Plasma levels of soluble urokinase-type plasminogen activator receptor associate with the clinical severity of acute Puumala hantavirus infection

Neutrophil-to-lymphocyte ratio is elevated in acute hantavirus infection and correlates with markers of disease severity

Pathogenic Eurasian hantaviruses cause hemorrhagic fever with renal syndrome (HFRS), which is characterized by acute kidney injury. The clinical course shows a broad range of severity and is influenced by direct and immune-mediated effects. The neutrophil-to-lymphocyte ratio (NLR) is a marker of systemic inflammation and predicts severity and outcome in various diseases. Therefore, we examined the role of NLR in HFRS caused by hantavirus Puumala (PUUV) and its association with disease severity and kidney injury. We detected elevated NLR levels on admission (NLRadm: median 3.82, range 1.75-7.59), which increased during acute HFRS. Maximum NLR levels (NLRmax: median 4.19, range 1.75-13.16) were 2.38-fold higher compared to the reference NLR level of 1.76 in the general population. NLR levels on admission correlate with markers of severity (length of hospital stay, serum creatinine) but not with other markers of severity (leukocytes, platelets, C-reactive protein, lactate dehydrogenase, serum albumin, proteinuria). Interestingly, levels of nephrin, which is a specific marker of podocyte damage in kidney injury, are highest on admission and correlate with NLRmax, but not with NLRadm. Together, we observed a correlation between systemic inflammation and the severity of HFRS, but our results also revealed that podocyte damage precedes these inflammatory processes.

[Factors of the hemostasis system as biomarkers of severe course of acute viral infections]

The authors give literature review of hemostasis and immune system factors intraction as main biomarkers of a severe cause of viral infectious diseases. Pro-inflamatory cytokines as the main markers of inflammation, can serve both as biomarkers of the clinical severity of the infectious process and reflect the state of the hemostatic and fibrinolytic systems, since components of these systems are present in various structures of the central nervous system and affect the development of neurons and synaptic plasticity. An inverse correlation has been proven between the concentration of D-dimer and the oxygenation index, and the development of DIC is not associated with the presence of respiratory failure in patients with influenza type A, while the ferritin concentration directly reflects the severity of the disease. One of the markers of endothelial damage may be soluble thrombomodulin, which, however, is rarely used in routine clinical practice. Cytoflavin is a highly effective pathogenetic drug that affects various parts of the hemostasis system, has anti-ischemic, antioxidant, antihypoxic, immunocorrective effect, which is indicated for any generalized infectious disease since its debut.

Comparison of C-reactive protein with distinct hyperinflammatory biomarkers in association with COVID-19 severity, mortality and SARS-CoV-2 variants

C-reactive protein (CRP) has been one of the most investigated inflammatory-biomarkers during the ongoing COVID-19 pandemics caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The severe outcome among patients with SARS-CoV-2 infection is closely related to the cytokine storm and the hyperinflammation responsible for the acute respiratory distress syndrome and multiple organ failure. It still remains a challenge to determine which of the hyperinflammatory biomarkers and cytokines are the best predictors for disease severity and mortality in COVID-19 patients. Therefore, we evaluated and compared the outcome prediction efficiencies between CRP, the recently reported inflammatory modulators (suPAR, sTREM-1, HGF), and the classical biomarkers (MCP-1, IL-1β, IL-6, NLR, PLR, ESR, ferritin, fibrinogen, and LDH) in patients confirmed with SARS-CoV-2 infection at hospital admission. Notably, patients with severe disease had higher serum levels of CRP, suPAR, sTREM-1, HGF and classical biomarkers compared to the mild and moderate cases. Our data also identified CRP, among all investigated analytes, to best discriminate between severe and non-severe forms of disease, while LDH, sTREM-1 and HGF proved to be excellent mortality predictors in COVID-19 patients. Importantly, suPAR emerged as a key molecule in characterizing the Delta variant infections.

suPAR to Risk-Stratify Patients With Malaria

Severe malaria (SM) is a leading cause of global morbidity and mortality, particularly in children in sub-Saharan Africa. However, existing malaria diagnostic tests do not reliably identify children at risk of severe and fatal outcomes. Dysregulated host immune and endothelial activation contributes to the pathogenesis of SM. Current research suggests that measuring markers of these pathways at presentation may have clinical utility as prognostic indicators of disease progression and risk of death. In this review, we focus on the available evidence implicating soluble urokinase-type plasminogen activator receptor (suPAR) as a novel and early predictor of severe and fatal malaria and discuss its potential utility for malaria triage and management.

Clinical and Immunological Predictors of Hemorrhagic Fever with Renal Syndrome Outcome during the Early Phase

The ability to accurately predict the early progression of hemorrhagic fever with renal syndrome (HFRS) is crucial for reducing morbidity and mortality rates in severely affected patients. However, the utility of biomarkers for predicting clinical outcomes remains elusive in HFRS. The aims of the current study were to analyze the serum levels of immune function-related proteins and identify novel biomarkers that may help ascertain clinical outcomes of HFRS. Enzyme-linked immunosorbent assay, Luminex, and bioanalyzer assays were used to quantitatively detect 15 biomarkers in 49 serum samples of 26 patients with HFRS. High hemoglobin (HGB) and low urine output (UO) levels were identified as potential biomarkers associated with the acute HFRS. The serum soluble urokinase plasminogen activator receptor (suPAR) and C-X-C motif chemokine ligand 10 (CXCL10) values increased in the early phase of diseases. Elevated suPAR, interleukin-10 (IL-10), CXCL10, and decreased transforming growth factor-beta 3 (TGF-β3) were representative predictors of the disease severity. Upregulation of the HGB showed a significant correlation with high levels of suPAR and CXCL10. Reduced UO positively correlated with increased suPAR, CXCL10, and TGF-β2, and decreased vascular endothelial growth factor and TGF-β3. The changing HGB and UO criteria, high suPAR, IL-10, CXCL10, and low TGF-β3 of HFRS raise significant awareness for physicians regarding prospective biomarkers for monitoring early warning signs of HFRS. This study provides critical insights into the clinical and immunological biomarkers for disease severity and progression in patients with HFRS to identify early predictions of fatal outcomes.

Severity Biomarkers in Puumala Hantavirus Infection

Annually, over 10,000 cases of hemorrhagic fever with renal syndrome (HFRS) are diagnosed in Europe. Puumala hantavirus (PUUV) causes most of the European HFRS cases. PUUV causes usually a relatively mild disease, which is rarely fatal. However, the severity of the infection varies greatly, and factors affecting the severity are mostly unrevealed. Host genes are known to have an effect. The typical clinical features in PUUV infection include acute kidney injury, thrombocytopenia, and increased vascular permeability. The primary target of hantavirus is the endothelium of the vessels of different organs. Although PUUV does not cause direct cytopathology of the endothelial cells, remarkable changes in both the barrier function of the endothelium and the function of the infected endothelial cells occur. Host immune or inflammatory mechanisms are probably important in the development of the capillary leakage. Several immunoinflammatory biomarkers have been studied in the context of assessing the severity of HFRS caused by PUUV. Most of them are not used in clinical practice, but the increasing knowledge about the biomarkers has elucidated the pathogenesis of PUUV infection.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) Independently Predicts Severity and Length of Hospitalisation in Patients With COVID-19

Background: Efficient healthcare based on prognostic variables in hospitalised patients with COVID-19 could reduce the risk of complications and death. Recently, soluble urokinase Plasminogen Activator Receptor (suPAR) was shown to predict respiratory failure, kidney injury, and clinical outcome in patients with SARS-CoV-2 infection. The aim of this study was to investigate the value of suPAR as a prognostic tool, in comparison with other variables, regarding disease severity and length of hospital stay in patients with COVID-19. Patients and Methods: Individuals hospitalised with COVID-19 (40 males, 20 females; median age 57.5 years) with a median symptom duration of 10 days and matched, healthy controls (n = 30) were included. Admission levels of suPAR were measured in serum by enzyme-linked immunosorbent assay. Blood cell counts, C-reactive protein (CRP) levels, lactate dehydrogenase (LDH), plasma creatinine and estimated glomerular filtration rates were analysed and oxygen demand, level of care and length of hospitalisation recorded. Results: Patients had significantly higher suPAR levels compared to controls (P < 0.001). Levels were higher in severely/critically (median 6.6 ng/mL) compared with moderately ill patients (median 5.0 ng/mL; P = 0.002). In addition, suPAR levels correlated with length of hospitalisation (rho = 0.35; P = 0.006). Besides suPAR, LDH, CRP, neutrophil count, neutrophil-to-monocyte and neutrophil-to-lymphocyte ratio, body mass index and chronic renal failure were discriminators of COVID-19 severity and/or predictors of length of hospitalisation. Conclusion: Admission levels of suPAR were higher in patients who developed severe/critical COVID-19 and associated with length of hospital stay. In addition, we showed that suPAR functioned as an independent predictor of COVID-19 disease severity.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) as a Biomarker of Systemic Chronic Inflammation

Systemic chronic inflammation (SCI) is persistent, health-damaging, low-grade inflammation that plays a major role in immunosenescence and in development and progression of many diseases. But currently, there are no recognized standard biomarkers to assess SCI levels alone, and SCI is typically measured by combining biomarkers of acute inflammation and infection, e.g., CRP, IL-6, and TNFα. In this review, we highlight 10 properties and characteristics that are shared by the blood protein soluble urokinase plasminogen activator receptor (suPAR) and SCI, supporting the argument that suPAR is a biomarker of SCI: (1) Expression and release of suPAR is upregulated by immune activation; (2) uPAR and suPAR exert pro-inflammatory functions; (3) suPAR is associated with the amount of circulating immune cells; (4) Blood suPAR levels correlate with the levels of established inflammatory biomarkers; (5) suPAR is minimally affected by acute changes and short-term influences, in contrast to many currently used markers of systemic inflammation; (6) Like SCI, suPAR is non-specifically associated with multiple diseases; (7) suPAR and SCI both predict morbidity and mortality; (8) suPAR and SCI share the same risk factors; (9) suPAR is associated with risk factors and outcomes of inflammation above and beyond other inflammatory biomarkers; (10) The suPAR level can be reduced by anti-inflammatory interventions and treatment of disease. Assessing SCI has the potential to inform risk for morbidity and mortality. Blood suPAR is a newer biomarker which may, in fact, be a biomarker of SCI since it is stably associated with inflammation and immune activation; shares the same risk factors as many age-related diseases; is both elevated by and predicts age-related diseases. There is strong evidence that suPAR is a prognostic marker of adverse events, morbidity, and mortality. It is associated with immune activity and prognosis across diverse conditions, including kidney disease, cardiovascular disease, cancer, diabetes, and inflammatory disorders. Thus, we think it likely represents a common underlying disease-process shared by many diseases; that is, SCI. We review the supporting literature and propose a research agenda that can help test the hypothesis that suPAR indexes SCI, with the potential of becoming the new gold standard for measuring SCI.

Soluble Urokinase Plasminogen Activator Receptor as a Decision Marker for Early Discharge of Patients with COVID-19 Symptoms in the Emergency Department

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (The Covid-19 pandemic) strains health care capacity. Better risk stratification, with discharge of patients with a predicted mild disease trajectory, can ease this burden. Elevated blood-soluble urokinase plasminogen activator receptor (suPAR) has previously been shown to be associated with risk of intubation in confirmed COVID-19 patients.

OBJECTIVE

To evaluate whether point-of-care measures of suPAR in patients presenting to the emergency department (ED) with symptoms of COVID-19 can identify patients that can be safely discharged.

METHODS

Observational cohort study including all patients in the ED with symptoms of COVID-19 from March 19 to April 3, 2020. SuPAR was measured at first presentation. Review of electronic patient records 14 days after admission was used to assess disease trajectory. Primary endpoints were mild, moderate, severe, or very severe trajectory. The predictive value of suPAR, National Early Warning Score (NEWS), C-reactive protein (CRP), and duration of symptoms was calculated using receiver operating characteristics (ROC).

RESULTS

Of 386 patients, 171 (44%) had a mild disease trajectory, 79 (20%) a moderate, 63 (16%) a severe, and 73 (19%) a very severe disease trajectory. Low suPAR was a strong marker of mild disease trajectory. Results suggest a cut-off for discharge for suPAR < 2.0 ng/mL if suPAR is used as a single parameter, and <3.0 ng/mL when combined with NEWS ≤ 4 and CRP < 10 mg/L.

CONCLUSION

suPAR is a potential biomarker for triage and safe early discharge of patients with COVID-19 symptoms in the ED. suPAR can be used even before SARS-CoV-2 status is known.

suPAR Cut-Offs for Risk Stratification in Patients With Symptoms of COVID-19

Objectives

Elevated soluble urokinase Plasminogen Activator Receptor (suPAR) is a biomarker associated with adverse outcomes. We aimed to investigate the associations between plasma suPAR levels (testing the cut-offs ⩽4, 4-6, and ⩾6 ng/mL) with risk of 14-day mortality, and with the risk of mechanical ventilation in patients that tested positive for SARS-CoV-2.

Methods

Observational cohort study of patients presenting with symptoms of COVID-19 at Department of Emergency Medicine, Amager and Hvidovre Hospital, Denmark from March 19th, 2020 to April 3rd, 2020. Plasma suPAR was measured using suPARnostic technologies. Patients were followed for development of mechanical ventilation and mortality for 14 days. Validation of our findings were carried out in a similar sized COVID-19 patient cohort from Mikkeli Central Hospital, Finland.

Results

Among 386 patients with symptoms of COVID-19, the median (interquartile range) age was 64 years (46-77), 57% were women, median suPAR was 4.0 ng/mL (2.7-5.9). In total, 35 patients (9.1%) died during the 14 days follow-up. Patients with suPAR ⩽4 ng/mL (N = 196; 50.8%) had a low risk of mortality (N = 2; 1.0%; negative predictive value of 99.0%, specificity 55.3%, sensitivity 95.2%, positive predictive value 17.4%). Among patients with suPAR ⩾6 ng/mL (N = 92; 23.8%), 16 died (17.4%). About 99 patients (25.6%) tested positive for SARS CoV-2 and of those 12 (12.1%) developed need for mechanical ventilation. None of the SARS-CoV-2 positive patients with suPAR ⩽4 ng/mL (N = 28; 38.8%) needed mechanical ventilation or died. The Mikkeli Central Hospital validation cohort confirmed our findings concerning suPAR cut-offs for risk of development of mechanical ventilation and mortality.

Conclusions

Patients with symptoms of COVID-19 and suPAR ⩽4 or ⩾6 ng/mL had low or high risk, respectively, concerning the need for mechanical ventilation or mortality. We suggest cut-offs for identification of risk groups in patients presenting to the ED with symptoms of or confirmed COVID-19.

Coagulopathy in Acute Puumala Hantavirus Infection

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome (HFRS), also called nephropathia epidemica (NE), which is mainly endemic in Europe and Russia. The clinical features include a low platelet count, altered coagulation, endothelial activation, and acute kidney injury (AKI). Multiple connections between coagulation pathways and inflammatory mediators, as well as complement and kallikrein–kinin systems, have been reported. The bleeding symptoms are usually mild. PUUV-infected patients also have an increased risk for disseminated intravascular coagulation (DIC) and thrombosis.

Soluble urokinase-type plasminogen activator receptor predicts peripheral artery disease severity and outcomes

Soluble urokinase-type plasminogen activator receptor (suPAR) is associated with chronic kidney disease (CKD) severity and peripheral artery disease (PAD). We hypothesize an association of PAD severity and suPAR in patients without advanced CKD and further risk stratification according to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. For study purposes, suPAR was measured in 334 PAD patients (34% women, age 69 (62–78) years, eGFR 68 ± 20 mL/min/1.72 m²) by commercial ELISA. Patients were followed for 10 years to assess long-term all-cause survival by Cox regression. Higher suPAR levels were associated with lower ankle–brachial index (R = −0.215, p = 0.001) in patients with PAD without media-sclerosis (n = 236). suPAR levels inversely correlated with decreased glomerular filtration rate (R = −0.476, p < 0.001) and directly correlated with urinary albumin-to-creatinine ratio (R = 0.207, p < 0.001). Furthermore, higher suPAR levels associated with a higher KDIGO risk score (p < 0.001). Baseline suPAR was significantly associated with all-cause mortality (HR 1.40 (95% CI 1.16–1.68), p < 0.001) over 10 years. suPAR remained associated with mortality (HR 1.29 (1.03–1.61), p = 0.026) after multivariable adjustment for age, sex, cardiovascular risk factors, and eGFR. Future research may define a standard role for suPAR assessment in PAD’s work-up and treatment, especially in patients with CKD.

Glomerular filtration barrier dysfunction in a self-limiting, RNA virus-induced glomerulopathy resembles findings in idiopathic nephrotic syndromes

Podocyte injury has recently been described as unifying feature in idiopathic nephrotic syndromes (INS). Puumala hantavirus (PUUV) infection represents a unique RNA virus-induced renal disease with significant proteinuria. The underlying pathomechanism is unclear. We hypothesized that PUUV infection results in podocyte injury, similar to findings in INS. We therefore analyzed standard markers of glomerular proteinuria (e.g. immunoglobulin G [IgG]), urinary nephrin excretion (podocyte injury) and serum levels of the soluble urokinase plasminogen activator receptor (suPAR), a proposed pathomechanically involved molecule in INS, in PUUV-infected patients. Hantavirus patients showed significantly increased urinary nephrin, IgG and serum suPAR concentrations compared to healthy controls. Nephrin and IgG levels were significantly higher in patients with severe proteinuria than with mild proteinuria, and nephrin correlated strongly with biomarkers of glomerular proteinuria over time. Congruently, electron microcopy analyses showed a focal podocyte foot process effacement. suPAR correlated significantly with urinary nephrin, IgG and albumin levels, suggesting suPAR as a pathophysiological mediator in podocyte dysfunction. In contrast to INS, proteinuria recovered autonomously in hantavirus patients. This study reveals podocyte injury as main cause of proteinuria in hantavirus patients. A better understanding of the regenerative nature of hantavirus-induced glomerulopathy may generate new therapeutic approaches for INS.

Flash-Like Albuminuria in Acute Kidney Injury Caused by Puumala Hantavirus Infection

Transient proteinuria and acute kidney injury (AKI) are characteristics of Puumala virus (PUUV) infection. Albuminuria peaks around the fifth day and associates with AKI severity. To evaluate albuminuria disappearance rate, we quantified albumin excretion at different time points after the fever onset. The study included 141 consecutive patients hospitalized due to acute PUUV infection in Tampere University Hospital, Finland. Timed overnight albumin excretion (cU-Alb) was measured during the acute phase in 133 patients, once or twice during the convalescent phase within three months in 94 patients, and at six months in 36 patients. During hospitalization, 30% of the patients had moderately increased albuminuria (cU-Alb 20-200 μg/min), while 57% presented with severely increased albuminuria (cU-Alb >200 μg/min). Median cU-Alb was 311 μg/min (range 2.2-6460) ≤7 days after fever onset, 235 μg/min (range 6.8-5479) at 8-13 days and 2.8 μg/min (range 0.5-18.2) at 14-20 days. After that, only one of the measurements showed albuminuria (35.4 μg/min at day 44). At six months, the median cU-Alb was 2.0 μg/min (range 0.6-14.5). Albuminuria makes a flash-like appearance in PUUV infection and returns rapidly to normal levels within 2-3 weeks after fever onset. In the case of AKI, this is a unique phenomenon.

Soluble urokinase-type plasminogen activator receptor and incident end-stage renal disease in Chinese patients with chronic kidney disease

BACKGROUND

Soluble urokinase-type plasminogen activator receptor (suPAR), a marker of immune activation, was shown to be associated with outcomes and kidney disease among various patient populations. The prognostic role of circulating suPAR levels in patients with chronic kidney disease (CKD) needs to be investigated in a cohort with large sample size of renal diseases.

METHODS

We measured serum suPAR concentration in 2391 CKD patients in the multicenter Chinese Cohort Study of Chronic Kidney Disease, and investigated the association of serum suPAR with the prespecified endpoint event, end-stage renal disease (ESRD), using Cox proportional hazards regression model.

RESULTS

Altogether, 407 ESRD events occurred during the median follow-up of 54.8 (interquartile range: 47.5-62.2) months. The higher levels of serum suPAR were independently associated with increased risk of incident ESRD after adjusting for potential confounders including the baseline estimated glomerular filtration rate categories, with the hazard ratios (HRs) of 1.53 [95% confidence intervals (CIs) 1.10-2.12] for the top tertile (≥3904 pg/mL) compared with the bottom tertile (<2532 pg/mL). When stratified by the etiologies of CKD, among patients with glomerulonephritis (GN), serum suPAR levels were also independently associated with the higher risk of ESRD, with an HR of 1.61 (95% CI 1.03-2.53) in the top tertile compared with the bottom tertile.

CONCLUSIONS

Circulating suPAR level was independently associated with an increased risk of progression to ESRD in Chinese CKD patients, especially in those with an etiology of GN.

Glycoprotein YKL-40 Is Elevated and Predicts Disease Severity in Puumala Hantavirus Infection

Most cases of hemorrhagic fever with renal syndrome (HFRS) in Europe are caused by the Puumala hantavirus (PUUV). Typical features of the disease are increased vascular permeability, acute kidney injury (AKI), and thrombocytopenia. YKL-40 is an inflammatory glycoprotein involved in various forms of acute and chronic inflammation. In the present study, we examined plasma YKL-40 levels and the associations of YKL-40 with disease severity in acute PUUV infection. A total of 79 patients treated in Tampere University Hospital during 2005–2014 were studied. Plasma YKL-40 was measured in the acute phase, the recovery phase, and one year after hospitalization. Plasma YKL-40 levels were higher during the acute phase compared to the recovery phase and one year after hospitalization (median YKL-40 142 ng/mL, range 11–3320, vs. 45 ng/mL, range 15–529, vs. 32 ng/mL, range 3–213, p < 0.001). YKL-40 level was correlated with the length of hospital stay (r = 0.229, p = 0.042), the levels of inflammatory markers—that is, blood leukocytes (r = 0.234, p = 0.040), plasma C-reactive protein (r = 0.332, p = 0.003), and interleukin-6 (r = 0.544, p < 0.001), and maximum plasma creatinine level (r = 0.370, p = 0.001). In conclusion, plasma YKL-40 levels were found to be elevated during acute PUUV infection and correlated with the overall severity of the disease, as well as with the degree of inflammation and the severity of AKI.

Motility of human renal cells is disturbed by infection with pathogenic hantaviruses

Background

Hemorrhagic fever with renal syndrome (HFRS) caused by pathogenic hantaviruses in Europe and Asia is often characterized by acute kidney injury (AKI) with massive proteinuria. Renal filtration depends on the integrity of epithelial and endothelial monolayers in the tubular and glomerular apparatus. Tubular and glomerular cells represent target cells of hantavirus infection. However, the detailed mechanisms of renal impairment induced by hantaviruses are not well understood.

Methods

We analyzed the cellular consequences of hantavirus infection by measuring adhesion and migration capacity of human renal cells infected with Puumala (PUUV) or Hantaan (HTNV) virus. The impact of hantaviral nucleocapsid proteins (N proteins) on motility was examined by transfection of podocytes.

Results

Infection of kidney cells with hantavirus species PUUV and HTNV causes a significant reduction of migration capacity. The impaired motility depends on viral replication and transfection of podocytes with N protein of PUUV or HTNV reveals that the expression of N protein alone is sufficient to deteriorate podocyte function. The cellular effects are more pronounced for the more pathogenic HTNV than for PUUV that causes a milder form of HFRS.

Conclusions

The direct impairment of migration capacity of renal cells by hantaviral N proteins may contribute substantially to proteinuria observed in the clinical picture of hantavirus infection.

High plasma resistin associates with severe acute kidney injury in Puumala hantavirus infection

Background

Puumala hantavirus (PUUV) infected patients typically suffer from acute kidney injury (AKI). Adipokines have inflammation modulating functions in acute diseases including AKI. We examined plasma levels of three adipokines (resistin, leptin, and adiponectin) in acute PUUV infection and their associations with disease severity.

Methods

This study included 79 patients hospitalized due to acute PUUV infection. Plasma resistin, leptin, adiponectin, as well as IL-6 and CRP, were measured at the acute phase, recovery phase and one year after hospitalization.

Results

Plasma resistin levels were significantly higher in the acute phase compared to the recovery phase and one year after (median resistin 28 pg/mL (11–107) vs. 17 pg/mL (7–36) vs. 14 pg/mL (7–31), p<0.001). Maximum resistin concentration correlated with maximum plasma creatinine levels (r = 0.63; p<0.001). The higher the amount of albuminuria in the urine dipstick test (0–1+, 2+ or 3+) at admission, the higher the median of maximum resistin (24.7 pg/mL, 25.4 pg/mL and 39.6 pg/mL, respectively, p = 0.002). High resistin was also an independent risk factor for severe AKI (creatinine ≥353.6μmol/L) (OR 1.08, 95% CI 1.02–1.14). Neither plasma leptin nor adiponectin level had any correlation with creatinine concentration or the amount of albuminuria.

Conclusions

Plasma resistin independently associates with the severity of AKI in acute PUUV infection. The association of resistin with the amount of albuminuria suggests that the level of plasma resistin is not only influenced by renal clearance but could have some role in the pathogenesis of AKI during PUUV infection.

Kidney disease in Puumala hantavirus infection

Acute kidney injury (AKI) remains a predominant clinical expression of nephropathia epidemica (NE). Its pathogenesis is not yet fully understood. Here, we describe the tissue injury comprehensively and present new data aimed to characterize the injury and explain its pathophysiology. When compared to tubulointerstitial nephritis of a wide variety of other aetiologies, a high degree of proteinuria is a distinguished trait of NE, a finding that is also helpful in the clinical suspicion of the disease. Recently, novel biomarkers for the prediction of severe AKI, including neutrophil gelatinase-associated lipocalin (NGAL), have been identified and ultrastructural tissue changes have been more accurately described. A role for soluble urokinase-type plasminogen activator (suPAR) in the pathogenesis of NE has been suggested, and data on gene polymorphisms, in relation to the severity of AKI have been presented. Smoking is a risk factor for NE and smoking is also associated with aggravated AKI in NE. Although no specific treatment is in sight, recent case reports concerning therapy directed against vascular permeability and vasodilation are of interest. In fact, future work trying to explain the pathophysiology of AKI might need concentrated efforts towards the mechanisms of increased vascular permeability and vasodilatation, which irrespective of organ manifestation, are two major determinants of NE.

HMGB1 Is a Potential Biomarker for Severe Viral Hemorrhagic Fevers

Hemorrhagic fever with renal syndrome (HFRS) and Crimean-Congo hemorrhagic fever (CCHF) are common representatives of viral hemorrhagic fevers still often neglected in some parts of the world. Infection with Dobrava or Puumala virus (HFRS) and Crimean-Congo hemorrhagic fever virus (CCHFV) can result in a mild, nonspecific febrile illness or as a severe disease with hemorrhaging and high fatality rate. An important factor in optimizing survival rate in patients with VHF is instant recognition of the severe form of the disease for which significant biomarkers need to be elucidated. To determine the prognostic value of High Mobility Group Box 1 (HMGB1) as a biomarker for disease severity, we tested acute serum samples of patients with HFRS or CCHF. Our results showed that HMGB1 levels are increased in patients with CCHFV, DOBV or PUUV infection. Above that, concentration of HMGB1 is higher in patients with severe disease progression when compared to the mild clinical course of the disease. Our results indicate that HMGB1 could be a useful prognostic biomarker for disease severity in PUUV and CCHFV infection, where the difference between the mild and severe patients group was highly significant. Even in patients with severe DOBV infection concentrations of HMGB1 were 2.8-times higher than in the mild group, but the difference was not statistically significant. Our results indicated HMGB1 as a potential biomarker for severe hemorrhagic fevers.

Thrombocytopenia associates with the severity of inflammation and variables reflecting capillary leakage in Puumala Hantavirus infection, an analysis of 546 Finnish patients

BACKGROUND

Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) in humans. Hantavirus infections are characterized by thrombocytopenia. Our objective was to assess the association of thrombocytopenia with disease severity in HFRS induced by Puumala hantavirus (PUUV).

METHODS

Altogether 546 patients treated for acute serologically confirmed PUUV infection during 1982-2013 at Tampere University Hospital, Finland, were examined. Blood platelet count was determined daily and analysed in relation to different variables reflecting disease severity. The patients were divided into two groups according to the minimum platelet count: severe thrombocytopenia (<69 × 10(9)/L, i.e. below median) and no severe thrombocytopenia (≥69 × 10(9)/L).

RESULTS

Thrombocytopenia (platelet count <150 × 10(9)/L) was detected in 90% of patients, and in 28% of patients platelet count was <50 × 10(9)/L. Patients with severe thrombocytopenia had longer stay (8 versus 7 days, p = 0.002) and greater weight gain (2.8 versus 2.0 kg, p < 0.001) at the hospital, higher blood leukocyte count (11.2 × 10(9)/L versus 9.6 × 10(9)/L, p < 0.001), plasma C-reactive protein (81 versus 59 mg/L, p < 0.001), maximum hematocrit (0.44 versus 0.42, p < 0.001), urinary protein excretion (1.7 versus 1.1 g/24 h, p = 0.002), and lower plasma albumin concentration (27 versus 32 g/L, p < 0.001) than patients without severe thrombocytopenia (comparisons between medians). Maximum creatinine concentration did not differ between patients with or without severe thrombocytopenia (median 235 versus 214 μmol/L, p = 0.217).

CONCLUSIONS

The severity of thrombocytopenia associates with the degree of inflammation and variables reflecting capillary leakage, but not with the severity of acute kidney injury in PUUV infected Finnish patients.

Circulating Permeability Factors in Primary Focal Segmental Glomerulosclerosis: A Review of Proposed Candidates

Primary focal segmental glomerulosclerosis (FSGS) is a major cause of the nephrotic syndrome and often leads to end-stage renal disease. This review focuses on circulating permeability factors in primary FSGS that have been implicated in the pathogenesis for a long time, partly due to the potential recurrence in renal allografts within hours after transplantation. Recently, three molecules have been proposed as a potential permeability factor by different groups: the soluble urokinase plasminogen activator receptor (suPAR), cardiotrophin-like cytokine factor-1 (CLCF-1), and CD40 antibodies. Both CLCF-1 and CD40 antibodies have not been validated by independent research groups yet. Since the identification of suPAR, different studies have questioned the validity of suPAR as a biomarker to distinguish primary FSGS from other proteinuric kidney diseases as well as suPAR's pathogenic role in podocyte damage. Researchers have suggested that cleaved molecules of suPAR have a pathogenic role in FSGS but further studies are needed to determine this role. In future studies, proposed standards for the research of the permeability factor should be carefully followed. The identification of the permeability factor in primary FSGS would be of great clinical relevance as it could influence potential individual treatment regimen.

Urinary Neutrophil Gelatinase-Associated Lipocalin (NGAL) and proteinuria predict severity of acute kidney injury in Puumala virus infection

BACKGROUND

Nephropathia epidemica (NE) is a mild form of hemorrhagic fever with renal syndrome (HFRS) that is caused by the Puumala virus. Periodic outbreaks have been described in endemic areas, with a substantial number of previously healthy individuals developing acute kidney injury (AKI). There is a considerable diversity in the clinical course of the disease, and few patients require renal replacement therapy.

METHODS

We tested whether urinary neutrophil gelatinase associated lipocalin (uNGAL), urine albumin/creatinine ratio (uACR), urine protein/creatinine ratio (uPCR), urine dipstick protein, C-reactive protein, procalcitonin, leukocyte and platelet count, determined on admission to the hospital, can predict the severity of AKI. Sixty-one patients were analyzed during admission in the emergency department.

RESULTS

The variables most strongly associated with peak plasma creatinine concentration were uNGAL (β = 0.70, p <0.0001), uPCR (β = 0.64, p = 0.001), uACR (β = 0.61, p = 0.002), and dipstick proteinuria (β = 0.34, p = 0.008). The highest AUC-ROC to predict stage 3 AKI according to the acute kidney injury network's (AKIN) classification was seen for uNGAL (0.81, p = 0.001).

CONCLUSION

uNGAL accurately predicts the severity of AKI in NE. This could help emergency room physicians predict disease severity and allow for initial risk stratification.

Clinical course and long-term outcome of hantavirus-associated nephropathia epidemica, Germany

The consequences of associated hematuria may be long-lasting, and hantavirus IgG is detectable years after acute infection.

Human infection with Puumala virus (PUUV), the most common hantavirus in Central Europe, causes nephropathia epidemica (NE), a disease characterized by acute kidney injury and thrombocytopenia. To determine the clinical phenotype of hantavirus-infected patients and their long-term outcome and humoral immunity to PUUV, we conducted a cross-sectional prospective survey of 456 patients in Germany with clinically and serologically confirmed hantavirus-associated NE during 2001–2012. Prominent clinical findings during acute NE were fever and back/limb pain, and 88% of the patients had acute kidney injury. At follow-up (7–35 mo), all patients had detectable hantavirus-specific IgG; 8.5% had persistent IgM; 25% had hematuria; 23% had hypertension (new diagnosis for 67%); and 7% had proteinuria. NE-associated hypertension and proteinuria do not appear to have long-term consequences, but NE-associated hematuria may. All patients in this study had hantavirus-specific IgG up to years after the infection.

Increased plasma level of soluble urokinase plasminogen activator receptor is associated with incidence of heart failure but not atrial fibrillation

AIMS

Soluble urokinase plasminogen activator receptor (suPAR) in plasma is a novel inflammatory marker thought to be released from the cell surface of neutrophils, T cells, and macrophages. Other inflammatory markers, mainly acute phase proteins produced in the liver, have been associated with the incidence of heart failure (HF) and atrial fibrillation (AF). We investigated the association between suPAR and incident HF and AF in a population-based cohort.

METHODS AND RESULTS

Soluble urokinase plasminogen activator receptor was measured in 4530 subjects (aged 46–68 years, 61% women), who participated in the Malmö Diet and Cancer study during 1991–1996. Incident cases of HF and AF were identified from the Swedish hospital discharge register during a median follow-up of 16.3 years. During follow-up, 109 subjects (55% men) were diagnosed with new-onset HF and 321 individuals (50% men) with AF. suPAR was significantly associated with increased plasma levels of NT-proBNP (P<0.001). suPAR was significantly associated with incidence of HF [hazard ratio (HR) for the third vs. first tertile 3.33, 95% confidence interval (CI) 1.91–5.81 after adjustment for age and sex; and HR 1.82, 95% CI 1.02–3.27, P for trend 0.018 after adjustment for conventional risk factors and biomarkers]. suPAR was significantly associated with incidence of AF, when adjusted for age and sex (HR 1.40, 95% CI 1.06–1.85). However, this relationship was non-significant after adjustment for conventional risk factors and biomarkers.

CONCLUSION

Soluble urokinase plasminogen activator receptor was associated with increased plasma levels of NT-proBNP and incidence of HF, but not with AF among middle-aged subjects.

Smoking is associated with aggravated kidney injury in Puumala hantavirus-induced haemorrhagic fever with renal syndrome

BACKGROUND

Previous studies indicate that smoking affects the outcome of some infections and is a risk factor for Puumala virus (PUUV) infection. The aim of this study was to assess the effect of smoking on the clinical severity of PUUV infection and the prevalence of smoking in patients with PUUV infection.

METHODS

A questionnaire on smoking habits was sent to 494 patients in 2012, who had been treated in Tampere University Hospital, Finland, for serologically confirmed PUUV infection during years 1982-2012.

RESULTS

Of all patients, 357 (72%) participated. Maximum plasma creatinine level measured during acute illness was significantly higher in current smokers than in non-smokers (median: 273 versus 184 µmol/L, P < 0.001). Current smokers had a higher maximum blood leucocyte count than non-smokers (median: 10.8 versus 8.9 × 10(9)/L, P < 0.001) and they were younger than non-smokers (38 versus 45 years, P < 0.001). There were no differences between current smokers and non-smokers in the other variables reflecting the severity of PUUV infection. Altogether 51% were current smokers at the time of onset of the illness, 57% of males and 36% of females. During these years in Finland, smoking among males in the same aged population has decreased from 33 to 22% and among females, smoking has varied between 14 and 20%.

CONCLUSIONS

Smoking is common in patients with PUUV infection. Current smokers suffer from more severe acute kidney injury (AKI) and they have higher leucocyte count than non-smokers in PUUV infection. Smoking cessation decreases the risk of severe AKI to the same level as observed in never-smokers.

Community Acquired Severe Acute Kidney Injury Caused by Hantavirus-Induced Hemorrhagic Fever with Renal Syndrome Has a Favorable Outcome

BACKGROUND

Puumala hantavirus (PUUV) induces an acute tubulointerstitial nephritis and acute kidney injury (AKI). Our aim was to evaluate the prognosis of severe AKI associated with PUUV infection.

METHODS

We examined 556 patients who were treated at Tampere University Hospital during 1982-2013 for acute, serologically confirmed PUUV infection. Plasma creatinine was measured during hospitalization, convalescence, and 1, 2, and 5 years after the acute infection.

RESULTS

Plasma creatinine concentration was elevated (>100 μmol/l) in 459 (83%) patients, while altogether 189 patients (34%) had severe AKI defined as Kidney Disease: Improving Global Outcomes (KDIGO) stage 3, that is, plasma creatinine ≥353.6 μmol/l (4.0 mg/dl) or need of dialysis. There were no fatal cases during the hospitalization or the following 3 months. Fatality rate during the years following PUUV infection did not differ between patients who had suffered from severe AKI versus those without severe AKI. Post-hospitalization plasma creatinine values were available for 188 (34%) patients. One month after the acute infection, patients with prior severe AKI had higher median plasma creatinine concentration (82 µmol/l, range 54-184) than patients without severe AKI (74 µmol/l, range 55-109, p = 0.005). After 1 year, no significant difference existed in median plasma creatinine concentrations between patients with (71 µmol/l, range 36-123) and without prior severe AKI (72 µmol/l, range 34-116, p = 0.711). After 5 years all but 1 patient had normal creatinine levels.

CONCLUSIONS

In contrast to the worldwide well-accepted KDIGO criteria, severe AKI associated with PUUV infection is not associated with excess fatality but has a very good prognosis, both in the short and long terms.

The fundamental role of endothelial cells in hantavirus pathogenesis

Hantavirus, a genus of rodent- and insectivore-borne viruses in the family Bunyaviridae, is a group of emerging zoonotic pathogens. Hantaviruses cause hemorrhagic fever with renal syndrome and hantavirus cardiopulmonary syndrome in man, often with severe consequences. Vascular leakage is evident in severe hantavirus infections, and increased permeability contributes to the pathogenesis. This review summarizes the current knowledge on hantavirus interactions with hematopoietic and endothelial cells, and their effects on the increased vascular permeability.

Urine soluble urokinase-type plasminogen activator receptor levels correlate with proteinuria in Puumala hantavirus infection

OBJECTIVES

Urokinase-type plasminogen activator receptor (uPAR) is upregulated during inflammation and known to bind to β3 -integrins, receptors used by pathogenic hantaviruses to enter endothelial cells. It has been proposed that soluble uPAR (suPAR) is a circulating factor that causes focal segmental glomerulosclerosis and proteinuria by activating β3 -integrin in kidney podocytes. Proteinuria is also a characteristic feature of hantavirus infections. The aim of this study was to evaluate the relation between urine suPAR levels and disease severity in acute Puumala hantavirus (PUUV) infection.

DESIGN

A single-centre, prospective cohort study.

SUBJECTS AND METHODS

Urinary suPAR levels were measured twice during the acute phase and once during convalescence in 36 patients with serologically confirmed PUUV infection. Fractional excretion of suPAR (FE suPAR) and of albumin (FE alb) was calculated.

RESULTS

The FE suPAR was significantly elevated during the acute phase of PUUV infection compared to the convalescent phase (median 3.2%, range 0.8-52.0%, vs. median 1.9%, range 1.0-5.8%, P = 0.005). Maximum FE suPAR was correlated markedly with maximum FE alb (r = 0.812, P < 0.001) and with several other variables that reflect disease severity. There was a positive correlation with the length of hospitalization (r = 0.455, P = 0.009) and maximum plasma creatinine level (r = 0.780, P < 0.001) and an inverse correlation with minimum urinary output (r = -0.411, P = 0.030). There was no correlation between FE suPAR and plasma suPAR (r = 0.180, P = 0.324).

CONCLUSION

Urinary suPAR is markedly increased during acute PUUV infection and is correlated with proteinuria. High urine suPAR level may reflect local production of suPAR in the kidney during the acute infection.

Soluble urokinase receptor is a biomarker of cardiovascular disease in chronic kidney disease

Soluble urokinase-type plasminogen activator receptor (suPAR) accumulates in patients with chronic kidney disease (CKD). In various non-CKD populations, suPAR has been proposed as a prognostic marker for mortality and cardiovascular disease. However, it is not known whether suPAR holds prognostic information in patients with mild-to-moderate CKD. In a prospective observational study of 476 patients with mild-to-moderate kidney disease, we examined multivariate associations between suPAR, overall mortality, and cardiovascular events. After a mean follow-up of 57 months, 52 patients died and 76 patients had at least one fatal or nonfatal cardiovascular event. Higher suPAR was directly and significantly associated with both overall mortality (univariate hazard ratio 5.35) and cardiovascular events (univariate hazard ratio 5.06). In multivariate analysis, suPAR remained significantly associated with cardiovascular events (full model, hazard ratio 3.05). Thus, in patients with mild-to-moderate CKD, suPAR concentrations show a clear, direct, and graded association with a higher risk for new-onset cardiovascular disease.

Correlation of biomarkers for parasite burden and immune activation with acute kidney injury in severe falciparum malaria

Background

Acute kidney injury (AKI) complicating severe Plasmodium falciparum malaria occurs in up to 40% of adult patients. The case fatality rate reaches 75% in the absence of renal replacement therapy (RRT). The precise pathophysiology of AKI in falciparum malaria remains unclear. Histopathology shows acute tubular necrosis with localization of host monocytes and parasitized red blood cells in the microvasculature. This study explored the relationship of plasma soluble urokinase-type plasminogen activator receptor (suPAR), as a proxy-measure of mononuclear cell activation, and plasma P. falciparum histidine rich protein 2 (PfHRP2), as a measure of sequestered parasite burden, with AKI in severe malaria.

Methods

Admission plasma suPAR and PfHRP2 concentrations were assessed in Bangladeshi adults with severe falciparum malaria (n = 137). Patients were stratified according to AKI severity based on admission creatinine clearance.

Results

A total of 106 (77%) patients had AKI; 32 (23%), 42 (31%) and 32 (23%) were classified into ‘mild, ‘moderate’ and ‘severe’ AKI groups, respectively. Plasma suPAR and PfHRP2 concentrations increased with AKI severity (test-for-trend P <0.0001) and correlated with other markers of renal dysfunction. Admission plasma suPAR and PfHRP2 concentrations were higher in patients who later required RRT (P <0.0001 and P = 0.0004, respectively). In a multivariate analysis, both increasing suPAR and PfHRP2 were independently associated with increasing urine neutrophil gelatinase-associated lipocalin concentration, a marker of acute tubular necrosis (β = 16.54 (95% CI 6.36-26.71) and β = 0.07 (0.02-0.11), respectively).

Conclusions

Both sequestered parasite burden and immune activation contribute to the pathogenesis of AKI in severe falciparum malaria.

Old World hantaviruses: aspects of pathogenesis and clinical course of acute renal failure

Hantavirus-associated diseases represent emerging infections that are ranked in the highest priority group of communicable diseases for surveillance and epidemiological research. In the last years, several novel hantavirus species were described and the number of host reservoir species harboring hantaviruses is also increasing. Reports of cases with severe or atypical clinical courses become also more frequent. These facts raise more and more questions concerning host reservoir specificity, pathogenicity and molecular mechanism of pathogenesis. Hantavirus disease is characterized by vascular leakage due to increased capillary permeability. The infection manifests often in the lung (hantaviral cardiopulmonary syndrome; HCPS) or in the kidney (hemorrhagic fever with renal syndrome, HFRS). The underlying mechanisms of both syndromes are probably similar despite the difference in organ tropism. Characterization of hantaviral replication cycle and of patient-specific determinants will help to identify factors responsible for the clinical symptoms and course.

The pathogenesis of nephropathia epidemica: new knowledge and unanswered questions

Puumala virus (PUUV) causes an acute hemorrhagic fever with renal syndrome (HFRS), a zoonosis also called nephropathia epidemica (NE). The reservoir host of PUUV is the bank vole (Myodes glareolus). Herein we review the main clinical manifestations of NE, acute kidney injury, increased vascular permeability, coagulation abnormalities as well as pulmonary, cardiac, central nervous system and ocular manifestations of the disease. Several biomarkers of disease severity have recently been discovered: interleukin-6, pentraxin-3, C-reactive protein, indoleamine 2,3-dioxygenase, cell-free DNA, soluble urokinase-type plasminogen activator, GATA-3 and Mac-2 binding protein. The role of cytokines, vascular endothelial growth hormone, complement, bradykinin, cellular immune response and other mechanisms in the pathogenesis of NE as well as host genetic factors will be discussed. Finally therapeutic aspects and directions for further research will be handled.