Biology subjects

Kergoat, L.

Publications and source records attributed to Kergoat, L..

14 recordsLinked to original sources

bioRxiv2026

Host response against SARS-CoV-2 infection is impacted by allosteric modulation of cholinergic and purinergic receptors

The COVID-19 pandemic has caused nearly 8 million deaths and a broad spectrum of clinical manifestations driven by dysregulated host inflammation, notably involving key signalling proteins IL-6, CXCL10, and CXCL5. We previously demonstrated that ivermectin (IVM) improves clinical outcomes and reduces the IL-6/IL-10 ratio in the lungs of SARS-CoV-2-infected hamsters. Here, combining high-throughput confocal microscopy and transcriptomics in human cell co-cultures and a hamster model, we dissected how IVM modulates host cells responses via 7nAChR and purinergic receptors. In vitro, IVM acted independently of 7nAChR, instead triggering a P2X4-dependent drop in intracellular ATP, rapidly upregulating CXCL10 in macrophages, and suppressing CXCL5 and IL-6. In vivo, however, 7nAChR antagonists abolished IVMs clinical benefit, as did the P2X4 blocker BX430; moreover, whereas the orthosteric agonist EVP-6124 was ineffective, the positive allosteric modulators (PAMs) IVM and GAT-107 reduced lung pathology and anosmia. Thus, IVM operates through a dynamic, context-dependent interplay: P2X4 drives early innate responses in cellular systems including macrophages, whereas the situation in vivo is more complex with 7nAChR being essential for tissue protection. These data position selective PAMs and the CXCL10/CXCL5 axis as promising targets for host-directed therapy in COVID-19.

pathology↗

bioRxiv2026

SARS-CoV-2 ORF9b exploits mitochondrial recruitment to TOMM70 for proteasomal protection and tunes inflammatory remodeling during lung infection

Mitochondrial outer membrane proteins are exploited by diverse intracellular pathogens, to modulate cell metabolism and innate sensing pathways. Here, we demonstrate that TOMM70-dependent mitochondrial recruitment is required to protect SARS-CoV-2 ORF9b from proteasomal degradation, a dependency conserved across ORF9b homologs from related coronaviruses. ORF9b mitochondrial recruitment requires the E477 residue of TOMM70, a surface distinct from that used by the parasite Toxoplasma gondii to engage host mitochondria. We further show that TOMM70 is not a passive scaffold: its depletion activates interferon-stimulated gene expression independently of infection and remodels host immunity distinctly from ORF9b, establishing the receptor and viral protein as mechanistically separable. Using ORF9b-deficient SARS-CoV-2, we demonstrate that ORF9b is dispensable for viral replication and pathological responses in human respiratory epithelial cells and lungs of infected golden Syrian hamsters. Omics profiling of SARS-CoV-2 infected lungs revealed an induction of pathways related to COVID-19 in the absence of ORF9b. Notably, ORF9b-deficient virus-infected lungs show elevated expression of C15ORF48, a nuclear-encoded mitochondrial protein that substitutes for Complex IV subunit NDUFA4 to attenuate inflammation. Collectively, we propose that ORF9b is a receptor-gated viral protein whose principal measurable consequence during authentic infection is a restraint on inflammatory respiratory-chain remodeling.

cell biology↗

bioRxiv2026

Spatial organization of mAbs in complex with the virus glycoprotein determines the success of intravenous rabies therapy

Rabies is a complex disease that has defied efforts to develop an effective treatment. Although it can be successfully prevented through vector control or pre- or post-exposure prophylaxis, no therapeutic options exist for symptomatic rabies, and the disease is still responsible for about 59 000 human deaths each year. Following our successful attempts to use the human monoclonal antibodies RVC20 and RVC58 for intracerebroventricular treatment of rabies, we report here on the effects of these mAbs when administered intravenously and intramuscularly to symptomatic mice. Only a small proportion of mAbs was detected to cross the blood-brain barrier, yet this limited amount sufficiently cleared the viral infection and improved the survival rate of infected mice. Remarkably, these mAbs appeared more effective when used individually than when combined as a cocktail. RVC58 achieved an 80% survival rate, potentially due to its distinct binding topography, potent viral neutralization, and enhanced Fc{gamma}R engagement in the presence of virions. These findings suggest that monotherapy with a single mAb fully capable of engaging Fc{gamma}R may be possible, which could substantially lower the costs and improve treatment accessibility in under-resourced settings, potentially contributing to improved equity of global health. Taken together, this study supports mAb therapy as a promising preclinical approach for symptomatic rabies and provides a foundation for further development of an accessible treatment option.

microbiology↗

bioRxiv2025

RABV L protein plays a role in immune escape through its methyltransferase activity

Viruses in the Mononegavirales order encode a large protein that orchestrates replication, transcription, and the capping of viral RNA. This protein, comprising over 2.000 amino acids, contains an RNA-dependent RNA polymerase, a capping domain, and a methyltransferase (MTase) domain involved in methylating the cap structure. The MTase domain features a conserved K-D-K-E catalytic tetrad -typical of 2'O-methyltransferases-which is essential for methylating viral mRNA caps at both the N7 and 2'O positions. However, the role of these residues in other epitranscriptomic modifications of rabies virus (RABV) RNAs remains poorly characterized. To further explore the role of mRNA cap methylation in the immune evasion strategies of RABV, we investigated the functional contribution of the K-D-K-E motif within the MTase domain, using the Thai isolate as a model. Using reverse genetics, we demonstrated that the mutation K1830R in the K-D-K-E tetrad of the Tha MTase domain induces changes in the methylation landscape of viral mRNAs and, intriguingly, of host mRNAs. In addition, viruses harbouring the K1830R mutation are more sensitive to interferon- and exhibit a less pathogenic phenotype in vitro and in vivo compared to the wild-type virus. Overall, these results suggest that the regulation of viral and cellular RNA methylation landscapes plays a crucial role in controlling RABV infection. Although the exact role of these epitranscriptomic modifications is not yet fully understood, some of these methylations appear to have proviral effects and enhance viral propagation by allowing RABV to efficiently evade the hosts antiviral response. ImportanceThis study highlights the pivotal role of the K-D-K-E catalytic domain included in the methyltransferase domain of the large protein of Rabies virus, by modelling viral RNAs with epitranscriptomic changes. For the first time, we identify specific methylations on the viral RNA, such as 2-O and m6A methylations, which seem to enable the virus to mask its RNA and evade detection by the hosts pattern recognition receptors. These epitranscriptomic modifications affect not only viral RNAs but also cellular RNAs, underscoring a complex interplay between viral and host mechanisms. We further demonstrate that RABV harbouring an altered K-D-R-E catalytic domain, exhibit differential methylation patterns correlated with increased sensitivity to IFN and lower pathogenicity. This emphasizes the importance of this domain in virulence and immune evasion.

microbiology↗

bioRxiv2024

Host and rabies virus gene expression is shaped by human brain cell type and reveals a preexisting pro-viral transcriptional state in astrocytes

How virus-host cell interactions and innate immune antagonism shape neurotropic infection dynamics across diverse brain cell types are largely unknown. To "unmask" and study how innate immune inhibition affects cell type-specific transcriptional regulation of the human and viral genome, we performed single-cell RNA sequencing of human brain cell co-cultures, comparing an isolate of rabies virus (RABV) to its mutant incapable of antagonizing interferon- and NF-{kappa}B-dependent responses. RABV gene expression was shaped by host cell type. RABV induced small-scale, cell-type conserved transcriptional programs that likely support infection by 1) hijacking negative transcriptional feedback of pro-viral factors while 2) reducing anti-viral RNAs. Unexpectedly, disinhibited innate immune signaling increased RABV transcription, most strikingly in an infection-independent "pro-viral" astrocyte subpopulation. Further analysis suggested that "pro-viral"-like astrocytes are a rare subtype in the human brain and are primed to protect the brain during viral infection in concert with interferon-sensitive microglia recalcitrant to infection.

neuroscience↗

bioRxiv2024

Hamsters with long Covid exhibits a neurodegenerative signature in the brainstem

After infection with SARS-CoV-2, patients may present with one or more symptoms that appear or persist over time, including fatigue, respiratory, cardiovascular and neurological disorders. Neurological symptoms include anxiety, depression and impaired short-term memory. However, the exact underlying mechanisms of long Covid are not yet decrypted. Using the golden hamster as a model, we provide further evidence that SARS-CoV-2 is neuroinvasive and can persist in the central nervous system, as we found viral RNA and replicative virus in the brainstem after 80 days of infection. Infected hamsters presented a neurodegenerative signature in the brainstem, with overexpression of innate immunity genes, impacted dopaminergic and glutamatergic synapses, altered energy metabolism. Finally, the infected hamsters manifested persistent signs of depression and impaired short-term memory, as well as late-onset signs of anxiety, as a valuable model to study long Covid. Conclusively, we provide evidence that virus-related and neurodegenerative and immunometabolic mechanisms coexist in the brainstem of infected hamsters and contribute to the manifestation of neuropsychiatric and cognitive symptoms. HighlightsO_LISARS-CoV-2 infects and persists in the brainstem of intranasally-inoculated hamsters C_LIO_LIPersistent neuropsychiatric and cognitive consequences are observed in SARS-CoV-2-infected hamsters C_LIO_LIThe brainstem present distinct transcriptome profiles in acute and in long Covid C_LIO_LIThe dopaminergic and glutamatergic systems are affected in long Covid C_LIO_LIThe SARS-CoV-2 infection affects the expression of genes related to neurodegenerative processes in acute and in long Covid C_LI

pathology↗

bioRxiv2024

The SARS-CoV-2 envelope PDZ Binding Motif acts as a virulence factor disrupting host's epithelial cell-cell junctions

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus responsible for the COVID-19 pandemic, has significantly impacted global health, emphasizing the need to understand its pathogenicity and virulence mechanisms. SARS-CoV-2 disrupts the alveolar epithelial barrier and exacerbates airway inflammation, leading to acute respiratory failure, but the molecular details remain unclear. Additionally, SARS-CoV-2 infection causes neurological symptoms, potentially due to its weakly understood ability to cross the blood-brain barrier. The viral multifunctional Envelope (E) protein is crucial for its virulence, playing a key role in virus assembly, budding, and release. The E protein contains a PDZ-binding motif (PBM) that interacts with host PDZ domain-containing proteins, potentially affecting host signaling pathways and contributing to pathogenicity. This study focuses on the E protein PBM and its role in virulence, disrupting respiratory epithelial barriers and exacerbating airway inflammation. We generated recombinant mutant viruses lacking the PBM and conducted both in vitro and in vivo experiments to elucidate its impact on viral fitness, pathogenicity, and effects on the epithelial integrity. In vitro, the viral mutants showed delayed replication and reduced cytopathic effects. In vivo, experiments with hamsters revealed that PBM-deficient viruses caused less weight loss, lower viral loads, and reduced inflammation, indicating decreased pathogenicity. Histological analyses confirmed less airway damage in these hamsters compared to those infected with the wild-type virus. Additionally, PBM-deficient viruses had impaired interactions with tight junction proteins like ZO-1, a PDZ-containing protein, crucial for maintaining epithelial barrier integrity. Our findings also demonstrate that the PBM does not play a significant role in neuroinvasion during the acute phase of infection, as evidenced by comparable viral RNA loads across brain regions in infected hamsters, regardless of PBM presence. Histopathological and transcriptomic analyses further support this observation, suggesting that the PBM primarily affects specific epithelial barriers. Additionally, RNA-seq analysis on lung and brainstem from infected hamsters reveals that the PBM modulates inflammatory and immune responses, with a stronger impact in lung tissue than in the brainstem. PBM-deficient viruses induce lower levels of inflammation and cytokine expression, suggesting PBMs specific role in enhancing viral pathogenicity through the activation of pathways such as NF-{kappa}B and TNF. Thus, the E protein PBM plays a critical role in SARS-CoV-2s fitness, virulence, and pathogenicity, through the disruption of cell junctions and inflammation, underscoring its potential as a target for therapeutic interventions.

pathology↗

bioRxiv2024

High-throughput Tn-seq screens identify both known and novel Pseudomonas putida KT2440 genes involved in metal resistance

Chemical waste with toxic effects is released into the environment by industrial and urban activities. Pseudomonas putida, a rhizosphere bacterium, harbors a wide variety of genes capable of degrading hydrocarbons and xenobiotic compounds in its natural environment. This bacterium harbors also a large set of metal resistance genes. Most studies that identify genes involved in metal resistance in P. putida focus on over/underexpressed genes and may miss other genes important for metal resistance whose expression does not change. In this study, we used a Tn-seq approach to determine the essential genome of P. putida required for growth in the presence of an excess of metals in a culture medium. Tn-seq enables the detection of mutants with reduced or increased fitness in the presence of metal excess. We validated our screen by identifying known metal resistance gene such as czcA-1 (PP_0043), cadA-3 (PP_5139), cadR (PP_5140) and pcoA2 (PP_5380). Their mutants were underrepresented in the presence of zinc, cadmium (for cadA-3 and cadR) or copper respectively. In this study, we demonstrate by targeted mutagenesis and complementation assay that PP_5337 and PP_0887 are putative transcriptional regulators involved in copper and cadmium resistance, respectively, in P. putida. The study revealed the role of two genes, PP_1663 and PP_5002, in cadmium and cobalt resistance respectively. This is the first evidence linking these genes to metal resistance and highlights the incomplete understanding of metal resistance mechanisms in P. putida.

microbiology↗

bioRxiv2022

Hippocampal ripples coincide with ''up-state'' and cortical spindles in Retrosplenial Cortex

During NREM sleep hippocampal Sharp-wave ripples (SWR) events are thought to stabilize memory traces for long-term storage in downstream neocortical structures. Within the neocortex, Default Mode Network (DMN) areas interact preferentially with the hippocampus purportedly to consolidate those traces. Transient bouts of slow oscillations and sleep spindles in DMN areas are often observed around SWRs, suggesting that these two activities are related and that their interplay possibly contributes to memory consolidation. To investigate how SWRs interact with the DMN and spindles, we combined cortical wide-field voltage imaging, ECoG, and hippocampal LFP recordings in anesthetized and sleeping mice. Here we show that, during SWR, "up-states" and spindles reliably co-occur in a cortical subnetwork centered around the Retrosplenial cortex. Furthermore, Retrosplenial transient activations and spindles predict Slow Gamma oscillations in CA1 during SWRs. Together, our results suggest that Retrosplenial-hippocampal interaction may be a central source of information exchange between cortex and hippocampus.

neuroscience↗

bioRxiv2022

Neuroinvasion and anosmia are independent phenomena upon infection with SARS-CoV-2 and its variants

SUMMARYAnosmia was identified as a hallmark of COVID-19 early in the pandemic, however, with the emergence of variants of concern, the clinical profile induced by SARS-CoV-2 infection has changed, with anosmia being less frequent. Here, we assessed the clinical, olfactory and neuroinflammatory conditions of golden hamsters infected with the original Wuhan SARS-CoV-2 strain, its isogenic ORF7-deletion mutant and three variants: Gamma, Delta, and Omicron/BA.1. We show that infected animals developed a variant-dependent clinical disease including anosmia, and that the ORF7 of SARS-CoV-2 contributes to the induction of olfactory dysfunction. Conversely, all SARS- CoV-2 variants were found to be neuroinvasive, regardless of the clinical presentation they induce. Taken together, this confirms that neuroinvasion and anosmia are independent phenomena upon SARS-CoV-2 infection. Using newly generated nanoluciferase-expressing SARS-CoV-2, we validated the olfactory pathway as a major entry point into the brain in vivo and demonstrated in vitro that SARS-CoV-2 travels retrogradely and anterogradely along axons in microfluidic neuron-epithelial networks. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=151 HEIGHT=200 SRC="FIGDIR/small/505985v2_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@8225ceorg.highwire.dtl.DTLVardef@80342aorg.highwire.dtl.DTLVardef@e0dfd1org.highwire.dtl.DTLVardef@1861e13_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages

SARS-CoV-2 Omicron sublineages carry distinct spike mutations and represent an antigenic shift resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters result in potent plasma neutralizing activity against Omicron BA.1 and BA.2 and that breakthrough infections, but not vaccination-only, induce neutralizing activity in the nasal mucosa. Consistent with immunological imprinting, most antibodies derived from memory B cells or plasma cells of Omicron breakthrough cases cross-react with the Wuhan-Hu-1, BA.1 and BA.2 receptor-binding domains whereas Omicron primary infections elicit B cells of narrow specificity. While most clinical antibodies have reduced neutralization of Omicron, we identified an ultrapotent pan-variant antibody, that is unaffected by any Omicron lineage spike mutations and is a strong candidate for clinical development.

immunology↗

bioRxiv2022

Recognition of copy-back defective interfering rabies virus genomes by RIG-I triggers the antiviral response against vaccine strains

Rabies virus (RABV) is a lethal neurotropic virus that causes 60,000 human deaths every year around the world. A typical feature of RABV infection is the suppression of type I and III interferon (IFN)-mediated antiviral response. However, molecular mechanisms leading to RABV sensing by RIG-I-like receptors (RLR) to initiate IFN signaling remain elusive. Here, we showed that RABV RNAs are recognized by RIG-I (retinoic acid-inducible gene I) sensor resulting in an IFN response of the infected cells but that this global feature was differently modulated according to the type of RABV used. RNAs from pathogenic RABV strain, THA, were poorly detected in the cytosol by RIG-I and therefore mediated a weak antiviral response. On the opposite, we revealed a strong interferon activity triggered by the RNAs of the attenuated RABV vaccine SAD strain mediated by RIG-I. Using next-generation sequencing (NGS) combined with bioinformatics tools, we characterized two major 5copy-back defective interfering (5cb DI) genomes generated during SAD replication. Furthermore, we identified a specific interaction of 5cb DI genomes and RIG-I that correlated with a high stimulation of the type I IFN signaling. This study indicates that RNAs from a wild-type RABV poorly activate the RIG-I pathway, while the presence of 5cb DIs in vaccine SAD strain serves as an intrinsic adjuvant that strengthens its efficiency by enhancing RIG-I detection and therefore strongly stimulates the IFN response. HighlightsO_LIRABV pathogenic strain replication in vitro is characterized by the absence of defective interfering genomes thus induces a weak RLR-mediated innate immunity antiviral response. C_LIO_LIRABV vaccine attenuated strain shows a high release of 5 copy-back defective interfering genomes during replication in vitro and therefore enhances a strong antiviral response upon infection. C_LIO_LIRIG-I is the main sensor for RABV RNA detection within cells. C_LI

microbiology↗

bioRxiv2020

Anti-COVID-19 efficacy of ivermectin in the golden hamster

The devastating coronavirus disease 2019 (COVID-19) pandemic, due to SARS-CoV-2, has caused more than 47 million confirmed cases and more than 1.2 million human deaths around the globe1, and most of the severe cases of COVID-19 in humans are associated with neurological symptoms such as anosmia and ageusia, and uncontrolled inflammatory immune response2-5. Among therapeutic options6-8, the use of the anti-parasitic drug ivermectin (IVM), has been proposed, given its possible anti-SARS-CoV-2 activity9. Ivermectin is a positive allosteric modulator of the -7 nicotinic acetylcholine receptor10, which has been suggested to represent a target for the control of Covid-19 infection11, with a potential immunomodulatory activity12. We assessed the effects of IVM in SARS-CoV-2-intranasally-inoculated golden Syrian hamsters. Even though ivermectin had no effect on viral load, SARS-Cov-2-associated pathology was greatly attenuated. IVM had a sex-dependent and compartmentalized immunomodulatory effect, preventing clinical deterioration and reducing olfactory deficit in infected animals. Importantly, ivermectin dramatically reduced the Il-6/Il-10 ratio in lung tissue, which likely accounts for the more favorable clinical presentation in treated animals. Our data support IVM as a promising anti-COVID-19 drug candidate.

immunology↗

bioRxiv2020

COVID-19-associated olfactory dysfunction reveals SARS-CoV-2 neuroinvasion and persistence in the olfactory system

While recent investigations have revealed viral, inflammatory and vascular factors involved in SARS-CoV-2 lung pathogenesis, the pathophysiology of neurological disorders in COVID-19 remains poorly understood. Yet, olfactory and taste dysfunction are rather common in COVID-19, especially in pauci-symptomatic patients which constitutes the most frequent clinical manifestation of the infection. We conducted a virologic, molecular, and cellular study of the olfactory system from COVID-19 patients presenting acute loss of smell, and report evidence that the olfactory epithelium represents a highly significant infection site where multiple cell types, including olfactory sensory neurons, support cells and immune cells, are infected. Viral replication in the olfactory epithelium is associated with local inflammation. Furthermore, we show that SARS-CoV-2 induces acute anosmia and ageusia in golden Syrian hamsters, both lasting as long as the virus remains in the olfactory epithelium and the olfactory bulb. Finally, olfactory mucosa sampling in COVID-19 patients presenting with persistent loss of smell reveals the presence of virus transcripts and of SARS-CoV-2-infected cells, together with protracted inflammation. Viral persistence in the olfactory epithelium therefore provides a potential mechanism for prolonged or relapsing symptoms of COVID-19, such as loss of smell, which should be considered for optimal medical management and future therapeutic strategies.

neuroscience↗