evasion and antigenicity will inform safer vaccine and antibody strategies against RSV.

immunology↗
bioRxiv2025

EXPERIMENTAL KINETIC MECHANISM OF P53 CONDENSATION-AMYLOID AGGREGATION

The tumor suppressor p53 modulates the transcription of a variety of genes constituting a protective barrier against anomalous cellular proliferation. High frequency "hot-spot" mutations result in loss-of-function by the formation of amyloid-like aggregates that correlate with cancerous progression. We show that full-length p53 undergoes spontaneous homotypic condensation at sub-micromolar concentrations and in the absence of crowders, to yield dynamic coacervates that are stoichiometrically dissolved by DNA. These coacervates fuse and evolve into hydrogel-like clusters with strong thioflavin-T binding capacity, which further evolve into fibrillar species with a clearcut branching growth pattern. The amyloid-like coacervates can be rescued by the HPV master regulator E2 protein to yield large regular droplets. Furthermore, we kinetically dissected an overall condensation mechanism which consists of a nucleation-growth process by sequential addition of p53 tetramers, leading to discretely-sized and monodisperse early condensates followed by coalescence into bead-like coacervates that slowly evolve to the fibrillar species. Our results suggest strong similarities to condensation-to-amyloid transitions observed in neurological aggregopathies. Mechanistic insights uncover novel key early and intermediate stages of condensation that can be targeted for p53 rescuing drug discovery. SIGNIFICANT STATEMENTKnown as "the guardian of the genome", the tumor suppressor protein p53 becomes activated by injuries to the DNA genome, and determines whether the cell must undergo self-destruction to avoid cancerous proliferation. P53 is in fact inactivated by mutations in over 50% of all cancers, and restoring its function is recognized as a therapeutic cancer target. A recent biochemical revolution in cell physiology and pathology are liquid entities known as biomolecular condensates. We show that p53 form condensates en route to pathological forms in a surprisingly similar manner to neurological amyloid diseases such as Alzheime[r]s and Parkinso[n]s. We uncover the sequence of steps in the reaction, exposing flanks for a novel drug development platform based on the condensates paradigm.

biophysics↗