T-cell recovery and evidence of persistent immune activation 12 months after severe COVID-19.

BACKGROUND: T-cell lymphopenia and functional impairment is a hallmark of severe acute coronavirus disease 2019 (COVID-19). How T-cell numbers and function evolve at later timepoints after clinical recovery remains poorly investigated. METHODS: We prospectively enrolled and longitudinally sampled 173 individuals with asymptomatic to critical COVID-19 and analyzed phenotypic and functional characteristics of T cells using flow cytometry, 40-parameter mass cytometry, targeted proteomics, and functional assays. RESULTS: The extensive T-cell lymphopenia observed particularly in patients with severe COVID-19 during acute infection had recovered 6 months after infection, which was accompanied by a normalization of functional T-cell responses to common viral antigens. We detected persisting CD4+ and CD8+ T-cell activation up to 12 months after infection, in patients with mild and severe COVID-19, as measured by increased HLA-DR and CD38 expression on these cells. Persistent T-cell activation after COVID-19 was independent of administration of a COVID-19 vaccine post-infection. Furthermore, we identified a subgroup of patients with severe COVID-19 that presented with persistently low CD8+ T-cell counts at follow-up and exhibited a distinct phenotype during acute infection consisting of a dysfunctional T-cell response and signs of excessive pro-inflammatory cytokine production. CONCLUSION: Our study suggests that T-cell numbers and function recover in most patients after COVID-19. However, we find evidence of persistent T-cell activation up to 12 months after infection and describe a subgroup of severe COVID-19 patients with persistently low CD8+ T-cell counts exhibiting a dysregulated immune response during acute infection.

Autoantibodies in COVID-19 correlate with antiviral humoral responses and distinct immune signatures.

BACKGROUND: Several autoimmune features occur during coronavirus disease 2019 (COVID-19), with possible implications for disease course, immunity, and autoimmune pathology. In this study, we longitudinally screened for clinically relevant systemic autoantibodies to assess their prevalence, temporal trajectory, and association with immunity, comorbidities, and severity of COVID-19. METHODS: We performed highly sensitive indirect immunofluorescence assays to detect antinuclear antibodies (ANA) and antineutrophil cytoplasmic antibodies (ANCA), along with serum proteomics and virome-wide serological profiling in a multicentric cohort of 175 COVID-19 patients followed up to 1 year after infection, eleven vaccinated individuals, and 41 unexposed controls. RESULTS: Compared with healthy controls, similar prevalence and patterns of ANA were present in patients during acute COVID-19 and recovery. However, the paired analysis revealed a subgroup of patients with transient presence of certain ANA patterns during acute COVID-19. Furthermore, patients with severe COVID-19 exhibited a high prevalence of ANCA during acute disease. These autoantibodies were quantitatively associated with higher SARS-CoV-2-specific antibody titers in COVID-19 patients and in vaccinated individuals, thus linking autoantibody production to increased antigen-specific humoral responses. Notably, the qualitative breadth of antibodies cross-reactive with other coronaviruses was comparable in ANA-positive and ANA-negative individuals during acute COVID-19. In autoantibody-positive patients, multiparametric characterization demonstrated an inflammatory signature during acute COVID-19 and alterations of the B-cell compartment after recovery. CONCLUSION: Highly sensitive indirect immunofluorescence assays revealed transient autoantibody production during acute SARS-CoV-2 infection, while the presence of autoantibodies in COVID-19 patients correlated with increased antiviral humoral immune responses and inflammatory immune signatures.

Systemic and mucosal antibody responses specific to SARS-CoV-2 during mild versus severe COVID-19.

BACKGROUND: Whereas severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody tests are increasingly being used to estimate the prevalence of SARS-CoV-2 infection, the determinants of these antibody responses remain unclear. OBJECTIVES: Our aim was to evaluate systemic and mucosal antibody responses toward SARS-CoV-2 in mild versus severe coronavirus disease 2019 (COVID-19) cases. METHODS: Using immunoassays specific for SARS-CoV-2 spike proteins, we determined SARS-CoV-2-specific IgA and IgG in sera and mucosal fluids of 2 cohorts, including SARS-CoV-2 PCR-positive patients (n = 64) and PCR-positive and PCR-negtive health care workers (n = 109). RESULTS: SARS-CoV-2-specific serum IgA titers in patients with mild COVID-19 were often transiently positive, whereas serum IgG titers remained negative or became positive 12 to 14 days after symptom onset. Conversely, patients with severe COVID-19 showed a highly significant increase of SARS-CoV-2-specific serum IgA and IgG titers after symptom onset. Very high titers of SARS-CoV-2-specific serum IgA were correlated with severe acute respiratory distress syndrome. Interestingly, some health care workers with negative SARS-CoV-2-specific serum antibody titers showed SARS-CoV-2-specific IgA in mucosal fluids with virus-neutralizing capacity in some cases. SARS-CoV-2-specific IgA titers in nasal fluids were inversely correlated with age. CONCLUSIONS: Systemic antibody production against SARS-CoV-2 develops mainly in patients with severe COVID-19, with very high IgA titers seen in patients with severe acute respiratory distress syndrome, whereas mild disease may be associated with transient production of SARS-CoV-2-specific antibodies but may stimulate mucosal SARS-CoV-2-specific IgA secretion.

RSPO3 impairs barrier function of human vascular endothelial monolayers and synergizes with pro-inflammatory IL-1.

BACKGROUND: Endothelial barrier dysfunction characterized by hyperpermeability of the vascular endothelium is a key factor in the pathogenesis of chronic inflammatory diseases and affects clinical outcomes. In states of chronic inflammation, mediators secreted by activated immune cells or vascular endothelium may affect the barrier function and permeability of the vascular endothelium. The matricellular R-spondin family member RSPO3 is produced by inflammatory-activated human monocytes and vascular endothelial cells, but its effects in the regulation of vascular endothelial barrier function remains elusive. METHODS: The present study investigates the effects of RSPO3 on the barrier function of adult human primary macro- and micro- vascular endothelial monolayers. Tight monolayers of primary endothelial cells from human coronary and pulmonary arteries, and cardiac, brain, and dermal microvascular beds were treated with RSPO3 either alone or in combination with pro-inflammatory mediator IL-1ß. Endothelial barrier function was assessed non-invasively in real-time using Electric Cell-substrate Impedance Sensing. RESULTS: RSPO3 treatment critically affected barrier function by enhancing the permeability of all vascular endothelial monolayers investigated. To confer hyperpermeable phenotype in vascular endothelial monolayers, RSPO3 induced inter-endothelial gap formation by disrupting the ß-catenin and VE-cadherin alignment at adherens junctions. RSPO3 synergistically enhanced the barrier impairing properties of the pro-inflammatory mediator IL-1ß. CONCLUSION: Here, we show that the matricellular protein RSPO3 is a mediator of endothelial hyperpermeability that can act in synergy with the inflammatory mediator IL-1ß. This finding stimulates further studies to delineate the endothelial barrier impairing properties of RSPO3 and its synergistic interaction with IL-1ß in chronic inflammatory diseases.

Effect of diagnosis related groups implementation on the intensive care unit of a Swiss tertiary hospital: a cohort study.

BACKGROUND: In 2013 the Swiss Diagnosis Related Groups ((Swiss)-DRG) was implemented in Intensive Care Units (ICU). Its impact on hospitalizations has not yet been examined. We compared the number of ICU admissions, according to clinical severity and referring institution, and screened whether implementation of Swiss-DRG affected admission policy, ICU length-of-stay (ICU-LOS) or ICU mortality. METHODS: Retrospective, single centre, cohort study conducted at the University Hospital Zurich, Switzerland between January 2009 and end of September 2013. Demographic and clinical data was retrieved from a quality assurance database. RESULTS: Admissions (n = 17,231) before the introduction of Swiss-DRG were used to model expected admissions after DRG, and then compared to the observed admissions. Forecasting matched observations in patients with a high clinical severity admitted from internal units and external hospitals (admitted / predicted: 709 / 703, [95% Confidence Interval (CI), 658-748] and 302 / 332, [95% CI, 269-365] respectively). In patients with low severity of disease, in-house admissions became more frequent than expected and external admission were less frequent (admitted / predicted: 1972 / 1910, [95% CI, 1898-1940] and 436 / 518, [95% CI, 482-554] respectively). Various mechanisms related to Swiss-DRG may have led to these changes. DRG could not be linked to significant changes in regard to ICU-LOS and ICU mortality. CONCLUSIONS: DRG introduction had not affected ICU admissions policy, except for an increase of in-house patients with a low clinical severity of disease. DRG had neither affected ICU mortality nor ICU-LOS.

[Survey involving Swiss heads of departments: somatic causes of fatigue]. / Enquête auprès des médecins-chefs: les causes somatiques de la fatigue.

Patients often complain of fatigue, sleepiness or tiredness to their treating physician. Somatic causes should not be missed. According to answers in a survey involving experienced Swiss Heads of medicine departments, somatic causes of fatigue are discussed in this article with focus on obstacles and near-missed cases. Diagnostic tools and treatment options, if available, are mentioned.

Immunoglobulin signature predicts risk of post-acute COVID-19 syndrome.

Following acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) a significant proportion of individuals develop prolonged symptoms, a serious condition termed post-acute coronavirus disease 2019 (COVID-19) syndrome (PACS) or long COVID. Predictors of PACS are needed. In a prospective multicentric cohort study of 215 individuals, we study COVID-19 patients during primary infection and up to one year later, compared to healthy subjects. We discover an immunoglobulin (Ig) signature, based on total IgM and IgG3 levels, which - combined with age, history of asthma bronchiale, and five symptoms during primary infection - is able to predict the risk of PACS independently of timepoint of blood sampling. We validate the score in an independent cohort of 395 individuals with COVID-19. Our results highlight the benefit of measuring Igs for the early identification of patients at high risk for PACS, which facilitates the study of targeted treatment and pathomechanisms of PACS.

Hyperregenerative macrocytic anaemia: the role of copper and zinc.

In a patient with a history of bariatric surgery, severe copper deficiency presenting with macrocytic hyperregenerative anaemia was diagnosed. Besides the impaired intestinal absorption due to a short bowel syndrome, the enteral zinc supplementation competitively decreased the intestinal copper uptake. Once the zinc supplementation was stopped, enteral copper replacement ensued and normalised haemoglobin levels with decreasing median corpuscular volume were observed during follow-up visits.

Stroke management in a Swiss community hospital - in close collaboration with a stroke centre.

BACKGROUND: Despite the universal recognition that stroke is a major burden of public health in developed countries, little is known concerning its epidemiology and care outside of stroke centres. The objective of our study was to provide information concerning risk factors for stroke, stroke management and quality of care in a community hospital in Switzerland. METHODS: Retrospective observational in-hospital study of adult stroke patients treated in a community hospital in Switzerland in collaboration with a nearby stroke centre. Patients were identified by the corresponding ICD-10 codes from July 2017 to December 2018. RESULTS: We included 261 patients with a median age of 78 years (interquartile range [IQR] 68–85). Sixty-four percent (166) had ischaemic strokes, 18% (46) transient ischaemic attacks and 19% (49) intracranial bleeding. The most frequent risk factors were arterial hypertension in 195 (75%) patients, dyslipidaemia in 124 (48%) patients and overweight/obesity in 102 (39%). Dyslipidaemia and atrial fibrillation were undiagnosed at admission in 47 (38%) and 16 (27%) patients, respectively. Ninety-one (37%) patients with an out-of-hospital stroke presented within 4.5 hours after symptom onset. Intravenous thrombolysis was initiated in 27 patients (49% of the out-of-hospital ischaemic strokes presenting within 4.5 hours) and the median door-to-needle time was 55 minutes (IQR 40–67) and within 60 minutes in 16 (59%) patients. The most frequent poststroke complications were aspiration pneumonia in 22 (8%) followed by urinary tract infection in 14 (5%). The referral rate to a stroke centre or neurosurgical unit was 18%. CONCLUSION: Our findings support further education of the population in recognition of stroke symptoms and assessment of cardiovascular risk factors according to guidelines. Telemedical cooperation with a local stroke centre can result in adequate quality of care in these patients.

Transcriptional Regulation of Drug Metabolizing CYP Enzymes by Proinflammatory Wnt5A Signaling in Human Coronary Artery Endothelial Cells.

Downregulation of drug metabolizing enzymes and transporters by proinflammatory mediators in hepatocytes, enterocytes and renal tubular epithelium is an established mechanism affecting pharmacokinetics. Emerging evidences indicate that vascular endothelial cell expression of drug metabolizing enzymes and transporters may regulate pharmacokinetic pathways in heart to modulate local drug bioavailability and toxicity. However, whether inflammation regulates pharmacokinetic pathways in human cardiac vascular endothelial cells remains largely unknown. The lipid modified protein Wnt5A is emerging as a critical mediator of proinflammatory responses and disease severity in sepsis, hypertension and COVID-19. In the present study, we employed transcriptome profiling and gene ontology analyses to investigate the regulation of expression of drug metabolizing enzymes and transporters by Wnt5A in human coronary artery endothelial cells. Our study shows for the first time that Wnt5A induces the gene expression of CYP1A1 and CYP1B1 enzymes involved in phase I metabolism of a broad spectrum of drugs including chloroquine (the controversial drug for COVID-19) that is known to cause toxicity in myocardium. Further, the upregulation of CYP1A1 and CYP1B1 expression is preserved even during inflammatory crosstalk between Wnt5A and the prototypic proinflammatory IL-1ß in human coronary artery endothelial cells. These findings stimulate further studies to test the critical roles of vascular endothelial cell CYP1A1 and CYP1B1, and the potential of vascular-targeted therapy with CYP1A1/CYP1B1 inhibitors in modulating myocardial pharmacokinetics in Wnt5A-associated inflammatory and cardiovascular diseases.

Severe refeeding syndrome after human chorionic gonadotropin diet: a potentially lethal complication.

We present the case of a young male patient who presented with paralysing muscle weakness due to severe hypokalaemia and hypophosphataemia. The initial patient history evaluations could not establish the aetiology. Only after we reviewed the patient's history did he reveal that he had been following a severe calorie-restricted regime, the human chorionic gonadotropin diet, which had ended 2 days prior to developing symptoms. This information then allowed us to diagnose severe refeeding syndrome. As a further complication, the patient developed rhabdomyolysis. After correction of serum electrolytes, symptoms resolved completely. This case emphasises the potential harm of severely calorie-restricted diets, often recommended by online 'experts'. Furthermore, we underline the importance of thorough history taking.

A distinct innate immune signature marks progression from mild to severe COVID-19.

Coronavirus disease 2019 (COVID-19) manifests with a range of severities, but immune signatures of mild and severe disease are still not fully understood. Here, we use mass cytometry and targeted proteomics to profile the innate immune response of patients with mild or severe COVID-19 and of healthy individuals. Sampling at different stages allows us to reconstruct a pseudo-temporal trajectory of the innate response. A surge of CD169+ monocytes associated with an IFN-γ+MCP-2+ signature rapidly follows symptom onset. At later stages, we observe a persistent inflammatory phenotype in patients with severe disease, dominated by high CCL3 and CCL4 abundance correlating with the re-appearance of CD16+ monocytes, whereas the response of mild COVID-19 patients normalizes. Our data provide insights into the dynamic nature of inflammatory responses in COVID-19 patients and identify sustained innate immune responses as a likely mechanism in severe patients, thus supporting the investigation of targeted interventions in severe COVID-19.

The wnt pathway: a macrophage effector molecule that triggers inflammation.

Wnt proteins are members of the highly conserved wingless family of proteins responsible for cell differentiation and development and for neoplastic and degenerative processes. Recently, Toll-like receptor-mediated Wnt signaling was found to be associated with innate immunity in Drosophila. Upregulation of Wnt5A in human macrophages upon microbial challenge indicated a similar mechanism. Toll-like receptor-mediated Wnt5A expression is a key process for sustained inflammatory macrophage activation through autocrine and paracrine signaling. Downregulation of Wnt5A expression and subsequent attenuation of inflammatory macrophage responses by activated protein C supports the link between inflammation and coagulation, another highly conserved biologic system. Direct evidence for the relevance of Wnt5A in severe systemic inflammation is provided by the finding of higher Wnt5A levels in patients with sepsis than in healthy individuals. The fact that Wnt5A signaling can be modulated by anti-inflammatory mediators makes this effector molecule an attractive target for therapeutic intervention in inflammatory diseases.

Wnt5A/CaMKII signaling contributes to the inflammatory response of macrophages and is a target for the antiinflammatory action of activated protein C and interleukin-10.

OBJECTIVE: Sepsis is a major cause of death for intensive care patients. High concentrations of inflammatory cytokines are characteristic of severe systemic inflammation and activated monocytes are their predominant cellular source. To identify targets for antiinflammatory intervention, we investigated the response of human macrophages to inflammatory and antiinflammatory mediators. METHODS AND RESULTS: We profiled gene expression in human macrophages exposed to lipopolysaccharide (LPS) and interferon (IFN)-gamma in the presence or absence of recombinant activated protein C (APC) or IL-10 and identified Wnt5A as one of the transcripts most highly induced by LPS/IFN-gamma and suppressed by APC and IL-10. We confirmed regulation of Wnt5A protein in macrophages and detected it in sera and bone marrow macrophages of patients with severe sepsis. We established that a functional Wnt5A/frizzled-5/CaMKII signaling pathway was essential for macrophage inflammatory activation. To prove the essential contribution of Wnt5A we measured inflammatory cytokines after stimulation with Wnt5A, silenced Wnt5A by siRNA, and blocked receptor binding with soluble Frizzled-related peptide-1 (sFRP1). CONCLUSIONS: Wnt5A is critically involved in inflammatory macrophage signaling in sepsis and is a target for antiinflammatory mediators like APC or antagonists like sFRP1.

Transient global amnesia - not so rare after all.

QUESTION: Transient global amnesia (TGA) is characterised by the sudden occurrence of amnesia while lacking other neurological symptoms. Complete remission occurs within 24 hours. The pathogenesis remains unknown. The objective of this study was to evaluate the prevalence of TGA in a primary referral hospital in Uster, Switzerland and examine the accuracy of the diagnostic procedure and outcome. METHODS: We conducted a retrospective review of patients with TGA admitted to the Uster hospital, Switzerland between 1/2005 and 10/2007. Of 8166 patients, 20 consecutive cases fulfilled the diagnostic criteria and were further analysed. We included presenting symptoms, diagnostic tests performed, treatment and outcome. A questionnaire to investigate the treating doctor's knowledge of TGA was conducted. A follow up was conducted in all patients at 19.1 +/- 7.1 months after presentation. RESULTS: The incidence was 6.8/100 000/year. In all patients the symptoms resolved within 24 hours and all patients were seen by a consultant neurologist. Drug related causes were excluded. 25% episodes started after some form of exercise, 20% after emotional distress. All patients underwent cerebral imaging. 76% of the questionnaires sent to in-hospital physicians were returned. Diagnostic criteria of TGA were fully known in 75%. In 30% the diagnosis on admission was not TGA and had to be adjusted during the hospital stay. Follow up showed relapse in 10%. CONCLUSION: TGA is a syndrome of which emergency physicians should be aware. The diagnosis is made clinically and the prognosis is good, although relapses may occur. Missed diagnoses may lead to uncertainty in patients and their relatives.

Portal vein thrombus and liver failure in a patient with pheochromocytoma crisis.

A 51-year-old man with known pheochromocytoma refused surgical treatment over several years and subsequently presented in catecholamine crisis with shock and multiple organ failure. Laboratory testing revealed liver failure with elevated liver enzymes and coagulation abnormalities, and imaging showed ischemia of extended parts of the right liver lobe. It also revealed a large thrombus in the right portal vein, which together with severe arterial vasoconstriction impaired the dual blood supply of the liver. The patient recovered after effective medical treatment and finally underwent surgical tumor resection. Thereafter, antihypertensive treatment could be stopped. We present this exceptional case of adrenal crisis and discuss the mechanisms leading to liver failure in general and portal vein thrombosis in particular.

An echo to Choosing Wisely® in Switzerland.

BACKGROUND: Inspired by the US Choosing Wisely®, in 2016 the Swiss Society of General Internal Medicine released a list of five treatments or diagnostic tests used in the hospital and considered unnecessary based on not improving patient care and adding to health care costs. These "Smarter Medicine" recommendations were implemented in the Department of Internal Medicine, Uster Hospital, in August 2016. They were supported by lectures and weekly email communications. We analyzed the number of blood draws before and after implementation of the recommendation aimed at reducing blood tests. METHODS: This retrospective analysis was conducted in the Department of Internal Medicine, Uster Hospital, Canton of Zurich, Switzerland. Patients hospitalized in the 3 months before and after implementation were analyzed. RESULTS: A total of 2023 hospitalizations were analyzed. There was a significant decrease in the number of blood draws after introduction of the recommendation: before implementation, the median number of blood draws per patient was 4 (interquartile range [IQR], 2-7); after implementation, the median was 4 (IQR, 2-6; P = 0.002). Indeed, since 46% of the patients in the first group had more than four blood tests, this ratio decreased to 39% after implementation. DISCUSSION: Inappropriate blood draws may lead to anemia, patient discomfort and false-positive results. The simple and low-cost interventions used to implement "Smarter Medicine" have changed physician behavior by reducing the number of blood orders. These results are promising. Whether such recommendations will impact patient and clinical outcomes remains unknown; hence, further studies are needed to clarify this issue.

Functional expression of the CD163 scavenger receptor on acute myeloid leukemia cells of monocytic lineage.

The hemoglobin-haptoglobin (Hb-Hp) scavenger receptor CD163 is a monocyte/macrophage-restricted surface antigen, whose expression is strongly up-regulated by glucocorticoids. We have previously shown that CD163 is expressed by acute myeloid leukemia (AML) cells of monocytic lineage. Herein, we expand this finding by demonstrating constitutive and glucocorticoid-enhanced CD163 expression on French-American-British M4/M5 AML cells, and leukemic blasts of other AML subtypes and normal hematopoietic progenitor cells do not express CD163. We provide evidence that the functional characteristics of CD163 are preserved on malignant cells by showing the capability of types M4/M5 blast cells to internalize Hb-Hp by a CD163-mediated mechanism. Together, our results identify CD163 as a potential target for therapeutic intervention. It is important that CD163 does not appear to be released from leukemic blasts under noninflammatory conditions, thus reducing the probability of off-target side-effects as a result of competitive binding of potential therapeutic ligands to nonmembrane-bound CD163.

WIF1 prevents Wnt5A mediated LIMK/CFL phosphorylation and adherens junction disruption in human vascular endothelial cells.

BACKGROUND: Wnt5A is released by activated macrophages and elevated levels have been detected in sepsis patients with severe systemic inflammation. However, the signalling and functional effects of Wnt5A in the vascular endothelial cells (VEC) remained unclear. Recently, we showed that Wnt5A affects barrier function in human VEC through Ryk interaction. Wnt5A/Ryk signalling activates LIMK to inactivate the actin depolymerisation factor CFL by phosphorylation, promotes actin polymerisation and disrupts endothelial adherens junctions. FINDINGS: Here, we investigate the antagonistic effect of the Ryk specific secreted Wnt antagonist Wnt inhibitory factor (WIF)-1 on Wnt5A-mediated activation/inactivation of LIMK/CFL, and adherens junction disruption in human VEC. In human coronary artery endothelial cells (HCAEC), treatment with Wnt5A enhanced the phosphorylation of LIMK and CFL that was significantly prevented by WIF1. The presence of WIF1 suppressed Wnt5A-mediated disruption of ß-catenin and VE-cadherin adherens junctions in HCAEC, thereby preventing barrier dysfunction caused by Wnt5A. CONCLUSION: We conclude that WIF1 or molecules with similar properties could be potent tools for the prevention of vascular leakage due to Wnt5A-mediated actin cytoskeleton remodeling in diseases associated with systemic inflammation.

Wnt5A/Ryk signaling critically affects barrier function in human vascular endothelial cells.

Satisfactory therapeutic strategies for septic shock are still missing. Previously we found elevated levels of Wnt5A in patients with severe sepsis and septic shock. Wnt5A is released by activated macrophages but knowledge of its effects in the vascular system remains scant. Here we investigate the response of human coronary artery endothelial cells (HCAEC) to Wnt5A. We used a genome-wide differential expression approach to define novel targets regulated by Wnt5A. Gene ontology analysis of expression profiles revealed clusters of genes involved in actin cytoskeleton remodeling as the predominant targets of Wnt5A. Wnt5A targeted Rho-associated protein serine/threonine kinase (ROCK), leading to phosphorylation of LIM kinase-2 (LIMK2) and inactivation of the actin depolymerization factor cofilin-1 (CFL1). Functional experiments recording cytoskeletal rearrangements in living cells showed that Wnt5A enhanced stress fiber formation as a consequence of reduced actin depolymerization. The antagonist Wnt inhibitory factor 1 (WIF1) that specifically interferes with the WIF domain of Ryk receptors prevented actin polymerization. Wnt5A disrupted ß-catenin and VE-cadherin adherens junctions forming inter-endothelial gaps. Functional experiments targeting the endothelial monolayer integrity and live recording of trans-endothelial resistance revealed enhanced permeability of Wnt5A-treated HCAEC. Ryk silencing completely prevented Wnt5A-induced endothelial hyperpermeability. Wnt5A decreased wound healing capacity of HCAEC monolayers; this was restored by the ROCK inhibitor Y-27632. Here we show that Wnt5A acts on the vascular endothelium causing enhanced permeability through Ryk interaction and downstream ROCK/LIMK2/CFL1 signaling. Wnt5A/Ryk signaling might provide novel therapeutic strategies to prevent capillary leakage in systemic inflammation and septic shock.