Elevated thrombopoietin and platelet indices confirm active thrombopoiesis but fail to predict clinical severity of puumala hantavirus infection

Maturing neutrophils of lower density associate with thrombocytopenia in Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome

Puumala orthohantavirus-caused hemorrhagic fever with renal syndrome (PUUV-HFRS) is characterized by strong neutrophil activation. Neutrophils are the most abundant immune cell type in the circulation and are specially equipped to rapidly respond to infections. They are more heterogenous than previously appreciated, with specific neutrophil subsets recently implicated in inflammation and immunosuppression. Furthermore, neutrophils can be divided based on their density to either low-density granulocytes (LDGs) or "normal density" polymorphonuclear cell (PMN) fractions. In the current study we aimed to identify and characterize the different neutrophil subsets in the circulation of PUUV-HFRS patients. PMNs exhibited an activation of antiviral pathways, while circulating LDGs were increased in frequency following acute PUUV-HFRS. Furthermore, cell surface marker expression analysis revealed that PUUV-associated LDGs are primarily immature and most likely reflect an increased neutrophil production from the bone marrow. Interestingly, both the frequency of LDGs and the presence of a "left shift" in blood associated with the extent of thrombocytopenia, one of the hallmarks of severe HFRS, suggesting that maturing neutrophils could play a role in disease pathogenesis. These results imply that elevated circulating LDGs might be a general finding in acute viral infections. However, in contrast to the COVID-19 associated LDGs described previously, the secretome of PUUV LDGs did not show significant immunosuppressive ability, which suggests inherent biological differences in the LDG responses that can be dependent on the causative virus or differing infection kinetics.

Direct and indirect effects of Puumala hantavirus on platelet function

Thrombocytopenia is a cardinal symptom of hantavirus-induced diseases including Puumala virus (PUUV)-induced hemorrhagic fever with renal syndrome (HFRS), which is associated with impaired platelet function, bleeding manifestations and augmented thrombotic risk. However, the underlying mechanisms causing thrombocytopenia and platelet hypo-responsiveness are unknown. Thus, we investigated the direct and indirect impact of PUUV on platelet production, function and degradation. Analysis of PUUV-HFRS patient blood revealed that platelet hypo-responsiveness in PUUV infection was cell-intrinsic and accompanied by reduced platelet-leukocyte aggregates (PLAs) and upregulation of monocyte tissue factor (TF), whereas platelet vasodilator-stimulated phosphoprotein (VASP) phosphorylation was comparable to healthy controls. Plasma CXCL4 levels followed platelet count dynamics throughout disease course. PUUV activated both neutrophils and monocytes in vitro, but platelet desialylation, degranulation and GPIIb/IIIa activation as well as PLA formation and endothelial adhesion under flow remained unaltered in the presence of PUUV. Further, MEG-01 megakaryocytes infected with PUUV displayed unaltered polyploidization, expression of surface receptors and platelet production. However, infection of endothelial cells with PUUV significantly increased platelet sequestration. Our data thus demonstrate that although platelet production, activation or degradation are not directly modulated, PUUV indirectly fosters thrombocytopenia by sequestration of platelets to infected endothelium. Upregulation of immunothrombotic processes in PUUV-HFRS may further contribute to platelet dysfunction and consumption. Given the pathophysiologic similarities of hantavirus infections, our findings thus provide important insights into the mechanisms underlying thrombocytopenia and highlight immune-mediated coagulopathy as potential therapeutic target.

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.

Tibial growth plate vascularization is inhibited by the dithiocarbamate pesticide thiram in chickens: potential relationship to peripheral platelet counts alteration

The widespread use of thiram has raised concerns for health and its toxic effects, but the underlying toxicity mechanism on platelets and bones is poorly defined. Here, we found a significant increase in the number of platelets in chickens with the thiram intake, due to the increased expression of thrombopoietin mRNA in the dysfunction liver. Furthermore, the decreased vascular distribution and cell death of chondrocytes in the tibial growth plates (TGPs) were observed, resulting in bone growth inhibition, which is associated with the abnormal activation of platelets leading to the extraordinary decrease of vascular endothelial growth factor A (VEGFA) and angiopoietin-1 protein were released and their corresponding receptors VEGFR2 and Tie-2 expressions were also reduced in the TGPs. Taken together, these findings revealed that thiram has an adverse effect on bones and platelets, which may have a high risk of thrombosis and osteoarthritis.

Hypopituitarism after Orthohantavirus Infection: What is Currently Known?

Several case reports have described hypopituitarism following orthohantavirus infection, mostly following Puumala virus. The pathogenesis of this seemingly rare complication of orthohantavirus infection remains unknown. This review explores the possible pathophysiological mechanisms of pituitary damage due to orthohantavirus infection. In only three out of the 28 reported cases, hypopituitarism was detected during active infection. In the remaining cases, detection of pituitary damage was delayed, varying from two months up to thirteen months post-infection. In these cases, hypopituitarism remained undetected during the acute phase of infection or only occurred weeks to months post infection. Both ischemic and hemorrhagic damage of the pituitary gland have been detected in radiographic imaging and post-mortem studies in the studied case reports series. Ischemic damage could be caused by hypotension and/or vasospasms during the acute phase of hemorrhagic fever with renal syndrome (HFRS) while hemorrhage could be caused by thrombocytopenia, thrombopathy, and other known causes of coagulation disorders during orthohantavirus infection. Also, hypophysitis due to the presence of auto-antibodies have been suggested in the literature. In conclusion, a significant number of case reports and series describe hypopituitarism after orthohantavirus infection. In most cases hypopituitarism was diagnosed with a delay and therefore could very well be underreported. Clinicians should be aware of this potential endocrine complication, with substantial morbidity, and if unrecognized, significant mortality.

Diminished coagulation capacity assessed by calibrated automated thrombography during acute Puumala hantavirus infection

: Coagulation abnormalities are associated with Puumala-virus-induced hemorrhagic fever with renal syndrome (PUUV-HFRS). We evaluated the coagulation capacity of plasma during acute PUUV-HFRS by measuring thrombin generation using calibrated automated thrombography (CAT). The study cohort comprised 27 prospectively collected, consecutive, hospital-treated patients with acute PUUV infection. Blood samples were drawn in the acute phase and at the control visit approximately 5 weeks later. To evaluate thrombin generation, the lag time of initiation, endogenous thrombin potential (ETP), and peak and time to peak thrombin concentration were assessed by CAT in platelet poor plasma without corn trypsin inhibitor. Plasma levels of D-dimer, fibrinogen and prothrombin fragments (F1 + 2) were also evaluated. When the acute phase was compared with the control phase, ETP was decreased (median 1154 nmol/l/min, range 67-1785 vs. median 1385 nmol/l/min, range 670-1970; P < 0.001), while the lag time was prolonged (median 3.8 min, range 2.1-7.7 vs. median 2.9 min, range 2.0-4.1; P < 0.001). Low ETP correlated with low peak thrombin concentration (r = 0.833, P < 0.001). Prolonged time to peak associated with the lag time (r = 0.78, P < 0.001). ETP was associated with thrombocytopenia (r = 0.472, P = 0.015) and weakly with fibrinogen level (r = 0.386, P = 0.047). The measured CAT parameters did not associate with D-dimer and F1 + 2 levels. Decreased ETP together with low peak and prolonged lag time indicate decreased plasma potential for thrombin generation in vitro. Together with low platelet count and enhanced fibrinolysis, this further refers to altered blood coagulation and increased propensity toward bleeding in acute PUUV-HFRS.

Is the mean platelet volume a predictive marker of a high in-hospital mortality of acute cardiorenal syndrome patients receiving continuous renal replacement therapy?

A high mean platelet volume (MPV) level has been demonstrated to predict poor clinical outcomes in patients with cardiovascular disease. However, the relationship between MPV and mortality in patients with acute cardiorenal syndrome (ACRS) is unknown. Therefore, we investigated the predictive value of MPV for in-hospital mortality of patients with ACRS who received continuous renal replacement therapy (CRRT) in this study.We retrospectively analyzed the demographics, etiology, severity of illness, prognosis, and risk factors of ACRS patients who underwent CRRT in our hospital from January 2009 to December 2014. Patients were classified into 2 groups based on the prognosis and timing of CRRT. The receiver operating characteristic curve was used to examine the performance of MPV in predicting in-hospital mortality. Baseline characteristics, clinical, and hematological parameters at CRRT initiation were compared between the 2 groups. Factors influencing in-hospital mortality were analyzed by univariate logistic regression analysis.The median age of patients was 74 years. Acute myocardial infarction was the most common cause of ACRS, followed by acute decompensated heart failure. The in-hospital mortality was 51.4%. Age, number of organ failure, APACHE II score, and MPV in the nonsurvivors were significantly higher than those in the survivors (P < .05). However, the cardiac function and mean arterial pressure were significantly lower in the nonsurvivors (P < .05). The prognosis of the early intervention group was better than the late-intervention group, but no significant difference was found (P > .05). The area under the curve (AUC) for in hospital mortality based on MPV was 0.735. Univariate analysis showed that age, cardiac function NYHA class, number of organ failure, APACHE II score, MAP, MPV, and use of vasopressors were associated with the prognosis of patients (P < .05).These findings suggest that the prognosis of patients with ACRS who received CRRT was poor, and MPV might be useful as a marker for predicting the in-hospital mortality of these patients.