Biology subjects

Hazra, B.

Publications and source records attributed to Hazra, B..

6 recordsLinked to original sources

bioRxiv2026

CX3CR1+ microglia/macrophages, activated T cells, and IFN-γ-driven stimulation confer age-dependent protective immunity in young-adult mice following β-coronavirus infection.

Age-dependent variation in the immune response is a critical determinant of host susceptibility, disease severity, and long-term sequelae in coronavirus infections, a principle strikingly demonstrated by the COVID-19 pandemic caused by SARS-CoV-2. Although primarily pneumotropic, coronaviruses carry significant neurotropic potential, driving neurological complications whose severity is profoundly determined by host age. Elderly individuals and often children suffer disproportionately severe disease, whereas young adults relatively mount protective responses; yet the cellular and molecular determinants of this age-dependent neuroprotection remain poorly characterized. Using juvenile and young-adult C57BL/6 mice intracranially inoculated with {beta}-coronavirus MHV-RSA59, a murine equivalent of human coronaviruses, we examined immune dynamics at days 5 (innate-acute), 7 (innate-to-adaptive transition), and 30 (chronic) post-infection. Young-adult mice exhibited only occasional demyelination, in stark contrast to the extensive demyelination observed across all spinal cord levels in juveniles. This differential outcome was attributable to enhanced age-dependent immune maturation, characterized by efficient T cell-microglia/macrophage crosstalk enabling effective viral control by day 7 post-infection. Young adults displayed greater glial activation, heightened cytokine release, CX3CR1+ microglia activation, and augmented CNS trafficking of CX3CR1+ and MHC II+ monocytes/macrophages, IFN-{gamma}+ CD4+/CD8+ T cells, and CXCR3+ effector T cells relative to juveniles. Reduced naive T cell frequencies and elevated effector/central memory T cell populations in cervical lymph nodes further indicate a robust adaptive memory response conferring long-term protection. Additionally, greater regulatory T cell accumulation in young adults facilitates timely suppression of excessive neuroinflammation as viral burden subsides. Together, these findings define the age-dependent immune landscape that underpins neuroprotection in {beta}-coronavirus infection.

immunology↗

bioRxiv2026

CD40 Signaling Restricts Retrograde Viral Spread and Provides Neuroprotection to Retinal Ganglion Cells in a Murine β-Coronavirus Model of Optic Neuritis

CD40, a co-stimulatory receptor of the tumor necrosis factor receptor superfamily expressed on microglia and macrophages, is an upstream regulator of innate antiviral defense in coronavirus-induced neuroinflammation, but its specific role in the visual system remains undefined. Here, we demonstrate that CD40 signaling is essential for restricting retrograde axonal transport of the murine {beta}-coronavirus RSA59 from the brain to the retina and for preventing chronic neurodegeneration in a model of viral optic neuritis. Wild-type and CD40-/- mice were intracranially inoculated with RSA59, and viral burden, neuroinflammation, and neurodegeneration were assessed at acute (day 5), bridging (day 7), and chronic (day 30) stages. CD40-/- mice exhibited significantly increased clinical severity and [~]30% mortality by day 12 post-infection, compared to 100% survival in WT mice. CD40 deficiency resulted in elevated viral loads in the optic nerve and enhanced retrograde viral dissemination across all retinal layers, whereas in WT mice, the virus was largely confined to the ganglion cell layer. CD40-/- mice exhibited impaired early microglial activation and compensatory astrogliosis during the acute and bridging phases. By day 30 p.i., although viral-N protein was undetectable by immunohistochemistry in both genotypes, CD40-/- optic nerves retained significantly higher persistent viral RNA and exhibited extensive demyelination, oligodendrocyte loss, axonal depletion, and upregulation of phagocytic markers. Critically, CD40-/- retinas showed persistent astrogliosis, accumulation of phagocytic microglia/macrophages, and a significant loss of Brn3a+ retinal ganglion cells. These findings establish CD40 as a critical molecular node governing coronavirus optic neuritis, linking early innate immune regulation to long-term neuronal survival.

immunology↗

bioRxiv2024

Phosphatidylinositol-3,5-bisphosphate mediated vacuolar morphology modulation is integral to ethanol stress response

Vacuoles enlarge in response to ethanol. We used quantitative imaging to show that even brief exposure to ethanol causes a rapid transition from multilobed vacuoles to a single compartment. Vacuole unlobing is essential as mutants restricted for vacuole fusion exhibit greater ethanol sensitivity. This response involves the inhibition of vacuole fission via downregulation of the activity of Fab1, a lipid kinase generating the signaling lipid phosphatidylinositol-3,5-bisphosphate. Ethanol exposure results in the redistribution of a phosphatidylinositol-3,5-bisphosphate sensor from the perivauolar dots to the cytoplasm and the dissociation of the effector of this lipid, Atg18, from the vacuolar membrane to the cytoplasm. Impaired Atg18 membrane recruitment also entails a loss of interaction between a scaffold of the Fab1 complex, Vac14, and Atg18. A hyperactive Fab1 mutant, with elevated pools of phosphatidylinositol-3,5-bisphosphate, shows delayed vacuole enlargement; the partial relocation of the phosphatidylinositol-3,5-bisphosphate probe to the perivacuolar dots and of Atg18 to the vacuole membrane. Since Atg18 is responsible for vacuole fragmentation, our results show that, under ethanol stress, cells actively regulate vacuole morphology by modulating phosphatidylinositol-3,5-bisphosphate levels.

cell biology↗

bioRxiv2024

Divergent Functions of Late ESCRT Components in Giardia lamblia: Insights from Subcellular Distributions and Protein Interactions

Giardia lamblia, a human gut pathogen, possesses a minimal ESCRT (Endosomal Sorting Complex Required for Transport) machinery. Paradoxically, there are multiple paralogs of some late-ESCRT components. There are three paralogs for Vps4, GlVps4a, GlVps4b, and GlVps4c, and two for Vps46, GlVps46a, and GlVps46b. This study addressed whether these paralogs discharge overlapping and/or distinct cellular functions by determining the sub-cellular distribution of the paralogs in trophozoites and during encysting. Consistent with the distribution of orthologs in model organisms, most of these components were found to be associated with various cellular membranes, particularly in regions of acute membrane bending. Some of these paralogs are also associated with microtubule structures, such as cytoplasmic axonemes and the median body. Considering their diverse sub-cellular distributions, it is likely that they perform non-overlapping functions within the cell. Furthermore, their redistribution during encystation indicates that they may play a role in the morphological and functional changes accompanying this transition. The study also characterized GlIst1, an ESCRT-III accessory protein that undergoes unique post-translational myristoylation at lysine 43, potentially aiding its membrane recruitment. GlIst1 selectively interacts with GlVps4b through non-canonical MIT-MIM interactions. GlIst1 also exhibits selective interaction with GlVps46b. Such selective interaction of GlIst1 with only specific paralogs of GlVps4 and GlVps46 further underscores the distinct cellular roles of these paralogs. Author SummaryGiardia lamblia, a unicellular protozoan parasite, is the causative agent of giardiasis, a water-transmitted disease affecting millions globally. This disease poses a substantial threat to public health, especially in less developed countries, where clean water and proper sanitation are scarce. The parasite manifests in two morphologically distinct forms, trophozoites and cysts. Transformation between these forms is essential for the organisms survival, spread, and infection processes. Trophozoites, the active and motile form of Giardia, inhabit the small intestine of the host and trigger infections. These trophozoites can transform into cysts through encystation, enabling the parasite to endure harsh external environments and spread between hosts through contaminated water or food sources. The transition between these states necessitates extensive membrane restructuring. Such changes are likely to involve the Endosomal Sorting Complex Required for Transport (ESCRT) machinery, as it has been shown to participate in both prokaryotic and eukaryotic membrane remodeling events. Our research sheds light on the ESCRT machinery in G. lamblia, a crucial membrane-shaping system that may facilitate the transition between trophozoites and cysts. The ESCRT machinery in G. lamblia is distinct from that in yeast and humans, representing one of the most basic ESCRT systems. Our investigation provides valuable information about the intracellular distribution of various late-ESCRT components under different conditions, their potential functions, and their interactions with other late-ESCRT components. These findings may contribute significantly to our understanding of the basic operation of the ESCRT machinery in this parasite.

cell biology↗

bioRxiv2019

Novel strategy for treating neurotropic viral infections using hypolipidemic drug Atorvastatin

Chandipura virus (CHPV) and Japanese Encephalitis Virus (JEV) are known to infect neurons followed by their successful propagation. Increased incidences of central nervous system invasion by the abovementioned viruses have been reported in case of children and elderly thus culminating into severe neurological damage. Literature suggests induction of endoplasmic reticulum (ER)-stress related proteins upon CHPV and JEV infection which help promote viral reproduction. Since earlier studies underscore the pleotropic role of atorvastatin (AT) in neuroprotection against flaviviruses like Hepatitis C and dengue, it was hypothesized that AT might also act as a neuroprotective agent against RNA viruses like CHPV and JEV. AT-mediated antiviral activity was evaluated by assessing survivability of virus-infected mouse pups treated with the drug. Balb C mice were used for in vivo experiments. Neuro2A cell line was used as the model for in vitro experiments. Cells subjected to AT treatment were infected by CHPV and JEV followed by evaluation of ER stress-related and apoptosis-related proteins by immunoblotting technique and immunofluorescence microscopy. Interaction of host protein with viral genome was assessed by RNA-Co-IP. AT treatment exhibited significant anti-viral activity against CHPV and JEV infections via hnRNPC-dependent manner. Viral genome-hnRNPC interaction was found to be abrogated upon AT action. AT was also observed to reduce secretion of proinflammatory cytokines by the neurons in response to viral infection. Moreover, AT treatment was also demonstrated to reduce neuronal death by abrogating virus-induced miR-21 upregulation in hnRNPC-dependent fashion. This study thus suggests probable candidature of AT as antiviral against CHPV and JEV infections.

microbiology↗

bioRxiv2019

Identification and classification of hubs in miRNA target gene networks in human neural stem/progenitor cells following Japanese encephalitis virus infection

Micro RNA dysregulation is observed in many viral diseases. RNA viruses modulate host miRNA machinery for their own benefit. JEV, a neurotropic RNA virus has been reported to manipulate several miRNAs in neuron or microglia. However, no report indicates a complete sketch of the miRNA profile of NSPCs contributing to viral persistence; hence being focused in our current study. We performed a miRNA array of 84 miRNAs in human neuronal progenitor cell line and primary neural precursor cells isolated from aborted foetus. Several fold down-regulation of hsa-miR-9-5p, hsa-miR-22-3p, hsa-miR-124-3p and hsa-miR-132-3p were found in both of the cells. Subsequently, we screened for the target genes of these miRNAs and looked for the important biological pathways the genes significantly regulate. Then we sorted out the target genes which are involved in two or more than two pathways. We constructed a protein-protein interaction (PPI) network of the miRNA target genes based on their interaction patterns. A binary adjacency matrix for each gene network was prepared. Different modules or communities were identified in those networks using community detection algorithms. Mathematically, we identified the hub genes by analyzing their degree centrality and participation co-efficient in the network. The hub genes were classified either as provincial (P<0.4) or connector hubs (P>0.4). We validated the expression of hub genes in both cell line and primary cells through qRT-PCR post JEV infection and respective miR-mimic transfection. Taken together, our findings highlight the importance of specific target gene networks of miRNAs affected by JEV infection in NSPCs.\n\nImportanceJEV damages the neural stem/progenitor cell population of mammalian brain. However, JEV induced alteration in miRNA expression pattern of the cell population remains an open question, hence warrants our present study. In this study, we specifically address the down-regulation of four miRNAs and we prepared a protein-protein interaction network of miRNA target genes. We identified two types of hub genes in the PPI network namely connector hubs and provincial hubs. These two types of miRNA target hub genes critically influence the participation strength in the networks and thereby significantly influence up and down regulation in several key biological pathways. Computational analysis of the PPI networks identifies key protein interactions and hubs in those modules which opens up the possibility of precise identification and classification of host factors for viral infection in NSPCs and how RNA viruses modulate host miRNA machinery for their own benefit post JEV infection to the cells.

microbiology↗