Hantaviruses are the causative agents of haemorrhagic fever with renal syndrome (HFRS) in Eurasia and of hantavirus cardiopulmonary syndrome (HCPS) in the Americas. The case fatality rate varies between different hantaviruses and can be up to 40%. At present, there is no specific treatment available. The hantavirus pathogenesis is not well understood, but most likely, both virus-mediated and host-mediated mechanisms are involved. The aim of the present study was to investigate the association among Puumala hantavirus (PUUV) viral RNA load, humoral immune response and disease severity in patients with HFRS. We performed a study of 105 PUUV-infected patients that were followed during the acute phase of disease and for up to 1–3 months later. Fifteen of the 105 patients (14%) were classified as having moderate/severe disease. A low PUUV-specific IgG response (p <0.05) and also a higher white blood cell count (p <0.001) were significantly associated with more severe disease. The PUUV RNA was detected in a majority of patient plasma samples up to 9 days after disease onset; however, PUUV RNA load or longevity of viraemia were not significantly associated with disease severity. We conclude that a low specific IgG response was associated with disease severity in patients with HFRS, whereas PUUV RNA load did not seem to affect the severity of HFRS. Our results raise the possibility of passive immunotherapy as a useful treatment for hantavirus-infected patients.

Background. Endothelial activation and dysfunction play a central role in the pathogenesis of sepsis and viral hemorrhagic fevers. Hantaviral disease is a viral hemorrhagic fever and is characterized by capillary dysfunction, although the underlying mechanisms for hantaviral disease are not fully elucidated.Methods. The temporal course of endothelial activation and repair were analyzed during Puumala hantavirus infection and associated with disease outcome and a marker for hypoxia, insulin-like growth factor binding protein 1 (IGFBP-1). The following endothelial activation markers were studied: endothelial glycocalyx degradation (syndecan-1) and leukocyte adhesion molecules (soluble vascular cellular adhesion molecule 1, intercellular adhesion molecule 1, and endothelial selectin). Cytokines associated with vascular repair were also analyzed (vascular endothelial growth factor, erythropoietin, angiopoietin, and stromal cell-derived factor 1).Results. Most of the markers we studied were highest during the earliest phase of hantaviral disease and associated with clinical and laboratory surrogate markers for disease outcome. In particular, the marker for glycocalyx degradation, syndecan-1, was significantly associated with levels of thrombocytes, albumin, IGFBP-1, decreased blood pressure, and disease severity.Conclusions. Hantaviral disease outcome was associated with endothelial dysfunction. Consequently, the endothelium warrants further investigation when designing future medical interventions.

Puumala orthohantavirus causes hemorrhagic fever with renal syndrome (HFRS) characterized by acute kidney injury (AKI), an abrupt decrease in renal function. Creatinine is routinely used to detect and quantify AKI; however, early AKI may not be reflected in increased creatinine levels. Therefore, kidney injury markers that can predict AKI are needed. The potential of the kidney injury markers urea, cystatin C, α1-microglobulin (A1M) and neutrophil gelatinase-associated lipocalin (NGAL) to detect early AKI during HFRS was studied by quantifying the levels of these markers in consecutively obtained plasma (P) and urine samples (U) for 44 HFRS patients. P-cystatin C and U-A1M levels were significantly increased during early HFRS compared to follow-up. In a receiver operating characteristic (ROC) curve analysis, P-cystatin C, U-A1M and P-urea predicted severe AKI with area under the curve 0.72, 0.73 and 0.71, respectively, whereas the traditional kidney injury biomarkers creatinine and U-albumin did not predict AKI. Nearly half of the HFRS patients (41%) fulfilled the criteria for shrunken pore syndrome, which was associated with the level of inflammation as measured by P-CRP. P-cystatin C and U-A1M are more sensitive and earlier markers compared to creatinine in predicting kidney injury during HFRS.

Background Puumala (PUUV) orthohantavirus causes hemorrhagic fever with renal syndrome (HFRS). HFRS patients have an activated coagulation system with increased risk of disseminated intravascular coagulation (DIC) and venous thromboembolism (VTE). The aim of the study was to determine if circulating extracellular vesicle tissue factor (EVTF) activity levels associates with DIC and VTE (grouped as intravascular coagulation) in HFRS patients. Methods Longitudinal samples were collected from 88 HFRS patients. Patients were stratified into groups of those with intravascular coagulation (n=27) and those who did not (n=61). We measured levels of circulating EVTF activity, fibrinogen, activated partial prothrombin time, prothrombin time international normalized ratio, D-dimer, tissue plasminogen activator (tPA), plasminogen activator inhibitor 1 (PAI-1) and platelets. Results Plasma EVTF activity was transiently increased during HFRS. Levels of EVTF activity significantly associated with plasma tPA and PAI-1, suggesting endothelial cells as a potential source. Patients with intravascular coagulation had significantly higher peak EVTF activity levels compared to those who did not. The peak EVTF activity value predicting intravascular coagulation was 0.51 ng/L with 63% sensitivity and 61% specificity with AUC 0.63 (95% CI 0.51 – 0.76), p-value 0.046. Conclusions Increased circulating EVTF activity during HFRS is associated with intravascular coagulation.

To assess the current coronavirus pandemic, there is a pressing need to determine the exposure and seroconversion to SARS-CoV-2 on a local and global level. Here, we demonstrate a sensitive and specific S-protein based assay that is well suited for detection of weak SARS- CoV-2-directed IgG responses, and that could identify exposed individuals with asymptomatic infection without the requirement of PCR diagnostics. Our results raise the possibility that on- going population-based studies using less sensitive state-of-the-art serological assays may significantly underestimate the frequency of exposure and seroconversion to SARS-CoV-2.

Human hantavirus infections can cause hemorrhagic fever with renal syndrome (HFRS), major signs of the disease being thrombocytopenia and transient kidney dysfunction. By a comprehensive and longitudinal study of circulating B cells, we demonstrate that these two pathologies associate with distinct effects on the humoral immune system during HFRS. Low thrombocyte counts strongly associated with an abnormal frequency of plasmablasts in circulation, whereas kidney dysfunction was indicative of an accumulation of CD27 -B cells and plasmablasts. Finally, we provide evidence that high levels of extracellular ATP in circulation during HFRS correlates with shedding of surface CD27 on B cells via a metallomatrix proteinase-8-mediated mechanism. Since extracellular ATP is known to regulate kidney function, our study reveals a link between kidney dysfunction and the generation of CD27 -IgD -B cells, and a potential molecular target for treatment of the symptomatic phase of HFRS. Dobrava, Seol and Puumala (PUUV) strains, where PUUV is endemic to Scandinavia. To date, no efficacious treatment or vaccination regimen exists to protect against severe hantavirus infections.Well controlled human studies have shown that hantavirus infections cause aberrant activation of both innate and adaptive immunity (5)(6)(7)(8). A potent antiviral IgG-response is associated with protection from severe disease during both HPS and HFRS (9-12) and passive transfer of serum antibodies could reduce case fatality rate in a small cohort of HPS patients (13). These findings clearly demonstrate that activation of the humoral immune system and subsequent elicitation of antiviral antibodies play a central role in the control of viremia and/or pathogenesis during hantavirus infections.A recent study of HPS demonstrated that very high levels of plasmablasts (PBs) and CD27 -IgD -B cells were detected in circulation of patients (14). The rapid and extensive PB-response is similar to that reported during acute dengue virus infection and contrasts to the comparably moderate levels of PBs that are found in circulation during influenza infection or after influenza vaccination (15). An expansion of the CD27 -IgD -B cell subset has previously been shown for numerous inflammatory and infectious diseases, as well as during ageing and cancer (16-21), yet their functional role in humoral immunity remains undetermined. The CD27 -IgD -B cells resemble memory B cells, have isotype switched and hypermutated B cell receptors and therefore likely originate from T cell-dependent germinal center reactions in secondary lymphoid organs (16, 20). In systemic lupus erythematosus (SLE), an expanded population of CD27 -IgD -B cells was associated with the manifestation of nephritis in patients (16). This suggests that their detection in blood may be linked to reduced kidney function, but the cause for their expansion remains to be determined.During HFRS-causing hantavirus infections, reduced kidney function occurs independently of the induced thrombocytopenia (22, 23). We therefor...

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B-cell responses during hantavirus infectionPF Kerkman et al.