TLR2 and TLR7 mediate distinct immunopathological and antiviral plasmacytoid dendritic cell responses to SARS-CoV-2 infection

Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS-CoV-2 infection is critical for developing treatments for severe COVID-19. Here, we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID-19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL-6. Using an in vitro stem cell-based human pDC model, we further demonstrate that pDCs, while not supporting SARS-CoV-2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL-6, IL-8, CXCL10) cytokines that protect epithelial cells from de novo SARS-CoV-2 infection. Via targeted deletion of virus-recognition innate immune pathways, we identify TLR7-MyD88 signaling as crucial for production of antiviral interferons, whereas TLR2 is responsible for the inflammatory IL-6 response. We further show that SARS-CoV-2 engages the receptor neuropilin-1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL-6 response, suggesting neuropilin-1 as potential therapeutic target for stimulation of TLR7-mediated antiviral protection.

Targeted regulation of transcription in primary cells using CRISPRa and CRISPRi

Targeted transcriptional activation or interference can be induced with the CRISPR-Cas9 system (CRISPRa/CRISPRi) using nuclease-deactivated Cas9 fused to transcriptional effector molecules. These technologies have been used in cancer cell lines, particularly for genome-wide functional genetic screens using lentiviral vectors. However, CRISPRa and CRISPRi have not yet been widely applied to ex vivo cultured primary cells with therapeutic relevance owing to a lack of effective and nontoxic delivery modalities. Here we develop CRISPRa and CRISPRi platforms based on RNA or ribonucleoprotein (RNP) delivery by electroporation and show transient, programmable gene regulation in primary cells, including human CD34+ hematopoietic stem and progenitor cells (HSPCs) and human CD3+ T cells. We show multiplex and orthogonal gene modulation using multiple sgRNAs and CRISPR systems from different bacterial species, and we show that CRISPRa can be applied to manipulate differentiation trajectories of HSPCs. These platforms constitute simple and effective means to transiently control transcription and are easily adopted and reprogrammed to new target genes by synthetic sgRNAs. We believe these technologies will find wide use in engineering the transcriptome for studies of stem cell biology and gene function, and we foresee that they will be implemented to develop and enhance cellular therapeutics.

Ascorbic acid supports ex vivo generation of plasmacytoid dendritic cells from circulating hematopoietic stem cells

Plasmacytoid dendritic cells (pDCs) constitute a rare type of immune cell with multifaceted functions, but their potential use as a cell-based immunotherapy is challenged by the scarce cell numbers that can be extracted from blood. Here, we systematically investigate culture parameters for generating pDCs from hematopoietic stem and progenitor cells (HSPCs). Using optimized conditions combined with implementation of HSPC pre-expansion, we generate an average of 465 million HSPC-derived pDCs (HSPC-pDCs) starting from 100,000 cord blood-derived HSPCs. Furthermore, we demonstrate that such protocol allows HSPC-pDC generation from whole-blood HSPCs, and these cells display a pDC phenotype and function. Using GMP-compliant medium, we observe a remarkable loss of TLR7/9 responses, which is rescued by ascorbic acid supplementation. Ascorbic acid induces transcriptional signatures associated with pDC-specific innate immune pathways, suggesting an undescribed role of ascorbic acid for pDC functionality. This constitutes the first protocol for generating pDCs from whole blood and lays the foundation for investigating HSPC-pDCs for cell-based immunotherapy.

Seminal plasma promotes decidualization of endometrial stromal fibroblasts in vitro from women with and without inflammatory disorders in a manner dependent on interleukin-11 signaling

STUDY QUESTION

Do seminal plasma (SP) and its constituents affect the decidualization capacity and transcriptome of human primary endometrial stromal fibroblasts (eSFs)?

SUMMARY ANSWER

SP promotes decidualization of eSFs from women with and without inflammatory disorders (polycystic ovary syndrome (PCOS), endometriosis) in a manner that is not mediated through semen amyloids and that is associated with a potent transcriptional response, including the induction of interleukin (IL)-11, a cytokine important for SP-induced decidualization.

WHAT IS KNOWN ALREADY

Clinical studies have suggested that SP can promote implantation, and studies in vitro have demonstrated that SP can promote decidualization, a steroid hormone-driven program of eSF differentiation that is essential for embryo implantation and that is compromised in women with the inflammatory disorders PCOS and endometriosis.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional study involving samples treated with vehicle alone versus treatment with SP or SP constituents. SP was tested for the ability to promote decidualization in vitro in eSFs from women with or without PCOS or endometriosis (n = 9). The role of semen amyloids and fractionated SP in mediating this effect and in eliciting transcriptional changes in eSFs was then studied. Finally, the role of IL-11, a cytokine with a key role in implantation and decidualization, was assessed as a mediator of the SP-facilitated decidualization.

PARTICIPANTS/MATERIALS, SETTING, METHODS

eSFs and endometrial epithelial cells (eECs) were isolated from endometrial biopsies from women of reproductive age undergoing benign gynecologic procedures and maintained in vitro. Assays were conducted to assess whether the treatment of eSFs with SP or SP constituents affects the rate and extent of decidualization in women with and without inflammatory disorders. To characterize the response of the endometrium to SP and SP constituents, RNA was isolated from treated eSFs or eECs and analyzed by RNA sequencing (RNAseq). Secreted factors in conditioned media from treated cells were analyzed by Luminex and ELISA. The role of IL-11 in SP-induced decidualization was assessed through Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas-9-mediated knockout experiments in primary eSFs.

MAIN RESULTS AND THE ROLE OF CHANCE

SP promoted decidualization both in the absence and presence of steroid hormones (P < 0.05 versus vehicle) in a manner that required seminal proteins. Semen amyloids did not promote decidualization and induced weak transcriptomic and secretomic responses in eSFs. In contrast, fractionated SP enriched for seminal microvesicles (MVs) promoted decidualization. IL-11 was one of the most potently SP-induced genes in eSFs and was important for SP-facilitated decidualization.

LARGE SCALE DATA

RNAseq data were deposited in the Gene Expression Omnibus repository under series accession number GSE135640.

LIMITATIONS, REASONS FOR CAUTION

This study is limited to in vitro analyses.

WIDER IMPLICATIONS OF THE FINDINGS

Our results support the notion that SP promotes decidualization, including within eSFs from women with inflammatory disorders. Despite the general ability of amyloids to induce cytokines known to be important for implantation, semen amyloids poorly signaled to eSFs and did not promote their decidualization. In contrast, fractionated SP enriched for MVs promoted decidualization and induced a transcriptional response in eSFs that overlapped with that of SP. Our results suggest that SP constituents, possibly those associated with MVs, can promote decidualization of eSFs in an IL-11-dependent manner in preparation for implantation.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported by NIH (R21AI116252, R21AI122821 and R01AI127219) to N.R.R. and (P50HD055764) to L.C.G. The authors declare no conflict of interest.

Highly Efficient and Marker-free Genome Editing of Human Pluripotent Stem Cells by CRISPR-Cas9 RNP and AAV6 Donor-Mediated Homologous Recombination

Genome editing of human pluripotent stem cells (hPSCs) provides powerful opportunities for in vitro disease modeling, drug discovery, and personalized stem cell-based therapeutics. Currently, only small edits can be engineered with high frequency, while larger modifications suffer from low efficiency and a resultant need for selection markers. Here, we describe marker-free genome editing in hPSCs using Cas9 ribonucleoproteins (RNPs) in combination with AAV6-mediated DNA repair template delivery. We report highly efficient and bi-allelic integration frequencies across multiple loci and hPSC lines, achieving mono-allelic editing frequencies of up to 94% at the HBB locus. Using this method, we show robust bi-allelic correction of homozygous sickle cell mutations in a patient-derived induced PSC (iPSC) line. Thus, this strategy shows significant utility for generating hPSCs with large gene integrations and/or single-nucleotide changes at high frequency and without the need for introducing selection genes, enhancing the applicability of hPSC editing for research and translational uses.

P885Cardiovascular events in patients with suspected ST-elevation myocardial infarction and no obstructive coronary artery disease

Background

Patients with suspected ST-elevation myocardial infarction (STEMI) and no obstructive coronary artery disease (CAD) comprise a heterogeneous group with varying prognoses.

Purpose

To evaluate the prognostic value of cardiac troponin T (cTnT) in patients with suspected STEMI and no obstructive CAD.

Methods

Patients with suspected STEMI and no obstructive (<50% diameter stenosis) CAD were consecutively included from 2009–2014. Patients were classified as having normal cTnT, dynamic cTnT elevation, or stationary cTnT elevation. All patients were followed with respect to major adverse cardiovascular events (MACE), cardiovascular readmission, and repeat coronary procedures, until 1 year after discharge.

Results

The study included 502 patients with suspected STEMI and no obstructive CAD: 165 (33%) had normal cTnT, 293 (58%) had dynamic cTnT elevation and 44 (9%) had stationary cTnT elevation. Within one year after admission, 40 (8%) had MACE, 81 (16%) had cardiovascular readmission, and 8 (2%) underwent repeat coronary procedures. The risk of MACE was elevated in patients with stationary cTnT elevation compared with normal cTnT (OR 13.6, 95% CI 2.3–80.2, p=0.004). There was no statistically significant difference between those with dynamic cTnT elevation and normal cTnT (OR 2.9, 95% CI 0.6–14.0, p=0.189). Adding cTnT pattern to a conventional risk model, area under the receiver operating curve for predicting the 1-year risk of MACE improved significantly (80% vs. 85%, p=0.004, Figure 1).

Figure 1

Conclusion

In patients with suspected STEMI and no obstructive CAD, cTnT pattern during acute hospitalization is associated with the 1-year risk of MACE and improves risk prediction for the individual patient.

Acknowledgement/Funding

The Danish Heart Foundation, the A.P. Møller Foundation, the Foundation of Reinholdt W. Jorck and Wife, Rigshospitalet's Research Foundation

Electroporation-Based CRISPR/Cas9 Gene Editing Using Cas9 Protein and Chemically Modified sgRNAs

CRISPR/Cas9 is an effective and easy-to-use tool for editing the genome of many human cancer cell lines. However, in some hard-to-transfect cell lines and primary cells, gene editing is more challenging. This protocol details an electroporation-based protocol for the delivery of Cas9 protein from Streptococcus pyogenes complexed with chemically modified sgRNAs. We have found this protocol to work very efficiently in numerous cell lines and primary cells that are difficult to transfect by conventional chemical-based transfection methods.

Interferon priming is essential for human CD34+ cell-derived plasmacytoid dendritic cell maturation and function

Plasmacytoid dendritic cells (pDC) are essential for immune competence. Here we show that pDC precursor differentiated from human CD34+ hematopoietic stem and progenitor cells (HSPC) has low surface expression of pDC markers, and has limited induction of type I interferon (IFN) and IL-6 upon TLR7 and TLR9 agonists treatment; by contrast, cGAS or RIG-I agonists-mediated activation is not altered. Importantly, after priming with type I and II IFN, these precursor pDCs attain a phenotype and functional activity similar to that of peripheral blood-derived pDCs. Data from CRISPR/Cas9-mediated genome editing of HSPCs further show that HSPC-pDCs with genetic modifications can be obtained, and that expression of the IFN-α receptor is essential for the optimal function, but dispensable for the differentiation, of HSPC-pDC percursor. Our results thus demonstrate the biological effects of IFNs for regulating pDC function, and provide the means of generating of gene-modified human pDCs.

Mucosal stromal fibroblasts markedly enhance HIV infection of CD4+ T cells

Understanding early events of HIV transmission within mucosal tissues is vital for developing effective prevention strategies. Here, we report that primary stromal fibroblasts isolated from endometrium, cervix, foreskin, male urethra, and intestines significantly increase HIV infection of CD4+ T cells-by up to 37-fold for R5-tropic HIV and 100-fold for X4-tropic HIV-without themselves becoming infected. Fibroblasts were more efficient than dendritic cells at trans-infection and mediate this response in the absence of the DC-SIGN and Siglec-1 receptors. In comparison, mucosal epithelial cells secrete antivirals and inhibit HIV infection. These data suggest that breaches in the epithelium allow external or luminal HIV to escape an antiviral environment to access the infection-favorable environment of the stromal fibroblasts, and suggest that resident fibroblasts have a central, but previously unrecognized, role in HIV acquisition at mucosal sites. Inhibiting fibroblast-mediated enhancement of HIV infection should be considered as a novel prevention strategy.

Targeted, homology-driven gene insertion in stem cells by ZFN-loaded 'all-in-one' lentiviral vectors

Biased integration remains a key challenge for gene therapy based on lentiviral vector technologies. Engineering of next-generation lentiviral vectors targeting safe genomic harbors for insertion is therefore of high relevance. In a previous paper (Cai et al., 2014a), we showed the use of integrase-defective lentiviral vectors (IDLVs) as carriers of complete gene repair kits consisting of zinc-finger nuclease (ZFN) proteins and repair sequences, allowing gene correction by homologous recombination (HR). Here, we follow this strategy to engineer ZFN-loaded IDLVs that insert transgenes by a homology-driven mechanism into safe loci. This insertion mechanism is driven by time-restricted exposure of treated cells to ZFNs. We show targeted gene integration in human stem cells, including CD34(+) hematopoietic progenitors and induced pluripotent stem cells (iPSCs). Notably, targeted insertions are identified in 89% of transduced iPSCs. Our findings demonstrate the applicability of nuclease-loaded 'all-in-one' IDLVs for site-directed gene insertion in stem cell-based gene therapies.

Listeria monocytogenes induces IFNβ expression through an IFI16-, cGAS- and STING-dependent pathway

Listeria monocytogenes is a gram-positive facultative intracellular bacterium, which replicates in the cytoplasm of myeloid cells. Interferon β (IFNβ) has been reported to play an important role in the mechanisms underlying Listeria disease. Although studies in murine cells have proposed the bacteria-derived cyclic-di-AMP to be the key bacterial immunostimulatory molecule, the mechanism for IFNβ expression during L. monocytogenes infection in human myeloid cells remains unknown. Here we report that in human macrophages, Listeria DNA rather than cyclic-di-AMP is stimulating the IFN response via a pathway dependent on the DNA sensors IFI16 and cGAS as well as the signalling adaptor molecule STING. Thus, Listeria DNA is a major trigger of IFNβ expression in human myeloid cells and is sensed to activate a pathway dependent on IFI16, cGAS and STING.

Monitoring the startup of a wet detention pond equipped with sand filters and sorption filters

The startup of a wet retention pond designed for extended stormwater treatment was monitored by more than one year of continual measurement of hydraulic parameters, nutrients and quality parameters in the pond itself (pH, temperature, dissolved oxygen, turbidity). The data revealed that photosynthesis played an important role for dissolved oxygen and pH for most of the year. Another important observation was that the pond behaved more like a completely mixed reactor than like a plug flow reactor--even though the length to width ratio was as high as 4.5:1. The pond was equipped with sand filters and sorption filters whereby very good nutrient removal efficiencies were achieved.