Biology subjects

Baud, D.

Publications and source records attributed to Baud, D..

7 recordsLinked to original sources

bioRxiv2025

Cellular determinants of parvovirus B19 infection in the human placenta

Parvovirus B19 (B19V) is a prevalent human pathogen that can cross the placenta by a mechanism that remains unknown, posing a risk of severe fetal complications, particularly during the first trimester of pregnancy. We investigated the expression of B19V-specific receptors in the three trophoblast cell types, cytotrophoblasts (CTBs), syncytiotrophoblasts (STBs), and extravillous trophoblasts (EVTs), and assessed their susceptibility to infection. VP1uR, the erythroid-specific receptor that mediates viral uptake and infection in erythroid progenitor cells, is expressed in CTBs and STBs, but not in EVTs. Globoside, a glycosphingolipid that is essential for the escape of the virus from endosomes, is also expressed in these cells, except for choriocarcinoma-derived CTBs. In the latter, the absence of globoside can be overcome by promoting endosomal leakage with polyethyleneimine. While erythropoietin receptor (EpoR) signaling is associated with the strict erythroid tropism of B19V, it is not required for infection in trophoblasts. Transfection experiments revealed that highly proliferative first-trimester CTBs are more permissive to B19V infection than the low-proliferative CTBs from term placenta. These findings demonstrate that B19V targets and infects specific trophoblast cells, where viral entry and replication are collectively mediated by VP1uR, globoside, and high cellular proliferative activity, but are independent of EpoR signaling. HighlightsO_LITrophoblasts express the specific receptors necessary for B19V entry. C_LIO_LISusceptibility and permissiveness to B19V vary by trophoblast subtype and gestational age. C_LIO_LIHighly proliferative first-trimester cytotrophoblasts show increased permissiveness to B19V. C_LIO_LIB19V infection in trophoblasts depends on globoside but is independent of EpoR signaling. C_LI

microbiology↗

bioRxiv2025

Cryo-electron tomography reveals lineage-specific replication features of Zika virus

Zika virus (ZIKV), a member of the Flavivirus genus, can cause severe neurodevelopmental disorders when infection occurs during pregnancy. Phylogenetic analyses classify ZIKV into two major lineages: African and Asian. Despite their genetic similarity, only the Asian lineage has been linked to congenital anomalies. ZIKV possesses a single-stranded RNA genome and replicates by remodelling the host endoplasmic reticulum (ER) to form membrane-bound replication complexes, which support viral RNA synthesis, virion assembly, and immune evasion. ZIKV also induces the formation of convoluted membranes (CMs), whose function remains unclear. Most ultrastructural studies of ZIKV replication have relied on transmission electron microscopy, which, despite its value, can alter membrane architecture due to sample preparation. To overcome these limitations, we employed cryo-focused ion beam milling combined with electron tomography to visualize ZIKV replication in a near-native state. By comparing infections with African and Asian ZIKV lineages, we uncovered lineage-specific ultrastructural features, despite similar replication dynamics and growth curves. In cells infected with the Asian strain, virions at different maturation stages were often co-packaged within the same compartment. In contrast, the African lineage ZIKV showed distinct compartmentalization of virions and vesicles. Furthermore, the ER-virion spacing was uniform in African-lineage-infected cells, while morphological heterogeneity was evident in the Asian lineage, including irregular viral sacs. Vesicle diameter was also significantly larger in cells infected with the Asian lineage. Together, these findings reveal both conserved and distinct replication structures between ZIKV lineages. The Asian lineage induces more extensive membrane remodelling and CM formation, potentially contributing to its association with congenital disease.

cell biology↗

bioRxiv2025

Structures of the honeybee GABAA RDL receptor illuminate allosteric modulation

Insect GABAA receptors are critical insecticide targets, with all 21st-century commercial compounds acting through a single allosteric membrane site. Here we describe three ligand binding sites and the associated receptor conformations for the honeybee RDL receptor, combining cryo-EM, electrophysiology and molecular dynamics. First the conservation of the GABA site explains the absence of insect-selective orthosteric compounds. Second, the classical modulation site, occupied here by abamectin, exists in a closed-pore conformation contrasting with ivermectin-bound states in other receptors. Third, using the fungal-derived Chrodrimamin B, we resolve an unanticipated membrane modulation pocket structurally analogous yet pharmacologically opposite to a neurosteroid site in mammalian receptors. Structures also reveal the existence of an intersubunit, conformation-dependent, PIP2 lipid site. We foresee our results to be the starting point for investigations on the physiological modulation of insect GABAA receptors. The honeybee receptor structures may also foster the search for environmentally benign insecticides.

biophysics↗

bioRxiv2024

Structural Determinants for Activity of the Antidepressant Vortioxetine at Human and Rodent 5-HT3 receptors

Vortioxetine (VTX) is a recent antidepressant that targets a variety of serotonin receptors. We investigate the drugs molecular mechanism of operation at serotonin 5-HT3 receptors (5-HT3R), which features two mysterious properties: VTX acts differently on rodent and human 5-HT3R; VTX appears to suppress any subsequent response to agonists. Using a combination of cryo-EM, electrophysiology, and molecular dynamics, we show that VTX stabilizes a resting inhibited state of the mouse 5-HT3R and an agonist bound-like state of the human 5-HT3R, in line with the functional profile of the drug. We report four human 5-HT3R structures and show that the human receptor transmembrane domain is intrinsically fragile. We also explain the lack of recovery after VTX administration via a membrane partition mechanism.

biochemistry↗

bioRxiv2023

Mpox virus spreads from cell-to-cell and leads to neuronal injury in human cerebral organoids

In 2022-23, the world experienced the largest recorded monkeypox virus (MPXV) outbreak outside of endemic regions. Remarkably, cases of neurological manifestations were reported, some of which fatal. MPXV DNA and MPXV-specific antibodies were detected in the cerebrospinal fluid of encephalitis-affected patients, suggesting neuroinvasive potential of MPXV. We explored the susceptibility of neural tissue to MPXV infection using human neural organoids (hNOs) exposed to a primary isolate belonging to clade IIb lineage. The virus efficiently replicates in hNOs as indicated by the exponential increase of infectious viral loads and the elevated frequency of MPXV-positive cells over time. Electron microscopy imaging revealed the presence of viral particles as well as perinuclear viral factories. We observed susceptibility of several cell types to the virus, including neural progenitor cells and neurons. Furthermore, we detected the presence of viral antigen in neurites and in foci of grouped cells distributed throughout the tissue. In line with this, we documented significantly more cell-associated than released infectious virus, suggesting viral spread by cell-to-cell contact. Using an mNeonGreen-expressing recombinant MPXV, we confirmed cell-associated virus transmission through live-cell imaging. While hNOs displayed no evident outer morphological changes upon infection, we detected the formation of beads in neurites, a phenomenon commonly associated with neurodegenerative disorders. Live-cell imaging further confirmed the recurrent formation of neuritic beads in neurons in the days following MPXV infection, with bead formation preceding neurite-initiated cell death. Notably, treatment of MPXV infected hNOs with the antiviral drug tecovirimat resulted in a significant reduction of infectious viral loads by several orders of magnitude. Taken together, our findings suggest viral manipulation of axonal transport driving neuronal degeneration and identify a mechanism potentially contributing to MPXV-mediated neuropathology that may have therapeutic implications.

microbiology↗

bioRxiv2023

Interaction of genital microbiota in infertile couples

Bacteria colonise most of the human body and the genital tract is not an exception. While it has been known for decades that a vaginal microbiota exists, other genital sites have traditionally been viewed as sterile environments, with bacterial presence associated only with pathological conditions. However, recent studies identified specific patterns of bacterial colonisation in most genital sites. Shifts in the bacterial colonisation of the female genital tract have been linked to impairment of reproduction and adverse pregnancy outcomes, such as preterm birth. The goal of this project is to understand the association between the genital microbiota of couples seeking assisted procreation aid and the outcome of this treatment. Male and female partners will be studied as a unit ("couple microbiota") and the interaction between their microbiota will be evaluated. We have characterised microbial samples coming from vaginal and penile swabs, as well as follicular fluid and semen, using next generation sequencing (16S rRNA profiling). The results were linked to clinical data of the patients included in the study and particularly to the results of the fertility treatment process. With this project, we aim to gain a better understanding of how the male genital microbiota could influence the lower (vagina) and upper (follicular fluid) female genital tracts.

microbiology↗

bioRxiv2018

Colistin heteroresistance and the involvement of the PmrAB regulatory system in Acinetobacter baumannii

Multidrug-resistant Acinetobacter baumannii infection has recently emerged as a worldwide clinical problem and colistin is increasingly being used as last resort therapy. Despite its favorable bacterial killing, resistance and heteroresistance to colistin have been described. Mutations in the PmrAB regulatory pathway have been already associated with colistin resistance whereas the mechanisms for heteroresistance remain largely unknown. The purpose of the present study is to investigate the role of PmrAB in laboratory-selected mutants representative of global epidemic strains. During brief colistin exposure, colistin resistant and colistin heteroresistant mutants were selected in a one-step strategy. Population Analysis Profiling (PAP) was performed to confirm the suspected phenotype. Upon withdrawal of selective pressure, compensatory mutations were evaluated in another one-step strategy. A trans-complementation assay was designed to delineate the involvement of the PmrAB regulatory system using qPCR and PAP. Mutations in the PmrAB regulatory pathway were associated with colistin resistance and colistin heteroresistance as well. The transcomplementation assay provides a proof for the role played by changes in the PmrAB regulatory pathway. The level of colistin resistance is correlated to the level of expression of pmrC. The resistance phenotype was partially restored since the complemented strain became heteroresistant. This report shows the role of different mutations in the PmrAB regulatory pathway and warns on the development of colistin heteroresistance that could be present but not easily detected with routine testing.

microbiology↗