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Mani, S.

Publications and source records attributed to Mani, S..

At least 19 recordsLinked to original sources

Dose-additive and dose-dependent fetal testis toxicity of a nine-phthalate mixture in the rat

Phthalates (ortho-phthalic acid diesters) are used in a variety of manufacturing processes, particularly as non-covalent plasticizers in flexible polyvinyl chloride. Phthalates are male reproductive toxicants that disrupt the development of the fetal testis, resulting in malformed seminiferous cords, multinucleated germ cells (MNGs), and decreased testosterone production. We previously reported that MNGs were a sensitive, dose-dependent marker of dipentyl phthalate (DPEP) germ cell toxicity. To test whether germ cell effects of phthalates are dose-additive, we measured the induction of MNGs by a phthalate mixture. We treated timed pregnant Sprague Dawley rats with an equipotent mixture of nine phthalates, spanning a two-log dose range, from GD 17-21. We found that the phthalate mixture effects on morphogenesis of the testis, assessed through histological analysis of MNGs and seminiferous cord diameter were dose-additive. Consistent with prior results, we also found that the testosterone-reducing effect of the phthalate mixture was dose-additive and dose-dependent. Induction of MNGs had the lowest effective dose of any endpoint that we measured, with a benchmark dose (BMD10) of 9.402 (6.093, 13.13) mg ({sum} all phthalates)/kg/d, which is equivalent to a BMD10 of 3.517 (2.275, 4.919) mg DPEP/kg/d, based on relative potency factors. Quantitative analysis of phthalate metabolites in dam serum showed that the metabolites were present in approximately the same relative concentrations as the parent compounds in the dosing mixture, but with lower levels of monocyclohexyl phthalate and monobenzyl phthalate. Proteomic and spatial transcriptomic analyses showed significant decreases in expression of Leydig cell genes and proteins involved in steroid hormone biosynthesis, as well as enrichment of proteins related to metabolism of lipids and amino acids. Proteomic BMD analysis produced a lowest BMDmedian of 2.156 (0.204, 27.830) mg ({sum} all phthalates)/kg/d, which was within a 4.36-fold margin of the lowest apical endpoint BMD.

pharmacology and toxicology↗

Subtype-specific downregulation of voltage-gated sodium channels shapes neuronal responses to neuroinflammation

Epilepsy is one of the most common neurological disorders, affecting more than 50 million people worldwide. Among the genetic etiologies of epilepsy, variants in genes coding for ion channels are vastly represented and characterized. Notably, loss-of-function (LoF) mutations in voltage-gated sodium channels (NaV) genes can result in a wide range of phenotypes including West syndrome, autism spectrum disorder, or Dravet Syndrome. Although the implication of NaV subtypes in epileptic syndromes and the relationship between seizures and inflammation have been extensively described, subtype-specific neuronal responses to inflammation in the context of NaV loss-of-function remain poorly understood. In this study, we investigated the consequences of subtype-specific downregulation of NaV expression in primary mouse cortical neurons. Using shRNA-mediated silencing of Scn1a, Scn2a, or Scn8a, we generated neuronal cultures with reduced expression of NaV1.1, NaV1.2, or NaV1.6 and evaluated neuronal survival, inflammatory gene expression, and global transcriptomic responses under basal conditions and following an inflammatory challenge. Subtype-specific NaV downregulations did not produce a uniform phenotype. Rather, minor differences under basal conditions led to important discrepancies following exposure to an inflammatory stimulus. Notably, NaV1.1 reduction was associated with synaptic transcriptional changes, whereas NaV1.6 downregulation led to a substantial inflammatory signaling remodeling. Our observations suggest that the consequences of NaV dysfunction are not only determined by their role in neuronal excitability but also depend on subtype-specific responses to inflammatory cues. They notably shed light on the relevance of inflammatory events in the onset and progression of epileptic syndromes related to NaV loss-of-function mutations.

neuroscience↗

Stable and robust differentiation programs are predominantly irreversible

Multicellular differentiation programs are almost always irreversible, with cells rarely revisiting states observed during earlier developmental stages. An important factor contributing to such irreversibility may be the cellular context: the dependence of each cells fate decisions on inductive signals from other, simultaneously present cell types. Using a class of rule-based models for context-dependent cell fate decisions we examine the evolutionary basis for the observed prevalence of irreversibility. Our study suggests that irreversibility, instead of being directly selected for, could be widespread due to its association with two other key traits, stability and robustness, which are essential for reproducible, cancer-free organismal formation. We identify further structural properties of desirable fate-decision programs and illustrate how explicit knowledge of cellular context is required for predicting developmental outcomes.

evolutionary biology↗

ANCHOR : Atlas of Neurochemical Characterization of the Human Brainstem with 3D Reconstruction

The human brainstem is a complex division of the brain comprised of more than 200 nuclei and fiber tracts. The brainstem is essential for the functioning of the entire body. We introduce here the most detailed human brainstem Atlas across the human lifespan: fetus, child, adult. ANCHOR, the Atlas of Neurochemical Characterization of the Human Brainstem, is an online platform that includes more than 800 serial histological sections, stained for Nissl and seven immunochemical (IHC) markers, from the human brainstem of three ages: 25 fetal gestational weeks (GW), 9 years old, and 54 years old. This makes ANCHOR the most comprehensive human brainstem Atlas to date. In these three brainstems, we identified and manually annotated over 200 structures. We further characterized these structures with the seven IHC markers. We specifically describe the catecholaminergic groups in the human brainstem across all three age groups. In addition, we identified the protoplasmic commissural dendrites of the hypoglossal nucleus and we describe the pretectal nuclei in the Nissl-stained fetal 25 GW brainstem. ANCHOR includes an online viewer that integrates multimodal data, from magnetic resonance imaging and block face imaging to Nissl- and IHC-stained serial sections and 3D reconstruction of the entire brainstem. For the 9-year-old specimen, the online viewer allows simultaneous navigation of annotated sections with corresponding IHC, for viewing the specific region-wise cellular features accessible at https://anchor.humanbrain.in/.

neuroscience↗

Puromycin-sensitive aminopeptidase acts as an inhibitory auxiliary subunit of volume-regulated anion channels

Volume-regulated anion channels (VRACs) are large-pore channels present in nearly all vertebrate cells, playing key roles in cell volume regulation and autocrine/paracrine signaling. Here, we identify the ubiquitously expressed puromycin-sensitive aminopeptidase (PSA) as a binding partner of the obligatory VRAC subunit SWELL1 (also known as LRRC8A) and report the cryo-electron microscopy structure of the SWELL1-PSA complex. Three PSA molecules associate with a single SWELL1 hexamer, coupling adjacent leucine-rich repeat (LRR) domains into local dimers. Functionally, PSA overexpression suppresses VRAC activation, whereas its deletion results in elevated basal channel activity. Notably, PSAs regulatory role on VRACs is independent of its aminopeptidase activity. Our findings identify PSA as the first auxiliary subunit of VRACs, highlight the role of intracellular LRR domains in allosteric channel gating, and propose a new strategy for modulating VRAC function in diverse physiological contexts, including cGAMP transport and STING signaling.

molecular biology↗

Interleukin-27 is antiviral at the maternal-fetal interface.

Congenital viral infections can have severe consequences for pregnancy and fetal outcomes. Remarkably, the fetal-derived placenta serves as a robust barrier to infection through meticulous regulation by immune effectors and a diverse repertoire of cytokines. Yet, the regulatory roles of many cytokines remain undefined at the maternal-fetal interface. Interleukin 27 (IL-27) is a highly expressed cytokine in the placenta whose functional consequence during congenital infection is unknown. Here, we utilized trophoblast organoids (TO) derived from primary human placentas and a mouse model of congenital viral infection to uncover the functional role of IL-27 signaling during pregnancy. We show that TOs constitutively express IL-27 and its receptor, IL27RA, and demonstrate that IL-27 signaling restricts Zika virus (ZIKV) infection of TOs. Through bulk RNA-sequencing of TOs in the absence and presence of IL-27 signaling, we demonstrate IL-27-mediated upregulation of antiviral genes. Finally, we show that IL-27 signaling is critical within the context of congenital murine ZIKV infection, as IL-27 restricts placental ZIKV burdens and protects against pathologic fetal outcomes early in gestation. These findings collectively demonstrate a novel role for IL-27 in the placenta and establish IL-27 as an innate antiviral defense at the maternal-fetal interface during congenital viral infection.

microbiology↗

Immunogenicity and protection efficacy of self-amplifying and circular mRNA vaccines for SARS-CoV-2

Recent advances in vaccine technology have positioned messenger RNA (mRNA) vaccines as safe and reliable options for human use. Conventionally, mRNA vaccines were designed using linear or self-amplifying mRNA (SAM), the latter considered to be superior. However, limited success was achieved with SAM vaccines during the COVID-19 pandemic. Further, studies on Circular mRNA (Circ-RNA) vaccines against the SARS-CoV-2, Ebola and monkey pox proved their efficacy. Circ-RNAs are highly stable, neither they induce inflammatory response nor require any extracellular protein for their function. Here, we compared the efficacy of SAM- and Circ-RNA vaccines using the SARS-CoV-2-RBD (receptor binding domain) as the antigen. Both SAM-RBD and Circ-RBD induced a comparable anti-RBD IgG titer and virus-neutralizing antibody titer. However, the latter induced a significantly higher memory T-cell response. Immunization with SAM- and Circ-RBD showed no mortality and improved lung pathophysiology against acute SARS-CoV-2 infection in mice. The Circ-RBD vaccine is stable for 4 weeks at 40C. A bivalent vaccine containing Circ-RBD of both delta and omicron SARS-CoV-2 variants potently neutralized these viruses. These findings demonstrate Circ-RNA-RBD as an excellent vaccine candidate against COVID-19 and also provide a platform for developing bivalent Circ-RNA vaccine candidates against SARS-CoV-2 or other viruses with rapidly emerging variants.

microbiology↗

Spatial model of cell-fate choice uncovers strong links between tissue morphology and tissue regeneration

Multicellular tissues are immensely diverse, and yet are notably similar at the microanatomical level - most tissues are organized into distinct domains with well-defined cellular compositions and precise adjacencies among themselves. Concurrently, tissues across organisms are also similar in an important functional property: the ability to heal from injury, even in organisms with poor regenerative capacities, such as mammals. Both the cellular organization within tissues and the ability of tissues to heal are outcomes of developmental processes, suggesting that the two may be intrinsically linked. In this work, we explore this connection using an agent-based model of developmental cell-fate decisions. Our model produces a rich diversity of tissue morphologies: By tuning only four parameters, which control the density of intercellular interactions and the propensity of cellular differentiation, we generate tissue structures ranging from disordered and sparse to tissues organized into dense, contiguous domains. Only tissues with large contiguous domains had the ability to heal from injuries, thus demonstrating that tissue healing is strongly coupled to tissue morphology. Moreover, model-generated tissues predominantly heal through the replacement of injured cells by cells dividing in the neighborhood, which recapitulates natural mechanisms in animals as well as plants. More generally, our modeling framework allows a systematic sampling of diverse developmental programs and reproduces healing mechanisms in organisms as phylogenetically distant as plants and animals. Our work thus points to general patterns which often are difficult to directly compare in empirical research. Despite the multiple evolutionary origins of multicellularity, the demonstrated link between tissue domain-level organization and healing capacity may represent a unifying feature of multicellular life.

developmental biology↗

Unlocking the Potential: FKK6 as a Microbial Mimicry Based Therapy for Chronic Inflammation-Associated Colorectal Cancer in a Murine Model

Chronic intestinal inflammation significantly contributes to the development of colorectal cancer (CRC) and remains a pertinent clinical challenge, necessitating novel therapeutic approaches. Indole-based microbial metabolite mimics FKK6, which is a ligand and agonist of the pregnane X receptor (PXR), was recently demonstrated to have PXR-dependent anti-inflammatory and protective effects in a mouse model of dextran sodium sulfate (DSS)-induced acute colitis. Here, we examined the therapeutic potential of FKK6 in a mouse model (C57BL/6 FVB humanized PXR mice) of colitis-associated colon cancer (CAC) induced by azoxymethane (AOM) and dextran sodium sulfate (DSS). FKK6 (2 mg/kg) displayed substantial anti-tumor activity, as revealed by reduced size and number of colon tumors, improved colon histopathology, and decreased expression of tumor markers (c-MYC, {beta}-catenin, Ki-67, cyclin D) in the colon. In addition, we carried out the chronic toxicity (30 days) assessment of FKK6 (1 mg/kg and 2 mg/kg) in C57BL/6 mice. Histological examination of tissues, biochemical blood analyses, and immunohistochemical staining for Ki-67 and {gamma}-H2AX showed no difference between FKK6-treated and control mice. Comparative metabolomic analyses in mice exposed for 5 days to DSS and administered with FKK6 (0.4 mg/kg) revealed no significant effects on several classes of metabolites in the mouse fecal metabolome. Ames and micronucleus tests showed no genotoxic and mutagenic potential of FKK6 in vitro. In conclusion, anticancer effects of FKK6 in AOM/DSS-induced CAC, together with FKK6 safety data from in vitro tests and in vivo chronic toxicity study, and comparative metabolomic study, are supportive of the potential therapeutic use of FKK6 in the treatment of CAC.

pharmacology and toxicology↗

Type I interferon alters invasive extravillous trophoblast function.

Inappropriate type I interferon (IFN) signaling during embryo implantation and placentation is linked to poor pregnancy outcomes. Here, we evaluated the consequence of elevated type I IFN exposure on implantation using a biomimetic model of human implantation in an organ-on-a-chip device. We found that type I IFN reduced extravillous trophoblast (EVT) invasion capacity. Analyzing single-cell transcriptomes, we uncovered that IFN truncated endovascular EVT emergence in the implantation-on-a-chip device by stunting EVT epithelial-to-mesenchymal transition. Disruptions to the epithelial-to-mesenchymal transition is associated with the pathogenesis of preeclampsia, a life-threatening hypertensive disorder of pregnancy. Strikingly, unwarranted IFN stimulation induced genes associated with increased preeclampsia risk and a preeclamptic gene-like signature in EVTs. These dysregulated EVT phenotypes ultimately reduced EVT-mediated endothelial cell vascular remodeling in the implantation-on-a-chip device. Overall, our work indicates IFN signaling can alter EVT epithelial-to-mesenchymal transition progression which results in diminished EVT-mediated spiral artery remodeling and a preeclampsia gene signature upon sustained stimulation. Our work implicates unwarranted type I IFN as a maternal disturbance that can result in abnormal EVT function that could trigger preeclampsia.

immunology↗

COVID-19 during pregnancy alters circulating extracellular vesicle cargo and their effects on trophoblast

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and resulting coronavirus disease (COVID-19) causes placental dysfunction, which increases the risk of adverse pregnancy outcomes. While abnormal placental pathology resulting from COVID-19 is common, direct infection of the placenta is rare. This suggests that pathophysiology associated with maternal COVID-19, rather than direct placental infection, is responsible for placental dysfunction and alteration of the placental transcriptome. We hypothesized that maternal circulating extracellular vesicles (EVs), altered by COVID-19 during pregnancy, contribute to placental dysfunction. To examine this hypothesis, we characterized maternal circulating EVs from pregnancies complicated by COVID-19 and tested their effects on trophoblast cell physiology in vitro. We found that the gestational timing of COVID-19 is a major determinant of circulating EV function and cargo. In vitro trophoblast exposure to EVs isolated from patients with an active infection at the time of delivery, but not EVs isolated from Controls, altered key trophoblast functions including hormone production and invasion. Thus, circulating EVs from participants with an active infection, both symptomatic and asymptomatic cases, can disrupt vital trophoblast functions. EV cargo differed between participants with COVID-19 and Controls, which may contribute to the disruption of the placental transcriptome and morphology. Our findings show that COVID-19 can have effects throughout pregnancy on circulating EVs and circulating EVs are likely to participate in placental dysfunction induced by COVID-19.

pathology↗

Coordinated Immune Cell Networks in the Bone Marrow Microenvironment Define the Graft versus Leukemia Response with Adoptive Cellular Therapy

Understanding how intra-tumoral immune populations coordinate to generate anti-tumor responses following therapy can guide precise treatment prioritization. We performed systematic dissection of an established adoptive cellular therapy, donor lymphocyte infusion (DLI), by analyzing 348,905 single-cell transcriptomes from 74 longitudinal bone-marrow samples of 25 patients with relapsed myeloid leukemia; a subset was evaluated by protein-based spatial analysis. In acute myelogenous leukemia (AML) responders, diverse immune cell types within the bone-marrow microenvironment (BME) were predicted to interact with a clonally expanded population of ZNF683+GZMB+ CD8+ cytotoxic T lymphocytes (CTLs) which demonstrated in vitro specificity for autologous leukemia. This population, originating predominantly from the DLI product, expanded concurrently with NK and B cells. AML nonresponder BME revealed a paucity of crosstalk and elevated TIGIT expression in CD8+ CTLs. Our study highlights recipient BME differences as a key determinant of effective anti-leukemia response and opens new opportunities to modulate cell-based leukemia-directed therapy.

cancer biology↗

DIISCO: A Bayesian framework for inferring dynamic intercellular interactions from time-series single-cell data

Characterizing cell-cell communication and tracking its variability over time is essential for understanding the coordination of biological processes mediating normal development, progression of disease, or responses to perturbations such as therapies. Existing tools lack the ability to capture time-dependent intercellular interactions, such as those influenced by therapy, and primarily rely on existing databases compiled from limited contexts. We present DIISCO, a Bayesian framework for characterizing the temporal dynamics of cellular interactions using single-cell RNA-sequencing data from multiple time points. Our method uses structured Gaussian process regression to unveil time-resolved interactions among diverse cell types according to their co-evolution and incorporates prior knowledge of receptor-ligand complexes. We show the interpretability of DIISCO in simulated data and new data collected from CAR-T cells co-cultured with lymphoma cells, demonstrating its potential to uncover dynamic cell-cell crosstalk. AvailabilityDIISCO is publicly accessible at https://github.com/azizilab/DIISCO_public. All data will be deposited to GEO upon publication.

bioinformatics↗

In Vitro Safety Signals for Potential Clinical Development of the Anti-Inflammatory Pregnane X Receptor Agonist FKK6

Background and purposeBased on the mimicry of microbial metabolites, functionalized indoles were demonstrated as the ligands and agonists of the pregnane X receptor (PXR). The lead indole, FKK6, displayed PXR-dependent protective effects in DSS-induced colitis in mice and in vitro cytokine-treated intestinal organoid cultures. Here, we performed the initial in vitro pharmacological profiling of FKK6. Experimental approachA complex series of cell-free and cell-based assays were employed. The organic synthesis, and advanced analytical chemistry methods were used. Key resultsFKK6-PXR interactions were characterized by hydrogen-deuterium exchange mass spectrometry. Screening FKK6 against potential cellular off-targets revealed high PXR selectivity. FKK6 has poor aqueous solubility but was highly soluble in simulated gastric and intestinal fluids. FKK6 was bound to plasma proteins and chemically stable in plasma. The partition coefficient of FKK6 was 2.70, and FKK6 moderately partitioned into red blood cells. In Caco2 cells, FKK6 displayed high permeability (A-B: 22.8 x 10-6 cm.s-1) and no active efflux. These data are indicative of essentially complete in vivo absorption of FKK6. FKK6 was rapidly metabolized by cytochromes P450, notably by CYP3A4 in human liver microsomes. Two oxidized FKK6 derivatives, including N6-oxide and C19-phenol, were detected, and these metabolites had 5-7 x lower potency as PXR agonists than FKK6. This implies that despite high intestinal absorption, FKK6 is rapidly eliminated by the liver, and its PXR effects are predicted to be predominantly in the intestines. Conclusion and implicationsThe PXR ligand and agonist FKK6 has a suitable pharmacological profile supporting its potential preclinical development. BULLET POINT SUMMARYWhat is already known: O_LIMicrobial metabolite mimic FKK6 is a hPXR agonist with anti-inflammatory properties in mice and human. C_LIO_LIThe in vitro PXR binding, absorption, and metabolism have not been completely characterized. C_LI What this study adds: O_LIPXR selectivity with unique binding mode, high intestinal cell permeability, rapid and complex microsomal metabolism. C_LIO_LIInitial testing for predicted metabolites shows reduced potency as PXR agonists. C_LI Clinical significance: O_LIPXR effects of FKK6 are predicted to be predominantly in the intestines. C_LIO_LIFKK6 has a suitable pharmacological profile supporting its potential preclinical development. C_LI

biochemistry↗

SARS-CoV-2 antibodies cross-react and enhance dengue infection

The presence of non-neutralizing antibodies of any dengue serotype, increase the severity of subsequent infection by other dengue serotypes. During SARS-CoV-2 pandemic, the number of symptomatic dengue cases increased in India. We describe that antibodies isolated from convalescent plasma from COVID-19 patients enhances DENV2 infection in vitro. CR3022, one antibody against SARS-CoV-2 spike protein, also showed elevated DENV2 infection in vitro. In silico protein-protein interactions between the spike antibodies and the DENV2 E-protein revealed significant interactions. Likewise, few monoclonal/polyclonal antibodies against SARS-CoV-2 showed increased dengue infection in vitro. Importantly, the AG129 mice infected with SARS-CoV-2 three-weeks prior to DENV2 infection, showed elevated dengue pathogenesis. Thus, highlighting the possibilities of elevated infection and symptomatic dengue disease in COVID-19 survivors.

immunology↗

Natural Product Screen Identifies Asiatic Acid Targeting Mutant p53

Mutations in p53 are common in different cancer types and are reported to protect cancer via different mechanisms. R175H, R248Q, and R273H are the hotspot mutations of p53 and are suggested to increase aerobic glycolysis in cancer cells. Cancer cells rely mostly upon aerobic glycolysis, so it will be interesting to target these three p53 mutants for designing alternative cancer therapy. The class of compounds studied for their potential to target energy metabolism of cancer cells is called mitocans. The current study is an approach to explore if these selected 3 mutants of p53 may act as suitable target(s) for natural mitocans. Hereby, we selected 60 phytocompounds altogether from Andrographis paniculata and Centella asiatica and docked against all three p53 mutants, using Autodock vina. 11 compounds were sorted based on their binding energies and drug-like properties, and toxicity levels prediction showed asiatic acid to be the most significant. As asiatic acid was observed to significantly bind with R248Q only, R248Q-Asiatic acid was identified for molecular dynamics simulation using GROMACS which showed significant interactions. In conclusion, mutant R248Q was observed to be the best target for asiatic acid, though additional in-vitro experiments are important to validate the findings of this study.

cancer biology↗

Host inducible-HSP70A1A is an irresistible drug target to combat SARS-CoV-2 infection and pathogenesis

One of the fundamental mechanisms developed by the host to contain the highly infectious and rapidly proliferating SARS coronavirus is elevation of body temperature, a natural fallout of which is Heat Shock Protein (HSP) over-expression. Here, for the first time, we demonstrate that the SARS-CoV-2 virus exploits the host Hsp70 chaperone for its entry and propagation and blocking it can combat the infection. SARS-CoV-2 infection as well as febrile temperature enhanced Hsp70 overexpression in host Vero E6 cells. In turn, Hsp70 overexpression elevated the host cell autophagic response that is a prerequisite for viral propagation. Suppressive and prophylactic treatment of Vero E6 cells with HSP70 inhibitor PES-Cl, a small molecule derivative of Pifithrin , abrogated viral infection more potently than the currently used drug Remdesivir by suppressing host HSP70 and autophagic response. In conclusion, our study not only provides a fundamental insight into the role of host Hsp70 in SARS-CoV-2 pathogenesis, it paves the way for the development of potent and irresistible anti-viral therapeutics.

microbiology↗

Human endogenous retrovirus-R envelope is a host restriction factor against severe acute respiratory syndrome-coronavirus-2

Coronavirus induced disease-19 (COVID-19), caused by the SARS-CoV-2 remains a major global health challenge. Human endogenous retroviruses (HERVs) represent retroviral elements that got integrated into the ancestral human genome. HERVs are important in development and diseases, including cancer, inflammation and viral infections. Here, we analyzed the expression of several HERVs in SARS-CoV-2 infected cells and observed increased activity of HERV-E, HERV-V, HERV-FRD, HERV-MER34, HERV-W and HERV-KHML2. In contrast, HERV-R-envelope was downregulated in cell-based models and COVID-19 patient PBMCs. HERV-R overexpression inhibited SARS-CoV-2 replication, suggesting its antiviral action. Further studies demonstrated the role of extracellular signal-regulated kinase (ERK) in regulating HERV-R antiviral activity. Cross-talk between the ERK and p38 MAPK controls HERV-R envelope synthesis, which in turn modulates the replication of SARS-CoV-2. These findings establish the importance of HERV-R envelope as a host restriction factor against SARS-CoV-2 and illustrate the advantage of integration and evolutionary maintenance of retroviral-elements in the human genome.

microbiology↗