Xavier Montagutelli

Clinical and epidemiological data support the link between viral encephalitis and neurodegeneration but its causal mechanism remains mostly unknown. Zika virus (ZIKV) is an emerging, neurotropic flavivirus susceptible to induce cognitive impairments in infected adults. In this work we have analyzed the capacity of ZIKV to induce the accumulation of pathological phosphorylated Tau protein (pTau), a major driver of neurodegenerative disorders such as Alzheimer's disease, throughout the infection of adult immunocompetent mice. The capacity of ZIKV to induce pTau in vivo, was analyzed in the long term in three Collaborative Cross mouse strains displaying different responses to ZIKV. The establishment and propagation of pTau was quantified up to 60 days post-infection (dpi) in correlation with the level and localization of neuronal viral infection and of microglia activation using immunofluorescence, immunohistochemistry, wide field and confocal microscopy and gene expression analysis. Strength, coordination, memory and social behavior were evaluated before and following the establishment and progression of pTau. The role of microglia on ZIKV-induced pTau was investigated by partially depleting microglial cells using PLX3397 (PLX). ZIKV infection induced a significant accumulation of pTau starting at 15 that persisted at least until 60 dpi. At 15 dpi, pTau was observed in ZIKV-infected neurons in the CA2 and CA1 regions of the hippocampus and in non-infected cortical neurons in association with neuroinflammation and social behavior alterations. At 30 dpi, pTau progressed independently of infection and inflammation, positively correlated to PLX-susceptible Apoe gene expression in association with short-term memory defects. These results shed light on how brain viral infections, which are a major concern for public health, drive pTau accumulation and propagation in link with memory impairment and social behavior alterations laying the groundwork for potential new therapeutic treatments.

Zika virus (ZIKV) is an emerging, neurotropic flavivirus susceptible to induce brain damage and neurological disorders in adults. In human and mice adult b

The continuous emergence of antibody-escape variants of SARS-CoV-2 demands the identification of alternative methods of protection against infection that do not directly target viral proteins. Here, we generated heavy-chain-only antibody (VHHs) from an alpaca immunized with the human angiotensin-converting enzyme 2 (hACE2), the major entry receptor for SARS-CoV-2. The VHHs bind hACE2 without affecting its enzymatic activity, and two of them (B07 and B09) inhibit all SARS-CoV-2 isolates tested (Delta, BA.1, BQ1.1, XBB.1.5, XBB.1.16.1, EG.5.1.3, BA.2.86.1). Their X-ray structure in complex with hACE2 show that their epitope overlaps with the footprint of the receptor binding domain (RBD) of the SARS-CoV-2 spike on hACE2. A dimeric B07-Fc fusion construct avidly binds hACE2 with an apparent dissociation constant of 0.1 nM and inhibits in vitro infection of previously tested variants and, of JN.1.1 and KP.3.3 variants, with an IC50 ~ 1 nM. In vivo experiments using K18-hACE2 mice show that intranasal prophylactic administration of B07-Fc confer a dose-dependent protection against SARS-CoV-2 D614G and Omicron variants. These VHHs targeting hACE2 represent potential broad-spectrum therapeutic candidates against potential new emerging coronaviruses using hACE2 as a receptor.

Zika virus (ZIKV) is a mosquito-borne orthoflavivirus primarily transmitted among humans by Aedes aegypti. Over the past two decades, it has caused significant outbreaks associated with birth defects and neurological disorders. ZIKV consists of two main genotypes: the African and Asian lineages, each exhibiting distinct biological properties. African lineage strains are transmitted more efficiently by mosquitoes, but the genetic basis for this difference has been elusive. Here, we investigate this question by comparing recent African and Asian strains using chimeric viruses with swapped genome segments. Our results show that structural genes from the African strain enhance viral internalization, while non-structural genes improve genome replication and infectious particle production in mosquito cells. In vivo mosquito transmission is most significantly influenced by structural genes, although no single viral gene alone is decisive. We also develop a stochastic model of in vivo viral dynamics that reflects the observed patterns, suggesting the key difference between African and Asian strains lies in their ability to traverse mosquito salivary glands. Our findings imply the polygenic nature of ZIKV transmissibility has hindered Asian strains from achieving the same transmission efficiency as African strains, highlighting the role of lineage-specific adaptive landscapes in ZIKV evolution and emergence.

Interferon regulatory factor 3 (IRF3) is the first transcription factor activating the expression of type I interferons (IFN-I). It is present in the cytoplasm of most cell types under basal conditions and its activation by phosphorylation allows a rapid triggering of the IFN-I pathway in response to viral infection. This activation of IFN-I is amplified by IRF7, the other major IFN-I transcription factor which expression is induced, in most cell types, by the interferon response. However, recent data have shown that the role of IRF3 in viral infection extends beyond the IFN-I pathway. Here, we review the studies investigating the impact of IRF3 deficiencies in infected cells and in vivo, in mice and in humans. We discuss the discrepancies between and within studies, between isolated cells and whole organisms. While IRF3 is also involved in other pathological processes, we highlight how the newly discovered functions of IRF3 deepen our understanding of its multiple roles in viral infections, which could stimulate the development of pharmacological manipulation of its biological activities.

Tuberculosis (TB), caused by Mycobacterium tuberculosis , remains a leading cause of mortality worldwide. Granulomas, hallmark structures of TB in the lungs and other infected tissues, are critical sites of host-pathogen interactions, yet their full cellular composition is not completely understood. Here, we identify a previously unrecognized β3-tubulin (TUBB3)-positive cell population within TB granulomas in mice, guinea pigs, non-human primates, and TB patients. TUBB3 is a well-established pan-neuronal marker, yet these TUBB3 ⁺ cells are distinct from typical pulmonary resident cells and leukocytes. They exhibit a branched, elongated morphology, which is suggestive of neuron-like features. Intriguingly, their appearance is independent of adaptive immunity and is also observed in viral and fungal infections, but not in asthma. Our findings suggest the existence of a neuro-immune component within granulomas that may influence TB pathogenesis. Further investigation into the origin, function, and signaling pathways of these TUBB3+ cells is required to clarify their identity and potential role in host defense, which could reveal novel therapeutic targets for TB and other pulmonary infections.

Zika virus (ZIKV) is a mosquito-borne flavivirus primarily transmitted among humans by Aedes aegypti . Over the past two decades, it has caused significant outbreaks associated with birth defects and neurological disorders. Phylogenetically, ZIKV consists of two main genotypes referred to as the African and Asian lineages, each exhibiting distinct biological properties. African lineage strains are transmitted more efficiently by mosquitoes, but pinpointing the genetic basis of this difference has remained challenging. Here, we address this question by comparing recent African and Asian strains using chimeric viruses, in which segments of the parental genomes are swapped. Our results show that the structural genes from the African strain enhance viral internalization, while the non-structural genes improve genome replication and infectious particle production in mosquito cells. In vivo mosquito transmission is most significantly influenced by the structural genes, although no single viral gene alone determines this effect. Additionally, we develop a stochastic model of in vivo viral dynamics in mosquitoes that mirrors the observed patterns, suggesting that the primary difference between the African and Asian strains lies in their ability to traverse the mosquito salivary glands. Overall, our findings suggest that the polygenic nature of ZIKV transmissibility has prevented Asian lineage strains from achieving the same epidemic potential as African lineage strains, underscoring the importance of lineage-specific adaptive landscapes in shaping ZIKV evolution and emergence.

SARS-CoV-2 accumulates mutations over time leading to the emergence of variants, which become largely resistant to existing vaccines and spike protein-targeted antiviral treatment. Therefore, there is a need for other therapies with broad efficiency. Here, we targeted the angiotensin-converting enzyme 2 (ACE2), the major entry receptor for SARS-CoV-2. We purified three single domain heavy chain antibodies (VHHs) after immunization of an alpaca with the ectodomain of ACE2. These VHHs bound ACE2 with nanomolar affinity and specifically detected membrane-anchored ACE2. Two of them (B07 and B09) neutralized by a competitive mechanism multiple SARS-CoV-2 isolates, including Omicron variants (XBB.1.16.1; EG.5.1.3; BA.2.86.1), without impacting the proteolytic activity of the enzyme. Fusion of B07 with conventional Fc domain markedly improved its binding and neutralizing efficacy. This dimeric Fc-conjugated B07 (B07-Fc) recognized specific residues of the N-terminal helix 1 of ACE2. When administrated prophylactically and intranasally, B07-Fc induced a strong dose-dependent protection of mice expressing human ACE2 (K18-hACE2) from SARS-CoV-2 Omicron. Hamsters were weakly protected due to low binding of B07-Fc to hamster ACE2. These single domain antibodies targeting hACE2 represent potential broad-spectrum therapeutic candidates against any emerging viruses using ACE2 as a receptor. These inhalable neutralizing single domain antibodies also represent a non-invasive approach against respiratory viral infection.

Microglial cells are the phagocytic cells of the brain that under physiological conditions participate in brain homeostasis and surveillance. Under pathogenic states, microglia undergoes strong morphological and transcriptional changes potentially leading to sustained neuroinflammation, brain damage, and cognitive disorders. Postnatal and adult Zika virus (ZIKV) brain infection is characterized by the induction of reactive microglia associated with brain inflammation, synapse loss and neuropathogenesis. Contrary to neurons, microglial cells are not infected by ZIKV thus raising the question of the mechanism governing ZIKV‐induced microglia's reactivity. In this work, we have questioned the role of exogenous, neuronal type I interferons (IFNs‐I) in regulating ZIKV‐induced microglia's reactivity. Primary cultured microglial cells were either treated with conditioned media from ZIKV‐infected mature neurons or co‐cultured with ZIKV‐infected neurons. Using either an antibody directed against the IFNAR receptor that neutralizes the IFNs‐I response or Ifnar−/−microglial cells, we demonstrate that IFNs‐I produced by ZIKV‐infected neurons are the main regulators of the phagocytic capacity and the pro‐inflammatory gene expression profile of reactive, non‐infected microglial cells. We identify protein kinase R (PKR), whose expression is activated by IFNs‐I, as a major regulator of the phagocytic capacity, pro‐inflammatory response, and morphological changes of microglia induced by IFNs‐I while up‐regulating STAT1 phosphorylation and IRF1 expression. Results obtained herein in vitro with primary cultured cells and in vivo in ZIKV‐infected adult immunocompetent mice, unravel a role for IFNs‐I and PKR in directly regulating microglia's reactivity that could be at work in other infectious and non‐infectious brain pathologies.

Few therapeutic options are available to treat COVID-19. The KEAP1/NRF2 pathway, the major redox-responsive pathway, has emerged as a potential therapeutic target for COVID-19 as it regulates redox homeostasis and inflammation that are altered during SARS-CoV-2 infection. Here, we characterized the effects of NRF2-agonist Sulfodyne^®, a stabilized natural Sulforaphane, in cellular and animal models of SARS-CoV-2 infection. In pulmonary or colonic epithelial cell lines, Sulfodyne^® elicited a more efficient inhibition of SARS-CoV-2 replication than NRF2-agonists DMF and CDDO. This antiviral activity was not dependent on NRF2 but was associated with the regulation of several metabolic pathways, including the inhibition of ER stress and mTOR signaling, which are activated during SARS-CoV-2 infection. Sulfodyne^® also decreased SARS-CoV-2 mediated inflammatory responses by inhibiting the delayed induction of IFNB1 and type I IFN-stimulated genes in infected epithelial cell lines and by reducing the activation of human by-stander monocytes recruited after SARS-CoV-2 infection. In K18-hACE2 mice infected with SARS-CoV-2, Sulfodyne^® treatment reduced both early lung viral load and disease severity by fine-tuning IFN-beta levels. Altogether, these results provide evidence for multiple mechanisms that underlie the antiviral and anti-inflammatory activities of Sulfodyne^® and pinpoint Sulfodyne^® as a potent therapeutic agent against pathogenic effects of SARS-CoV-2 infection.