Biology subjects

Remot, A.

Publications and source records attributed to Remot, A..

12 recordsLinked to original sources

bioRxiv2026

Functional divergence of regulatory and conventional bovine neutrophils following Mycobacterium bovis infection

Bovine tuberculosis (bTB), due to Mycobacterium bovis (Mb) infection, is a chronic cattle disease and neglected cause of zoonotic tuberculosis. The role of neutrophils in bTB is overlooked. We recently identified a new neutrophil subset in cattle and mice with a similar morphology to conventional inflammatory neutrophils (Nconv). However, unlike Nconv, these regulatory neutrophils (Nreg) express MHC-II at their surface and can suppress lymphocyte proliferation. In this study, we compared the responses of bovine Nconv and Nreg to infection with a virulent Mb strain circulating in France and the attenuated Mb BCG vaccine. Nreg and Nconv had different transcriptional profiles and were differentially activated by Mb infection. Both Nreg and Nconv efficiently killed Mb, but Nreg had higher levels of phagocytosis activity and ROS production. Nreg had higher levels of mitochondrial activity and an ultrastructural organization different from that of Nconv. Our results provide the first insight into the functional characterization of bovine neutrophil subsets during Mb infection and highlight a new layer of complexity in their functional diversity that must be taken into account to improve our understanding of bTB pathophysiology, which is urgently required to improve the management of this costly disease.

immunology↗

bioRxiv2025

Early-Life Commensal Lung Bacteria Shape Immune Responses and RSV Susceptibility in Neonatal Mice

The lung mucosa during the neonatal period and early infancy is especially susceptible to respiratory syncytial virus (RSV) infection. Respiratory disease severity is strongly influenced by the age at first exposure, which may also affect the trajectory of airway function. Early life represents a critical window for lung development and initial microbiota colonization, both of which shape mucosal immune responses to RSV. The contribution of early lung-colonizing bacterial strains to the establishment of the lung microbiota and susceptibility to RSV infection in neonatal mice remains poorly characterized. In the present study, we showed that early-life primo-colonizing bacterial strains in the mouse lung differentially induce innate immune responses and influence RSV susceptibility in ex vivo models using lung explants and alveolar macrophages (AMs). We identified a specific bacterial strain (strain 17) whose prior exposure enhances type I interferon (IFN-I) responses in AMs upon RSV infection and reduces viral replication both ex vivo and in vivo in lung tissues. Intranasal administration of this strain during early life prevented the development of immunopathological responses upon RSV reinfection in adult mice. Finally, using a translational human airway epithelium model, we demonstrated that pre-exposure to strain 17 restricts RSV spread without cytotoxicity, likely via enhanced {beta}-defensin 2 production. These findings highlight the potential of early-life microbiota modulation as a promising intervention for preventing RSV disease and its long-term respiratory consequences. Author summaryRespiratory syncytial virus (RSV) is a major cause of severe respiratory infections in newborns and infants, a period during which the lungs and immune system are still maturing. Simultaneously, the respiratory tract undergoes its first microbial colonization by so-called primo-colonizing bacteria -- the first bacterial species to establish themselves on neonatal lower respiratory mucosal surfaces. These early microbial pioneers may play an unsuspected role in shaping how the immature immune system responds to viral threats. In this study, we investigated whether these early lung-colonizing strains influence RSV susceptibility. Using neonatal mouse models, lung explants, and alveolar macrophages, we found that distinct bacterial strains trigger markedly different innate immune responses. Prior exposure to one strain in particular, strain 17, was associated with enhanced type I interferon responses, reduced viral replication, and protection against harmful inflammation upon RSV reinfection later in life. In a human airway epithelium model, pre-exposure to strain 17 also restricted RSV spread without tissue damage, potentially through increased {beta}-defensin 2 production. These findings provide proof-of-concept that the bacterial strains establishing in the neonatal lung can influence future immune reactivity and antiviral responses, and suggest that early-life respiratory microbiota modulation could represent a promising strategy to prevent severe RSV disease.

immunology↗

bioRxiv2025

Nutritional supplementation with vitamin E or plant extracts affects redox and immune response in early lactating dairy cows

In dairy cows, early lactation is a period prone to oxidative stress, inflammation and health problems. Our objective was to investigate the effects of the nutritional supplementation of early lactating cows with plant extracts or vitamin E on physiological and immunological status. Forty-five Holstein cows were divided into three groups: control group (n = 15), vitamin E group (n = 16) (3,000 IU/d for 3 weeks before and 1,000 IU/d after calving), and plant extract group (n = 14) (10 g/d only after calving). Their redox and immune status were monitored during the first 12 weeks of lactation, every four week. In week 12, plasma malondialdehyde levels in plasma were lower in the vitamin E and plant extract groups than in the control group. The vitamin E and plant extract groups had lower ex vivo plasma CCL4, IL6 and IL8 cytokine levels, lower proportions of blood regulatory neutrophils, and less ROS production by blood neutrophils than the control group. In terms of immune response, vitamin E and plant extracts down-regulated the gene expression of FABP3 in the milk mammary epithelial cells of multiparous cows. Therefore, supplementation with either vitamin E or plant extracts could prevent systemic hyper-inflammation and improve the immune response during early lactation.

physiology↗

bioRxiv2025

Nutritional vitamin E or plant extracts affect the immune response and mammary epithelium integrity during intramammary lipopolysaccharide challenge in early lactation

BackgroundEarly lactation is a period at risk for mastitis. Our objective was to investigate the influence of nutritional vitamin E and plant extracts on redox and immune status at the systemic and local mammary levels during an inflammatory challenge in dairy cows. Thirty-six Holstein cows were placed in three groups: a control group (n = 11) unsupplemented; a vitamin E group (n = 13), supplemented with 3000 IU/d for 4 weeks before calving and 1000 IU/d for 4 weeks after calving; and a plant extracts group (n = 14) supplemented with 10 g/d for 4 weeks before and after calving. Lipopolysaccharide (LPS) from Escherichia coli was infused into a one-udder quarter of the cows 5 weeks after calving. Blood and milk samples were collected before and 4, 7, 9, 28, and 76 h after the LPS infusion. ResultsIn the plant extract group, antioxidant gene (NQO1), superoxide dismutase activity 4 hours after the LPS challenge and total antioxidant capacity were increased compared to the control group. In the vitamin E group, expression of the antioxidant gene (SOD3) and glutathione peroxidase activity were more elevated than in the control group. Systemic immunity appeared to be reduced by antioxidant supplementations, with a higher migration of classical neutrophils in the plant extract group and less ROS production of neutrophils in the vitamin E group. However, immune capacities were increased at the local level in classical neutrophils (ROS production and phagocytosis) in both the plant extract and vitamin E groups. Following the LPS infusion, supplementation did not reveal any differences in terms of rectal temperature, milk yield or milk cell counts, but it did have a positive effect on mammary epithelium integrity (lower milk Na+:K+ ratio and higher OCLN gene expression). In addition, the plant extracts stimulated the synthesis of milk constituents, with higher milk protein gene expressions (LALBA, CSN3, CSN1S1) and a tendency towards a higher lactose content in milk. ConclusionThe LPS challenge showed that vitamin E or plant extracts enhanced the local inflammatory response while preserving systemic antioxidant capacities, integrity of the mammary gland and the composition of milk, and thus possibly contributing to preventing mammary infection in early lactating dairy cows.

physiology↗

bioRxiv2024

From tissue to subcellular level : imaging human precision-cut lung slices (PCLS) to gain insight into pandemic bacterial or viral infections

We describe a method for the generation and deep imaging of human precision-cut lung slices (PCLS). PCLS bridge the gap between in vivo and in vitro studies, providing a robust system for visualizing events from tissue to subcellular levels in the three-dimensional lung environment, with the preservation of all resident cell types and cell-cell interactions. They also constitute a validated model for studying host cell-pathogen interactions. Here, we detail the generation of human PCLS, followed by their infection and imaging by laser scanning confocal microscopy and transmission electron microscopy (TEM). We establish the conditions for ex vivo infection and replication of two pathogens of relevance to human respiratory health: a virus (SARS-CoV-2) and a bacterium (Mycobacterium tuberculosis, Mtb). PCLS can be obtained in a single day, infected the next day, and were successfully cultivated for up to a week in this study. Imaging was performed on fixed samples. The preparation of PCLS took one day for confocal imaging and five days for TEM imaging. All procedures are readily adaptable to explore other pathogens and other species and are easy to implement by users with experience in tissue culture. Some specialist equipment (an Alabama tissue slicer) is required for PCLS generation.

cell biology↗

bioRxiv2023

Neutrophil subsets play dual roles in tuberculosis by producing inflammasome dependent-IL-1β or suppressing T-cells via PD-L1

Neutrophils can be beneficial or deleterious during tuberculosis (TB). Based on the expression of MHC-II and programmed death ligand 1 (PD-L1), we distinguished two functionally and transcriptionally distinct neutrophil subsets in the lungs of mice infected with mycobacteria. Inflammatory [MHC-II-, PD-L1lo] neutrophils produced inflammasome-dependent IL-1{beta} in the lungs in response to virulent mycobacteria and "accelerated" deleterious inflammation, which was highly exacerbated in IFN-{gamma}R-/- mice. Regulatory [MHC-II+, PD-L1hi] neutrophils "brake" inflammation by suppressing T-cell proliferation and IFN-{gamma} production. Such beneficial regulation, which depends on PD-L1, is controlled by IFN-{gamma}R signaling in neutrophils. The hypervirulent HN878 strain from the Beijing genotype curbed PD-L1 expression by regulatory neutrophils, abolishing the braking function and driving deleterious hyper-inflammation in the lungs. These findings add a layer of complexity to the roles played by neutrophils in TB and may explain the reactivation of this disease observed in cancer patients treated with anti-PD-L1. One Sentence SummaryRegulatory and inflammatory neutrophil subsets play inverse roles in tuberculosis.

immunology↗

bioRxiv2023

Massive detection of cryptic recessive genetic defects in cattle mining millions of life histories

We present a data-mining framework designed to detect recessive defects in livestock that have been previously missed due to a lack of specific signs, incomplete penetrance, or incomplete linkage disequilibrium. This approach leverages the massive data generated by genomic selection. Its basic principle is to compare the observed and expected numbers of homozygotes for sliding haplotypes in animals with different life histories. Within three cattle breeds, we report 33 new loci responsible for increased risk of juvenile mortality and present a series of validations based on large-scale genotyping, clinical examination, and functional studies for candidate variants affecting the NOA1, RFC5, and ITGB7 genes. In particular, we describe disorders associated with NOA1 and RFC5 mutations for the first time in vertebrates. The discovery of these many new defects will help to characterize the genetic basis of inbreeding depression, while their management will improve animal welfare and reduce losses to the industry.

genetics↗

bioRxiv2023

Bovine blood and milk T-cell subsets in distinct states of activation and differentiation during subclinical Staphylococcus aureus mastitis

T-lymphocytes are key mediators of adaptive cellular immunity and knowledge about distinct subsets of these cells in healthy and infected mammary gland secretions remains limited. In this study, we used a multiplex cytometry panel to show that staphylococcal mastitis causes the activation of CD4+, CD8+ and {gamma}{delta} T-cells found in bovine milk. We also highlight remarkable differences in the proportions of naive and memory T-cells subsets found in blood and milk. These observations will contribute to a better understanding of cell-mediated immune mechanisms in the udder and to the development of new therapeutic and preventive strategies targeting mastitis.

immunology↗

bioRxiv2022

MHC-II expressing neutrophils circulate in blood and milk during mastitis and show high microbicidal activity

Bovine mastitis are mainly caused by bacterial infection. They are responsible for economic losses and have an impact on the health and welfare of animals. The increase in the somatic cell count in milk during mastitis is mainly due to the influx of neutrophils which have a crucial role in the elimination of pathogens. For a long time, these first line defenders has been view as microbes killers with limited role in the orchestration of the immune response. However, their role is more complex and we recently characterized a MHC-II expressing neutrophil subset with regulatory capacities in cattle. In this study, we questioned the implication of different neutrophils subsets in the mammary gland immunity during clinical and subclinical mastitis. Here, we described for the first time that, in blood as in milk, neutrophils are a heterogeneous population and encompass at least two subsets distinguishable with their expression of MHC-II. We observed higher bactericidal capacities of milk MHC-IIpos neutrophils as compared to their classical counterparts, due to a higher production of ROS and phagocytosis ability. MHC-IIpos neutrophils are enriched in milk during a subclinical mastitis as compared to blood. Moreover, we observed a positive and highly significant correlation between MHC-IIpos neutrophils and T lymphocytes present in milk during subclinical mastitis. To conclude, our study could open the way to the discovery of new biomarkers of mastitis inflammation.

immunology↗

bioRxiv2021

Mycobacterial infection of precision cut lung slices reveals that the type 1 interferon pathway is locally induced by Mycobacterium bovis but not M. tuberculosis in different cattle breeds

Tuberculosis exacts a terrible toll on human and animal health. While Mycobacterium tuberculosis (Mtb) is restricted to humans, Mycobacterium bovis (Mb) is present in a large range of mammalian hosts. In cattle, bovine TB (bTB) is a notifiable disease responsible for important economic losses in developed countries and underestimated zoonosis in the developing world. Early interactions that take place between mycobacteria and the lung tissue early after aerosol infection govern the outcome of the disease. In cattle, these early steps remain poorly characterized. The precision-cut lung slice (PCLS) model preserves the structure and cell diversity of the lung. We developed this model in cattle in order to study the early lung response to mycobacterial infection. In situ imaging of PCLS infected with fluorescent Mb revealed bacilli in the alveolar compartment, adjacent or inside alveolar macrophages (AMPs) and in close contact with pneumocytes. We analyzed the global transcriptional lung inflammation signature following infection of PCLS with Mb and Mtb in two French beef breeds: Blonde dAquitaine and Charolaise. Whereas lungs from the Blonde dAquitaine produced high levels of mediators of neutrophil and monocyte recruitment in response to infection, such signatures were not observed in the Charolaise in our study. In the Blonde dAquitaine lung, whereas the inflammatory response was highly induced by two Mb strains, AF2122 isolated from cattle in the UK and Mb3601 circulating in France, the response against two Mtb strains, H37Rv the reference laboratory strain and BTB1558 isolated from zebu in Ethiopia, was very low. Strikingly, the type I interferon pathway was only induced by Mb but not Mtb strains indicating that this pathway may be involved in mycobacterial virulence and host tropism. Hence, the PCLS model in cattle is a valuable tool to deepen our understanding of early interactions between lung host cells and mycobacteria. It revealed striking differences between cattle breeds and mycobacterial strains. This model could help deciphering biomarkers of resistance versus susceptibility to bTB in cattle as such information is still critically needed for bovine genetic selection programs and would greatly help the global effort to eradicate bTB.

immunology↗

bioRxiv2020

Neutrophils encompass a regulatory subset suppressing T cells in apparently healthy cattle and mice

Neutrophils that reside in the bone marrow are switly recruited from circulating blood to fight infections. For a long time, these first line defenders were considered as microbe killers. However their role is far more complex as cross talk with T cells or dendritic cells have been described for human or mouse neutrophils. In cattle, these new roles are not documented yet. We identified a new subset of regulatory neutrophils that is present in the mouse bone marrow or circulate in cattle blood under steady state conditions. These regulatory neutrophils that display MHC-II on the surface are morphologically indistinguishable from classical MHC-IIneg neutrophils. However MHC-IIpos and MHC-IIneg neutrophils display distinct transcriptomic profiles. While MHC-IIneg and MHC-IIpos neutrophils display similar bacterial phagocytosis or killing activity, MHC-IIpos only are able to suppress T cell proliferation under contact-dependent mechanisms. Regulatory neutrophils are highly enriched in lymphoid organs as compared to their MHC-IIneg counterparts and in the mouse they express PDL-1, an immune checkpoint involved in T-cell blockade. Our results emphasize neutrophils as true partners of the adaptive immune response, including in domestic species. They open the way for discovery of new biomarkers and therapeutic interventions to better control cattle diseases.

immunology↗

bioRxiv2020

The microbiota plays a critical role in the reactivity of lung immune components to innate ligands

The microbiota contributes to shaping efficient and safe immune defenses in the gut. However, little is known about the role of the microbiota in the education of pulmonary innate immune responses. Here, we tested whether the endogenous microbiota can modulate reactivity of pulmonary tissue to pathogen stimuli by comparing the response of specific pathogen-free (SPF) and germ-free (GF) mice. Using SPF and GF mice intranasally exposed to lipopolysaccharide (LPS), a component of Gram-negative bacteria, we observed earlier and greater inflammation in the pulmonary compartment of GF mice than that of SPF mice. Toll-like receptor 4 (TLR4) was more abundantly expressed in the lungs of GF mice than those of SPF mice at steady state, which could predispose the innate immunity of GF mice to strongly react to environmental stimuli. Lung explants were stimulated with different TLR agonists or infected with the human airways pathogen, respiratory syncytial virus (RSV), resulting in greater inflammation under almost all conditions for the GF explants. Finally, alveolar macrophages (AM) from GF mice presented a higher innate immune response upon RSV infection than those of SPF mice. Overall, these data suggest that the presence of microbiota in SPF mice induced a process of innate immune tolerance in the lungs by a mechanism which remains to be elucidated. Our study represents a step forward to establishing the link between the microbiota and the immune reactivity of the lungs. Plain Language summaryMicrobiota represents an important partner of immunologic system at the interface between immune cells and epithelium. It is well known, notably in the gut, that the microbiota contributes in shaping efficient and safe defenses. However, little is known about the role of the microbiota in the education of pulmonary innate immune responses. In this study, we postulate that endogenous microbiota could dampen an excessive reactivity of pulmonary tissue to external stimuli. Thus, we sought to study the innate immune reaction switched on by viral or bacterial ligands in respiratory tract cells coming from mice with or without microbiota (germ-free condition, GF). Altogether, our results show a higher inflammatory reaction in GF condition. This study represents a step forward to better establish the link between the microbiota and the reactivity of the lung tissue. Not only these data demonstrate that the microbiota educates the pulmonary innate immune system, but also contributes the emerging concept of using respiratory commensal bacteria as potential next-generation probiotics to prevent susceptibility to respiratory diseases.

immunology↗