Biology subjects

Hot, D.

Publications and source records attributed to Hot, D..

5 recordsLinked to original sources

bioRxiv2025

Inflammation-enhanced synapse-specific phagocytosis by adult APP microglia in a microfluidic neuron-microglia co-culture model

Microglia play a critical role in synapse remodeling and neuroinflammation, both of which are dysregulated in Alzheimers disease (AD). However, most in vitro models rely on neonatal or immortalized microglia, limiting their relevance to adult pathophysiological context. Here, we present a compartmentalized microfluidic co-culture platform that enables spatially controlled interactions between primary cortical neurons and adult microglia from wild-type (WT) and APP-transgenic mice. This system allows precise functional analysis of microglia-synapse interactions under defined inflammatory conditions. Upon lipopolysaccharide (LPS) stimulation, APP microglia exhibited exaggerated morphological activation, elevated IL-1{beta} secretion, and selectively increased engulfment of synaptic material. In contrast, phagocytosis of non-specific substrates such as pHrodo Zymosan remained unchanged, suggesting a substrate-specific enhancement of microglial phagocytic activity. Blocking the complement receptor CD11b abolished the LPS-induced increase in synaptic uptake, confirming the role of complement-dependent pathways. Transcriptomic profiling revealed robust inflammatory responses in both genotypes, with selectively heightened expression of proinflammatory genes in APP microglia, consistent with a primed immune phenotype. Importantly, increased synaptic uptake occurred without measurable loss of global synaptic connectivity, highlighting the specificity and sensitivity of the system to detect microglial functional changes. This model captures genotype-dependent microglial reactivity (revealing phenotypes not fully captured by transcriptomic rofiling) and provides a physiologically relevant, tractable in vitro platform for dissecting microglial contributions to synaptic pathology in neurodegenerative disease.

neuroscience↗

bioRxiv2025

Flagellin nebulization enhances respiratory immune responses in the porcine model

Respiratory delivery of the Toll-like receptor 5 agonist FLAMOD, a recombinant flagellin, offers a promising approach for treating bacterial pneumonia. FLAMOD stimulates the airway epithelium, mobilizing and activating immune cells and effectors to combat infections. While previous evidences were obtained in mouse models, this study represents the first comprehensive assessment of FLAMOD delivered by nebulization in pigs. Our results demonstrate that a single nebulization of FLAMOD did not cause any adverse effects on clinical parameters. Histological analysis supported that FLAMOD treatment led to immune cell infiltration in the lung tissue, indicative of an active immune response. Flow cytometry confirmed granulocyte recruitment in conducting airways. RNA sequencing established immune activation across the respiratory tract, from the nose, trachea, bronchi to the lungs, highlighting innate immunity, bacterial defense, cytokine and chemokine signaling, and granulocyte chemotaxis as key biological pathways. These findings demonstrated the capacity of FLAMOD to induce a robust and common immune response throughout the porcine respiratory system as well as specific compartmentalized immune signatures. This study establishes FLAMOD as a potent activator of innate immunity, providing a proof-of-concept for inhalation-based therapeutic strategies to combat bacterial pneumonia in the clinical setting.

immunology↗

bioRxiv2024

Integrative metagenomics and metabolomics reveal age-associated gut microbiota and metabolite alterations in experimental COVID-19

Aging is a key contributor of morbidity and mortality during acute viral pneumonia. The potential role of age-associated dysbiosis on disease outcomes is still elusive. In the current study, we used high-resolution shotgun metagenomics and targeted metabolomics to characterize SARS-CoV-2-associated changes in the gut microbiota from young (2-month-old) and aged (22-month-old) hamsters, a valuable model of COVID-19. We show that age-related dysfunctions in the gut microbiota are linked to disease severity and long-term sequelae in older hamsters. Our data also reveal age-specific changes in the composition and metabolic activity of the gut microbiota during both the acute phase (day 7 post-infection, D7) and the recovery phase (D22) of infection. Aged hamsters exhibited the most notable shifts in gut microbiota composition and plasma metabolic profiles. Through an integrative analysis of metagenomics, metabolomics, and clinical data, we identified significant associations between bacterial taxa, metabolites and disease markers in the aged group. On D7 (high viral load and lung epithelial damage) and D22 (body weight loss and fibrosis), numerous amino acids, amino acid-related molecules, and indole derivatives were found to correlate with disease markers. In particular, a persistent decrease in phenylalanine, tryptophan, glutamic acid, and indoleacetic acid in aged animals positively correlated with poor recovery of body weight and/or lung fibrosis by D22. In younger hamsters, several bacterial taxa (Eubacterium, Oscillospiraceae, Lawsonibacter) and plasma metabolites (carnosine and cis-aconitic acid) were associated with mild disease outcomes. These findings support the need for age-specific microbiome-targeting strategies to more effectively manage acute viral pneumonia and long-term disease outcomes.

immunology↗

bioRxiv2024

Targeted delivery of flagellin by nebulization offers optimized respiratory immunity and defense against pneumococcal pneumonia

Novel therapeutic strategies are urgently needed to combat pneumonia caused by Streptococcus pneumoniae strains resistant to standard-of-care antibiotics. Previous studies have shown that targeted stimulation of lung innate immune defenses through intranasal administration of the Toll-like receptor 5 agonist flagellin, improves the treatment of pneumonia when combined with antibiotics. To promote translation to the clinic application, this study assessed the direct delivery of flagellin to the airways through nebulization using a vibrating mesh nebulizer in mice. Intranasal delivery achieved approximately 40% lung deposition of the administered flagellin dose, whereas nebulization yielded less than 1%. Despite these differences, nebulized flagellin induced a transient activation of lung innate immunity characterized by cytokine/chemokine production and neutrophil infiltration into airways analogous to intranasal administration. Furthermore, inhalation by nebulization resulted in an accelerated resolution of systemic pro-inflammatory responses. Lastly, adjunct therapy combining nebulized flagellin and amoxicillin proved effective against antibiotic-resistant pneumococcal pneumonia in mice. We posit that flagellin aerosol therapy represents a safe and promising approach to address bacterial pneumonia within the context of antimicrobial resistance.

microbiology↗

bioRxiv2021

The fate of Hepatitis E virus capsid protein is regulated by an Arginine-Rich Motif

Hepatitis E virus (HEV) infection is the most common cause of acute viral hepatitis worldwide. Hepatitis E is usually asymptomatic and self-limiting but it can become chronic in immunocompromised patients and is associated with increased fulminant hepatic failure and mortality rates in pregnant women. HEV genome encodes three proteins including the ORF2 protein that is the viral capsid protein. Interestingly, HEV produces 3 isoforms of the ORF2 capsid protein which are partitioned in different subcellular compartments and perform distinct functions in the HEV lifecycle. Notably, the infectious ORF2 (ORF2i) protein is the structural component of virions, whereas the genome-free secreted and glycosylated ORF2 proteins likely act as a humoral immune decoy. Here, by using a series of ORF2 capsid protein mutants expressed in the infectious genotype 3 p6 HEV strain as well as chimeras between ORF2 and the CD4 glycoprotein, we demonstrated how an Arginine-Rich Motif (ARM) located in the ORF2 N-terminal region controls the fate and functions of ORF2 isoforms. We showed that the ARM controls ORF2 nuclear translocation, promoting regulation of host antiviral responses. This motif also regulates the dual topology and functionality of ORF2 signal peptide, leading to the production of either cytosolic infectious ORF2i or reticular non-infectious glycosylated ORF2 forms. It serves as maturation site of glycosylated ORF2 by cellular proteases, and promotes ORF2-host cell membrane interactions. The identification of ORF2 ARM as a unique central regulator of the HEV lifecycle uncovers how viruses settle strategies to condense their genetic information and hijack cellular processes. Author summaryHepatitis E virus (HEV) is the major cause of acute viral hepatitis worldwide. Although infection with HEV is usually self-resolving, it can cause up to 30% mortality in pregnant women in the third trimester. There is no specific treatment nor universal vaccine to fight against HEV. In our study, we focused on the HEV ORF2 capsid protein which is produced as different forms that perform distinct functions in the HEV lifecycle. The infectious ORF2i form is the structural component of virions, while the other forms likely act as an immune decoy. Herein, we deciphered the molecular determinants of ORF2 multifunctionality. We identified an Arginine-Rich Motif (ARM) located in the ORF2 N-terminal region that controls the subcellular localization, the fate and functions of ORF2 forms. It also promotes ORF2-host cell interactions. Our observations highlight the ORF2 ARM as a unique central regulator of ORF2 addressing that finely controls the HEV lifecycle.

microbiology↗