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Antibodies are a principal determinant of immunity for most RNA viruses and have promise to reduce infection or disease during major epidemics. The novel coronavirus SARS-CoV-2 has caused a global pandemic with millions of infections and hundreds of thousands of deaths to date1,2. In response,we used a rapid antibody discovery platform to isolate hundreds of human monoclonal antibodies (mAbs) against the SARS-CoV-2 spike (S) protein. We stratify these mAbs into five major classes on the basis of their reactivity to subdomains of S protein as well as their cross-reactivity to SARS-CoV. Many of these mAbs inhibit infection of authentic SARS-CoV-2 virus,with most neutralizing mAbs recognizing the receptor-binding domain (RBD) of S. This work defines sites of vulnerability on SARS-CoV-2 S and demonstrates the speed and robustness of advanced antibody discovery platforms. View Publication

Cytokine-inducible SH2-containing protein (CIS; encoded by the gene CISH) is a key negative regulator of interleukin-15 (IL-15) signaling in natural killer (NK) cells. Here,we develop human CISH-knockout (CISH-/-) NK cells using an induced pluripotent stem cell-derived NK cell (iPSC-NK cell) platform. CISH-/- iPSC-NK cells demonstrate increased IL-15-mediated JAK-STAT signaling activity. Consequently,CISH-/- iPSC-NK cells exhibit improved expansion and increased cytotoxic activity against multiple tumor cell lines when maintained at low cytokine concentrations. CISH-/- iPSC-NK cells display significantly increased in vivo persistence and inhibition of tumor progression in a leukemia xenograft model. Mechanistically,CISH-/- iPSC-NK cells display improved metabolic fitness characterized by increased basal glycolysis,glycolytic capacity,maximal mitochondrial respiration,ATP-linked respiration,and spare respiration capacity mediated by mammalian target of rapamycin (mTOR) signaling that directly contributes to enhanced NK cell function. Together,these studies demonstrate that CIS plays a key role to regulate human NK cell metabolic activity and thereby modulate anti-tumor activity. View Publication

Endogenous repair of osteochondral defect is usually limited by the insufficient number of cells in the early stage and incomplete cell differentiation in the later stage. The development of drug delivery systems for sequential release of pro-migratory and pro-chondrogenic molecules to induce endogenous bone marrow-derived mesenchymal stem cells (BMSCs) recruitment and chondrogenic differentiation is highly desirable for in situ osteochondral regeneration. In this study,a novel,all-silk-derived sequential delivery system was fabricated by incorporating the tunable drug-loaded silk fibroin (SF) nanospheres into a SF porous matrix. The loading efficiency and release kinetics of biomolecules depended on the initial SF/polyvinyl alcohol (PVA) concentrations (0.2{\%},1{\%} and 5{\%}) of the nanospheres,as well as the hydrophobicity of the loaded molecules,resulting in controllable and programmed delivery profiles. Our findings indicated that the 5{\%} nanosphere-incorporated matrix showed a rapid release of E7 peptide during the first 120 h,whereas the 0.2{\%} nanosphere-incorporated matrix provided a slow and sustained release of Kartogenin (KGN) longer than 30 days. During in vitro culture of BMSCs,this functional SF matrix incorporated with E7/KGN nanospheres showed good biocompatibility,as well as enhanced BMSCs migration and chondrogenic differentiation through the release of E7 and KGN. Furthermore,when implanted into rabbit osteochondral defect,the SF nanosphere matrix with sequential E7/KGN release promoted the regeneration of both cartilage and subchondral bone. This work not only provided a novel all-silk-derived drug delivery system for sequential release of molecules,but also a functional tissue-engineered scaffold for osteochondral regeneration. View Publication

Stress granules (SGs) are non-membrane-bound RNA-protein granules that assemble through phase separation in response to cellular stress. Disturbances in SG dynamics have been implicated as a primary driver of neurodegenerative diseases,including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD),suggesting the hypothesis that these diseases reflect an underlying disturbance in the dynamics and material properties of SGs. However,this concept has remained largely untestable in available models of SG assembly,which require the confounding variable of exogenous stressors. Here we introduce a light-inducible SG system,termed OptoGranules,based on optogenetic multimerization of G3BP1,which is an essential scaffold protein for SG assembly. In this system,which permits experimental control of SGs in living cells in the absence of exogenous stressors,we demonstrate that persistent or repetitive assembly of SGs is cytotoxic and is accompanied by the evolution of SGs to cytoplasmic inclusions that recapitulate the pathology of ALS-FTD. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter). View Publication

Purpose The topical application of exosomes secreted by mesenchymal stem cells (MSC-Exos) on the skin is a very new and interesting topic in the medical field. In this study,we aimed to investigate whether marine sponge Haliclona sp. spicules (SHSs) could effectively enhance the skin delivery of human umbilical cord-derived MSC-Exos (hucMSC-Exos),and further evaluate the topical application of hucMSC-Exos combined with SHSs in rejuvenating photoaged mouse skin. Materials and Methods SHSs were isolated from the explants of sponge Haliclona sp. with our proprietary method,and hucMSC-Exos were prepared from the conditioned medium of hucMSCs using ultracentrifugation. The effects of SHSs on the skin penetration of fluorescently labeled hucMSC-Exos were determined using confocal microscopy in vitro (porcine skin) and in vivo (mouse skin). The therapeutic effects of hucMSC-Exos coupled with SHSs against UV-induced photoaging in mice were assessed by using microwrinkles analysis,pathohistological examination and real-time RT-PCR. We also tested the skin irritation caused by the combination of hucMSC-Exos and SHSs in guinea pigs. Results In vitro results showed that hucMSC-Exos could not readily penetrate through porcine skin by themselves. However,SHSs increased the skin absorption of exosomes by a factor of 5.87 through creating microchannels. Similar penetration enhancement of hucMSC-Exos was observed after SHSs treatment in mice. The combined use of hucMSC-Exos and SHSs showed significant anti-photoaging effects in mice,including reducing microwrinkles,alleviating histopathological changes,and promoting the expression of extracellular matrix constituents,whereas hucMSC-Exos alone produced considerably weaker effects. Skin irritation test showed that the combination of hucMSC-Exos and SHSs caused slight irritation,and the skin recovered shortly. Conclusion SHSs provide a safe and effective way to enhance the skin delivery of MSC-Exos. Moreover,the combination of MSC-Exos and SHSs may be of much use in the treatment of photoaging. View Publication

Although obesity is known to be critical for cancer development,how obesity negatively impacts antitumor immune responses remains largely unknown. Here,we show that increased fatty acid oxidation (FAO) driven by activated STAT3 in CD8+ T effector cells is critical for obesity-associated breast tumor progression. Ablating T cell Stat3 or treatment with an FAO inhibitor in obese mice spontaneously developing breast tumor reduces FAO,increases glycolysis and CD8+ T effector cell functions,leading to inhibition of breast tumor development. Moreover,PD-1 ligation in CD8+ T cells activates STAT3 to increase FAO,inhibiting CD8+ T effector cell glycolysis and functions. Finally,leptin enriched in mammary adipocytes and fat tissues downregulates CD8+ T cell effector functions through activating STAT3-FAO and inhibiting glycolysis. We identify a critical role of increased oxidation of fatty acids driven by leptin and PD-1 through STAT3 in inhibiting CD8+ T effector cell glycolysis and in promoting obesity-associated breast tumorigenesis. View Publication

Continual efferocytic clearance of apoptotic cells (ACs) by macrophages prevents necrosis and promotes injury resolution. How continual efferocytosis is promoted is not clear. Here,we show that the process is optimized by linking the metabolism of engulfed cargo from initial efferocytic events to subsequent rounds. We found that continual efferocytosis is enhanced by the metabolism of AC-derived arginine and ornithine to putrescine by macrophage arginase 1 (Arg1) and ornithine decarboxylase (ODC). Putrescine augments HuR-mediated stabilization of the mRNA encoding the GTP-exchange factor Dbl,which activates actin-regulating Rac1 to facilitate subsequent rounds of AC internalization. Inhibition of any step along this pathway after first-AC uptake suppresses second-AC internalization,whereas putrescine addition rescues this defect. Mice lacking myeloid Arg1 or ODC have defects in efferocytosis in vivo and in atherosclerosis regression,while treatment with putrescine promotes atherosclerosis resolution. Thus,macrophage metabolism of AC-derived metabolites allows for optimal continual efferocytosis and resolution of injury. View Publication