Biology subjects

Blanchard, N.

Publications and source records attributed to Blanchard, N..

9 recordsLinked to original sources

bioRxiv2026

Single-cell characterization of the human immune landscape reveals dysfunction in monocyte-mediated cellular interactions in symptomatic malaria

Plasmodium falciparum infection results in a wide range of phenotypes including chronic asymptomatic and symptomatic individuals. The malaria outcome depends, at least in part, on host immune responses mediated by specific cell subsets. Here, we investigated the immune landscape of chronic asymptomatic and symptomatic children using single-cell RNA sequencing. Unexpectedly, we uncovered biologically relevant immune cell complexes, which were further confirmed by imaging flow cytometry. Symptomatic infection was associated with a decrease of cell-cell interactions, particularly between non-classical monocytes and T cells. Non-classical monocytes from symptomatic children exhibited profiles with increased inflammation characterized by enhanced S100A8-S100A9 expression together with decreased expression of interaction-associated genes such as CD86 or ITGAL. Moreover, we demonstrated that inflammatory and cell interaction programs could not be activated simultaneously within the same cell. In addition, the concomitant expression of inflammatory genes and members of the LILR gene family was predominantly observed in monocytes from symptomatic individuals. These findings raise the possibility that enhanced S100A8/S100A9-LILRB1 signaling may contribute to the altered functional state of monocytes in symptomatic malaria and, potentially, may impair their interactions with T cells. Together, our results suggest that immune cell complexes may therefore reveal an additional layer of immune regulation associated with the development of clinical malaria.

genomics↗

bioRxiv2024

Toxoplasma gondii chronic infection decreases visceral nociception through peripheral opioid receptor signaling

By eliciting immune activation in the digestive tract, intestinal pathogens may perturb gut homeostasis. Some gastrointestinal infections can indeed increase the risk of developing post-infectious irritable bowel syndrome (PI-IBS). Intriguingly, the prevalent foodborne parasite Toxoplasma gondii has not been linked to the development of PI-IBS and the impact of this infection on colon homeostasis remains ill-defined. We show in a mouse model that latent T. gondii decreases visceral nociceptive responses in an opioid signaling-dependent manner. Despite the accumulation of Th1 and cytotoxic T cells in the colon of latently infected mice, the selective invalidation of enkephalin gene in T cells ruled out the involvement of T cell-derived enkephalins in hypoalgesia. These findings provide clues about how this widespread infection durably shapes the gut immune landscape and modifies intestinal physiological parameters. They suggest that in contrast to other gut microbes, T. gondii infection could be negatively associated with abdominal pain. TeaserLatent toxoplasmosis decreases gut nociception in the mouse, suggesting a negative association with abdominal pain in humans

physiology↗

bioRxiv2024

Id2 levels determine the development of effector vs. exhausted tissue-resident memory CD8+ T cells during CNS chronic infection

Tissue-resident memory T cells (Trm) are essential for regional immunity in non-lymphoid tissues. Although single-cell transcriptomics have revealed Trm heterogeneity in various diseases, the molecular mechanisms behind this diversity are unclear. To investigate this, we used Toxoplasma gondii (T. gondii) infection, which persists in the central nervous system (CNS) and is controlled by brain CD8+ Trm. Our single-cell transcriptomic analysis of brain CD8+ T cells from T. gondii-infected mice showed heterogeneous expression of the transcriptional regulator Id2, correlating with different functional states. Using mixed bone marrow chimeras, we found that Id2-deficiency in T cells caused parasite-specific Trm to develop an altered phenotype with diminished effector functions and reduced expression of CD49a. Furthermore, loss of Id2 in brain-infiltrating CD8+ T cells led to the accumulation of exhausted PD1+Tox+CD8+ Trm cells, while Id2 overexpression repressed T cell exhaustion. Overall, our study shows that Id2 levels dictate the acquisition of effector vs. exhausted phenotypes in CD8+ Trm during chronic CNS infection. One sentence SummaryId2 expression level regulates the functional heterogeneity of brain Trm during CNS chronic infection

immunology↗

bioRxiv2024

CD4+ Trm sustain the chronic phase of auto-immune neuroinflammatory disease

Therapeutic options against multiple sclerosis (MS) preventing T cell migration to the central nervous system (CNS) have remarkable clinical effects against the relapsing-remitting (RRMS) form of the disease, while they are poorly effective against its progressive form (PMS). Disability progression in PMS is thought to result from an interplay between smoldering local inflammation and neurodegeneration. We postulated that an ongoing inflammatory process mediated by CNS-resident memory CD4+ T cells (CD4+ Trm) could contribute to promote disease chronicity independently of de novo recruitment of peripheral autoreactive T cells. Indeed, our results revealed the presence of bona fide CD4+ Trm expressing CD69, CXCR6, P2RX7, CD49a and the transcription factor Hobit in the CNS of mice with chronic experimental autoimmune encephalomyelitis (EAE) and in the brain of persons with PMS. Single-cell transcriptional analysis uncovered their transcriptional heterogeneity and inflammatory potential and, accordingly, CD4+ Trm preferentially localized within inflammatory lesions. Finally, depletion of both the recirculating and the CNS-resident CD4+ T cell compartments was required to alleviate neurological signs during the chronic phase of EAE. Our results, therefore, indicate that CD4+ Trm actively contribute to maintain a chronic inflammatory state in the CNS, promoting damage and/or preventing repair, and suggest that new therapeutic strategies for the treatment of PMS should consider targeting the CNS-resident T cell compartment.

immunology↗

bioRxiv2024

Protective function and differentiation cues of brain-resident CD8+ T cells during immune surveillance of chronic latent Toxoplasma gondii infection

Chronic T. gondii infection induces brain-resident CD8+ T cells (bTr) but their protective functions and differentiation cues remain undefined. Here, we used a mouse model of latent infection by T. gondii leading to effective CD8+ T cell-mediated parasite control. Thanks to antibody depletion approaches, we found that peripheral circulating CD8+ T cells are dispensable for brain parasite control during chronic stage, indicating that CD8+ bTr are sufficient to prevent brain parasite reactivation. We observed that the retention markers CD69, CD49a and CD103 are sequentially acquired by brain parasite-specific CD8+ T cells throughout infection, and that a majority of CD69/CD49a/CD103 triple-positive (TP) CD8+ T cells also express Hobit, a transcription factor associated with tissue residency. This TP subset develops in a CD4+ T cell-dependent manner, and is associated with effective parasite control during chronic stage. Conditional invalidation of TAP-mediated MHC class I presentation showed that presentation of parasite antigens by glutamatergic neurons and microglia regulate the differentiation of CD8+ bTr into TP cells. Single-cell transcriptomic analyses upon T. gondii latency vs. encephalitis revealed that resistance to encephalitis is associated with the expansion of stem-like subsets of CD8+ bTr. In summary, parasite-specific brain-resident CD8+ T cells are functionally heterogeneous and autonomously ensure parasite control during T. gondii latent infection. Their differentiation is shaped by neuronal and microglial MHC I presentation. A more detailed understanding of local T cell-mediated immune surveillance of this common parasite is needed for harnessing brain-resident CD8+ T cells in order to enhance control of chronic brain infections.

immunology↗

bioRxiv2024

Chronic IL-1-induced DNA double-strand break response in hippocampal neurons drives cognitive deficits

Chronic inflammation characterized by increased cytokine levels, such as interleukin-1 (IL-1), accompanies many neurological diseases but little is known about IL-1 contribution to cognitive impairment and its interplay with epigenetic processes, including the DNA double-strand break (DSB) response. Here, we demonstrate that H2A.X-dependent DSB signaling in hippocampal neurons drives cognitive deficits upon chronically elevated IL-1. Mice persistently and latently infected with Toxoplasma gondii display impaired spatial memory consolidation along with elevated IL-1{beta} in the hippocampus. We find that neuronal IL-1 signaling in excitatory neurons is required for the spatial memory deficits caused by T. gondii infection and by chronic systemic infusion of IL-1{beta}. In both cases, the deficit in spatial memory was prevented by the abrogation of neuronal H2A.X-dependent signaling. Our results highlight the instrumental role of cytokine-induced DSB-dependent signaling in spatial memory defects. This novel pathological mechanism in inflammation control of neuronal function may extend to several neurological diseases.

animal behavior and cognition↗

bioRxiv2023

The apicoplast is important for the viability and persistence of Toxoplasma gondii bradyzoites

Toxoplasma gondii is responsible for toxoplasmosis, a disease that can be serious when contracted during pregnancy, but can also be a threat for immunocompromised individuals. Acute infection is associated with the tachyzoite form that spreads rapidly within the host. However, under stress conditions, some parasites can differentiate into cyst-forming bradyzoites, residing mainly in the central nervous system, retina and muscle. Because this latent form of the parasite is resistant to all currently available treatments, and is central to persistence and transmission of the parasite, new specific therapeutic strategies targeting this developmental stage need to be discovered. T. gondii contains a plastid of endosymbiotic origin called the apicoplast, which is an appealing drug target because it is essential for tachyzoite viability and contains several key metabolic pathways that are largely absent from the mammalian host. Its function in bradyzoites, however, is unknown. Our objective was thus to study the contribution of the apicoplast to the viability and persistence of bradyzoites during chronic toxoplasmosis. We have used complementary strategies based on stage-specific promoters to generate conditional bradyzoite mutants of essential apicoplast genes. Our results show that specifically targeting the apicoplast in both in vitro or in vivo-differentiated bradyzoites leads to a loss of long-term bradyzoite viability, highlighting the importance of this organelle for this developmental stage. This validates the apicoplast as a potential area to look for new therapeutic targets in bradyzoites, with the aim to interfere with this currently incurable parasite stage. Significance StatementIn its intermediate hosts, the parasite Toxoplasma gondii can persist as a cyst-contained developmental form that might reactivate and cause severe pathologies. Importantly, this form is resistant to current anti-parasitic drugs. T. gondii harbors a plastid of endosymbiotic origin called the apicoplast, containing important and potentially druggable metabolic pathways, but whose contribution to the fitness and viability of persistent parasites has never been assessed. We have generated conditional mutants specifically affected for the homeostasis of the apicoplast in cyst-contained parasites and showed that this organelle is important for persistence of these particular developmental forms. Our work thus validates the apicoplast as a relevant drug target in the context of chronic T. gondii infection.

microbiology↗

bioRxiv2022

A common mechanism of Sec61 translocon inhibition by small molecules

The Sec61 complex forms a protein-conducting channel in the endoplasmic reticulum (ER) membrane that is required for secretion of soluble proteins and production of many membrane proteins. Several natural and synthetic small molecules specifically inhibit the Sec61 channel, generating cellular effects that are potentially useful for therapeutic purposes, but their inhibitory mechanisms remain unclear. Here we present near-atomic-resolution structures of the human Sec61 channel inhibited by a comprehensive panel of structurally distinct small molecules-- cotransin, decatransin, apratoxin F, ipomoeassin F, mycolactone, cyclotriazadisulfonamide (CADA) and eeyarestatin I (ESI). Remarkably, all inhibitors bind to a common lipid-exposed pocket formed by the partially open lateral gate and plug domain of the channel. Mutations conferring resistance to the inhibitors are clustered at this binding pocket. The structures indicate that Sec61 inhibitors stabilize the plug domain of Sec61 in a closed state, thereby preventing the protein-translocation pore from opening. Our study reveals molecular interactions between Sec61 and its inhibitors in atomic detail and offers the structural framework for further pharmacological studies and drug design.

biochemistry↗

bioRxiv2019

A virus hosted in malaria-infected blood protects against T cell-mediated inflammatory diseases by impairing DC function in a type I IFN-dependent manner

Co-infections shape the host immune status, thereby influencing the development of inflammatory diseases, which can result in detrimental or beneficial effects. For example, co-infections with concurrent Plasmodium species can alter malaria clinical evolution and malaria infection itself has the ability to modulate autoimmune reactions but, in both cases, the underlying mechanisms remain ill-defined.\n\nHere, we demonstrate that the protective effects of certain rodent malaria strains on T cell-mediated inflammatory pathologies are due to an RNA virus co-hosted in malaria-parasitized blood. We show that live as well as extracts of blood parasitized by P. berghei K173 or P. yoelii 17X YM, confer full protection against Pb ANKA (PbA)-induced Experimental Cerebral Malaria (ECM) and MOG/CFA-induced experimental autoimmune encephalomyelitis (EAE), and that this is associated with a strong type I IFN signature. We detected the presence of a viral element, the RNA virus Lactate Dehydrogenase-elevating Virus (LDV), in the protective Plasmodium stabilates and we established that infection with LDV alone recapitulates the protective effects on ECM and EAE. In ECM, we further show that protection results from an IFN-I-mediated reduction in the abundance of splenic conventional dendritic cell and in their ability to produce the Th1-inducing IL-12p70, leading to a decrease in pathogenic CD4+ Th1 responses. In EAE, protection is achieved by IFN-I mediated blunting of IL-12 and IL-23, preventing the differentiation of IFN-{gamma}-, IL-17- and GM-CSF-producing encephalitogenic CD4+ T cells.\n\nThus, our results identify a virus that is co-hosted in several Plasmodium stabilates across the community and has major consequences on the host immune system. Moreover, our data emphasize the importance of considering concurrent infections for the understanding of autoimmunity and malaria-associated inflammatory complications.

immunology↗