Biology subjects

Kumar, M.

Publications and source records attributed to Kumar, M..

At least 127 records · Page 7Linked to original sources

bioRxiv2022

Differential pathogenesis of SARS-CoV-2 variants of concern in human ACE2-expressing mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic resulting in millions of deaths worldwide. Increasingly contagious variants of concern (VoC) have fueled recurring global infection waves. A major question is the relative severity of disease caused by the previous and currently circulating variants of SARS-CoV-2. In this study, we evaluated the pathogenesis of SARS-CoV-2 variants in human ACE-2-expressing (K18-hACE2) mice. Eight-week-old K18-hACE2 mice were inoculated intranasally with a representative virus from the original B.1 lineage, or the emerging B.1.1.7 (alpha), B.1.351 (beta), B.1.617.2 (delta) or B.1.1.529 (omicron) lineages. We also infected a group of mice with the mouse-adapted SARS-CoV-2 (MA10). Our results demonstrate that B.1.1.7, B.1.351 and B.1.617.2 viruses are significantly more lethal than B.1 strain in K18-hACE2 mice. Infection with B.1.1.7, B.1.351 and B.1.617.2 variants resulted in significantly higher virus titers in the lungs and brain of mice compared to the B.1 virus. Interestingly, mice infected with the B.1.1.529 variant exhibited less severe clinical signs and high survival rate. We found that B.1.1.529 replication was significantly lower in the lungs and brain of infected mice in comparison to other VoC. Transcription levels of cytokines and chemokines in the lungs of the B.1.1.529-infected mice were significantly less when compared to those challenged with the B.1.1.7 virus. Together, our data provide insights into the pathogenesis of the previous and circulating SARS-CoV-2 VoC in mice.

microbiology↗

bioRxiv2022

Remdesivir, Zidovudine (AZT) and Nevirapine inhibit Chandipura virus replication through high energy interactions with the RdRp domain of the polymerase protein L

Chandipura Virus (CHPV), a rhabdovirus belonging to mononegavirales, is an emerging pathogen in Indian subcontinent. The virus infection causes fever, brain encephalitis among the young children below 14 yrs of age. In recent past, several outbreaks and deaths among children were reported from in India. There are no targeted drugs or vaccines available against CHPV and symptomatic treatments are the only option. In this background, we aimed to investigate the inhibitory effects of some priviously known viral RNA polymerase inhibitor drugs on CHPV replication. First, we examined remdesivir, which is known to inhibit HCV, Ebola and SARS-CoV-2 replication and close structural similarity along with conserved residues in the finger region of RNA dependent RNA polymerase (RdRp) domain is the basis of replication inhibition. Our results showed that remdesivir inhibits CHPV replication in vero E6 cells to a significant level. In this study we have also included non-nucleoside anti-retroviral inhibitor (NNRTI) drug nevirapine, and nucleoside inhibitor (NRTI) drug AZT (Zidovudine) to determine if these are also able to inhibit CHPV replication. Interestingly, we observed inhibition of CHPV replication by both nevirapine and AZT (in the order nevirapine>AZT), albeit to a lesser extent compared to remdesivir. We next performed molecular docking and modeling study to get an insight about the interactions of these drugs with CHPV polymerase protein. Modeling study predicts that remdesivir has most favourable CHPV polymerase binding energy among these three drugs. Both remdesivor and AZT binds near the polymerase active site through interctions with residues in finger and palm regions of RdRp. In contrast, nevirapine binds to the N-terminal domain (NTD) of the RdRp. In summary, we found remdesivir as a potent inhibitor of CHPV. A combination therapy including remdesivir, nevirapine and AZT may be a better drug cocktail to treat CHPV disease. Our findings warrant further studies of these drugs against CHPV in animal models for clinical use in near future.

microbiology↗

bioRxiv2022

CriSNPr: a single interface for the curated and de-novo design of gRNAs for CRISPR diagnostics using diverse Cas systems

Nucleic acid detection and variant calling through CRISPR-based diagnostics (CRISPRDx) has facilitated clinical decision-making, particularly during the COVID-19 pandemic. This has been further accelerated through the discovery of newer and engineered CRISPR effectors, expanding the portfolio of such diagnostic applications to a wide variety of pathogenic and non-pathogenic conditions. However, each diagnostic CRISPR pipeline requires customized detection schemes originating from fundamental principles of the Cas protein used, its guide RNA (gRNA) design parameters, and the assay readout. This is particularly relevant for variant detection, an attractive low-cost alternative to sequencing-based approaches for which no in silico pipeline for the ready-to-use design of CRISPR-based diagnostics currently exists. In this manuscript, we fill this lacuna using a unified webserver CriSNPr (CRISPR based SNP recognition), which provides the user the opportunity to de-novo design gRNAs based on six CRISPRDx proteins of choice (Fn/enFnCas9, LwCas13a, LbCas12a, AaCas12b, and Cas14a) and query for ready-to-use oligonucleotide sequences for validation on relevant samples. In addition, we provide a database of curated pre-designed gRNAs and target/off-target for all human and SARS-CoV-2 variants reported so far. CriSNPr has been validated on multiple Cas proteins and highlights its broad and immediate scope of utilization across multiple detection platforms. CriSNPr is available at URL http://crisnpr.igib.res.in/.

bioinformatics↗

bioRxiv2022

Knockout of Sorbs2 in Cardiomyocytes Leads to Dilated Cardiomyopathy in Mice

2.RationaleSorbs2 is a cardiomyocyte-enriched, cytoskeletal adaptor protein, and given some evidence for its dysregulated expression in failing hearts, there is growing interest in understanding its roles in cardiac biology and disease. While Sorbs2 global knockout mice display lethal cardiomyopathy with severe arrhythmias, the underlying mechanisms remain unclear, and whether this results from intrinsic loss of Sorbs2 in cardiomyocytes is unknown, as Sorbs2 is also well-expressed in the nervous system and vasculature. In addition, the potential relevance of Sorbs2 in human cardiomyopathy remains underexplored. ObjectiveTo characterize the effects and potential underlying mechanisms of cardiomyocyte- specific deletion of Sorbs2 on cardiac structure and function in mice, and to further examine Sorbs2 dysregulation in failing hearts and explore potential links between Sorbs2 genetic variations and human cardiovascular disease phenotypes. Methods and ResultsWe report that myocardial Sorbs2 expression is consistently upregulated in humans with ischemic and idiopathic cardiomyopathies, and in experimental animal models of heart failure (HF). We generated mice with cardiomyocyte-specific loss of Sorbs2 (Sorbs2-cKO) and found early atrial and ventricular conduction abnormalities, despite unaltered expression of primary action potential ion channels and gap junction proteins. At mid-life, Sorbs2-cKO mice exhibit impaired cardiac contractility with cardiomyofibers failing to maintain adequate mechanical tension. As a result, these mice develop progressive diastolic and systolic dysfunction, enlarged cardiac chambers, and die with congestive HF at approximately one year of age. Comprehensive survey of potential underlying mechanisms revealed that Sorbs2-cKO hearts exhibit defective microtubule polymerization and compensatory upregulation of structural proteins desmin, vinculin, and tubulins. Finally, consistent with our observations in mice, we identified suggestive links between Sorbs2 genetic variants and related human cardiac phenotypes, including conduction abnormalities, atrial enlargement, and dilated cardiomyopathy. ConclusionsOur studies show that Sorbs2 is essential for maintaining cytoskeletal structural integrity in cardiomyocytes likely through strengthening the interactions between microtubules and other structural proteins at crosslink sites. Overall, this study provides key insights into the critical role for Sorbs2 in cardiomyocytes and likely other cell types in maintaining normal cardiac structure and function and highlights its potential clinical relevance.

physiology↗

bioRxiv2022

Influenza virus-like particle-based hybrid vaccine containing RBD induces immunity against influenza and SARS-CoV-2 viruses

Several approaches have produced an effective vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the influence of immune responses induced by other vaccinations on the durability and efficacy of the immune response to SARS-CoV-2 vaccine is still unknown. We have developed a hybrid vaccine for SARS-CoV-2 and influenza viruses using influenza virus-like particles (VLP) incorporated by protein transfer with glycosylphosphatidylinositol (GPI)-anchored SARS-CoV-2 S1 RBD fused to GM-CSF as an adjuvant. GPI-RBD-GM-CSF fusion protein was expressed in CHO-S cells, purified and incorporated onto influenza VLPs to develop the hybrid vaccine. Our results show that the hybrid vaccine induced a strong antibody response and protected mice from both influenza virus and mouse-adapted SARS-CoV-2 challenges, with vaccinated mice having significantly lower lung viral titers compared to naive mice. These results suggest that the hybrid vaccine strategy is a promising approach for developing multivalent vaccines to prevent influenza A and SARS-CoV-2 infections.

immunology↗

bioRxiv2021

Novel inhibitors designing against the potential drug target of Plasmodium falciparum M17 Leucyl Aminopeptidase - PfM17LAP

Malaria is one of the major disease of concern worldwide especially in the African regions. According to the recent WHO reports, African regions share 95% of the total deaths worldwide that occurs due to malaria. Plasmodium falciparum M17 Leucyl Aminopeptidase (PfM17LAP) plays an important role in the regulation of amino acids release and for the survival of the parasite. We performed molecular docking and simulation studies to find the potential inhibitors against PfM17LAP using ChEMBL antimalarial library. Molecular docking studies and post-docking analysis revealed that molecules CHEMBL369831 and CHEMBL176888 showed better binding than the reference molecule BESTATIN. LibDock and X-SCORES of molecules BES, CHEMBL369831 and CHEMBL176888 are 130.071, 230.38, 223.56 and -8.75 Kcal/mol, -10.90 Kcal/mol, -11.05 Kcal/mol respectively. ADMET profiling of the top ten ranked molecules was done by using the Discovery Studio. Molecular dynamic studies revealed that the complex PfM17LAP-CHEMBL369831 is stable throughout the simulation. Finally, we have reported novel inhibitors which possess more binding affinity towards PfM17LAP.

bioinformatics↗

bioRxiv2021

Deficiency in endocannabinoid synthase DAGLB contributes to Parkinson's disease and dopaminergic neuron dysfunction

2-arachidonoyl-glycerol (2-AG), the most abundant endocannabinoid (eCB) in the brain, regulates diverse neural functions. However, whether 2-AG deficiency contributes to Parkinsons disease (PD) and nigral dopaminergic neurons (DANs) dysfunction is unclear. Diacylglycerol lipase and {beta} (DAGLA and DAGLB) mediate the biosynthesis of 2-AG. Using homozygosity mapping and whole-exome sequencing, we linked multiple homozygous loss-of-function mutations in DAGLB to a form of early-onset autosomal recessive PD. We then used RNA sequencing and fiber photometry with genetically encoded eCB sensors to demonstrate that DAGLB is the main 2-AG synthase in nigral DANs. Genetic knockdown of Daglb by CRISPR/Cas9 in mouse nigral DANs substantially reduces 2-AG levels in the substantia nigra (SN). The SN 2-AG levels are markedly correlated with the vigor of movement during the acquisition of motor skills, while Daglb-deficiency impairs motor learning. Conversely, pharmacological enhancement of 2-AG levels increases nigral DAN activity and dopamine release and improves motor learning. Together, we demonstrate that DAGLB-deficiency contributes to the etiopathogenesis of PD, reveal the importance of DAGLB-mediated 2-AG biosynthesis in nigral DANs in regulating neural activity and dopamine release, and provide preclinical evidence for the beneficial effects of 2-AG augmentation in PD treatment.

neuroscience↗

bioRxiv2021

Inactivation mechanism and efficacy of grape seed extract for Human Norovirus surrogate

Proper disinfection of harvested food and water is critical to minimize infectious disease. Grape seed extract (GSE), a commonly used health supplement, is a mixture of plant-derived polyphenols. Polyphenols possess anti-microbial and -fungal properties, but anti-viral effects are not well-known. Here we show that GSE outperformed chemical disinfectants (e.g., free chlorine and peracetic acids) in inactivating Tulane virus, a human norovirus surrogate. GSE induced virus aggregation, an event that correlated with a decrease in virus titers. This aggregation and disinfection was not reversible. Molecular docking simulations indicate that polyphenols potentially formed hydrogen bonds and strong hydrophobic interactions with specific residues in viral capsid proteins. Together, these data suggest that polyphenols physically associate with viral capsid proteins to aggregate viruses as a means to inhibit virus entry into the host cell. Plant-based polyphenols like GSE are an attractive alternative to chemical disinfectants to remove infectious viruses from water or food. ImportanceHuman noroviruses are major food- and water-borne pathogens, causing approximately 20% of all cases of acute gastroenteritis cases in developing and developed countries. Proper sanitation or disinfection are critical strategies to minimize human norovirus-caused disease until a reliable vaccine is created. Grape seed extract (GSE) is a mixture of plant-derived polyphenols that is used as a health supplement. Polyphenols are known for antimicrobial, antifungal, and antibiofilm activities, but antiviral effects are not well-known. In studies here, plant-derived polyphenols outperformed chemical disinfectants (e.g., free chlorine and peracetic acids) in inactivating Tulane virus, a human norovirus surrogate. Based on data from additional molecular assays and molecular docking simulations, the current model is that the polyphenols in GSE bind to the Tulane virus capsid, an event that triggers virion aggregation. It is thought that this aggregation prevents Tulane virus from entering host cells.

biochemistry↗

bioRxiv2021

Waning grasslands: a quantitative temporal evaluation of the grassland habitats across human-dominated upper Gangetic Plains, north India

Grassland habitats currently face severe anthropogenic exploitations leading to cascading effects on the survival of grassland-dependent biodiversity globally, particularly in non-protected areas. Significant amount of such biodiversity-rich grasslands in India are found outside protected areas but lack quantitative information on their status. We evaluated the current and historical (30 years) status of the grasslands using a combination of intensive field surveys and GIS tools across one of the most fertile, human-dominated region: the upper Gangetic Plains of north India. On-ground mapping and visual classifications revealed 57% decline in grassland habitats between 1985 (418 km2) and 2015 (178km2), mostly driven by conversion to croplands (74% contribution). Radio-telemetry data from the largest endemic cervid swamp deer (n=2) showed grassland-dominated average home range (50% BBMM) size of 1.02 km2. The animals highly preferred these patches (average Ivlevs index- 0.85) and showed highest temporal continuity (88%) compared to other LULC classes. Camera trapping within the core habitats suggests critical use of these patches as fawning/breeding grounds. Habitat suitability analysis indicates only [~]18% of the entire area along Ganges is suitable for swamp deer. Accurate mapping (86% accuracy) and characterization of four major grass species revealed a total 144.04 km{superscript 2} vegetation area, dominted by Saccharum sp. (35%). We recommend protection and recovery of these critical grassland patches to maintain dynamic corridors and other appropriate management strategies involving multiple stakeholders to ensure survival of this critical ecosystem. Such evaluations, if spatially expanded, would be critical to restore this rapidly vanishing ecosystem worldwide.

ecology↗

bioRxiv2021

A ROLE FOR CORTICAL DOPAMINE IN THE PARADOXICAL CALMING EFFECTS OF PSYCHOSTIMULANTS

Attention deficit hyperactivity disorder (ADHD) affects young children and manifests symptoms such as hyperactivity, impulsivity and cognitive disabilities. Psychostimulants, which are the primary treatment for ADHD, target monoamine transporters and have a paradoxical calming effect, but their mechanism of action, is unclear. Studies using the dopamine (DA) transporter (DAT) knockout mice, which have elevated striatal DA levels and are considered an animal model of ADHD, have suggested that the paradoxical calming effect of psychostimulants might be through the actions on serotonin neurotransmission. On the other hand, newer non-stimulant class of drugs such as atomoxetine and Intuniv suggest that targeting the norepinephrine (NE) system in the PFC might explain this paradoxical calming effect. We sought to decipher the mechanism of this paradoxical effect of psychostimulants through an integrated approach using ex vivo monoamine efflux experiments, monoamine transporter knockout mice, drug infusions and behavior. Our ex vivo efflux experiments reveal that NE transporter (NET) blocker desipramine elevates both norepinephrine and dopamine but not serotonin levels, in PFC tissue slices from wild-type and DAT-KO but not NET KO mice. However, serotonin (5-HT) transporter (SERT) inhibitor fluoxetine elevates only serotonin in all three genotypes. Systemic administration of both desipramine and fluoxetine but local PFC infusion of only desipramine and not fluoxetine inhibits hyperactivity in the DAT-KO mice. In contrast, pharmacological norepinephrine depletion but dopamine elevation using Nepicastat also inhibits hyperactivity in DATKO mice. Together, these data suggest that elevation of PFC dopamine and not norepinephrine or serotonin as a convergent mechanism for the paradoxical psychostimulant effects observe in ADHD therapy.

neuroscience↗

bioRxiv2021

SARS-CoV-2 variants of concern infect the respiratory tract and induce inflammatory response in wild-type laboratory mice

The emergence of new severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants of concern poses a major threat to the public health due to possible enhanced virulence, transmissibility and immune escape. These variants may also adapt to new hosts in part through mutations in the spike protein. In this study, we evaluated the infectivity and pathogenicity of SARS-CoV-2 variants of concern in wild-type C57BL/6 mice. Six-week-old mice were inoculated intranasally with a representative virus from the original B.1 lineage or emerging B.1.1.7 and B.1.351 lineages. We also infected a group of mice with a mouse-adapted SARS-CoV-2 (MA10). Viral load and mRNA levels of multiple cytokines and chemokines were analyzed in the lung tissues on day 3 after infection. Our data show that unlike the B.1 virus, the B.1.1.7 and B.1.351 viruses are capable of infecting C57BL/6 mice and replicating at high concentrations in the lungs. The B.1.351 virus replicated to higher titers in the lungs compared to the B.1.1.7 and MA10 viruses. The levels of cytokines (IL-6, TNF-, IL-1{beta}) and chemokine (CCL2) were upregulated in response to the B.1.1.7 and B.1.351 infection in the lungs. Overall, these data indicate a greater potential for infectivity and adaptation to new hosts by emerging SARS-CoV-2 variants.

microbiology↗

bioRxiv2021

Dissection of function and recognition mechanism of M. tuberculosis ESX-1 secreted virulence factor EspC

Mycobacterium tuberculosis uses the ESAT-6 system-1/type VII (ESX-1) system for secretion of virulence proteins into the host cell, however the mechanism of virulence proteins secretion, molecular components and regulation of ESX-1 system are only partly understood. In the current study, we have analyzed the biological function and recognition mechanism between ESX-1 virulence EspC and EccA1 ATPase proteins. The EspC enters into A549 human lung carcinoma cells and exhibited cytotoxicity, as observed in MTT Assay. To understand the recognition mechanism between EspC and EccA1 ATPase, the EspC and EccA1 mutants were generated based on EspC~EccA1 interactions, as observed in molecular modeling. Binding analysis shows that EspC export arm interacts specifically to the {beta}-hairpin insertion motif of the TPR domain of EccA1 ATPase. Mutations in these epitopes lead to significant decrease/or abolish the binding between EspC and EccA1 ATPase. Our study provides insight into biological function and recognition mechanism between EspC and EccA1 ATPase, which can be used as target to prevent EspC secretion/ or in general virulence factor secretion by mycobacterial ESX-1 system.

biophysics↗

bioRxiv2021

Engineering large-scale perfused tissues via synthetic 3D soft microfluidics

The vascularization of engineered tissues and organoids has remained a major unresolved challenge in regenerative medicine. While multiple approaches have been developed to vascularize in vitro tissues, it has thus far not been possible to generate sufficiently dense networks of small-scale vessels to perfuse large de novo tissues. Here, we achieve the perfusion of multi-mm3 tissue constructs by generating networks of synthetic capillary-scale 3D vessels. Our 3D soft microfluidic strategy is uniquely enabled by a 3D-printable 2-photon-polymerizable hydrogel formulation, which allows for precise microvessel printing at scales below the diffusion limit of living tissues. We demonstrate that these large-scale engineered tissues are viable, proliferative and exhibit complex morphogenesis during long-term in-vitro culture, while avoiding hypoxia and necrosis. We show by scRNAseq and immunohistochemistry that neural differentiation is significantly accelerated in perfused neural constructs. Additionally, we illustrate the versatility of this platform by demonstrating long-term perfusion of developing liver tissue. This fully synthetic vascularization platform opens the door to the generation of human tissue models at unprecedented scale and complexity.

bioengineering↗

bioRxiv2021

Artemisinin acts by inhibiting Plasmodium falciparum Ddi1, a retropepsin, resulting into the accumulation of ubiquitinated proteins

Reduced sensitivity of the human malaria parasite, Plasmodium falciparum, to Artemisinin and its derivatives (ARTs) threatens the global efforts towards eliminating malaria. ARTs have been shown to cause ubiquitous cellular and genetic insults, which results in the activation of the unfolded protein response (UPR) pathways. The UPR restores protein homeostasis, which otherwise would be toxic to cellular survival. Here, we interrogated the role of DNA-damage inducible protein 1 (PfDdi1), a unique proteasome-interacting retropepsin in mediating the actions of the ARTs. We demonstrate that PfDdi1 is an active A2 family protease that hydrolyzes ubiquitinated substrates. We further show that treatment with ARTs lead to the accumulation of ubiquitinated proteins in the parasites and blocks the destruction of the ubiquitinated substrates by PfDdi1. Besides, whereas the PfDdi1 is predominantly localised in the cytoplasm, exposure of the parasites to ARTs leads to DNA fragmentation and increased recruitment of the PfDdi1 into the nucleus. Furthermore, Ddi1 knock-out Saccharomyces cerevisiae cells are more suceptible to ARTs and the PfDdI1 protein robustly restores the corresponding functions in the knock-out cells. Together, these results show that ARTs act by inducing DNA and protein damage, and impairing the damage recovery by inhibiting the activity of PfDdi1, an essential ubiquitin-proteasome retropepsin.

cell biology↗

bioRxiv2021

Development Of Novel Multiplex PCR For Rapid Diagnosis Of Coinfected Hemo-Parasites In Cattle

A novel, rapid and specific multiplex polymerase chain reaction has been developed for the diagnosis of hemo-parasitic infection in bovine blood by three of the most common hemo-parasites. The reported method relied on the detection of the three different bovine hemoparasites isolated from red blood cells (RBCs) of cattle by conventional Giemsa stained blood smear (GSBS) and confirmed by multiplex PCR. The designed multiplex primer sets can amplify 205, 313 and 422 bp fragments of apocytochrome b, sporozoite and macroschizont 2 (spm2) and 16S rRNA gene for Babesia bigemina, Theileria annulata and Anaplasma marginale, respectively. This multiplex PCR was sensitive with the ability to detect the presence of 150 ng of genomic DNA. The primers used in this multiplex PCR also showed highly specific amplification of specific gene fragments of each respective parasite DNA without the presence of non-specific and non-target PCR products. This multiplex PCR system was used to diagnose GSBS confirmed blood samples (N=12) found infected or co-infected with hemoparasites. A comparison of the two detection methods revealed that 58.33% of specimens showed concordant diagnoses with both techniques. The specificity, positive predictive value and kappa coefficient of agreement was highest for diagnosis of B. bigemina and lowest for A. marginale. The overall Kappa coefficient for diagnosis based on GSBS for multiple pathogen compared to multiplex PCR was 0.56 slightly behind the threshold of 0.6 of agreement. Therefore, confirmation should always be made based on PCR to rule out false positive due to differences in subjective observations, stain particles and false negative due to low level of parasitaemia. The simplicity and rapidity of this specific multiplex PCR method make it suitable for large-scale epidemiological studies and for follow-up of drug treatments.

molecular biology↗

bioRxiv2021

In-vitro Reconstitution of Membrane Contact Sites between the Endoplasmic Reticulum and Lipid Droplets

Coordinated cell function requires inter-organelle communication across Membrane Contact Sites (MCS). Here we deposit ER-enriched microsomes purified from rat liver or from cultured cells on a coverslip in the form of a continuous planar membrane. We visualize real-time protein and lipid exchanges across MCS that form between this ER-mimicking membrane and lipid droplets purified from rat liver. An Optical trap is used to demonstrate physical tethering of individual lipid droplets to the ER-mimicking membrane at MCS, and to directly measure the strength of this tether. In-vitro MCS formation changes dramatically in response to metabolic state and immune activation in the animal. Surprisingly, we find that the Rab18 GTPase and Phosphatidic acid are common molecular factors to control both of these pathways. This assay could possibly be adapted to interrogate MCS formation between other membranes (e.g. mitochondria, peroxisomes, endosomes etc.), and abnormalities therein that cause neurological, metabolic and pathogenic diseases.

cell biology↗

bioRxiv2021

ErpY-like lipoprotein of Leptospira outsmart host complement regulation by acquiring complement regulators, activating alternate pathway, and intervening membrane attack complex

The survival of pathogenic Leptospira in the host pivots on its proficiency to circumvent the immune response. These pathogens evade the complement system in serum by enticing and amassing the serum complement regulators onto their surface. ErpY-like lipoprotein, a surface-exposed protein of Leptospira spp., is conserved and exclusively present in the pathogenic spirochete. The recombinant form of this protein is comprehended to interact with multiple extracellular matrix (ECM) components and serum proteins like soluble complement regulators factor H (FH) and factor I (FI). Here, we document that the supplementation of recombinant ErpY-like protein (40 {micro}g/mL) in the host (humans) serum augments the viability of E. coli and saprophytic L. biflexa by more than 2-fold. Pure complement regulators FH and FI, when bound to rErpY-like protein, preserve their respective cofactor and protease activity mandated to cleave the complement component C3b. The supplementation of rErpY-like protein (40 {micro}g/mL) in serum ensued in [~]90 % reduction of membrane attack complex (C5b-9/MAC) deposition through alternate complement pathway (AP) activation. However, rErpY-like protein could moderately reduce ([~]16%) MAC deposition in serum through the classical pathway (CP). In addition, the rErpY-like protein solely activated the AP, suggesting its role in the rapid consumption and depletion of the complement components. Blocking the pathogenic L. interrogans surface with anti-rErpY resulted in an increase in MAC formation on the bacterial surface, indicating a specific role of the ErpY-like lipoprotein in complement-mediated immune evasion. This study underscores the role of the ErpY-like lipoprotein of Leptospira in complement evasion.

microbiology↗

bioRxiv2021

Crossbill: an open access single objective light-sheet microscopy platform

We present an open access scanned oblique plane microscopy platform Crossbill. It combines a new optical configuration, open hardware assembly, a systematic alignment protocol, and dedicated control software to provide a compact, versatile, high resolution single objective light-sheet microscopy platform. The demonstrated configuration yields the most affordable sub-micron resolution oblique plane microscopy system to date. We add galvanometer enabled tilt-invariant lateral scan for multi-plane, multi-Hz volumetric imaging capability. A precision translation stage extends stitched field of view to centimeter scale. The accompanying open software is optimized for Crossbill and can be easily extended to include alternative configurations. Using Crossbill, we demonstrate large volume structural fluorescence imaging with sub-micron lateral resolution in zebrafish and mouse brain sections. Crossbill is also capable of multiplane functional imaging, and time-lapse imaging. We suggest multiple alternative configurations to extend Crossbill to diverse microscopy applications.

neuroscience↗