Sonocatalytic therapy has emerged for efficient malignant tumor treatment due to its non-invasive characteristics, spatiotemporal precision, and deep tissue penetration capabilities. The defect engineering can improve charge carrier separation, and enhance reactive oxygen species (ROS) generation, but the current technological limitations in developing efficient hole trapping sites relative to electron traps still impose significant constraints on overall ROS production efficiency. In this work, the rational design of two-dimensional Fe-vacancy (FeV)-engineered FeOCl nanosheets (FeVOCl NSs) with iron vacancies enables simultaneous electron and hole (e--h+) trapping, which confers not only significantly enhanced sonocatalytic activity but also multienzyme-mimicking properties, including peroxidase-, oxidase-, and catalase-like activities. These capabilities collectively promote ROS generation, relieve tumor hypoxia, and reshape the tumor microenvironment. Density functional theory (DFT) calculations reveal that strategically engineered iron vacancies in FeVOCl NSs significantly improve ROS generation efficiency through facilitating charge carrier separation and increasing H2O2 adsorption capacity. This dual functionality under ultrasound (US) irradiation leads to efficient ROS-mediated activation of both apoptotic and pyroptotic cell death pathways in tumor cells, which achieve significant in vivo sonocatalytic tumor-eliminating capacity and efficacy across multiple cancer models, including hematologic and breast cancer. These findings highlight the essential role of strategic defect engineering coupled with enzyme-mimicking activity in optimizing sonocatalytic therapeutic outcomes for efficient cancer treatment.

To establish effective infection, viral pathogens employ diverse strategies through encoded proteins to interfere with host antiviral responses. While previous studies have predominantly focused on elucidating the mechanisms by which individual viral proteins regulate type I interferon (IFN) responses, this study presents the first demonstration that Japanese encephalitis virus (JEV)-encoded NS1 and NS4B proteins cooperatively target the TLR3 receptor signaling pathway to suppress IFN production. Here, we first discovered JEV-encoded multifunctional glycoprotein NS1, which inhibits TLR3-mediated IFN-β production by targeting TLR3 and TRIF. Mechanistically, NS1 interacts with these host factors and may induce their degradation via the autophagy pathway. Building on these findings, we further demonstrated that NS1 and NS4B act synergistically to suppress type I IFN production by enhancing TLR3 and TRIF degradation, thereby facilitating JEV replication. Structural simulation of the NS1-NS4B-TLR3 complex unveiled a dynamic mechanism that NS4B binding induces conformational changes in dimerized NS1, which leads to a tighter binding posture between NS1 and TLR3. Notably, NS4B binding expands the interface between NS1 and TLR3 by 1.5-fold that results in enhanced TLR3 degradation and downstream IFN-β suppression. Functional analysis confirmed that the C291/K293/R314 triple mutation in NS1 synergistically impairs TLR3 degradation. Collectively, using JEV as a model, this study reveals a novel mechanism by which two viral components can act synergistically to evade the host antiviral response. Given the common coexistence and functional interplay of viral-encoded proteins in naturally infected cells, this study establishes a framework for investigating cooperative interactions among multiple viral proteins. IMPORTANCE:Viruses evade host immunity through encoded viral proteins, while previous research has predominantly focused on single protein mechanisms. This study reveals a novel cooperative immune evasion strategy, demonstrating for the first time that Japanese encephalitis virus NS1 and NS4B proteins act synergistically to degrade the host's TLR3 and TRIF adaptor, thereby suppressing type I interferon production. Structural simulations show that NS4B induces conformational changes in NS1, enhancing its binding to TLR3 and accelerating its degradation. This work establishes a new paradigm for how multiple viral components can function cooperatively to subvert antiviral defenses. Given that viral proteins naturally coexist and interact, this study provides a crucial framework for investigating complex viral protein interplay, which is fundamental to understanding viral pathogenesis.

Porcine deltacoronavirus (PDCoV) is a globally distributed swine enteropathogenic virus that emerged in the last decade. A recent report of PDCoV infection in Haitian children also highlights potential public health implications. In this study, two monoclonal antibodies (mAbs), 1C2 and 5H5, were generated and showed high specificity for the PDCoV S protein. Both mAbs displayed high-titer neutralizing capabilities, suggesting their potential for passive immunotherapy. Epitope mapping revealed that the mAbs likely recognized conformational epitopes in the S1 subunit domains A and B of the native S protein, thereby blocking the interaction between the S1 receptor-binding domain and the cellular receptor, which could inhibit viral entry into host cells. This study offers new biological tools for PDCoV detection and lays the groundwork for the future development of porcine-specific antibodies for the prevention and treatment of PDCoV in piglets.

KP.3.1.1 became a dominant successor to JN.1 by the second half of 2024 but the intrinsic pathogenicity and virological feature of KP.3.1.1 remain incompletely understood. Here, we comprehensively evaluated the pathogenesis and characteristics of KP.3.1.1 in comparison to JN.1 and other JN.1-derived variants including JN.1.7, KP.2, and KP.3. The unique S31del mutation on KP.3.1.1 spike confers further evasion to the clinically authorized mAb Pemivibart and reduces convalescent serum neutralization efficiency. Structural analysis indicates that S31del induces novel glycosylation sites that facilitates evasion of neutralizing antibodies. We further reveal that S31del significantly enhances pseudovirus entry efficiency in all evaluated cell types including the human primary nasal epithelial cells. Nevertheless, the intrinsic pathogenicity of KP.3.1.1 is similar to JN.1 and KP.3, and higher than that of JN.1.7 and KP.2 in a male hamster model. Interestingly, the increased virus infectivity conferred by S31del in KP.3.1.1 spike is counterbalanced by the NSP10 S33C mutation. Overall, our study indicates that a single spike mutation can confer both enhanced immune escape and increased viral infectivity. The opposing effects of spike and non-spike mutations highlight the complex interplay of viral genomic elements in shaping their overall fitness, and reveal the high plasticity of coronavirus evolution.

Breakthrough infections in vaccinated population and continuous emergence of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) variants make it imperative to develop more efficacious medical countermeasures. Previously, an anti‐SARS‐CoV‐2 nanobody, Nanosota‐3A, that neutralizes the infection of live Omicron BA.1 with picomolar potency, is identified. Herein, Nanosota‐3A is fused with the crystallizable fragment (Fc) domain of human IgG1 that contains M252Y/S254T/T256E (YTE) substitutions, named Nanosota‐3A‐Fc‐YTE. Compared to Nanosota‐3A‐Fc, Nanosota‐3A‐Fc‐YTE exhibits identical binding to the SARS‐CoV‐2 spike protein yet displays eightfold higher binding affinity for human neonatal Fc receptor (hFcRn) at pH 6.0. In hFcRn transgenic mice, the half‐life of Nanosota‐3A‐Fc and Nanosota‐3A‐Fc‐YTE is 5.1 days and 24.8 days, respectively. The mice are challenged with intranasal exposure of Omicron B.1.1.529 virus 55 days after a single dose of Nanosota‐3A fusions (20 mg kg−1) is administered. Compared to the untreated controls, the lung viral titers in mice receiving Nanosota‐3A‐Fc‐YTE are reduced by 104.7‐fold (p = 0.007) with 50% of the mice free of detectable virus. By contrast, Nanosota‐3A‐Fc‐treated mice show only 3.5‐fold reduction in the viral titers (p = 0.41). The durable protection conferred by a single dose of Nanosota‐3A‐Fc‐YTE administered nearly 2 months prior to the virus exposure demonstrates the promise of long‐circulating nanobodies as powerful prophylactics against SARS‐CoV‐2.

ABSTRACT Venezuelan, western, and eastern equine encephalitis virus (VEEV, WEEV, and EEEV) cause a febrile illness that may result in fatal neurological disease in humans and equines. Human infections are typically from mosquito bites, although cases from respiratory exposure in laboratory accidents have been documented. In addition to natural mosquito-borne infection, the potential biothreat inherent in the ability to disseminate these viruses via the respiratory route has driven the development of antiviral drugs for this route of exposure. To address this gap, we tested the prophylactic administration of a novel brain-penetrant, antiviral, BDGR-49, against a lethal intranasal challenge of VEEV, WEEV, or EEEV in BALB/c mouse model. BDGR-49 conferred 100% protection with 6 mg kg −1 twice per day for 6 days for VEEV, but not EEEV or WEEV. By 8 days post-infection (dpi), infectious virus, viral RNA, and viral antigen in the brain of BDGR-49-treated mice were significantly reduced. Brains of VEEV TrD-infected, BDGR-49-treated mice showed a significant reduction in the expression of genes associated with inflammation ( IFNB1 , TNF , IL6 , and CCL5 ) and cell death ( CASP4 , GSDMD , PYCARD , and ZBP1 ). At dpi 14, histopathology showed that neuronal lesions and inflammatory cell infiltrates were essentially absent, and viral antigen was not detected in the brains of VEEV TrD-infected, BDGR-49-treated mice. In summary, although BDGR-49 treatment showed significant promise for the treatment of mice exposed intranasally to VEEV, the more rapid and efficient entry of EEEV and WEEV by this route into the central nervous system will require additional optimization of the dosing regimen. IMPORTANCE Prophylactic and therapeutic treatment of viruses that cause encephalitis requires fast-acting drugs that rapidly penetrate the blood-brain barrier. Currently, clinicians have only a limited set of antivirals for the treatment of neurotropic infections such as herpesviruses or HIV-1, and none for alphaviruses, and treatment outcomes remain poor. New medical countermeasures will address the gap in treatment of viral encephalitis such as those caused by the neurotropic alphaviruses and others.

Interferons (IFNs) are critical for immune defense against pathogens. While type-I and -III IFNs have been reported to inhibit SARS-CoV-2 replication, the antiviral effect and mechanism of type-II IFN against SARS-CoV-2 remain largely unknown. Here, we evaluate the antiviral activity of type-II IFN (IFN gamma) using human lung epithelial cells (Calu3) and ex vivo human lung tissues. In this study, we found that IFN gamma suppresses SARS-CoV-2 replication in both Calu3 cells and ex vivo human lung tissues. Moreover, IFN gamma treatment does not significantly modulate the expression of SARS-CoV-2 entry-related factors and induces a similar level of pro-inflammatory response in human lung tissues when compared with IFN beta treatment. Mechanistically, we show that overexpression of indoleamine 2,3-dioxygenase 1 (IDO1), which is most profoundly induced by IFN gamma, substantially restricts the replication of ancestral SARS-CoV-2 and the Alpha and Delta variants. Meanwhile, loss-of-function study reveals that IDO1 knockdown restores SARS-CoV-2 replication restricted by IFN gamma in Calu3 cells. We further found that the treatment of l-tryptophan, a substrate of IDO1, partially rescues the IFN gamma-mediated inhibitory effect on SARS-CoV-2 replication in both Calu3 cells and ex vivo human lung tissues. Collectively, these results suggest that type-II IFN potently inhibits SARS-CoV-2 replication through IDO1-mediated antiviral response.

Decabrominated diphenyl ether (BDE-209) is extensively used in the automotive sector as a legacy brominated flame retardant. Recycling materials from end-of-life vehicles contain high levels of BDE-209, posing substantial risks to human health and the environment. This study focuses on estimating the stocks, flows and the associated environmental impact of BDE-209 throughout the automobile sector’s life cycle in China from 2010 to 2050. In 2020, the scrap stage accounted for 60% of the newly introduced BDE-209 (7,370 tons). Car and Sport Utility Vehicle (SUVs) were the primary contributors to both in-use and scrap stages during 2020-2050. Emissions of BDE-209 are projected to rise to 7,854 kg by 2050, making an 11-fold increase from 2010 and predominantly affecting the atmosphere (56%) and soil (33%). Scenario analysis shows that elimination measures, such as enhancing scrapped vehicles recovery and refining automobile shredder residues (ASR) treatment, could potentially reduce the increment of BDE-209.

Highly pathogenic coronaviruses, including severe acute respiratory syndrome coronavirus 2 (refs. (1,2)) (SARS-CoV-2), Middle East respiratory syndrome coronavirus(3) (MERS-CoV) and SARS-CoV-1 (ref. (4)), vary in their transmissibility and pathogenicity. However, infection by all three viruses results in substantial apoptosis in cell culture(5-7) and in patient tissues(8-10), suggesting a potential link between apoptosis and pathogenesis of coronaviruses. Here we show that caspase-6, a cysteine-aspartic protease of the apoptosis cascade, serves as an important host factor for efficient coronavirus replication. We demonstrate that caspase-6 cleaves coronavirus nucleocapsid proteins, generating fragments that serve as interferon antagonists, thus facilitating virus replication. Inhibition of caspase-6 substantially attenuates lung pathology and body weight loss in golden Syrian hamsters infected with SARS-CoV-2 and improves the survival of mice expressing human DPP4 that are infected with mouse-adapted MERS-CoV. Our study reveals how coronaviruses exploit a component of the host apoptosis cascade to facilitate virus replication.

Host circular RNAs (circRNAs) play critical roles in the pathogenesis of viral infections. However, how viruses modulate the biogenesis of host proviral circRNAs to facilitate their replication remains unclear. We have recently shown that Middle East respiratory syndrome coronavirus (MERS-CoV) infection increases co-expression of circRNAs and their cognate messenger RNAs (mRNAs), possibly by hijacking specific host RNA binding proteins (RBPs). In this study, we systemically analysed the interactions between the representative circRNA-mRNA pairs upregulated upon MERS-CoV infection and host RBPs. Our analysis identified heterogeneous nuclear ribonucleoprotein C (hnRNP C) as a key host factor that governed the expression of numerous MERS-CoV-perturbed circRNAs, including hsa_circ_0002846, hsa_circ_0002061, and hsa_circ_0004445. RNA immunoprecipitation assay showed that hnRNP C could bind physically to these circRNAs. Specific knockdown of hnRNP C by small interfering RNA significantly (P < 0.05 to P < 0.0001) suppressed MERS-CoV replication in human lung adenocarcinoma (Calu-3) and human small airway epithelial (HSAEC) cells. Both MERS-CoV and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection increased the total and phosphorylated forms of hnRNP C to activate the downstream CRK-mTOR pathway. Treatment of MERS-CoV- (IC50: 0.618 mu M) or SARS-CoV-2-infected (IC50: 1.233 mu M) Calu-3 cells with the mTOR inhibitor OSI-027 resulted in significantly reduced viral loads. Collectively, our study identified hnRNP C as a key regulator of MERS-CoV-perturbed circRNAs and their cognate mRNAs, and the potential of targeting hnRNP C-related signalling pathways as an anticoronaviral strategy.

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that poses significant threats to global public health. Macrophages and dendritic cells are both key sentinel cells in the host immune response and play critical roles in the pathogenesis of flavivirus infections. Recent studies showed that ZIKV could productively infect monocyte-derived dendritic cells (moDCs), but the role of macrophages in ZIKV infection remains incompletely understood. In this study, we first compared ZIKV infection in monocyte-derived macrophages (MDMs) and moDCs derived from the same donors. We demonstrated that while both MDMs and moDCs were susceptible to epidemic (Puerto Rico) and pre-epidemic (Uganda) strains of ZIKV, virus replication was largely restricted in MDMs but not in moDCs. ZIKV induced significant apoptosis in moDCs but not MDMs. The restricted virus replication in MDMs was not due to inefficient virus entry but was related to post-entry events in the viral replication cycle. In stark contrast with moDCs, ZIKV failed to inhibit STAT1 and STAT2 phosphorylation in MDMs. This resulted in the lack of efficient antagonism of the host type I interferon-mediated antiviral responses. Importantly, depletion of STAT2 but not STAT1 in MDMs significantly rescued the replication of ZIKV and the prototype flavivirus yellow fever virus. Overall, our findings revealed a differential interplay between macrophages and dendritic cells with ZIKV. While dendritic cells may be exploited by ZIKV to facilitate virus replication, macrophages restricted ZIKV infection.

Infection by highly pathogenic coronaviruses results in substantial apoptosis. However, the physiological relevance of apoptosis in the pathogenesis of coronavirus infections is unknown. Here, with a combination of in vitro, ex vivo, and in vivo models, we demonstrated that protein kinase R-like endoplasmic reticulum kinase (PERK) signaling mediated the proapoptotic signals in Middle East respiratory syndrome coronavirus (MERS-CoV) infection, which converged in the intrinsic apoptosis pathway. Inhibiting PERK signaling or intrinsic apoptosis both alleviated MERS pathogenesis in vivo. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and SARS-CoV induced apoptosis through distinct mechanisms but inhibition of intrinsic apoptosis similarly limited SARS-CoV-2- and SARS-CoV-induced apoptosis in vitro and markedly ameliorated the lung damage of SARS-CoV-2-inoculated human angiotensin-converting enzyme 2 (hACE2) mice. Collectively, our study provides the first evidence that virus-induced apoptosis is an important disease determinant of highly pathogenic coronaviruses and demonstrates that this process can be targeted to attenuate disease severity.

Understanding the factors that contribute to efficient SARS-CoV-2 infection of human cells may provide insights on SARS-CoV-2 transmissibility and pathogenesis, and reveal targets of intervention. Here, we analyze host and viral determinants essential for efficient SARS-CoV-2 infection in both human lung epithelial cells and ex vivo human lung tissues. We identify heparan sulfate as an important attachment factor for SARS-CoV-2 infection. Next, we show that sialic acids present on ACE2 prevent efficient spike/ACE2-interaction. While SARS-CoV infection is substantially limited by the sialic acid-mediated restriction in both human lung epithelial cells and ex vivo human lung tissues, infection by SARS-CoV-2 is limited to a lesser extent. We further demonstrate that the furin-like cleavage site in SARS-CoV-2 spike is required for efficient virus replication in human lung but not intestinal tissues. These findings provide insights on the efficient SARS-CoV-2 infection of human lungs.

Background: Staphylococcus aureus is a common human pathogen capable of causing diverse illnesses with possible recurrent infections. Although recent studies have highlighted the role of cellular immunity in recurrent infections, the mechanism by which S. aureus evades host responses remains largely unexplored. Methods: This study utilizes in vitro and in vivo infection experiments to investigate difference of pro-inflammatory responses and subsequent adaptive immune responses between adsA mutant and WT S. aureus strain infection. Findings: We demonstrated that adenosine synthase A (AdsA), a potent S. aureus virulence factor, can alter Th17 responses by interfering with NLRP3 inflammasome-mediated IL-1 beta production. Specifically, S. aureus virulence factor AdsA dampens Th1 /Th17 immunity by limiting the release of IL-1 beta and other Th polarizing cytokines. In particular, AdsA obstructs the release of IL-1 beta via the adenosine/A2aR/NLRP3 axis. Using a murine infection model, pharmacological inhibition of Ala receptor enhanced S. aureus-specific Th17 responses, whereas inhibition of NLRP3 and caspase-1 downregulated these responses. Our results showed that AdsA contributes to recurrent S. aureus infection by restraining protective Th1/Th17 responses. Interpretation: Our study provides important mechanistic insights for therapeutic and vaccination strategies against S. aureus infections. (C) 2021 The Author(s). Published by Elsevier B.V.

Effective treatments for coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are urgently needed. Dexamethasone has been shown to confer survival benefits to certain groups of hospitalized patients, but whether glucocorticoids such as dexamethasone and methylprednisolone should be used together with antivirals to prevent a boost of SARS-CoV-2 replication remains to be determined. Here, we show the beneficial effect of methylprednisolone alone and in combination with remdesivir in the hamster model of SARS-CoV-2 infection. Treatment with methylprednisolone boosted RNA replication of SARS-CoV-2 but suppressed viral induction of proinflammatory cytokines in human monocyte-derived macrophages. Although methylprednisolone monotherapy alleviated body weight loss as well as nasal and pulmonary inflammation, viral loads increased and antibody response against the receptor-binding domain of spike protein attenuated. In contrast, a combination of methylprednisolone with remdesivir not only prevented body weight loss and inflammation, but also dampened viral protein expression and viral loads. In addition, the suppressive effect of methylprednisolone on antibody response was alleviated in the presence of remdesivir. Thus, combinational anti-inflammatory and antiviral therapy might be an effective, safer and more versatile treatment option for COVID-19. These data support testing of the efficacy of a combination of methylprednisolone and remdesivir for the treatment of COVID-19 in randomized controlled clinical trials.

BACKGROUND AND AIMS: Besides prominent respiratory involvement, gastrointestinal manifestations are commonly reported in Coronavirus Disease 2019 (COVID-19) patients. We compared infection of ex vivo human intestinal tissues by SARS-CoV-2 and SARS-CoV with respect to their replication kinetics and immune activation profile. METHODS: Human intestinal tissues were obtained from patients while undergoing surgical operations at Queen Mary Hospital, Hong Kong. Upon surgical removal, the tissues were immediately processed and infected with SARS-CoV-2 or SARS-CoV. Replication kinetics were determined with immunohistochemistry, qRT-PCR, and plaque assays. Immune activation in the infected intestinal tissues was assessed by detecting the gene expression of interferons and representative pro-nflammatory cytokines and chemokines. RESULTS: SARS-CoV-2 could infect and productively replicate in the ex vivo human intestinal tissues with release of infectious virus particles, but not in ex vivo human liver and kidney tissues. Importantly, SARS-CoV-2 replicated less efficiently than SARS-CoV, induced less cytopathology in the human intestinal epithelium, and induced a more robust innate immune response including the activation of both type I and type III interferons, than SARS-CoV in human intestinal tissues. CONCLUSION: Using the ex vivo human intestinal tissues as a physiologically relevant model, our data indicated that SARS-oV-2 could productively replicate in the human gut and suggested that the gastrointestinal tract might serve as an alternative route of virus dissemination. SARS-CoV-2 replicated less efficiently and induced less cytopathology than SARS-CoV in keeping with the clinical observations reported for COVID-19 and SARS, which might be the result of a more robust immune activation by SARS-CoV-2 than SARS-CoV in the human intestine.

Circular RNAs (circRNAs) are an integral component of the host competitive endogenous RNA (ceRNA) network. These noncoding RNAs are characterized by their unique splicing reactions to form covalently closed loop structures and play important RNA regulatory roles in cells. Recent studies showed that circRNA expressions were perturbed in viral infections and circRNAs might serve as potential antiviral targets. We investigated the host ceRNA network changes and biological relevance of circRNAs in human lung adenocarcinoma epithelial (Calu-3) cells infected with the highly pathogenic Middle East respiratory syndrome coronavirus (MERS-CoV). A total of ≥49337 putative circRNAs were predicted. Among the 7845 genes which generated putative circRNAs, 147 (1.9%) of them each generated ≥30 putative circRNAs and were involved in various biological, cellular, and metabolic processes, including viral infections. Differential expression (DE) analysis showed that the proportion of DE circRNAs significantly (P < 0.001) increased at 24 h-post infection. These DE circRNAs were clustered into 4 groups according to their time-course expression patterns and demonstrated inter-cluster and intra-cluster variations in the predicted functions of their host genes. Our comprehensive circRNA-miRNA-mRNA network identified 7 key DE circRNAs involved in various biological processes upon MERS-CoV infection. Specific siRNA knockdown of two selected DE circRNAs (circFNDC3B and circCNOT1) significantly reduced MERS-CoV load and their target mRNA expression which modulates various biological pathways, including the mitogen-activated protein kinase (MAPK) and ubiquitination pathways. These results provided novel insights into the ceRNA network perturbations, biological relevance of circRNAs, and potential host-targeting antiviral strategies for MERS-CoV infection.

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was reported from China in January, 2020. SARS-CoV-2 is efficiently transmitted from person to person and, in 2 months, has caused more than 82 000 laboratory-confirmed cases of coronavirus disease 2019 (COVID-19) and 2800 deaths in 46 countries. The total number of cases and deaths has surpassed that of the 2003 severe acute respiratory syndrome coronavirus (SARS-CoV). Although both COVID-19 and severe acute respiratory syndrome (SARS) manifest as pneumonia, COVID-19 is associated with apparently more efficient transmission, fewer cases of diarrhoea, increased mental confusion, and a lower crude fatality rate. However, the underlying virus-host interactive characteristics conferring these observations on transmissibility and clinical manifestations of COVID-19 remain unknown. Methods We systematically investigated the cellular susceptibility, species tropism, replication kinetics, and cell damage of SARS-CoV-2 and compared findings with those for SARS-CoV. We compared SARS-CoV-2 and SARS-CoV replication in different cell lines with one-way ANOVA. For the area under the curve comparison between SARS-CoV-2 and SARS-CoV replication in Calu3 (pulmonary) and Caco2 (intestinal) cells, we used Student's t test. We analysed cell damage induced by SARS-CoV-2 and SARS-CoV with one-way ANOVA. Findings SARS-CoV-2 infected and replicated to comparable levels in human Caco2 cells and Calu3 cells over a period of 120 h (p=0.52). By contrast, SARS-CoV infected and replicated more efficiently in Caco2 cells than in Calu3 cells under the same multiplicity of infection (p=0.0098). SARS-CoV-2, but not SARS-CoV, replicated modestly in U251 (neuronal) cells (p=0.036). For animal species cell tropism, both SARS-CoV and SARS-CoV-2 replicated in non-human primate, cat, rabbit, and pig cells. SARS-CoV, but not SARS-CoV-2, infected and replicated in Rhinolophus sinicus bat kidney cells. SARS-CoV-2 consistently induced significantly delayed and milder levels of cell damage than did SARS-CoV in non-human primate cells (VeroE6, p=0.016; FRhK4, p=0.0004). Interpretation As far as we know, our study presents the first quantitative data for tropism, replication kinetics, and cell damage of SARS-CoV-2. These data provide novel insights into the lower incidence of diarrhoea, decreased disease severity, and reduced mortality in patients with COVID-19, with respect to the pathogenesis and high transmissibility of SARS-CoV-2 compared with SARS-CoV. Copyright (C) 2020 The Author(s). Published by Elsevier Ltd.

Clinical manifestations of coronavirus disease 2019 (COVID-19) vary from asymptomatic virus shedding, nonspecific pharyngitis, to pneumonia with silent hypoxia and respiratory failure. Dendritic cells and macrophages are sentinel cells for innate and adaptive immunity that affect the pathogenesis of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). The interplay between SARS-CoV-2 and these cell types remains unknown. We investigated infection and host responses of monocyte-derived dendritic cells (moDCs) and macrophages (MDMs) infected by SARS-CoV-2. MoDCs and MDMs were permissive to SARS-CoV-2 infection and protein expression but did not support productive virus replication. Importantly, SARS-CoV-2 launched an attenuated interferon response in both cell types and triggered significant proinflammatory cytokine/chemokine expression in MDMs but not moDCs. Investigations suggested that this attenuated immune response to SARS-CoV-2 in moDCs was associated with viral antagonism of STAT1 phosphorylation. These findings may explain the mild and insidious course of COVID-19 until late deterioration.