Biology subjects

Thakur, N.

Publications and source records attributed to Thakur, N..

At least 19 recordsLinked to original sources

bioRxiv2026

Spatial Organization of Lipids Drives GPCR Conformational Equilibria

Despite the widespread use of lipid nanodiscs for structure-function studies of membrane proteins, little is known about how lipids are spatially organized within nanodiscs and how this organization influences embedded proteins. The activity and conformational equilibria of the human A2A adenosine receptor, a class A G protein-coupled receptor, are highly sensitive to anionic lipids that directly interact with the receptor. We leverage this lipid-dependent sensitivity to probe the accessibility of anionic lipids across nanodiscs of varying sizes. We identify a threshold concentration of anionic lipids required to fully populate active receptor conformations that is higher for POPS than for POPG. Computational simulations reveal that POPS and POPG each form lipid clusters reducing the effective availability of anionic lipids to interact with the receptor. This effect is stronger for POPS and scales with increasing nanodisc size, correlating with experimental biophysical and biochemical measurements. Simulations further identify positively charged residues within the membrane scaffold protein that coordinate anionic lipid headgroups. Targeted protein engineering reduces the threshold concentration of anionic lipids required for receptor activation, supporting strategies to control lipid accessibility within nanodiscs. Because membrane scaffold proteins are derived from apolipoprotein A-I, similar lipid-protein interactions may also influence lipid organization within biological systems such as HDL particles.

biophysics↗

bioRxiv2026

Characterisation of naturally occurring MERS-CoV Spike mutations and their impact on entry and neutralisation.

In this study the phenotypic consequences of naturally occurring single nucleotide polymorphisms (SNPs) in the MERS-CoV Spike protein were investigated. The impact of Spike mutations on virus entry and neutralisation of contemporary MERS-CoV strains is not currently well understood. Naturally occurring mutations were identified by aligning 584 MERS-CoV Spike sequences from either human clinical isolates collected between 2012 - 2024 or from viruses passaged in human cells. Fifteen SNPs of interest occurring in the NTD, RBD and adjacent to the S1/S2 cleavage site were selected for further characterisation based on their location in the Spike protein, frequency and identification in previous studies. A representative clade B, lineage 5 wildtype Spike sequence, which reflected those carried by MERS-CoV viruses circulating in the Middle East, was used in this study. The mutations of interest were introduced to the wildtype backbone to generate Spike variants. A lentiviral-based pseudotyping system was then used to investigate the impact of these Spike mutations on entry and neutralisation. I529T, E536K and L745F were shown to improve MERS-CoV entry. L411F, T424I, L506F, L745F and T746K were found to increase resistance to neutralisation by pooled patient sera. This study has identified novel naturally occurring Spike mutations that resulted in phenotypic differences in virus entry and neutralisation of contemporary MERS-CoV strains. Continued investigation of the phenotypic consequences of naturally occurring MERS-CoV Spike mutations is essential for assessing the risk to public health, especially given the pandemic potential of this virus. ImportanceThe main aim of this study was to investigate the impact of naturally occurring MERS-CoV Spike mutations on virus entry and neutralisation. The phenotypic consequences of mutations occurring in the Spike protein of contemporary MERS-CoV strains are not currently well understood. Improving our understanding is of particular importance due to MERS-CoV continuing to pose a public health risk, with frequent spillover events and mounting evidence of human-to-human transmission since the virus emerged in 2012. A major concern is that as MERS-CoV continues to evolve, it may become more infectious, resulting in increased transmission between humans. To add to this, surveillance is limited and there are currently no specific medical countermeasures available to treat MERS-CoV disease. The MERS-CoV Spike pseudotyping system developed in this study is a useful tool that could be used alongside surveillance systems to rapidly assess novel Spike mutations in functional assays. This MERS-CoV pseudotyping system could also be used to aid the development of medical countermeasures such as vaccines, antivirals and antibody therapies.

microbiology↗

bioRxiv2025

Mechanisms for cross-neutralisation of diverse bat sarbecoviruses

The continuing evolution of SARS-CoV-2 variants of concern, and the increasing spillover potential of sarbecoviruses into the human population presents an important and urgent need to discover cross-reactive monoclonal antibodies (mAbs) for future therapeutic use and identify conserved neutralising epitopes that can be used for rationale design of broadly protective sarbecovirus vaccines. Here we study the neutralising epitopes on WIV-1 Spike of three mAbs that confer broad sarbecovirues and SARS-CoV-2 variant neutralisation, including XEC and JN.1. mAb V1WT_06 binds a highly conserved RBD site V epitope that is mediated by the heavy chain alone. V1WT_06 contact residues are highly conserved in circulating viruses suggesting that the epitope is evolutionarily and functionally constrained. mAbs V1WT_41 and VA14_26 bind overlapping RBD class 4 epitopes with differing angles of approach that impact on the degree of ACE2 competition. We show that neutralisation by these mAbs is maintained when virus entry is via Japanese horseshoe bat and Halcyon horseshoe bat ACE2. These mAbs are ideal candidates for therapeutic antibody development and inform the rational design of pan-coronavirus vaccines.

microbiology↗

bioRxiv2025

Understanding the future risk of bat coronavirus spillover into humans: correlating sarbecovirus receptor usage, host range, and antigenicity.

Sarbecoviruses interact with their receptor, angiotensin converting enzyme 2 (ACE2), via the receptor binding domain (RBD) of Spike, the immunodominant target for neutralising antibodies. Understanding the interplay and correlation between ACE2-determined host range and antigenicity is vitally important for understanding the zoonotic potential of related bat sarbecoviruses. Using binding assays, pseudotype-entry assays and a diverse panel of mammalian ACE2 proteins, we examined the host range and related antigenicity of multiple bat coronaviruses. Broad bat ACE2 usage (a generalist phenotype) was most common in clade 1 sarbecoviruses, including SARS-CoV-2 and the BANAL isolates from Laos. In contrast, clade 3 (e.g., RhGB07) and 5 (e.g., Rc-o319) sarbecoviruses exhibited more restricted ACE2 usage (a specialist phenotype). A novel structure for RhGB07 Spike further helped to identify RBD residues associated with this receptor specialism. Interestingly, the generalist phenotypes were largely maintained with more diverse mammalian receptor libraries, including human, non-human primate, livestock, rodent ACE2 and potential intermediate reservoir hosts (e.g., civet, racoon dog, pangolin), while specialists, like RhGB07, exhibited wider phenotypic diversity. The impact of SARS-CoV-2s continued evolution in humans was also examined, identifying an expanding and/or shifting pattern of generalism for variants, especially Omicron and its sub-lineages. Furthermore, we compared and correlated these entry phenotypes with antigenicity using sera from SARS-CoV-2 convalescent individuals. Clade 1 viruses, phylogenetically related to SARS-CoV-2, were antigenically the most similar, with robust evidence for cross-neutralisation; however, there was still evidence for limited cross-neutralisation across the entire sub-genus. Finally, using monoclonal antibodies, derived from COVID-19 vaccinees with breakthrough infections, we pin-pointed the antibody epitope classes responsible for wider neutralisation. Our research indicates that generalist ACE2-using sarbecoviruses are phylogenetically and antigenically related to SARS-CoV-2.

microbiology↗

bioRxiv2025

A protective bispecific antibody targets both Nipah virus surface glycoproteins and limits viral escape

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic henipaviruses without approved human vaccines or therapies. Here, we report on a highly potent bispecific therapeutic that combines an anti-fusion (F) nanobody with an anti-receptor binding protein (RBP) antibody to deliver a dual-targeting biologic that is resistant to viral escape. We show that the nanobody, DS90, engages a unique, conserved site within prefusion F of NiV and HeV, and provides neutralization and complete protection from NiV disease. Bispecific engineering of DS90 with the anti-RBP mAb m102.4 results in neutralization, elimination of viral escape and superior protection from NiV disease compared to leading monovalent approaches. These findings carry implications for the development of cross-neutralizing immunotherapies that limit the emergence of henipaviral escape mutants.

microbiology↗

bioRxiv2024

M102, a combined NRF2 and HSF-1 activator for neuroprotection in amyotrophic lateral sclerosis.

M102 is a central nervous system (CNS) penetrant small molecule electrophile which activates in vivo the NFE2-related factor 2 antioxidant response element (NRF2-ARE) pathway, as well as transcription of heat-shock element (HSE) associated genes. In the TDP-43Q331K transgenic mouse model of ALS dosed subcutaneously at 5mg/kg OD or 2.5mg/kg BD with M102, significant improvements in compound muscle action potential (CMAP) amplitude of hind limb muscles and gait parameters were observed at 6 months of age, with associated target engagement. An oral dose response study of M102 in SOD1G93A transgenic mice showed a dose-dependent improvement in the CMAP of hindlimb muscles which correlated with preservation of lumbar spinal motor neurons at the same time point. These data enabled prediction of human efficacious exposures and doses, which were well within the safety margin predicted from Good Laboratory Practice (GLP) toxicology studies. A parallel program of work in vitro showed that M102 rescued motor neuron survival in co-culture with patient-derived astrocytes from sporadic, C9orf72 and SOD1 cases. Markers of oxidative stress, as well as indices of TDP-43 proteinopathy were also reduced by exposure to M102 in these in vitro models. This comprehensive package of preclinical efficacy data across two mouse models as well as patient-derived astrocyte toxicity assays, provides a strong rationale for clinical evaluation of M102 in ALS patients. Combined with the development of target engagement biomarkers and the completed preclinical toxicology package, a clear translational pathway to testing in ALS patients has been developed. One Sentence SummaryM102, a dual NRF2/HSF1 activator, slows disease progression in 2 mouse models and exerts neuroprotection in human cellular models of ALS.

neuroscience↗

bioRxiv2024

SARS-CoV-2 Nsp14 binds Tollip and activates pro-inflammatory pathways while downregulating interferon alpha and interferon gamma receptors

SARS coronavirus 2 (SARS-CoV-2) non-structural protein 14 (Nsp14) possesses an N-terminal exonuclease (ExoN) domain that provides a proofreading function for the viral RNA-dependent RNA polymerase and a C-terminal N7-methyltransferase (N7-MTase) domain that methylates viral mRNA caps. Nsp14 also modulates host functions. This includes the activation of NF-{kappa}B and downregulation of interferon alpha/beta receptor 1 (IFNAR1). Here we demonstrate that Nsp14 exerts broader effects, activating not only NF-{kappa}B responses but also ERK, p38 and JNK MAP kinase (MAPK) signaling, promoting cytokine production. Further, Nsp14 downregulates not only IFNAR1 but also IFN-{gamma} receptor 1 (IFNGR1), impairing cellular responses to both IFN and IFN{gamma}. IFNAR1 and IFNGR1 downregulation is via a lysosomal pathway and also occurs in SARS-CoV-2 infected cells. Analysis of a panel of Nsp14 mutants reveals a consistent pattern. Mutants that disable ExoN function remain active, whereas N7-MTase mutations impair both pro-inflammatory pathway activation and IFN receptor downregulation. Innate immune modulating functions also require the presence of both the ExoN and N7-MTase domains likely reflecting the need for the ExoN domain for N7-MTase activity. We further identify multi-functional host protein Tollip as an Nsp14 interactor. Interaction requires the phosphoinositide-binding C2 domain of Tollip and sequences C-terminal to the C2 domain. Full length Tollip or regions encompassing the Nsp14 interaction domain are sufficient to counteract both Nsp14-mediated and Nsp14-independent activation of NF-{kappa}B. Knockdown of Tollip partially reverses IFNAR1 and IFNGR1 downregulation in SARS-CoV-2 infected cells, suggesting relevance of Nsp14-Tollip interaction for Nsp14 innate immune evasion functions. SignificanceSARS-CoV-2 protein Nsp14 both activates NF-{kappa}B, which promotes virus replication and inflammation, and downregulates IFNAR1, which can render infected cells resistant to the antiviral effects of IFN-/{beta}. Our study demonstrates that Nsp14 also activates MAPK signaling and downregulates IFNGR1, causing broader impacts than previously recognized. Data from a panel of Nsp14 mutants suggests a common underlying effect of Nsp14 may be responsible for its multiple innate immune activities. We further describe a novel interaction between Nsp14 and Tollip, a selective autophagy receptor. We show that Tollip expression downregulates Nsp14 activation of NF-{kappa}B and that Tollip knockdown reverses IFNAR1 and IFNGR1 downregulation in SARS-CoV-2 infection, suggesting that Tollip functions as a regulator of Nsp14 innate immune modulation.

microbiology↗

bioRxiv2024

Exploring Probiotic Potential: A Comparative Genomics and In Silico Assessment of Genes within the Genus Geobacillus

The pursuit of new probiotic targets has seen a surge, aided by next-generation sequencing, facilitating a thorough exploration of bacterial traits. The genus Geobacillus stands out as a promising target for uncovering its potential as a probiotic. The study explored the genetic attributes of the genus Geobacillus for their resilience to gastrointestinal conditions, nutrient production, and immunomodulatory compound creation, revealing potential probiotic traits. Additionally, the research undertook predictive analyses of genomic elements such as prophages, CRISPR-Cas systems, insertion sequences, genomic islands, antibiotic resistance genes, and CAZymes. These evaluations aimed to assess the safety aspects associated with the genus Geobacillus. A comparative genomic analysis was also carried out using 18 validly published genomes of the genus Geobacillus and a few other genomes of Lactobacillus and Bifidobacterium were taken as control. Genes associated with probiotic traits like adhesion, stress tolerance (acid/bile, osmotic, oxidative), immune modulation, and molecular chaperones were uniformly detected in the Geobacillus genus. Notably, mobile genetic elements such as plasmids, prophages, and insertion sequences were absent, as were virulence factors, toxins, and Antibiotic resistance genes. Additionally, CRISPR-Cas systems and CAZymes were present. The pan-genome encompassed 25,284 protein-coding genes with translation. Comparative genomic analysis revealed an open pan-genome for Geobacillus. Pan-genome exhibited variability, particularly in genes linked to environmental interaction and secondary metabolite synthesis. In conclusion, Geobacillus appears potentially safe and well-suited for the gut habitat. However, further in vitro studies are essential to add to the knowledge of the probiotic potential of Geobacillus species. ImportanceThis comprehensive study highlights the significant probiotic potential and genetic makeup of the Geobacillus genus, shedding light on its unique attributes in adapting to extreme environmental conditions. Understanding the probiotic properties of Geobacillus is crucial amidst growing concerns over antibiotic resistance, offering promising alternatives for combating pathogenic microbes. Additionally, exploring the genetic diversity and adaptive mechanisms of Geobacillus through genomic and metagenomic approaches provides valuable insights into its biotechnological applications and evolutionary history. By employing in-silico methods and comparative analyses with established probiotic genera, this study contributes to elucidating the probiotic characteristics of Geobacillus, paving the way for further research in harnessing its beneficial traits for various applications in health, biotechnology, and environmental remediation.

microbiology↗

bioRxiv2024

Single-cell image-based genetic screens systematically identify regulators of Ebola virus subcellular infection dynamics

Ebola virus (EBOV) is a high-consequence filovirus that gives rise to frequent epidemics with high case fatality rates and few therapeutic options. Here, we applied image-based screening of a genome-wide CRISPR library to systematically identify host cell regulators of Ebola virus infection in 39,085,093 million single cells. Measuring viral RNA and protein levels together with their localization in cells identified over 998 related host factors and provided detailed information about the role of each gene across the virus replication cycle. We trained a deep learning model on single-cell images to associate each host factor with predicted replication steps, and confirmed the predicted relationship for select host factors. Among the findings, we showed that the mitochondrial complex III subunit UQCRB is a post-entry regulator of Ebola virus RNA replication, and demonstrated that UQCRB inhibition with a small molecule reduced overall Ebola virus infection with an IC50 of 5 M. Using a random forest model, we also identified perturbations that reduced infection by disrupting the equilibrium between viral RNA and protein. One such protein, STRAP, is a spliceosome-associated factor that was found to be closely associated with VP35, a viral protein required for RNA processing. Loss of STRAP expression resulted in a reduction in full-length viral genome production and subsequent production of non-infectious virus particles. Overall, the data produced in this genome-wide high-content single-cell screen and secondary screens in additional cell lines and related filoviruses (MARV and SUDV) revealed new insights about the role of host factors in virus replication and potential new targets for therapeutic intervention.

microbiology↗

bioRxiv2024

Global variation in prior exposure shapes antibody neutralization profiles of SARS-CoV-2 variants up to BA.2.86

The highly mutated SARS-CoV-2 variant, BA.2.86, and its descendants are now the most frequently sequenced variants of SARS-CoV-2. We analyze antibody neutralization data from eight laboratories from the UK, USA, Denmark, and China, including two datasets assessing the effect of XBB.1.5 vaccines, to determine the effect of infection and vaccination history on neutralization of variants up to and including BA.2.86, and produce antibody landscapes to describe these neutralization profiles. We find evidence for lower levels of immune imprinting on pre-Omicron variants in sera collected from Denmark and China, which may be explained by lower levels of circulation of the ancestral variant in these countries, and the use of an inactivated virus vaccine in China.

immunology↗

bioRxiv2023

Spatial Patterning Analysis of Cellular Ensembles (SPACE) enables statistically robust discovery of complex spatial organization at the cell and tissue level

Spatial patterns of cells and other biological elements drive both physiologic and pathologic processes within tissues. While many imaging and transcriptomic methods document tissue organization, discerning these patterns is challenging, especially when they involve multiple elements in complex arrangements. To address this challenge, we present Spatial Patterning Analysis of Cellular Ensembles (SPACE), an R package for analysis of high-plex spatial data. SPACE is compatible with any data collection modality that records values (i.e., categorical cell/structure types or quantitative expression levels) at fixed spatial coordinates (i.e., 2d pixels or 3d voxels). SPACE detects not only broad patterns of co-occurrence but also context-dependent associations, quantitative gradients and orientations, and other organizational complexities. Via a robust information theoretic framework, SPACE explores all possible ensembles of tissue elements - single elements, pairs, triplets, and so on - and ranks the most strongly patterned ensembles. For single images, rankings reflect patterns that differ from random assortment. For sets of images, rankings reflect patterns that differ across sample groups (e.g., genotypes, treatments, timepoints, etc.). Further tools then thoroughly characterize the nature of each pattern for intuitive interpretation. We validate SPACE and demonstrate its advantages using murine lymph node images for which ground truth has been defined. We then use SPACE to detect new patterns across varied datasets, including tumors and tuberculosis granulomas.

bioinformatics↗

bioRxiv2023

Membrane Mimetic-Dependence of GPCR Energy Landscapes

Protein function strongly depends on temperature, which is related to temperature-dependent changes in the equilibria of protein conformational states. We leveraged variable-temperature 19F-NMR spectroscopy to interrogate the temperature dependence of the conformational landscape of the human A2A adenosine receptor (A2AAR), a class A GPCR. Temperature-induced changes in the conformational equilibria of A2AAR in lipid nanodiscs were markedly dependent on the efficacy of bound drugs. While antagonist complexes displayed only modest changes as the temperature rose, both full and partial agonist complexes exhibited substantial increases in the active state population. Importantly, the temperature-dependent response of complexes with both full and partial agonists exhibited a pronounced sensitivity to the specific membrane mimetic employed. In striking contrast to observations within lipid nanodiscs, in detergent micelles the active state population exhibited different behavior for A2AAR complexes with both full and partial agonists. This underscores the importance of the protein environment in understanding the thermodynamics of GPCR activation. HighlightsO_LIActive A2AAR population increases with increasing temperature in lipid nanodiscs C_LIO_LIActive A2AAR population exhibits different temperature dependence in detergents C_LIO_LIPartial agonist complexes present a unique conformational state in nanodiscs C_LIO_LITemperature dependence of partial agonist equilibria depends on membrane mimetic C_LI

biophysics↗

bioRxiv2023

Surveillance of 16 UK native bat species through conservationist networks uncovers coronaviruses with zoonotic potential

There has been limited characterisation of bat-borne coronaviruses in Europe. Here, we screened for coronaviruses in 48 faecal samples from 16 of the 17 bat species breeding in the UK, collected through a bat rehabilitation and conservationist network. We recovered nine (two novel) complete genomes across six bat species: four alphacoronaviruses, a MERS-related betacoronavirus, and four closely related sarbecoviruses. We demonstrate that at least one of these sarbecoviruses can bind and use the human ACE2 receptor for infecting human cells, albeit suboptimally. Additionally, the spike proteins of these sarbecoviruses possess an R-A-K-Q motif, which lies only one nucleotide mutation away from a furin cleavage site (FCS) that enhances infectivity in other coronaviruses, including SARS-CoV-2. However, mutating this motif to an FCS does not enable spike cleavage. Overall, while UK sarbecoviruses would require further molecular adaptations to infect humans, their zoonotic risk is unknown and warrants closer surveillance.

genomics↗

bioRxiv2023

Anionic Phospholipids Control Mechanisms of GPCR-G Protein Recognition

G protein-coupled receptors (GPCRs) are embedded in phospholipids that strongly influence drug-stimulated signaling. Anionic lipids are particularly important for GPCR signaling complex formation, but a mechanism for this role is not understood. Using NMR spectroscopy, we visualized the impact of anionic lipids on the function-related conformational equilibria of the human A2A adenosine receptor (A2AAR) in bilayers containing defined mixtures of zwitterionic and anionic phospholipids. Anionic lipids primed the receptor to form complexes with G proteins through a conformational selection process. Without anionic lipids, signaling complex formation proceeded through a less favorable induced fit mechanism. In computational models, anionic lipids mimicked interactions between a G protein and positively charged residues in A2AAR at the receptor intracellular surface, stabilizing a pre-activated receptor conformation. Replacing these residues strikingly altered the receptor response to anionic lipids in experiments. High sequence conservation of the same residues among all GPCRs supports a general role for lipid-receptor charge complementarity in signaling.

biophysics↗

bioRxiv2022

An alpaca-derived nanobody neutralizes the SARS-CoV-2 omicron variant

The SARS-CoV2 Omicron variant sub-lineages spread rapidly through the world, mostly due to their immune-evasive properties. This has put a significant part of the population at risk for severe disease and underscores the need for anti-SARS-CoV-2 agents that are effective against emergent strains in vulnerable patients. Camelid nanobodies are attractive therapeutic candidates due to their high stability, ease of large-scale production and potential for delivery via inhalation. Here, we characterize the RBD-specific nanobody W25, which we previously isolated from an alpaca, and show superior neutralization activity towards Omicron lineage BA.1 in comparison to all other SARS-CoV2 variants. Structure analysis of W25 in complex with the SARS-CoV2 spike surface glycoprotein shows that W25 engages an RBD epitope not covered by any of the antibodies previously approved for emergency use. Furthermore, we show that W25 also binds the spike protein from the emerging, more infectious Omicron BA.2 lineage with picomolar affinity. In vivo evaluation of W25 prophylactic and therapeutic treatments across multiple SARS-CoV-2 variant infection models, together with W25 biodistribution analysis in mice, demonstrates favorable pre-clinical properties. Together, these data endorse prioritization of W25 for further clinical development.

microbiology↗

bioRxiv2022

Distinct antigenic properties of the SARS-CoV-2 Omicron lineages BA.4 and BA.5

Over the course of the pandemic variants have arisen at a steady rate. The most recent variants to emerge, BA.4 and BA.5, form part of the Omicron lineage and were first found in Southern Africa where they are driving the current wave of infection. In this report, we perform an in-depth characterisation of the antigenicity of the BA.4/BA.5 Spike protein by comparing sera collected post-vaccination, post-BA.1 or BA.2 infection, or post breakthrough infection of vaccinated individuals with the Omicron variant. In addition, we assess sensitivity to neutralisation by commonly used therapeutic monoclonal antibodies. We find sera collected post-vaccination have a similar ability to neutralise BA.1, BA.2 and BA.4/BA.5. In contrast, in the absence of vaccination, prior infection with BA.2 or, in particular, BA.1 results in an antibody response that neutralises BA.4/BA.5 poorly. Breakthrough infection with Omicron in vaccinees leads to a broad neutralising response against the new variants. The sensitivity of BA.4/BA.5 to neutralisation by therapeutic monoclonal antibodies was similar to that of BA.2. These data suggest BA.4/BA.5 are antigenically distinct from BA.1 and, to a lesser extent, BA.2. The enhanced breadth of neutralisation observed following breakthrough infection with Omicron suggests that vaccination with heterologous or multivalent antigens may represent viable strategies for the development of cross-neutralising antibody responses.

microbiology↗

bioRxiv2022

An ACAT inhibitor regulates SARS-CoV-2 replication and antiviral T cell activity

The severity of disease following infection with SARS-CoV-2 is determined by viral replication kinetics and host immunity, with early T cell responses and/or suppression of viraemia driving a favourable outcome. Recent studies have uncovered a role for cholesterol metabolism in the SARS-CoV-2 life cycle and in T cell function. Here we show that blockade of the enzyme Acyl-CoA:cholesterol acyltransferase (ACAT) with Avasimibe inhibits SARS-CoV-2 entry and fusion independent of transmembrane protease serine 2 expression in multiple cell types. We also demonstrate a role for ACAT in regulating SARS-CoV-2 RNA replication in primary bronchial epithelial cells. Furthermore, Avasimibe boosts the expansion of functional SARS-CoV-2-specific T cells from the blood of patients sampled in the acute phase of infection. Thus, re-purposing of available ACAT inhibitors provides a compelling therapeutic strategy for the treatment of COVID-19 to achieve both antiviral and immunomodulatory effects.

immunology↗

bioRxiv2022

The SARS-CoV-2 variant, Omicron, shows rapid replication in human primary nasal epithelial cultures and efficiently uses the endosomal route of entry.

The SARS-CoV-2 Omicron/BA.1 lineage emerged in late 2021 and rapidly displaced the Delta variant before being overtaken itself globally by, the Omicron/BA.2 lineage in early 2022. Here, we describe how Omicron BA.1 and BA.2 show a lower severity phenotype in a hamster model of pathogenicity which maps specifically to the spike gene. We further show that Omicron is attenuated in a lung cell line but replicates more rapidly, albeit to lower peak titres, in human primary nasal cells. This replication phenotype also maps to the spike gene. Omicron spike (including the emerging Omicron lineage BA.4) shows attenuated fusogenicity and a preference for cell entry via the endosomal route. We map the altered Omicron spike entry route and partially map the lower fusogenicity to the S2 domain, particularly the substitution N969K. Finally, we show that pseudovirus with Omicron spike, engineered in the S2 domain to confer a more Delta-like cell entry route retains the antigenic properties of Omicron. This shows a distinct separation between the genetic determinants of these two key Omicron phenotypes, raising the concerning possibility that future variants with large antigenic distance from currently circulating and vaccine strains will not necessarily display the lower intrinsic severity seen during Omicron infection.

microbiology↗