Biology subjects

Wang, L.-F.

Publications and source records attributed to Wang, L.-F..

At least 19 recordsLinked to original sources

bioRxiv2025

Restoration of MAIT cell function in healthcare-associated bacterial infections supports recovery of carbapenem efficacy against resistant bacteria

Antimicrobial resistance (AMR) presents a major clinical challenge to patients with healthcare-associated infections (HAIs), particularly among immunocompromised individuals and patients with comoribidites, who often exhibit an impaired mucosa-associated invariant T (MAIT) cell pool. MAIT cells are innate-like T cells enriched in mucosal tissues, possess potent antibacterial activity, and restoration of their function may offer a host-directed strategy against drug-resistant pathogens. We evaluated how stimulation with cognate antigen in combination with various cytokines, modulates MAIT cell cytotoxicity and enhances carbapenem activity. Under optimal conditions, MAIT cells exhibited increased expression of antimicrobial cytolytic proteins and efficiently killed cells pulsed with MAIT cell antigen. IL-15 or IL-2 plus IL-7 were particularly effective in promoting polyfunctional cytotoxic responses. Secretomes from cytokine-stimulated MAIT cells restored the activity of imipenem against engineered E. coli expressing the clinically relevant carbapenemases blaNDM-1, blaKPC-2, and blaOXA-48, strongly reducing bacterial growth, viability, and metabolic activity. Notably, IL-2 plus IL-7 stimulation enabled expansion and functional restoration of MAIT cells from HAI patients, whose baseline MAIT cell numbers and responses were diminished. These findings demonstrate that tailored stimulation can reinvigorate MAIT cell effector function and augment antibiotic efficacy, supporting a role for MAIT cells in adjunct immunotherapeutic strategy to combat AMR in vulnerable patient populations. Category of manuscript: Research Article.

immunology↗

bioRxiv2025

Cardiac Adaptations in the Cave Nectar Bat Eonycteris spelaea: Insights into Metabolic Resilience and Stress Response

AimsBats are unique mammals with remarkable adaptations, including powered flight, which demands significant energy expenditure. While previous studies have documented basic structural characteristics of bat hearts, a comprehensive understanding of their response to physiological stress remains unexplored. This study investigates the cardiac adaptations of the cave nectar bat Eonycteris spelaea to elucidate the mechanisms underlying their unique physiological capabilities. Methods and ResultsWe performed RNA sequencing to analyse the cardiac gene expression profile of E. spelaea and 6 other bat species in comparison to mouse and human hearts, revealing enriched transcriptomic signatures related to oxidative phosphorylation and fatty acid metabolism across multiple bat species. Metabolomic profiling compared acylcarnitine metabolites and tricarboxylic acid (TCA) cycle intermediates between bat and mouse hearts, indicating a distinct acylcarnitine profile and increased levels of TCA cycle intermediates in bats, suggesting enhanced metabolic capacity. Structural adaptations were assessed through anatomical and histological analyses on cardiac tissues, showing thicker left ventricular walls and increased vascular density in bats without pathological hypertrophy. Functional characteristics were evaluated using dobutamine stress echocardiography, demonstrating superior cardiac reserve in bats with significant increases in ejection fraction, stroke volume, and cardiac output under stress conditions. Additionally, isolated cardiomyocytes were treated with Angiotensin II (Ang II) to assess stress responses. Bat cardiomyocytes displayed resistance to Ang II-induced hypertrophy and mitochondrial dysfunction compared to mice, further highlighting their resilience to stress-induced damage. ConclusionThe unique adaptations observed in bat hearts, including enhanced metabolic pathways, structural remodelling, and cellular resilience contribute to their ability to meet the high energy demands of powered flight while maintain cardiac function under stress. These insights into bat cardiac physiology provide valuable information on cardioprotective mechanisms that could be applicable to other species. Translational PerspectiveBats exhibit remarkable cardiac adaptations that sustain the high energy demands of powered flight while resisting stress-induced damage. These insights into evolutionarily conserved cardioprotective mechanisms highlight potential therapeutic pathways for preventing heart failure, including resistance to hypertrophy and mitochondrial dysfunction under stress. Studying non-model organisms like bats may offer innovative approaches to enhance metabolic and stress resilience in human hearts, paving the way for translational research in cardiovascular disease management and treatment.

systems biology↗

bioRxiv2023

mRNA vaccines encoding membrane-anchored receptor-binding domains of SARS-CoV-2 mutants induce strong humoral responses and can overcome immune imprinting

To address the limitations of whole-spike COVID vaccines, we explored mRNA vaccines encoding membrane-anchored receptor-binding domain (RBD-TMs), each a fusion of a variant RBD, the transmembrane (TM) and cytoplasmic tail (CT) fragments of the SARS-CoV-2 spike protein. In naive mice, RBD-TM mRNA vaccines against ancestral SARS-CoV-2, Beta, Delta, Delta-plus, Kappa, Omicron BA.1 or BA.5, all induced strong humoral responses against the target RBD. Multiplex surrogate viral neutralization (sVNT) assays indicated broad neutralizing activity against a range of variant RBDs. In the setting of a heterologous boost, against the background of exposure to ancestral whole spike vaccines, sVNT studies suggested that RBD-TM vaccines were able to overcome the detrimental effects of immune imprinting. Omicron BA.1 and BA.5 RBD-TM booster vaccines induced serum antibodies with 12 and 22-fold higher neutralizing activity against the target RBD than their equivalent whole spike variants. Boosting with BA.1 or BA.5 RBD-TM provided good protection against more recent variants including XBB and XBB.1.5. Each RBD-TM mRNA is 28% of the length of its whole-spike equivalent. This advantage will enable tetravalent mRNA vaccines to be developed at well-tolerated doses of formulated mRNA. One Sentence SummarymRNA vaccines encoding membrane-anchored RBDs of SARS-CoV-2 mutants are effective vaccines that can overcome immune imprinting in mice

immunology↗

bioRxiv2023

Multi-omic analysis of bat versus human fibroblasts reveals altered central metabolism

Bats have unique characteristics compared to other mammals, including increased longevity and higher resistance to cancer and infectious disease. While previous studies have analyzed the metabolic requirements for flight, it is still unclear how bat metabolism supports these unique features, and no study has integrated metabolomics, transcriptomics, and proteomics to characterize bat metabolism. In this work, we performed a multi-omics data analysis using a computational model of metabolic fluxes to identify fundamental differences in central metabolism between primary lung fibroblast cell lines from the black flying fox fruit bat (Pteropus alecto) and human. Bat cells showed higher expression levels of Complex I components of electron transport chain (ETC), but, remarkably, a lower rate of oxygen consumption (OCR). Computational modeling interpreted these results as indicating that Complex II activity may be low or reversed, similar to an ischemic state. An ischemic-like state of bats was also supported by decreased levels of central metabolites and increased ratios of succinate to fumarate in bat cells. Ischemic states tend to produce reactive oxygen species (ROS), which would be incompatible with the longevity of bats. However, bat cells had higher antioxidant reservoirs (higher total glutathione and higher ratio of NADPH to NADP) despite higher mitochondrial ROS levels. In addition, bat cells were more resistant to glucose deprivation and had increased resistance to ferroptosis, one of the characteristics of which is oxidative stress. Thus, our studies revealed distinct differences in the ETC regulation and metabolic stress responses between human and bat cells.

systems biology↗

bioRxiv2022

Mucosal vaccination for SARS-CoV-2 elicits superior systemic T central memory function and cross-neutralizing antibodies against variants of concern

COVID-19 vaccines used in humans are highly effective in limiting disease and death caused by the SARS-CoV-2 virus, yet improved vaccines that provide greater protection at mucosal surfaces, which could reduce break-through infections and subsequent transmission, are still needed. Here we show that intranasal (I.N.) vaccination with the receptor binding domain of Spike antigen of SARS-CoV-2 (S-RBD) in combination with the mucosal adjuvant mastoparan-7 improved systemic T cell responses compared to an equivalent dose of antigen delivered by the sub-cutaneous (S.C.) route, adjuvanted by either M7 or the gold-standard adjuvant, alum. T cell phenotypes induced by I.N. vaccine administration included enhanced polyfunctionality (combined IFN-{gamma} and TNF expression) and greater numbers of T central memory (TCM) cells. These phenotypes were T cell-intrinsic and could be recalled in the lungs and/or brachial LNs upon antigen challenge after adoptive T cell transfer to naive recipients. Furthermore, mucosal vaccination induced antibody responses that were similarly effective in neutralizing the binding of the parental strain of S-RBD to its ACE2 receptor, but showed greater cross-neutralizing capacity against multiple variants of concern (VOC), compared to S.C. vaccination. These results highlight the role of nasal vaccine administration in imprinting an immune profile associated with long-term T cell retention and diversified neutralizing antibody responses, which could be applied to improve vaccines for COVID-19 and other infectious diseases.

immunology↗

bioRxiv2021

E3 ligase TRIM47 positively regulates endothelial activation and pulmonary inflammation through potentiating the K63-linked ubiquitination

Endothelial activation plays an essential role in the pathology of sepsis-induced acute lung injury, but the detailed regulatory mechanisms remain largely unknown. Here, we demonstrated that TRIM47, an ubiquitin E3 ligase of tripartite protein family, is highly expressed in vascular endothelial cells and is up-regulated during TNF-induced endothelial activation. Knockdown of TRIM47 in endothelial cells prevents the transcription of multiple pro-inflammatory cytokines, reduces monocyte adhesion and the expression of adhesion molecules, and inhibits the secretion of IL-1{beta} and IL-6 into the supernatant. By contrast, overexpression of TRIM47 promotes inflammatory response and monocyte adhesion upon TNF stimulation. TRIM47 modulates the activation of NF-{kappa}B and MAPK signaling pathways during endothelial activation. Further experiment confirmed that TRIM47 interacts with TRAF2 and mediates K63-linked ubiquitination. In addition, TRIM47-deficient mice are more resistant to lipopolysaccharide-induced acute lung injury and death, due to attenuated pulmonary inflammation. Taken together, our studies suggest that TRIM47 promotes pulmonary inflammation and injury at least partly through potentiating the K63-linked ubiquitination of TRAF2, which in turn activates NF-{kappa}B and MAPK signaling pathways to trigger inflammatory response in endothelial cells.

cell biology↗

bioRxiv2021

Rapid determination of the wide dynamic range of SARS-CoV-2 Spike T cell responses in whole blood of vaccinated and naturally infected

BackgroundAntibodies and T cells cooperate to control virus infections. The definition of the correlates of protection necessary to manage the COVID-19 pandemic, require both immune parameters but the complexity of traditional tests limits virus-specific T cell measurements. MethodsWe test the sensitivity and performance of a simple and rapid SARS-CoV-2 Spike-specific T cell test based on stimulation of whole blood with peptides covering the SARS-CoV-2 Spike protein followed by cytokine (IFN-{gamma}, IL-2) measurement in different cohorts including BNT162b2 vaccinated (n=112; 201 samples), convalescent asymptomatic (n=62; 62 samples) and symptomatic (n=68; 115 samples) COVID-19 patients and SARS-CoV-1 convalescent individuals (n=12; 12 samples). ResultsThe sensitivity of the rapid cytokine whole blood test equates traditional methods of T cell analysis (ELISPOT, Activation Induced Markers). Utilizing this test we observed that Spike-specific T cells in vaccinated preferentially target the S2 region of Spike and that their mean magnitude is similar between them and SARS-CoV-2 convalescents at 3 months after vaccine or virus priming respectively. However, a wide heterogeneity of Spike-specific T cell magnitude characterizes the individual responses irrespective of the time of analysis. No correlation between neutralizing antibody levels and Spike-specific T cell magnitude were found. ConclusionsRapid measurement of cytokine production in whole blood after peptide activation revealed a wide dynamic range of Spike-specific T cell response after vaccination that cannot be predicted from neutralizing antibody quantities. Both Spike-specific humoral and cellular immunity should be tested after vaccination to define the correlates of protection necessary to evaluate current vaccine strategies.

immunology↗

bioRxiv2021

A species-specific signature residue in the PB2 subunit of the bat influenza virus polymerase restricts viral RNA synthesis.

Bat influenza A viruses (H17N10 and H18N11) are genetically distant from conventional influenza A viruses and replicates poorly in non-bat hosts species. However, the reason behind the lower replication fitness of these viruses are yet to be elucidated. In this work, we have identified species-specific signature residues, present in viral PB2 protein, which is a major determinant of polymerase fitness in human, avian and bat cell lines. Through extensive sequence and structural comparison between the bat and non-bat influenza virus RNA polymerases, we have identified a previously uncharacterized PB2-282 residue, which is serine in bat virus PB2 protein but harbours highly conserved glutamic acid in conventional influenza A viruses. Introduction of these bat specific signatures in the polymerase of a human adapted strain of influenza A/H1N1 virus drastically reduces its polymerase activity and replication efficiency in cell lines of human, bat and canine origin. In contrast, introduction of the human specific signatures in bat virus PB2 (H17N10), significantly enhances its function in the context of a chimeric RNA polymerase. Interestingly, the PB2-282 resides within an evolutionary conserved "S-E-S" motif present across different genera of influenza viruses but is replaced with a "S-S-T" motif in bat influenza viruses, indicating that this E to S transition may serve as a species-specific adaptation signature that modulates the activity of bat virus polymerase in other host species. ImportanceRecent isolation of influenza A like viruses (H17N10 and H18N11) in bats raised concerns about their potential of zoonotic transmission in human. Here we present species-specific signature residues present in the bat influenza virus polymerase, which may act as critical modulators of bat virus propagation in non-bat host species. We utilize bioinformatics based comparative analysis followed by functional screening in order to identify the PB2-282nd position, which harbors a highly conserved glutamic acid in conventional influenza A viruses, but contains an unusual serine in case of bat influenza viruses. Human adapted polymerase, harboring bat specific signature (PB2-S282) performs poorly, while bat PB2 protein harboring human specific signature (PB2-E282) shows increased fitness in human cells. Together, our data identifies novel species-specific signatures present within the influenza virus polymerase that may serve as a key factor in the adaptation of influenza viruses from bat to non-bat host species and vice versa.

microbiology↗

bioRxiv2021

Comprehensive mapping of SARS-CoV-2 interactions in vivo reveals functional virus-host interactions

SARS-CoV-2 has emerged as a major threat to global public health, resulting in global societal and economic disruptions. Here, we investigate the intramolecular and intermolecular RNA interactions of wildtype (WT) and a mutant ({Delta}382) SARS-CoV-2 virus in cells using high throughput structure probing on Illumina and Nanopore platforms. We identified twelve potentially functional structural elements within the SARS-CoV-2 genome, observed that identical sequences can fold into divergent structures on different subgenomic RNAs, and that WT and {Delta}382 virus genomes can fold differently. Proximity ligation sequencing experiments identified hundreds of intramolecular and intermolecular pair-wise interactions within the virus genome and between virus and host RNAs. SARS-CoV-2 binds strongly to mitochondrial and small nucleolar RNAs and is extensively 2-O-methylated. 2-O-methylation sites in the virus genome are enriched in the untranslated regions and are associated with increased pair-wise interactions. SARS-CoV-2 infection results in a global decrease of 2-O-methylation sites on host mRNAs, suggesting that binding to snoRNAs could be a pro-viral mechanism to sequester methylation machinery from host RNAs towards the virus genome. Collectively, these studies deepen our understanding of the molecular basis of SARS-CoV-2 pathogenicity, cellular factors important during infection and provide a platform for targeted therapy.

genomics↗

bioRxiv2020

Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection

The efficacy of virus-specific T cells in clearing pathogens involves a fine balance between their antiviral and inflammatory features. SARS-CoV-2-specific T cells in individuals who clear SARS-CoV-2 infection without symptoms or disease could reveal non-pathological yet protective characteristics. We therefore compared the quantity and function of SARS-CoV-2-specific T cells in a cohort of asymptomatic individuals (n=85) with that of symptomatic COVID-19 patients (n=76), at different time points after antibody seroconversion. We quantified T cells reactive to structural proteins (M, NP and Spike) using ELISpot assays, and measured the magnitude of cytokine secretion (IL-2, IFN-{gamma}, IL-4, IL-6, IL-1{beta}, TNF- and IL-10) in whole blood following T cell activation with SARS-CoV-2 peptide pools as a functional readout. Frequencies of T cells specific for the different SARS-CoV-2 proteins in the early phases of recovery were similar between asymptomatic and symptomatic individuals. However, we detected an increased IFN-{gamma} and IL-2 production in asymptomatic compared to symptomatic individuals after activation of SARS-CoV-2-specific T cells in blood. This was associated with a proportional secretion of IL-10 and pro-inflammatory cytokines (IL-6, TNF- and IL-1{beta}) only in asymptomatic infection, while a disproportionate secretion of inflammatory cytokines was triggered by SARS-CoV-2-specific T cell activation in symptomatic individuals. Thus, asymptomatic SARS-CoV-2 infected individuals are not characterized by a weak antiviral immunity; on the contrary, they mount a robust and highly functional virus-specific cellular immune response. Their ability to induce a proportionate production of IL-10 might help to reduce inflammatory events during viral clearance.

immunology↗

bioRxiv2020

Early induction of SARS-CoV-2 specific T cells associates with rapid viral clearance and mild disease in COVID-19 patients

Virus-specific humoral and cellular immunity act synergistically to protect the host from viral infection. We interrogated the dynamic changes of virological and immunological parameters in 12 patients with symptomatic acute SARS-CoV-2 infection from disease onset to convalescence or death. We quantified SARS-CoV-2 viral RNA in the respiratory tract in parallel with antibodies and circulating T cells specific for various structural (NP, M, ORF3a and spike) and non-structural proteins (ORF7/8, NSP7 and NSP13). We observed that while rapid induction and quantity of humoral responses were associated with increased disease severity, an early induction of SARS-CoV-2 specific T cells was present in patients with mild disease and accelerated viral clearance. These findings provide further support for a protective role of SARS-CoV-2 specific T cells over antibodies during SARS-CoV-2 infection with important implications in vaccine design and immune-monitoring.

immunology↗

bioRxiv2020

Age and gender dependence of liver diffusion parameters and the evidence of intravoxel incoherent motion modelling of perfusion component is constrained by diffusion component.

ObjectivesTo establish reference values for middle aged subjects and investigate age and gender dependence of liver diffusion MRI parameters. MethodsThe IVIM type of liver diffusion scan was based on a single-shot spin-echo type echo-planar sequence using a 1.5-T magnet with 16 b-values. DDVD (diffusion-derived vessel density) was the signal difference between b=0 and b=2 s/mm2 images after removing visible vessels. IVIM analysis was performed with full-fitting and segmented-fitting, and with threshold b-value of 60 or 200 s/mm2, and fitting started from b=2 s/mm2. 32 men (age range: 25-71 years) and 26 men (age: 22-69 years) had DDVD and IVIM analysis respectively, while 36 women (age: 20-71 years) had DDVD and IVIM analysis. ResultsDDVD had an age-related reduction noted for women. IVIM results of full fitting had good agreement with segmented fitting with threshold b of 60 s/mm2 results, but less so with results of threshold b of 200 s/mm2. As age increases, female subjects Dslow measure had significant reduction, and PF and Dfast measure had significant increase. For the age group of 40-55 years, DDVD, Dslow, PF, and Dfast were 12.27{+/-}3.90, 1.072{+/-}0.067 (10-3mm2/s), 0.141{+/-}0.025, 61.0{+/-}14.0 (10-3mm2/s), and 13.4{+/-}3.6, 1.069{+/-}0.074 mm2/s, 0.119{+/-}0.014, 57.1{+/-}13.2 mm2/s, for men and women, respectively. ConclusionDDVD measure suggest that aging may be associated with reduction in liver perfusion. Lower Dslow measurement can lead to artificial higher PF and Dfast measurement, providing the evidence of IVIM modeling of perfusion component is constrained by diffusion component.

biophysics↗

bioRxiv2020

Origin and cross-species transmission of bat coronaviruses in China

Bats are presumed reservoirs of diverse coronaviruses (CoVs) including progenitors of Severe Acute Respiratory Syndrome (SARS)-CoV and SARS-CoV-2, the causative agent of COVID-19. However, the evolution and diversification of these coronaviruses remains poorly understood. We used a Bayesian statistical framework and sequence data from all known bat-CoVs (including 630 novel CoV sequences) to study their macroevolution, cross-species transmission, and dispersal in China. We find that host-switching was more frequent and across more distantly related host taxa in alpha-than beta-CoVs, and more highly constrained by phylogenetic distance for beta-CoVs. We show that inter-family and -genus switching is most common in Rhinolophidae and the genus Rhinolophus. Our analyses identify the host taxa and geographic regions that define hotspots of CoV evolutionary diversity in China that could help target bat-CoV discovery for proactive zoonotic disease surveillance. Finally, we present a phylogenetic analysis suggesting a likely origin for SARS-CoV-2 in Rhinolophus spp. bats.

evolutionary biology↗

bioRxiv2020

Different pattern of pre-existing SARS-COV-2 specific T cell immunity in SARS-recovered and uninfected individuals

Memory T cells induced by previous infections can influence the course of new viral infections. Little is known about the pattern of SARS-CoV-2 specific pre-existing memory T cells in human. Here, we first studied T cell responses to structural (nucleocapsid protein, NP) and non-structural (NSP-7 and NSP13 of ORF1) regions of SARS-CoV-2 in convalescent from COVID-19 (n=24). In all of them we demonstrated the presence of CD4 and CD8 T cells recognizing multiple regions of the NP protein. We then show that SARS-recovered patients (n=23), 17 years after the 2003 outbreak, still possess long-lasting memory T cells reactive to SARS-NP, which displayed robust cross-reactivity to SARS-CoV-2 NP. Surprisingly, we observed a differential pattern of SARS-CoV-2 specific T cell immunodominance in individuals with no history of SARS, COVID-19 or contact with SARS/COVID-19 patients (n=18). Half of them (9/18) possess T cells targeting the ORF-1 coded proteins NSP7 and 13, which were rarely detected in COVID-19- and SARS-recovered patients. Epitope characterization of NSP7-specific T cells showed recognition of protein fragments with low homology to "common cold" human coronaviruses but conserved among animal betacoranaviruses. Thus, infection with betacoronaviruses induces strong and long-lasting T cell immunity to the structural protein NP. Understanding how pre-existing ORF-1-specific T cells present in the general population impact susceptibility and pathogenesis of SARS-CoV-2 infection is of paramount importance for the management of the current COVID-19 pandemic.

immunology↗

bioRxiv2020

Bats Possess Unique Variants of the Antiviral Restriction Factor Tetherin

Bats are recognised as important reservoirs of viruses deadly to other mammals, including humans. These infections are typically non-pathogenic in bats raising questions about host response differences that might exist between bats and other mammals. Tetherin is a restriction factor which inhibits the release of a diverse range of viruses from host cells, including retroviruses, coronaviruses, filoviruses, and paramyxoviruses, some of which are deadly to humans and transmitted by bats. Here we characterise the tetherin genes from 27 species of bats, revealing that they have evolved under strong selective pressure, and that fruit bats and vesper bats express unique structural variants of the tetherin protein. Tetherin was widely and variably expressed across fruit bat tissue-types and upregulated in spleen tissue when stimulated with Toll-like receptor agonists. The expression of two computationally predicted splice isoforms of fruit bat tetherin was verified. We identified an additional third unique splice isoform which includes a C-terminal region that is not homologous to known mammalian tetherin variants but was functionally capable of restricting the release of filoviral virus-like particles. We also report that vesper bats possess and express at least five tetherin genes, including structural variants, a greater number than any other mammal reported to date. These findings support the hypothesis of differential antiviral gene evolution in bats relative to other mammals.

evolutionary biology↗

bioRxiv2020

Orthogonal genome-wide screenings in bat cells identify MTHFD1 as a target of broad antiviral therapy

Bats are responsible for the zoonotic transmission of several major viral diseases including the 2003 SARS outbreak and the ongoing COVID-19 pandemic. While bat genomic sequencing studies have revealed characteristic adaptations of the innate immune system, functional genomic studies are urgently needed to provide a foundation for the molecular dissection of the tolerance of viral infections in bats. Here we report the establishment and screening of genome-wide RNAi library and CRISPR library for the model megabat, Pteropus Alecto. We used the complementary RNAi and CRISPR libraries to interrogate Pteropus Alecto cells for infection with two different viruses, mumps virus and Influenza A virus, respectively. Screening results converged on the endocytosis pathway and the protein secretory pathway as required for both viral infections. Additionally, we revealed a general dependence of the C-1-tetrahydrofolate synthase gene, MTHFD1, for viral replication in bat cells as well as in human cells. MTHFD1 inhibitor carolacton potently blocked replication of several RNA viruses including SARS-CoV-2. Our studies provide a resource for systematic inquiry into the genetic underpinnings of bat biology and a potential target for developing broad spectrum antiviral therapy.

microbiology↗

bioRxiv2020

Discovery of a 382-nt deletion during the early evolution of SARS-CoV-2

To date, the SARS-CoV-2 genome has been considered genetically more stable than SARS-CoV or MERS-CoV. Here we report a 382-nt deletion covering almost the entire open reading frame 8 (ORF8) of SARS-CoV-2 obtained from eight hospitalized patients in Singapore. The deletion also removes the ORF8 transcription-regulatory sequence (TRS), which in turn enhances the downstream transcription of the N gene. We also found that viruses with the deletion have been circulating for at least four weeks. During the SARS-CoV outbreak in 2003, a number of genetic variants were observed in the human population [1], and similar variation has since been observed across SARS-related CoVs in humans and bats. Overwhelmingly these viruses had mutations or deletions in ORF8, that have been associated with reduced replicative fitness of the virus [2]. This is also consistent with the observation that towards the end of the outbreak sequences obtained from human SARS cases possessed an ORF8 deletion that may be associated with host adaptation [1]. We therefore hypothesise that the major deletion revealed in this study may lead to an attenuated phenotype of SARS-CoV-2.

microbiology↗

bioRxiv2020

Human MAIT cell cytolytic effector proteins synergize to overcome carbapenem resistance in Escherichia coli

Mucosa-associated invariant T (MAIT) cells are abundant antimicrobial T cells in humans, and recognize antigens derived from the microbial riboflavin biosynthetic pathway presented by the MHC-Ib-related protein (MR1). However, the mechanisms responsible for MAIT cell antimicrobial activity are not fully understood, and the efficacy of these mechanisms against antibiotic resistant bacteria has not been explored. Here, we show that MAIT cells mediate MR1-restricted antimicrobial activity against E. coli clinical strains in a manner dependent on the activity of cytolytic proteins, but independent of production of pro-inflammatory cytokines or induction of apoptosis in infected cells. The combined action of the pore-forming antimicrobial protein granulysin and the serine protease granzyme B released in response to TCR-mediated recognition of MR1-presented antigen is essential to mediate control against both cell-associated and free-living E. coli. Furthermore, MAIT cell-mediated bacterial control extend to multidrug-resistant E. coli primary clinical isolates additionally resistant to carbapenems, a class of last resort antibiotics. Notably, high levels of granulysin and granzyme B in the MAIT cell secretomes directly damage bacterial cells by increasing their permeability, rendering initially resistant E. coli susceptible to the bactericidal activity of carbapenems. These findings define the role of cytolytic effector proteins in MAIT cell-mediated antimicrobial activity, and indicate that granulysin and granzyme B synergize to restore carbapenem bactericidal activity and overcome carbapenem resistance in E. coli. One Sentence SummaryPotent antimicrobial activity of human MAIT cells overcomes carbapenem-resistance in control of Escherichia coli

immunology↗