PLA2G12A protects against diet-induced obesity and insulin resistance by enhancing energy expenditure and clearance of circulating triglycerides.

Secreted phospholipase A2s are involved in the development of obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease, which have become serious and growing health concerns worldwide. Integration of genome-wide association study and gene co-expression networks analysis showed that the secreted phospholipase A2 group XIIA (PLA2G12A) may participate in hepatic lipids metabolism. Nevertheless, the role of PLA2G12A in lipid metabolism and its potential mechanism remain elusive. Here, we used AAV9 vector carrying human PLA2G12A gene to exogenously express hPLA2G12A in the liver of mice. We demonstrated that the overexpression of hPLA2G12A resulted in a significant decrease in serum lipid levels in wild-type mice fed with chow diet or high-fat diet (HFD). Moreover, hPLA2G12A treatment protected against diet-induced obesity and insulin resistance in mice fed a HFD. Notably, we found that hPLA2G12A treatment confers protection against obesity and hyperlipidemia independent of its enzymatic activity, but rather by increasing physical activity and energy expenditure. Furthermore, we demonstrated that hPLA2G12A treatment induced upregulation of ApoC2 and Cd36 and downregulation of Angptl8, which contributed to the increase in clearance of circulating triglycerides and hepatic uptake of fatty acids without affecting hepatic de novo lipogenesis, very low-density lipoprotein secretion, or intestinal lipid absorption. Our study highlights the potential of PLA2G12A gene therapy as a promising approach for treating obesity, insulin resistance and T2DM.

Secreted phospholipase PLA2G2E contributes to regulation of T cell immune response against influenza virus infection.

The involvement of secreted phospholipase A2s in respiratory diseases, such as asthma and respiratory viral infections, is well-established. However, the specific role of secreted phospholipase A2 group IIE (PLA2G2E) during influenza virus infection remains unexplored. Here, we investigated the role of PLA2G2E during H1N1 influenza virus infection using a targeted mouse model lacking Pla2g2e gene (Pla2g2e-/-). Our findings demonstrated that Pla2g2e-/- mice had significantly lower survival rates and higher viral loads in lungs compared to wild-type mice following influenza virus infection. While Pla2g2e-/- mice displayed comparable innate and humoral immune responses to influenza virus challenge, the animals showed impaired influenza-specific cellular immunity and reduced T cell-mediated cytotoxicity. This indicates that PLA2G2E is involved in regulating specific T cell responses during influenza virus infection. Furthermore, transgenic mice expressing the human PLA2G2E gene exhibited resistance to influenza virus infection along with enhanced influenza-specific cellular immunity and T cell-mediated cytotoxicity. Pla2g2e deficiency resulted in perturbation of lipid mediators in the lung and T cells, potentially contributing to its impact on the anti-influenza immune response. Taken together, these findings suggest that targeting PLA2G2E could hold potential as a therapeutic strategy for managing influenza virus infections.IMPORTANCEThe influenza virus is a highly transmissible respiratory pathogen that continues to pose a significant public health concern. It effectively evades humoral immune protection conferred by vaccines and natural infection due to its continuous viral evolution through the genetic processes of antigenic drift and shift. Recognition of conserved non-mutable viral epitopes by T cells may provide broad immunity against influenza virus. In this study, we have demonstrated that phospholipase A2 group IIE (PLA2G2E) plays a crucial role in protecting against influenza virus infection through the regulation of T cell responses, while not affecting innate and humoral immune responses. Targeting PLA2G2E could therefore represent a potential therapeutic strategy for managing influenza virus infection.

Neutralizing monoclonal antibodies protect against human adenovirus type 55 infection in transgenic mice and tree shrews.

Re-emerging human adenovirus type 55 (HAdV55) has become a significant threat to public health due to its widespread circulation and the association with severe pneumonia, but an effective anti-HAdV55 agent remains unavailable. Herein, we report the generation of macaque-derived, human-like monoclonal antibodies (mAbs) protecting against HAdV55 infection with high potency. Using fluorophore-labelled HAdV55 virions as probes, we isolated specific memory B cells from rhesus macaques (Macaca mulatta) that were immunized twice with an experimental vaccine based on E1-, E3-deleted, replication-incompetent HAdV55. We cloned a total of 19 neutralizing mAbs, nine of which showed half-maximal inhibitory concentrations below 1.0 ng/ml. These mAbs recognized the hyper-variable-region (HVR) 1, 2, or 7 of viral hexon protein, or the fibre knob. In transgenic mice expressing human desmoglein-2, the major cellular receptor for HAdV55, a single intraperitoneal injection with hexon-targeting mAbs efficiently prevented HAdV55 infection, and mAb 29C12 showed protection at a dose as low as 0.004 mg/kg. Fibre-targeting mAb 28E8, however, showed protection only at a dose up to 12.5 mg/kg. In tree shrews that are permissive for HAdV55 infection and disease, mAb 29C12 effectively prevented HAdV55-caused pneumonia. Further analysis revealed that fibre-targeting mAbs blocked the attachment of HAdV55 to host cells, whereas hexon-targeting mAbs, regardless of their targeting HVRs, mainly functioned at post-attachment stage via inhibiting viral endosomal escape. Our results indicate that hexon-targeting mAbs have great anti-HAdV55 activities and warrant pre-clinical and clinical evaluation.

Deep immunoglobulin repertoire sequencing depicts a comprehensive atlas of spike-specific antibody lineages shared among COVID-19 convalescents.

Neutralizing antibodies are a key component in protective humoral immunity against SARS-CoV-2. Currently, available technologies cannot track epitope-specific antibodies in global antibody repertoires. Thus, the comprehensive repertoire of spike-specific neutralizing antibodies elicited by SARS-CoV-2 infection is not fully understood. We therefore combined high-throughput immunoglobulin heavy chain (IgH) repertoire sequencing, and structural and bioinformatics analysis to establish an antibodyomics pipeline, which enables tracking spike-specific antibody lineages that target certain neutralizing epitopes. We mapped the neutralizing epitopes on the spike and determined the epitope-preferential antibody lineages. This analysis also revealed numerous overlaps between immunodominant neutralizing antibody-binding sites and mutation hotspots on spikes as observed so far in SARS-CoV-2 variants. By clustering 2677 spike-specific antibodies with 360 million IgH sequences that we sequenced, a total of 329 shared spike-specific antibody clonotypes were identified from 33 COVID-19 convalescents and 24 SARS-CoV-2-naïve individuals. Epitope mapping showed that the shared antibody responses target not only neutralizing epitopes on RBD and NTD but also non-neutralizing epitopes on S2. The immunodominance of neutralizing antibody response is determined by the occurrence of specific precursors in human naïve B-cell repertoires. We identified that only 28 out of the 329 shared spike-specific antibody clonotypes persisted for at least 12 months. Among them, long-lived IGHV3-53 antibodies are likely to evolve cross-reactivity to Omicron variants through accumulating somatic hypermutations. Altogether, we created a comprehensive atlas of spike-targeting antibody lineages in COVID-19 convalescents and antibody precursors in human naïve B cell repertoires, providing a valuable reference for future vaccine design and evaluation.

Arsenic trioxide-induced apoptosis contributes to suppression of viral reservoir in SIV-infected rhesus macaques.

Latent viral reservoir is recognized as the major obstacle to achieving a functional cure for HIV infection. We previously reported that arsenic trioxide (As2O3) combined with antiretroviral therapy (ART) can reactivate the viral reservoir and delay viral rebound after ART interruption in chronically simian immunodeficiency virus (SIV)-infected macaques. In this study, we further investigated the effect of As2O3 independent of ART in chronically SIV-infected macaques. We found that As2O3-only treatment significantly increased the CD4/CD8 ratio, improved SIV-specific T cell responses, and reactivated viral latency in chronically SIVmac239-infected macaques. RNA-sequencing analysis revealed that As2O3 treatment downregulated the expression levels of genes related to HIV entry and infection, while the expression levels of genes related to transcription initiation, cell apoptosis, and host restriction factors were significantly upregulated. Importantly, we found that As2O3 treatment specifically induced apoptosis of SIV-infected CD4+ T cells. These findings revealed that As2O3 might not only impact viral latency, but also induce the apoptosis of HIV-infected cells and thus block the secondary infection of bystanders. Moreover, we investigated the therapeutic potential of this regimen in acutely SIVmac239-infected macaques and found that As2O3 + ART treatment effectively restored the CD4+ T cell count, delayed disease progression, and improved survival in acutely SIV-infected macaques. In sum, this work provides new insights to develop As2O3 as a component of the "shock-and-kill" strategy toward HIV functional cure. IMPORTANCE Although antiretroviral therapy (ART) can effectively suppress the viral load of AIDS patients, it cannot functionally cure HIV infection due to the existence of HIV reservoir. Strategies toward HIV functional cure are still highly anticipated to ultimately end the pandemic of AIDS. Herein, we investigated the direct role of As2O3 independent of ART in chronically SIV-infected macaques and explored the underlying mechanisms of the potential of As2O3 in the treatment of HIV/SIV infection. Meanwhile, we investigated the therapeutic effects of ART+As2O3 in acutely SIVmac239-infected macaques. This study showed that As2O3 has the potential to be launched into the "shock-and-kill" strategy to suppress HIV/SIV reservoir due to its latency-reversing and apoptosis-inducing properties.

SARS-CoV-2 induces cardiomyocyte apoptosis and inflammation but can be ameliorated by ACE inhibitor Captopril.

Although the clinical manifestation of COVID-19 is mainly respiratory symptoms, approximately 20% of patients suffer from cardiac complications. COVID-19 patients with cardiovascular disease have higher severity of myocardial injury and poor outcomes. The underlying mechanism of myocardial injury caused by SARS-CoV-2 infection remains unclear. Using a non-transgenic mouse model infected with Beta variant (B.1.351), we found that the viral RNA could be detected in lungs and hearts of infected mice. Pathological analysis showed thinner ventricular wall, disorganized and ruptured myocardial fiber, mild inflammatory infiltration, and mild epicardia or interstitial fibrosis in hearts of infected mice. We also found that SARS-CoV-2 could infect cardiomyocytes and produce infectious progeny viruses in human pluripotent stem cell-derived cardiomyocyte-like cells (hPSC-CMs). SARS-CoV-2 infection caused apoptosis, reduction of mitochondrial integrity and quantity, and cessation of beating in hPSC-CMs. In order to dissect the mechanism of myocardial injury caused by SARS-CoV-2 infection, we employed transcriptome sequencing of hPSC-CMs at different time points after viral infection. Transcriptome analysis showed robust induction of inflammatory cytokines and chemokines, up-regulation of MHC class I molecules, activation of apoptosis signaling and cell cycle arresting. These may cause aggravate inflammation, immune cell infiltration, and cell death. Furthermore, we found that Captopril (hypotensive drugs targeting ACE) treatment could alleviate SARS-CoV-2 induced inflammatory response and apoptosis in cardiomyocytes via inactivating TNF signaling pathways, suggesting Captopril may be beneficial for reducing COVID-19 associated cardiomyopathy. These findings preliminarily explain the molecular mechanism of pathological cardiac injury caused by SARS-CoV-2 infection, providing new perspectives for the discovery of antiviral therapeutics.

Intranasal booster using an Omicron vaccine confers broad mucosal and systemic immunity against SARS-CoV-2 variants.

The highly contagious SARS-CoV-2 Omicron subvariants severely attenuated the effectiveness of currently licensed SARS-CoV-2 vaccines based on ancestral strains administered via intramuscular injection. In this study, we generated a recombinant, replication-incompetent human adenovirus type 5, Ad5-S-Omicron, that expresses Omicron BA.1 spike. Intranasal, but not intramuscular vaccination, elicited spike-specific respiratory mucosal IgA and residential T cell immune responses, in addition to systemic neutralizing antibodies and T cell immune responses against most Omicron subvariants. We tested intranasal Ad5-S-Omicron as a heterologous booster in mice that previously received intramuscular injection of inactivated ancestral vaccine. In addition to inducing serum broadly neutralizing antibodies, there was a significant induction of respiratory mucosal IgA and neutralizing activities against Omicron subvariants BA.1, BA.2, BA.5, BA.2.75, BF.7 as well as pre-Omicron strains Wildtype, Beta, and Delta. Serum and mucosal neutralizing activities against recently emerged XBB, BQ.1, and BQ.1.1 could also be detected but were much lower. Nasal lavage fluids from intranasal vaccination contained multimeric IgA that can bind to at least 10 spike proteins, including Omicron subvariants and pre-Omicron strains, and possessed broadly neutralizing activities. Intranasal vaccination using Ad5-S-Omicron or instillation of intranasal vaccinee's nasal lavage fluids in mouse nostrils protected mice against Omicron challenge. Taken together, intranasal Ad5-S-Omicron booster on the basis of ancestral vaccines can establish effective mucosal and systemic immunity against Omicron subvariants and multiple SARS-CoV-2 variants. This candidate vaccine warrants further development as a safe, effective, and user-friendly infection and transmission-blocking vaccine.

ERRγ-DBD undergoes dimerization and conformational rearrangement upon binding to the downstream site of the DR1 element.

The estrogen-related receptor (ERR) family members are reported to bind DNA elements as either monomer or dimer. However, to date, only one solution NMR structure of ERRß in complex with a half-site DNA element has been reported. To better understand the DNA regulation mechanism, we determined the crystal structure of ERRγ-DBD bound to a natural DR1 element in Pla2g12b promoter to 2.2 Å resolution. Combined with biochemical assays, we show that ERRγ acts as a dimer and the C-terminal extension region undergoes conformational rearrangement when binding to the downstream DR1 element. In addition, the T-box region on the dimerization interface exhibits unique main-chain conformation. Thus, our structure presents a novel dimer interface for NR binding on DR1 DNA and provides a molecular basis for understanding the homodimer organization of ERR on DR1 elements.

Booster vaccination is required to elicit and maintain COVID-19 vaccine-induced immunity in SIV-infected macaques.

ABSTRACTProlonged infection and possible evolution of SARS-CoV-2 in patients living with uncontrolled HIV-1 infection highlight the importance of an effective vaccination regimen, yet the immunogenicity of COVID-19 vaccines and predictive immune biomarkers have not been well investigated. Herein, we report that the magnitude and persistence of antibody and cell-mediated immunity (CMI) elicited by an Ad5-vectored COVID-19 vaccine are impaired in SIV-infected macaques with high viral loads (> 105 genome copies per ml plasma, SIVhi) but not in macaques with low viral loads (< 105, SIVlow). After a second vaccination, the immune responses are robustly enhanced in all uninfected and SIVlow macaques. These responses also show a moderate increase in 70% SIVhi macaques but decline sharply soon after. Further analysis reveals that decreased antibody and CMI responses are associated with reduced circulating follicular helper T cell (TFH) counts and aberrant CD4/CD8 ratios, respectively, indicating that dysregulation of CD4+ T cells by SIV infection impairs the COVID-19 vaccine-induced immunity. Ad5-vectored COVID-19 vaccine shows no impact on SIV loads or SIV-specific CMI responses. Our study underscores the necessity of frequent booster vaccinations in HIV-infected patients and provides indicative biomarkers for predicting vaccination effectiveness in these patients.

Analysis of B Cell Receptor Repertoires Reveals Key Signatures of the Systemic B Cell Response after SARS-CoV-2 Infection.

A comprehensive study of the B cell response against SARS-CoV-2 could be significant for understanding the immune response and developing therapeutical antibodies and vaccines. To define the dynamics and characteristics of the antibody repertoire following SARS-CoV-2 infection, we analyzed the mRNA transcripts of immunoglobulin heavy chain (IgH) repertoires of 24 peripheral blood samples collected between 3 and 111 days after symptom onset from 10 COVID-19 patients. Massive clonal expansion of naive B cells with limited somatic hypermutation (SHM) was observed in the second week after symptom onset. The proportion of low-SHM IgG clones strongly correlated with spike-specific IgG antibody titers, highlighting the significant activation of naive B cells in response to a novel virus infection. The antibody isotype switching landscape showed a transient IgA surge in the first week after symptom onset, followed by a sustained IgG elevation that lasted for at least 3 months. SARS-CoV-2 infection elicited poly-germ line reactive antibody responses. Interestingly, 17 different IGHV germ line genes recombined with IGHJ6 showed significant clonal expansion. By comparing the IgH repertoires that we sequenced with the 774 reported SARS-CoV-2-reactive monoclonal antibodies (MAbs), 13 shared spike-specific IgH clusters were found. These shared spike-specific IgH clusters are derived from the same lineage of several recently published neutralizing MAbs, including CC12.1, CC12.3, C102, REGN10977, and 4A8. Furthermore, identical spike-specific IgH sequences were found in different COVID-19 patients, suggesting a highly convergent antibody response to SARS-CoV-2. Our analysis based on sequencing antibody repertoires from different individuals revealed key signatures of the systemic B cell response induced by SARS-CoV-2 infection. IMPORTANCE Although the canonical delineation of serum antibody responses following SARS-CoV-2 infection has been well established, the dynamics of antibody repertoire at the mRNA transcriptional level has not been well understood, especially the correlation between serum antibody titers and the antibody mRNA transcripts. In this study, we analyzed the IgH transcripts and characterized the B cell clonal expansion and differentiation, isotype switching, and somatic hypermutation in COVID-19 patients. This study provided insights at the repertoire level for the B cell response after SARS-CoV-2 infection.

Germline IGHV3-53-encoded RBD-targeting neutralizing antibodies are commonly present in the antibody repertoires of COVID-19 patients.

Monoclonal antibodies (mAbs) encoded by IGHV3-53 (VH3-53) targeting the spike receptor-binding domain (RBD) have been isolated from different COVID-19 patients. However, the existence and prevalence of shared VH3-53-encoded antibodies in the antibody repertoires is not clear. Using antibody repertoire sequencing, we found that the usage of VH3-53 increased after SARS-CoV-2 infection. A highly shared VH3-53-J6 clonotype was identified in 9 out of 13 COVID-19 patients. This clonotype was derived from convergent gene rearrangements with few somatic hypermutations and was evolutionary conserved. We synthesized 34 repertoire-deduced novel VH3-53-J6 heavy chains and paired with a common IGKV1-9 light chain to produce recombinant mAbs. Most of these recombinant mAbs (23/34) possess RBD binding and virus-neutralizing activities, and recognize ACE2 binding site via the same molecular interface. Our computational analysis, validated by laboratory experiments, revealed that VH3-53 antibodies targeting RBD are commonly present in COVID-19 patients' antibody repertoires, indicating many people have germline-like precursor sequences to rapidly generate SARS-CoV-2 neutralizing antibodies. Moreover, antigen-specific mAbs can be digitally obtained through antibody repertoire sequencing and computational analysis.

Longitudinal Peripheral Blood Transcriptional Analysis Reveals Molecular Signatures of Disease Progression in COVID-19 Patients.

Coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with some patients developing severe illness or even death. Disease severity has been associated with increased levels of proinflammatory cytokines and lymphopenia. To elucidate the atlas of peripheral immune response and pathways that might lead to immunopathology during COVID-19 disease course, we performed a peripheral blood RNA sequencing analysis of the same patient's samples collected from symptom onset to full recovery. We found that PBMCs at different disease stages exhibited unique transcriptome characteristics. We observed that SARS-CoV-2 infection caused excessive release of inflammatory cytokines and lipid mediators as well as an aberrant increase of low-density neutrophils. Further analysis revealed an increased expression of RNA sensors and robust IFN-stimulated genes expression but a repressed type I IFN production. SARS-CoV-2 infection activated T and B cell responses during the early onset but resulted in transient adaptive immunosuppression during severe disease state. Activation of apoptotic pathways and functional exhaustion may contribute to the reduction of lymphocytes and dysfunction of adaptive immunity, whereas increase in IL2, IL7, and IL15 may facilitate the recovery of the number and function of lymphocytes. Our study provides comprehensive transcriptional signatures of peripheral blood response in patients with moderate COVID-19.

A Live-Attenuated Zika Virus Vaccine with High Production Capacity Confers Effective Protection in Neonatal Mice.

Zika virus (ZIKV) infection during pregnancy has been linked to congenital abnormalities, such as microcephaly in infants. An efficacious vaccine is desirable for preventing the potential recurrence of ZIKV epidemic. Here, we report the generation of an attenuated ZIKV (rGZ02a) that has sharply decreased virulence in mice but grows to high titers in Vero cells, a widely approved cell line for manufacturing human vaccines. Compared to the wild-type ZIKV (GZ02) and a plasmid-launched rGZ02p, rGZ02a has 3 unique amino acid alterations in the envelope (E, S304F), nonstructural protein 1 (NS1, R103K), and NS5 (W637R). rGZ02a is more sensitive to type I interferon than GZ02 and rGZ02p, and causes no severe neurological disorders in either wild-type neonatal C57BL/6 mice or type I interferon receptor knockout (Ifnar1-/-) C57BL/6 mice. Immunization with rGZ02a elicits robust inhibitory antibody responses with a certain long-term durability. Neonates born to the immunized dams are effectively protected against ZIKV-caused neurological disorders and brain damage. rGZ02a as a booster vaccine greatly improves the protective immunity primed by Ad2-prME, an adenovirus-vectored vaccine expressing ZIKV prM and E proteins. Our results illustrate that rGZ02a-induced maternal immunity can be transferred to the neonates and confer effective protection. Hence, rGZ02a may be developed as an alternative live-attenuated vaccine and warrants further evaluation. IMPORTANCE Zika virus (ZIKV), a mosquito-borne flavivirus that has caused global outbreaks since 2013, is associated with severe neurological disorders, such as Guillian-Barré syndrome in adults and microcephaly in infants. The ZIKV epidemic has gradually subsided, but a safe and effective vaccine is still desirable to prevent its potential recurrence, especially in countries of endemicity with competent mosquito vectors. Here, we describe a novel live-attenuated ZIKV, rGZ02a, that carries 3 unique amino acid alterations compared to the wild-type GZ02 and a plasmid-launched rGZ02p. The growth capacity of rGZ02a is comparable to GZ02 in Vero cells, but the pathogenicity is significantly attenuated in two mice models. Immunization with rGZ02a elicits robust inhibitory antibody responses in the dams and effectively protects their offspring against ZIKV disease. Importantly, in a heterologous prime-boost regimen, rGZ02a effectively boosts the protective immunity primed by an adenovirus-vectored vaccine. Thus, rGZ02a is a promising candidate for a live-attenuated ZIKV vaccine.

Monoclonal Antibodies against Zika Virus NS1 Protein Confer Protection via Fcγ Receptor-Dependent and -Independent Pathways.

Zika virus (ZIKV) infection during pregnancy causes congenital defects such as fetal microcephaly. Monoclonal antibodies (MAbs) against the nonstructural protein 1 (NS1) have the potential to suppress ZIKV pathogenicity without enhancement of disease, but the pathways through which they confer protection remain obscure. Here, we report two types of NS1-targeted human MAbs that inhibit ZIKV infection through distinct mechanisms. MAbs 3G2 and 4B8 show a better efficacy than MAb 4F10 in suppressing ZIKV infection in C57BL/6 neonatal mice. Unlike MAb 4F10 that mainly triggers antibody-dependent cell-mediated cytotoxicity (ADCC), MAbs 3G2 and 4B8 not only trigger ADCC but inhibit ZIKV infection without Fcγ receptor-bearing effector cells, possibly at postentry stages. Destroying the Fc-mediated effector function of MAbs 3G2 and 4B8 reduces but does not abolish their protective effects, whereas destroying the effector function of MAb 4F10 eliminates the protective effects, suggesting that MAbs 3G2 and 4B8 engage both Fcγ receptor-dependent and -independent pathways. Further analysis reveals that MAbs 3G2 and 4B8 target the N-terminal region of NS1 protein, whereas MAb 4F10 targets the C-terminal region, implying that the protective efficacy of an NS1-targeted MAb may be associated with its epitope recognition. Our results illustrate that NS1-targeted MAbs have multifaceted protective effects and provide insights for the development of NS1-based vaccines and therapeutics.IMPORTANCE Zika virus (ZIKV) is a mosquito-borne flavivirus that has been linked to congenital microcephaly during recent epidemics. No licensed antiviral drug or vaccine is available. Monoclonal antibodies (MAbs) against the nonstructural protein 1 (NS1) inhibit ZIKV pathogenicity but do not enhance the disease as envelope protein-targeted MAbs do. However, the protection mechanisms are not fully understood. Here, we show that in the presence or absence of Fcγ receptor-bearing effector cells, NS1-targeted human MAbs 3G2 and 4B8 inhibit ZIKV infection. Compared to MAb 4F10 that has no inhibitory effects without effector cells, 3G2 and 4B8 confer better protection in ZIKV-infected neonatal mice. Destroying the Fc-mediated effector function reduces but does not abolish the protection of 3G2 and 4B8, suggesting that they engage both Fcγ receptor-dependent and -independent pathways. The protective efficacy of NS1-targeted MAbs may be associated with their epitope recognition. Our findings will help to develop NS1-based vaccines and therapeutics.

Longitudinal Analysis of T and B Cell Receptor Repertoire Transcripts Reveal Dynamic Immune Response in COVID-19 Patients.

Severe COVID-19 is associated with profound lymphopenia and an elevated neutrophil to lymphocyte ratio. We applied a novel dimer avoidance multiplexed polymerase chain reaction next-generation sequencing assay to analyze T (TCR) and B cell receptor (BCR) repertoires. Surprisingly, TCR repertoires were markedly diminished during the early onset of severe disease but recovered during the convalescent stage. Monitoring TCR repertoires could serve as an indicative biomarker to predict disease progression and recovery. Panoramic concurrent assessment of BCR repertoires demonstrated isotype switching and a transient but dramatic early IgA expansion. Dominant B cell clonal expansion with decreased diversity occurred following recovery from infection. Profound changes in T cell homeostasis raise critical questions about the early events in COVID-19 infection and demonstrate that immune repertoire analysis is a promising method for evaluating emergent host immunity to SARS-CoV-2 viral infection, with great implications for assessing vaccination and other immunological therapies.

Dysfunction of estrogen-related receptor alpha-dependent hepatic VLDL secretion contributes to sex disparity in NAFLD/NASH development.

Rationale: Men and postmenopausal women are more prone to developing non-alcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) than premenopausal women. However, the pathological links and underlying mechanisms of this disparity are still elusive. The sex-difference in hepatic very low-density lipoprotein (VLDL) assembly and secretion may contribute to NAFLD development. Estrogen-related receptor alpha (ERRα) is a key regulator of several metabolic processes. We hypothesized that ERRα plays a role contributing to the sex-difference in hepatic VLDL assembly and secretion. Methods: VLDL secretion and essential genes governing said process were assessed in male and female mice. Liver-specific ERRα-deficient (ERRαLKO) mice were generated to assess the rate of hepatic VLDL secretion and alteration in target gene expression. Overexpression of either microsomal triglyceride transfer protein (Mttp) or phospholipase A2 G12B (Pla2g12b) by adenovirus was performed to test if the fatty liver phenotype in male ERRαLKO mice was due to defects in hepatic VLDL secretion. Female ERRαLKO mice were put on a diet high in saturated fat, fructose and cholesterol (HFHC) to promote NASH development. Wild type female mice were either ovariectomized or treated with tamoxifen to induce a state of estrogen deficiency or disruption in estrogen signaling. Adenovirus was used to overexpress ERRα in these mice to test if ERRα was sufficient to rescue the suppressed VLDL secretion due to estrogen dysfunction. Finally, wild type male mice on a high-fat diet (HFD) were treated with an ERRα inverse agonist to assess if suppressing ERRα activity pharmacologically would lead to fatty liver development. Results: ERRα is an indispensable mediator modulating hepatic triglyceride-rich very low-density lipoprotein (VLDL-TG) assembly and secretion through coordinately controlling target genes apolipoprotein B (Apob), Mttp and Pla2g12b in a sex-different manner. Hepatic VLDL-TG secretion is blunted in ERRαLKO mice, leading to hepatosteatosis which exacerbates endoplasmic reticulum stress and inflammation paving ways for NASH development. Importantly, ERRα acts downstream of estrogen/ERα signaling in contributing to the sex-difference in hepatic VLDL secretion effecting hepatic lipid homeostasis. Conclusions: Our results highlight ERRα as a key mediator which contributes to the sex disparity in NAFLD development, suggesting that selectively restoring ERRα activity in the liver may be a novel strategy for treating NAFLD/NASH.

Human Desmoglein-2 and Human CD46 Mediate Human Adenovirus Type 55 Infection, but Human Desmoglein-2 Plays the Major Roles.

Human adenovirus type 55 (HAdV55) represents an emerging respiratory pathogen and causes severe pneumonia with high fatality in humans. The cellular receptors, which are essential for understanding the infection and pathogenesis of HAdV55, remain unclear. In this study, we found that HAdV55 binding and infection were sharply reduced by disrupting the interaction of viral fiber protein with human desmoglein-2 (hDSG2) but only slightly reduced by disrupting the interaction of viral fiber protein with human CD46 (hCD46). Loss-of-function studies using soluble receptors, blocking antibodies, RNA interference, and gene knockout demonstrated that hDSG2 predominantly mediated HAdV55 infection. Nonpermissive rodent cells became susceptible to HAdV55 infection when hDSG2 or hCD46 was expressed, but hDSG2 mediated more efficient HAd55 infection than hCD46. We generated two transgenic mouse lines that constitutively express either hDSG2 or hCD46. Although nontransgenic mice were resistant to HAdV55 infection, infection with HAdV55 was significantly increased in hDSG2+/+ mice but was much less increased in hCD46+/+ mice. Our findings demonstrate that both hDSG2 and hCD46 are able to mediate HAdV55 infection but hDSG2 plays the major roles. The hDSG2 transgenic mouse can be used as a rodent model for evaluation of HAdV55 vaccine and therapeutics.IMPORTANCE Human adenovirus type 55 (HAdV55) has recently emerged as a highly virulent respiratory pathogen and has been linked to severe and even fatal pneumonia in immunocompetent adults. However, the cellular receptors mediating the entry of HAdV55 into host cells remain unclear, which hinders the establishment of HAdV55-infected animal models and the development of antiviral approaches. In this study, we demonstrated that human desmoglein-2 (hDSG2) plays the major roles during HAdV55 infection. Human CD46 (hCD46) could also mediate the infection of HAdV55, but the efficiency was much lower than for hDSG2. We generated two transgenic mouse lines that express either hDSG2 or hCD46, both of which enabled HAd55 infection in otherwise nontransgenic mice. hDSG2 transgenic mice enabled more efficient HAdV55 infection than hCD46 transgenic mice. Our study adds to our understanding of HAdV55 infection and provides an animal model for evaluating HAdV55 vaccines and therapeutics.

Longitudinal analysis of the antibody repertoire of a Zika virus-infected patient revealed dynamic changes in antibody response.

The Zika virus (ZIKV) is a mosquito-borne flavivirus that causes neonatal abnormalities and other disorders. Antibodies to the ZIKV envelope (E) protein can block infection. In this study, next-generation sequencing (NGS) of immunoglobulin heavy chain (IgH) mRNA transcripts was combined with single-cell PCR cloning of E-binding monoclonal antibodies for analysing antibody response in a patient from the early stages of infection to more than one year after the clearance of the virus. The patient's IgH repertoire 14 and 64 days after symptom onset showed dramatic dominant clonal expansion but low clonal diversity. IgH repertoire 6 months after disease-free status had few dominant clones but increased diversity. E-binding antibodies appeared abundantly in the repertoire during the early stages of infection but quickly declined after clearance of the virus. Certain VH genes such as VH5-10-1 and VH4-39 appeared to be preferentially enlisted for a rapid antibody response to ZIKV infection. Most of these antibodies require relatively few somatic hypermutations to acquire the ability to bind to the E protein, pointing to a possible mechanism for rapid defence against ZIKV infection. This study provides a unique and holistic view of the dynamic changes and characteristics of the antibody response to ZIKV infection.