Hemorrhagic fever caused by a novel Bunyavirus in China: pathogenesis and correlates of fatal outcome

Association of gastrointestinal symptoms with mortality in patients with severe fever with thrombocytopenia syndrome

Background

The clinical significance of gastrointestinal (GI) symptoms in patients with severe fever and thrombocytopenia syndrome (SFTS) is poorly characterized. This study aimed to determine the prevalence and effect of GI symptoms on the prognosis of patients with SFTS.

Methods

This was a retrospective multi-center cohort study that included hospitalized patients with SFTS from three institutions between October 2010 and August 2022. The risk factors for mortality and intensive care unit (ICU) admission were identified by Cox and logistic regression analyses, respectively. Kaplan-Meier curves were used to analyze the cumulative mortality risk.

Results

Among 304 patients, the median age was 62.0 years and 51.0 % of the patients were male. A total of 202 patients (66.4 %) had at least one GI symptom on admission. Diarrhea (69.8 %) and nausea (57.4 %) were the most common symptoms. Patients with GI symptoms had lower male proportion (46.0 % vs. 60.8 %, P = 0.015), higher aspartate aminotransferase (177.5 U/L vs. 118.0 U/L, P = 0.010) and lactic dehydrogenase (771.0 U/L vs. 666.5 U/L, P = 0.017) levels than that of patients without GI symptoms. However, there was no significant difference in mortality rates (23.8 % vs. 21.6 %, P = 0.668) and ICU admission (14.4 % vs. 12.7 %, P = 0.701) between SFTS patients with and without GI symptoms. Multivariate analysis suggested that GI symptoms at admission were not associated with mortality and ICU admission.

Conclusions

GI symptoms are common in patients with SFTS. However, the presence of GI symptoms was not an independent risk factor for poor prognosis.

Machine learning for identifying risk of death in patients with severe fever with thrombocytopenia syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) has attracted attention due to the rising incidence and high severity and mortality rates. This study aims to construct a machine learning (ML) model to identify SFTS patients at high risk of death early in hospital admission, and to provide early intensive intervention with a view to reducing the risk of death.

Methods

Data of patients hospitalized for SFTS in two hospitals were collected as training and validation sets, respectively, and six ML methods were used to construct the models using the screened variables as features. The performance of the models was comprehensively evaluated and the best model was selected for interpretation and development of an online web calculator for application.

Results

A total of 483 participants were enrolled in the study and 96 (19.88%) patients died due to SFTS. After a comprehensive evaluation, the XGBoost-based model performs best: the AUC scores for the training and validation sets are 0.962 and 0.997.

Conclusion

Using ML can be a good way to identify high risk individuals in SFTS patients. We can use this model to identify patients at high risk of death early in their admission and manage them intensively at an early stage.

A nomogram and heat map based on LASSO-Cox regression for predicting the risk of early-stage severe fever with thrombocytopenia syndrome patients developing into critical illness at 7-day and 14-day

Severe fever with thrombocytopenia syndrome (SFTS) represents an emerging infectious disease characterized by a substantial mortality risk. Early identification of patients is crucial for effective risk assessment and timely interventions. In the present study, least absolute shrinkage and selection operator (LASSO)-Cox regression analysis was conducted to identify key risk factors associated with progression to critical illness at 7-day and 14-day. A nomogram was constructed and subsequently assessed for its predictive accuracy through evaluation and validation processes. The risk stratification of patients was performed using X-tile software. The performance of this risk stratification system was assessed using the Kaplan-Meier method. Additionally, a heat map was generated to visualize the results of these analyses. A total of 262 SFTS patients were included in this study, and four predictive factors were included in the nomogram, namely viral copies, aspartate aminotransferase (AST) level, C-reactive protein (CRP), and neurological symptoms. The AUCs for 7-day and 14-day were 0.802 [95% confidence interval (CI): 0.707-0.897] and 0.859 (95% CI: 0.794-0.925), respectively. The nomogram demonstrated good discrimination among low, moderate, and high-risk groups. The heat map effectively illustrated the relationships between risk groups and predictive factors, providing valuable insights with high predictive and practical significance.

TLR2/NF-кB signaling may control expansion and function of regulatory T cells in patients with severe fever with thrombocytopenia syndrome (SFTS)

Severe fever with thrombocytopenia syndrome (SFTS) is a recently identified infectious ailment triggered by a new strain of bunyavirus. It is distinguished by elevated fatality rates, ranging from 12 % to 30 %. The mechanism underlying the development of severe illness caused by SFTS bunyavirus (SFTSV) is not yet fully understood. To evaluate the role of the TLR2 receptor pathway in regulating Treg function in the progression of SFTS disease and possible mechanisms, sequential serum samples from 29 patients with SFTS (15 mild, 14 severe cases) were examined. Flow cytometry was employed to scrutinize the phenotypic and functional characteristics of TLR2 expression on circulating CD4 T cells, CD8 T cells, and Tregs. In all admitted patients, the evaluation of correlations between the frequencies of the aforementioned cells and SFTS index (SFTSI) was conducted. For SFTS, the levels of TLR2 on CD4 T cells and Tregs were significantly heightened when compared to those in healthy subjects. Additionally, the expression of TLR2 on Tregs exhibited a positive correlation with Ki-67 expression in Tregs and the severity of disease. Additionally, compared with those in uninfected controls, the expression levels of NF-κB in Tregs were significantly increased. Collectively, Tregs may be activated and proliferate through the stimulation of the TLR2/NF-кB pathway in reaction to SFTSV infection.

The use of glucocorticoid in severe fever with thrombocytopenia syndrome: a retrospective cohort study

Introduction

Severe fever with thrombocytopenia syndrome (SFTS) is prevalent in East Asia. However, the use of glucocorticoids (GCs) in the treatment of SFTS remains controversial.

Methods

In this retrospective cohort study, we collected the data from patients with SFTS at Wuhan Union Hospital to evaluate the effect of GC therapy. Mortality and secondary infections were compared as outcomes. After searching public databases, we also included articles that examined GC use in patients with SFTS for meta-analysis.

Results

Patients treated with GC had higher fatality rates (21.1% vs. 11.9%, respectively; P=0.006) and a longer length of stay (10.6 ± 5.1 vs. 9.5 ± 4.2, respectively; P=0.033). In cohorts adjusted using propensity score matching and inverse probability of treatment weighting, no significant differences in fatality rates and length of stay were observed. A meta-analysis of 4243 SFTS patient revealed that those treated with GCs had significantly higher mortality (OR=3.46, 95% CI =2.12-5.64, P<0.00001) and secondary infection rate (OR=1.97, 95% CI=1.45-2.67, P<0.0001).

Discussion

GC should be used cautiously when treating SFTS. No significant differences were identified in terms of mortality and secondary infection rates between patients with SFTS treated with or without GC.

Recent research advances in the development of Dabie Banda virus vaccines

Severe fever with thrombocytopenia syndrome (SFTS) is a newly identified tick-borne viral hemorrhagic fever caused by Dabie Banda virus (DBV). The virus was first discovered in eastern China in 2009 and is now considered an infectious disease with a mortality rate ranging from 6.3% to 30%. The best strategy for controlling SFTS is to develop effective vaccines. However, no approved vaccines are currently available to prevent this disease, despite the number of extensive and in-depth studies conducted on DBV in the past few years. This review focuses on the structure of DBV and the induced host immune responses which are the fundamental factors in vaccine development, and thoroughly summarizes the current research progress on DBV vaccines. The developing DBV vaccines include protein subunit vaccines, live attenuated vaccines, recombinant virus vector vaccines, and DNA vaccines. At present, almost all candidate vaccines for DBV are in the laboratory development or preclinical stages. There remain challenges in successfully developing clinically approved DBV vaccines.

Development of an all-in-one real-time PCR assay for simultaneous detection of spotted fever group rickettsiae, severe fever with thrombocytopenia syndrome virus and hantaan virus prevalent in central China

Central China has been reported to be one of the most important endemic areas of zoonotic infection by spotted fever group rickettsiae (SFGR), severe fever with thrombocytopenia syndrome virus (SFTSV) and hantaan virus (HTNV). Due to similar clinical symptoms, it is challenging to make a definite diagnosis rapidly and accurately in the absence of microbiological tests. In the present study, an all-in-one real-time PCR assay was developed for the simultaneous detection of nucleic acids from SFGR, SFTSV and HTNV. Three linear standard curves for determining SFGR-ompA, SFTSV-L and HTNV-L were obtained within the range of 101-106 copies/μL, with the PCR amplification efficiencies ranging from 93.46% to 96.88% and the regression coefficients R2 of >0.99. The detection limit was 1.108 copies/μL for SFGR-ompA, 1.075 copies/μL for SFTSV-L and 1.006 copies/μL for HTNV-L, respectively. Both the within-run and within-laboratory coefficients of variation on the cycle threshold (Ct) values were within the range of 0.53%-2.15%. It was also found there was no statistical difference in the Ct values between single template and multiple templates (PSFGR-ompA = 0.186, PSFTSV-L = 0.612, PHTNV-L = 0.298). The sensitivity, specificity, positive and negative predictive value were all 100% for determining SFGR-ompA and SFTSV-L, 97%, 100%, 100% and 99.6% for HTNV-L, respectively. Therefore, the all-in-one real-time PCR assay appears to be a reliable, sensitive, rapid, high-throughput and low cost-effective method to diagnose the zoonotic infection by SFGR, SFTSV and HTNV.

Effect of tocilizumab plus corticosteroid on clinical outcome in patients hospitalized with severe fever with thrombocytopenia syndrome: A randomized clinical trial

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral hemorrhagic fever with high fatality rates. The blockade of pro-inflammatory cytokines presents a promising therapeutic strategy.

METHODS

We conducted a randomized clinical trial at the 154th hospital, Xinyang, Henan Province. Eligible patients with severe SFTS disease were randomly assigned in a 1:2 ratio to receive either a single intravenous infusion of tocilizumab plus usual care; or usual care only. The primary outcome was the clinical status of death/survival at day 14, while secondary outcomes included improvement from baseline in liver and kidney damage and time required for hospital discharge. The efficacy of tocilizumab plus corticosteroid was compared to those receiving corticosteroid alone. The trial is registered with the Chinese Clinical Trial Registry website (ChiCTR2300076317).

RESULTS

63 eligible patients were assigned to the tocilizumab group and 126 to the control group. The addition of tocilizumab to usual care was associated with a reduced death rate (9.5%) compared to those received only usual care (23.0%), with an adjusted hazard ratio (aHR) of 0.37 (95% confidence interval [CI], 0.15 to 0.91, P = 0.029). Combination therapy of tocilizumab and corticosteroids was associated with a significantly reduced fatality (aHR, 0.21; 95% CI, 0.08 to 0.56; P = 0.002) compared to those receiving corticosteroids alone.

CONCLUSIONS

A significant benefit of reducing fatality in severe SFTS patients was observed by using tocilizumab. A combined therapy of tocilizumab plus corticosteroids was recommended for the therapy of severe SFTS.

Fibrinogen-to-prealbumin and C-reactive protein-to-prealbumin ratios as prognostic indicators in severe fever with thrombocytopenia syndrome

Background

The primary aim of this study is to investigate the correlation between serum levels of fibrinogen-to-prealbumin ratio (FPR) and C-reactive protein-to-prealbumin ratio (CPR) and prognostic outcomes among patients with severe fever with thrombocytopenia syndrome (SFTS). SFTS, characterized by elevated mortality rates, represents a substantial public health challenge as an emerging infectious disease.

Methods

The study included 159 patients with SFTS. Clinical and laboratory data were compared between the survival and death groups. Univariate and multivariate logistic regression analysis were utilized to identify independent risk factors for mortality. The predictive efficacy of FPR and CPR was evaluated using receiver operating characteristic (ROC) curve. Survival analysis was conducted using the Kaplan-Meier curve and the log-rank test was employed for comparison.

Results

The death group exhibited significantly elevated levels of FPR and CPR compared to the survival group (P < 0.05). Multivariate logistic regression analysis confirmed that both FPR and CPR independently correlated with a poorer prognosis among patients with SFTS. The ROC curve analysis indicated that FPR and CPR had superior predictive capabilities compared to C-reactive protein and fibrinogen. Kaplan-Meier survival analysis demonstrated that patients with SFTS who have FPR > 0.045 (log-rank test; χ2 = 17.370, P < 0.001) or CPR > 0.05 (log-rank test; χ2 = 19.442, P < 0.001) experienced significantly lower survival rates within a 30-day follow-up period.

Conclusion

Elevated levels of FPR and CPR serve as distinct risk factors for mortality among patients with SFTS, indicating their potential to predict an unfavorable prognosis in these patients.

Cytokines and lymphocyte subsets are associated with disease severity of severe fever with thrombocytopenia syndrome

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by severe fever with thrombocytopenia syndrome virus (SFTSV). Previous studies have indicated that SFTS patients have a high mortality rate, which may be related to cytokine storm and immune dysfunction. In our study, we analyzed differences in cytokines and lymphocyte subsets between severe and non-severe SFTS patients, with the aim of identifying predictors of severity.

METHODS

We retrospectively analyzed demographic characteristics, clinical data, cytokine profiles, and lymphocyte subsets from 96 laboratory confirmed SFTS patients between April 2021 and August 2023.

RESULTS

A total of 96 SFTS patients were enrolled, with a mean age of 65.05 (± 7.92) years old. According to our grouping criteria, 35 (36.5%) of these patients were classified as severe group, while 61 (63.5%) were classified as non-severe group. Univariate analysis revealed that age, interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), interferon-α (IFN-α), CD4 + T cell, and CD8 + T cell counts were risk predictors for the severity of SFTS. Further multivariable logistic regression analysis confirmed age, IL-6 levels, and CD4 + T cell counts as independent predictors of SFTS severity.

CONCLUSIONS

Severe SFTS patients may experience cytokine storms and immune dysfunction. Aging, elevated levels of IL-6, and decreased CD4 + T cell count may serve as independent predictors for the severity of SFTS.

Blood urea nitrogen to albumin ratio is a novel predictor of fatal outcome for patients with severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is associated with a high death rate and lacks a targeted therapy plan. The ratio of blood urea nitrogen to albumin, known as BAR, is a valuable method for assessing the outlook of various infectious diseases. The objective of this research was to evaluate the effectiveness of BAR in forecasting the outcome of individuals with SFTS. Four hundred and thirty-seven patients with SFTS from two clinical centers were included in this study according to inclusion and exclusion criteria. Clinical characteristics and test parameters of SFTS patients were analyzed between survival and fatal groups. Least absolute shrinkage and selection operator (LASSO) regression and Cox regression suggested that BAR might serve as a standalone prognostic indicator for patients with SFTS in the initial phase (hazard ratio = 18.669, 95% confidence interval [CI]: 8.558-40.725, p < 0.001). And BAR had a better predictive effectiveness in clinical outcomes in patients with SFTS with an AUC of 0.832 (95% CI: 0.788-0.876, p < 0.001), a cutoff value of 0.19, a sensitivity of 0.812, and a specificity of 0.726 compared to C-reactive protein, procalcitonin, and platelet to lymphocyte ratio via receiver operating characteristic curve. KM (Kaplan Meier) curves demonstrated that high level of BAR was associated with poor survival condition in patients with SFTS. Furthermore, the high level of BAR was associated with long hospital stays and test paraments of kidney, liver, and coagulation function in survival patients. So, BAR could be used as a promising early warning biomarker of adverse outcomes in patients with SFTS.

One-year mortality and morbidities of severe fever with thrombocytopenia syndrome compared with other diseases: A nationwide cohort study in South Korea

BACKGROUND

The long-term mortality and morbidity of patients with severe fever with thrombocytopenia syndrome (SFTS) remain unclear.

METHODS

This retrospective cohort study was conducted using the National Health Insurance Service dataset on hospitalized patients with SFTS aged ≥20 years between 2016 and 2021 (n = 1,217). Each SFTS case was matched with three controls hospitalized for non-SFTS-related diseases using propensity score matching. The all-cause mortality of patients with SFTS was evaluated during the one-year follow-up and compared with that of controls. Post-discharge events were investigated to determine the effects of SFTS on post-acute sequelae.

RESULTS

Finally, 1,105 patients with SFTS and 3,315 controls were included. Patients with SFTS had a higher risk of death during the one-year follow-up than that of controls (hazard ratio [HR], 2·26; 95% confidence interval [CI], 1·82-2·81). Thirty-day mortality was significantly higher in the SFTS group (HR, 3·99; 95% CI, 3·07-5·19) than in the control group. An increased risk of death after 31-365 days was observed among controls, though this difference was significant only among patients in their 80s (HR, 0·18; 95% CI, 0·06-0·57). For post-discharge events, patients in the SFTS group exhibited a higher risk of readmission (HR, 1·17; 95% CI, 1·04-1·32) and emergency room visit (HR, 2·32; 95% CI, 1·96-2·76) than those in the control group.

CONCLUSION

SFTS induces a higher risk of short-term mortality and post-acute sequelae in hospitalized patients during a one-year follow-up than non-SFTS-related diseases. Our results provide guidance for the management of SFTS.

Clinical Factors Associated with SFTS Diagnosis and Severity in Cats

Severe fever with thrombocytopenia syndrome (SFTS) is a potentially fatal tick-borne zoonosis caused by SFTS virus (SFTSV). In addition to tick bites, animal-to-human transmission of SFTSV has been reported, but little is known about feline SFTSV infection. In this study, we analyzed data on 187 cats with suspected SFTS to identify biomarkers for SFTS diagnosis and clinical outcome. Body weight, red and white blood cell and platelet counts, and serum aspartate aminotransferase and total bilirubin levels were useful for SFTS diagnosis, whereas alanine aminotransferase, aspartate aminotransferase and serum SFTSV RNA levels were associated with clinical outcome. We developed a scoring model to predict SFTSV infection. In addition, we performed a phylogenetic analysis to reveal the relationship between disease severity and viral strain. This study provides comprehensive information on feline SFTS and could contribute to the protection of cat owners, community members, and veterinarians from the risk of cat-transmitted SFTSV infection.

Nine-year seroepidemiological study of severe fever with thrombocytopenia syndrome virus infection in feral horses in Cape Toi, Japan

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal zoonosis caused by ticks in East Asia. As SFTS virus (SFTSV) is maintained between wildlife and ticks, seroepidemiological studies in wildlife are important to understand the behavior of SFTSV in the environment. Miyazaki Prefecture, Japan, is an SFTS-endemic area, and approximately 100 feral horses, called Misaki horses (Equus caballus), inhabit Cape Toi in Miyazaki Prefecture. While these animals are managed in a wild-like manner, their ages are ascertainable due to individual identification. In the present study, we conducted a seroepidemiological survey of SFTSV in Misaki horses between 2015 and 2023. This study aimed to understand SFTSV infection in horses and its transmission to wildlife. A total of 707 samples from 180 feral horses were used to determine the seroprevalence of SFTSV using enzyme-linked immunosorbent assay (ELISA). Neutralization testing was performed on 118 samples. In addition, SFTS viral RNA was detected in ticks from Cape Toi and feral horses. The overall seroprevalence between 2015 and 2023 was 78.5% (555/707). The lowest seroprevalence was 55% (44/80) in 2016 and the highest was 92% (76/83) in 2018. Seroprevalence was significantly affected by age, with 11% (8/71) in those less than one year of age and 96.7% (435/450) in those four years of age and older (p < 0.0001). The concordance between ELISA and neutralization test results was 88.9% (105/118). SFTS viral RNA was not detected in ticks (n = 516) or feral horses. This study demonstrated that horses can be infected with SFTSV and that age is a significant factor in seroprevalence in wildlife. This study provides insights into SFTSV infection not only in horses but also in wildlife in SFTS-endemic areas.

Prolonged coagulation times in severe fever with thrombocytopenia syndrome virus infection, the indicators of heparin-like effect and increased haemorrhagic risk

Prolonged coagulation times, such as activated partial thromboplastin time (APTT) and thrombin time (TT), are common in patients infected with severe fever with thrombocytopenia syndrome virus (SFTSV) and have been confirmed to be related to patient's poor outcome by previous studies. To find out the reason for prolonged coagulation time in patients with SFTSV infection, and whether it predicts haemorrhagic risk or not. Seventy-eight consecutive patients with confirmed SFTSV infection were enrolled in this prospective, single-centre, observational study. Several global and specific coagulation parameters of these patients on admission were detected, and the haemorrhagic events during hospitalization and their outcomes were recorded. Most of the enrolled patients had prolonged APTT (82.1%) and TT (80.8%), normal prothrombin time (83.3%) and intrinsic coagulation factors above haemostatic levels (97.4%). The heparin-like effect was confirmed by a protamine neutralization test and anti-Xa activity detection in most patients. Interestingly, the APTT and TT results were significantly positively correlated with the levels of endothelial markers and viral load, respectively. The APTT was independently associated with the haemorrhage of patients. The prolonged APTT and TT of SFTS patients may mainly be attributed to endogenous heparinoids and are associated with increased haemorrhagic risk.

Correlation between the Cycle Threshold Values in Detection of Severe Fever with Thrombocytopenia Syndrome Virus Using PowerChekTM SFTSV Real-Time PCR Kit and Viral Load: Prognostic Implications

BACKGROUND

This study aimed to analyze the correlation between the cycle threshold (Ct) values of severe fever with thrombocytopenia syndrome (SFTS) virus small (S) and middle (M) segments and the SFTS viral load, aiming to estimate the initial viral load and predict prognosis in the early clinical course.

METHOD

A retrospective study was conducted with confirmed SFTS patients at Jeju National University Hospital (2016-2022). Patients were categorized into non-fatal and fatal groups.

RESULTS

This study included 49 patients with confirmed SFTS (non-fatal group, n = 42; fatal group, n = 7). A significant negative correlation (-0.783) was observed between the log SFTS viral load and Ct values (p < 0.001). This negative correlation was notably stronger in the fatal group (correlation coefficient -0.940) than in the non-fatal group (correlation coefficient -0.345).

CONCLUSION

In this study, we established a correlation between SFTS viral load and Ct values for estimating the initial viral load and early predicting prognosis. These results are expected to offer valuable insights for SFTS patient treatment and prognosis prediction.

Antiviral immunity of severe fever with thrombocytopenia syndrome: current understanding and implications for clinical treatment

Dabie Banda virus (DBV), a tick-borne pathogen, was first identified in China in 2009 and causes profound symptoms including fever, leukopenia, thrombocytopenia and multi-organ dysfunction, which is known as severe fever with thrombocytopenia syndrome (SFTS). In the last decade, global incidence and mortality of SFTS increased significantly, especially in East Asia. Though previous studies provide understandings of clinical and immunological characteristics of SFTS development, comprehensive insight of antiviral immunity response is still lacking. Here, we intensively discuss the antiviral immune response after DBV infection by integrating previous ex- and in-vivo studies, including innate and adaptive immune responses, anti-viral immune responses and long-term immune characters. A comprehensive overview of potential immune targets for clinical trials is provided as well. However, development of novel strategies for improving the prognosis of the disease remains on challenge. The current review may shed light on the establishment of immunological interventions for the critical disease SFTS.

Clinical value of coagulation parameters in predicting the severity of severe fever with thrombocytopenia syndrome

Introduction

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by a novel bunyavirus infection with a high lethality rate. The purpose of this study was to investigate the changes in coagulation parameters in patients with SFTS, aiming to provide clinical evidence for early diagnosis, treatment, and disease analysis.

Methods

A total of 40 patients with SFTS attended from April 1, 2020 to May 21, 2022 in Nanjing Drum Tower Hospital were selected and grouped according to the duration of the disease, mild and severe disease, cure and death, with 50 healthy physical examiners as controls, and the risk of severe and death disease was predicted using ROC curves.

Results

Comparison between the healthy, mild and severe groups revealed that PT, INR, APTT, TT, D-D and vWF levels were higher than those in the healthy control group, and FII, FIX, FX, FXI, FXII, PC and PS levels were lower than those in the healthy control group, the differences were statistically significant (p < 0.05). Comparing the results of SFTS patients with different course times, the results of Fib, FV, FVII, FVIII, FIX, FX, FXI were statistically significant (p < 0.05). Among the survived and deceased patients, the PT, INR, DD and PS results of the deceased patients were higher than those of the survived patients, and the FVIII, FIX, FXI, FXII and PC were lower than those of the survived patients. The area under the ROC curve showed that D-D had higher predictive ability for the risk of severe disease (AUROC 0.93, sensitivity and specificity at a Cut-off value of 1.50 mg/L were 90.0 and 86.5%, respectively) and the risk of death occurring (AUROC 0.84, sensitivity and specificity at a Cut-off value of 3.39 mg/L were 87.5 and 80.0%, respectively).

Discussion

The monitoring of the coagulation parameters in patients with SFTS is great significance for identifying the severity and death of the patient's condition, and it is of great clinical value to provide early attention, timely intervention and maximum reduction of the mortality rate for patients at risk of severe disease.

Association of liver function and prognosis in patients with severe fever with thrombocytopenia syndrome

OBJECTIVES

Severe fever with thrombocytopenia syndrome (SFTS) is an epidemic emerging infectious disease with high mortality rate. We investigated the association between liver injury and clinical outcomes in patients with SFTS.

METHODS

A total of 291 hospitalized SFTS patients were retrospectively included. Cox proportional hazards model was adopted to identify risk factors of fatal outcome and Kaplan-Meier curves were used to estimate cumulative risks.

RESULTS

60.1% of patients had liver injury at admission, and the median alanine transaminase, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total bilirubin (TBil) levels were 76.4 U/L, 152.3 U/L, 69.8 U/L and 9.9 μmol/L, respectively. Compared to survivors, non-survivors had higher levels of AST (253.0 U/L vs. 131.1 U/L, P < 0.001) and ALP (86.2 U/L vs. 67.9 U/L, P = 0.006), higher proportion of elevated ALP (20.0% vs. 4.4%, P < 0.001) and liver injury (78.5% vs. 54.9%, P = 0.001) at admission. The presence of liver injury (HR 2.049, P = 0.033) at admission was an independent risk factor of fatal outcome.

CONCLUSIONS

Liver injury was a common complication and was strongly associated with poor prognosis in SFTS patients. Liver function indicators should be closely monitored for SFTS patients.

High CRP/PNI levels predict an unfavorable prognosis in severe fever with thrombocytopenia syndrome: A propensity score matching study

BACKGROUND

This study aimed to identify a novel inflammatory index and construct a nomogram for predicting in-hospital mortality due to severe fever with thrombocytopenia syndrome (SFTS).

METHODS

This cohort included 610 patients with SFTS hospitalized in Wuhan Union Hospital between March 2017 and November 2022. The ratio of C-reactive protein (CRP) to the prognostic nutritional index (PNI) was calculated and used to reflect patients' inflammatory status. Propensity score matching (PSM) was utilized to balance confounding factors between the low- and high-CRP/PNI groups. SFTS individuals from Jinyinhu Hospital were used as the validation cohort.

RESULTS

Patients with SFTS and high CRP/PNI were significantly correlated with a higher percentage of severe and critical SFTS types and higher in-hospital mortality rates than those with low CRP/PNI. CRP/PNI was the potent risk indicator for in-hospital mortality in individuals with SFTS. The CRP/PNI nomogram showed a good predictive value for in-hospital mortality in patients with SFTS. After PSM, the predictive performance of CRP/PNI for 28-day mortality was excellent. Finally, the CRP/PNI could still assess patients with SFTS at different risks based on SFTS data from another medical center.

CONCLUSION

The CPR/PNI ratio exhibited a strong positive correlation with the SFTS disease type and could predict in-hospital mortality in the early stages of SFTS. The CPR/PNI ratio could substantially help clinicians facilitate the early identification of patients with high-risk SFTS and the timely initiation of intensive therapy.

Host factor MxA restricts Dabie bandavirus infection by targeting the viral NP protein to inhibit NP-RdRp interaction and ribonucleoprotein activity

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with high case mortality rates, which is caused by Dabie bandavirus (DBV), a novel pathogen also termed as SFTS virus (SFTSV). Currently, no specific therapeutic drugs or vaccines are available for SFTS. Myxovirus resistance protein A (MxA) has been shown to inhibit multiple viral pathogens; however, the role of MxA in DBV infection is unknown. Here, we demonstrated that DBV stimulates MxA expression which, in turn, restricts DBV infection. Mechanistic target analysis revealed that MxA specifically interacts with the viral nucleocapsid protein (NP) in a manner independent of RNA. Minigenome reporter assay showed that in agreement with its targeting of NP, MxA inhibits DBV ribonucleoprotein (RNP) activity. In detail, MxA interacts with the NP N-terminal and disrupts the interaction of NP with the viral RNA-dependent RNA polymerase (RdRp) but not NP multimerization, the critical activities of NP for RNP formation and function. Furthermore, MxA N-terminal domain was identified as the functional domain inhibiting DBV infection, and, consistently, then was shown to interact with NP and obstruct the NP-RdRp interaction. Additionally, threonine 103 within the N-terminal domain is important for MxA inhibition to DBV, and its mutation (T103A) attenuates MxA binding to NP and obstruction of the NP-RdRp interaction. This study uncovers MxA inhibition of DBV with a series of functional and mechanistical analyses, providing insights into the virus-host interactions and probably helping inform the development of antiviral agents in the future.IMPORTANCEDBV/SFTSV is an emerging high-pathogenic virus. Since its first identification in China in 2009, cases of DBV infection have been reported in many other countries, posing a significant threat to public health. Uncovering the mechanisms of DBV-host interactions is necessary to understand the viral pathogenesis and host response and may advance the development of antiviral therapeutics. Here, we found that host factor MxA whose expression is induced by DBV restricts the virus infection. Mechanistically, MxA specifically interacts with the viral NP and blocks the NP-RdRp interaction, inhibiting the viral RNP activity. Further studies identified the key domain and amino acid residue required for MxA inhibition to DBV. Consistently, they were then shown to be important for MxA targeting of NP and obstruction of the NP-RdRp association. These findings unravel the restrictive role of MxA in DBV infection and the underlying mechanism, expanding our knowledge of the virus-host interactions.

Current Progress of Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) Vaccine Development

SFTSV is an emerging tick-borne virus causing hemorrhagic fever with a case fatality rate (CFR) that can reach up to 27%. With endemic infection in East Asia and the recent spread of the vector tick to more than 20 states in the United States, the SFTSV outbreak is a globally growing public health concern. However, there is currently no targeted antiviral therapy or licensed vaccine against SFTSV. Considering the age-dependent SFTS pathogenesis and disease outcome, a sophisticated vaccine development approach is required to safeguard the elderly population from lethal SFTSV infection. Given the recent emergence of SFTSV, the establishment of animal models to study immunogenicity and protection from SFTS symptoms has only occurred recently. The latest research efforts have applied diverse vaccine development approaches-including live-attenuated vaccine, DNA vaccine, whole inactivated virus vaccine, viral vector vaccine, protein subunit vaccine, and mRNA vaccine-in the quest to develop a safe and effective vaccine against SFTSV. This review aims to outline the current progress in SFTSV vaccine development and suggest future directions to enhance the safety and efficacy of these vaccines, ensuring their suitability for clinical application.

Changes in Cytokine Levels in Patients with Severe Fever with Thrombocytopenia Syndrome Virus

Purpose

To characterize the cytokine profile of patients with severe fever with thrombocytopenia syndrome (SFTS) in relation to disease severity.

Patients and Methods

60 laboratory-confirmed SFTS patients and 12 healthy individuals from multi-centers in Shandong Province of China were included, and all patients were divided into fatal patients (9) and recovered patients (51) due to their final outcomes. Multiplex-microbead immunoassays were conducted to estimate levels of 27 cytokines in the sera of patients and controls.

Results

The results showed that levels of IL-2, IL-4, IL-6, IL-7, IL-8, IL-15, IL-1RA, G-CSF, GM-CSF, IFN-γ, TNF-α, basic FGF, PDGF-BB, RANTES, IP-10, MIP-1α, MIP-1β, MCP-1, and Eotaxin differed significantly among the SFTS fatal patients, recovered patients, and the healthy controls (all p<0.05). Compared to the healthy controls, the fatal patients and recovered patients had reduced levels of IL-2, IL-4, IL-7, PDGF-BB, RANTES, and Eotaxin, while the levels of PDGF-BB and RANTES were significantly lower in fatal patients compared to recovered patients. The increasing levels of IL-6, IL-8, IL-15, IL-1RA, G-CSF, GM-CSF, IFN-γ, TNF-α, basic FGF, IP-10, MIP-1α, MIP-1β, and MCP-1 were observed in fatal patients (all p<0.05), and the levels of IL-6, IP-10, MIP-1α, and MCP-1 were significantly higher than other two groups. The Spearman correlation analysis indicated a positive correlation between platelet count and PDGF-BB levels (p<0.05), while the white blood cell count had a negative correlation with MIP-1 level (p<0.05).

Conclusion

The research exhibited that the SFTS virus (SFTSV) caused an atypical manifestation of cytokines. The levels of IL-6, IP-10, MIP-1α, and MCP-1 had been observed a positive association with the severity of the illness.

A model based on meta-analysis to evaluate poor prognosis of patients with severe fever with thrombocytopenia syndrome

Background

Early identification of risk factors associated with poor prognosis in Severe fever with thrombocytopenia syndrome (SFTS) patients is crucial to improving patient survival.

Method

Retrieve literature related to fatal risk factors in SFTS patients in the database, extract the risk factors and corresponding RRs and 95% CIs, and merge them. Statistically significant factors were included in the model, and stratified and assigned a corresponding score. Finally, a validation cohort from Yantai Qishan Hospital in 2021 was used to verify its predictive ability.

Result

A total of 24 articles were included in the meta-analysis. The model includes six risk factors: age, hemorrhagic manifestations, encephalopathy, Scr and BUN. The analysis of lasso regression and multivariate logistic regression shows that model score is an independent risk factor (OR = 1.032, 95% CI 1.002-1.063, p = 0.034). The model had an area under the curve (AUC) of 0.779 (95% CI 0.669-0.889, P<0.001). The validation cohort was divided into four risk groups with cut-off values. Compared with the low-medium risk group, the mortality rate of high-risk and very high-risk patients was more significant (RR =5.677, 95% CI 4.961-6.496, P<0.001).

Conclusion

The prediction model for the fatal outcome of SFTS patients has shown positive outcomes.Systematic review registration:https://www.crd.york.ac.uk/prospero/ (CRD42023453157).

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie Bandavirus in aged ferrets

Dabie Bandavirus (DBV), previously known as Severe Fever with Thrombocytopenia Syndrome (SFTS) Virus, induces a characteristic thrombocytopenia with a mortality rate ranging from 12% to as high as 30%. The sero-prevalence of DBV in healthy people is not significantly different among age groups, but clinically diagnosed SFTS patients are older than ~50 years, suggesting that age is the critical risk factor for SFTS morbidity and mortality. Accordingly, our immune-competent ferret model demonstrates an age (>4 years old)-dependent DBV infection and pathogenesis that fully recapitulates human clinical manifestation. To protect the aged population from DBV-induced SFTS, vaccine should carry robust immunogenicity with high safety profile. Previous studies have shown that glycoproteins Gn/Gc are the most effective antigens for inducing both neutralizing antibody (NAb)- and T cell-mediated immunity and, thereby, protection. Here, we report the development of a protein subunit vaccine with 24-mer self-assembling ferritin (FT) nanoparticle to present DBV Gn head region (GnH) for enhanced immunogenicity. Anion exchange chromatography and size exclusion chromatography readily purified the GnH-FT nanoparticles to homogeneity with structural integrity. Mice immunized with GnH-FT nanoparticles induced robust NAb response and T-cell immunity against DBV Gn. Furthermore, aged ferrets immunized with GnH-FT nanoparticles were fully protected from DBV challenge without SFTS symptoms such as body weight loss, thrombocytopenia, leukopenia, and fatality. This study demonstrates that DBV GnH-FT nanoparticles provide an efficient vaccine efficacy in mouse and aged ferret models and should be an outstanding vaccine candidate targeted for the aged population against fatal DBV infection.

The pathogenic and clinical characteristics of severe fever with thrombocytopenia syndrome patients with co-infections

Objective

The study aimed to comprehensively describe and evaluate the pathogenic and clinical characteristics of severe fever with thrombocytopenia syndrome (SFTS) patients with co-infections.

Methods

We retrospectively collected clinical data and laboratory indicators of the SFTS patients at Tongji Hospital from October 2021 to July 2023.

Results

A total of 157 patients with SFTS virus (SFTSV) infection were involved in the analysis, including 43 co-infection and 114 non-co-infection patients. The pathogens responsible for co-infection were primarily isolated from respiratory specimens. Fungal infections, primarily Aspergillus fumigatus, were observed in 22 cases. Bacterial infections, with Klebsiella pneumoniae and carbapenem-resistant Acinetobacter baumannii as the main pathogens, were identified in 20 cases. SFTS patients with co-infection exhibited higher mortality (P=0.011) compared to non-co-infection patients. Among SFTS patients co-infected with both bacteria and fungi (8 cases) or specific drug-resistant strains (11 cases), the mortality rate was as high as 70% (14/19). In comparison with the non-co-infection group, SFTS patients with co-infection displayed significant alteration in inflammatory markers, coagulation function, and liver function indicators.

Conclusion

The mortality rate of SFTS patients with co-infection is relatively high, underscoring the need for enhanced monitoring and timely, appropriate treatment to minimize the mortality rate.

A Case of Severe Fever With Thrombocytopenia Syndrome With Recurrent Shock and Erythema

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal infectious disease often transmitted through tick bites and exposure to fluids from infected individuals. Early diagnosis is critical due to the high mortality rates of the disease; however, it might be challenging if a patient's history of tick contact is unclear. We report a detailed diagnosis of SFTS in a 69-year-old man with atypical symptoms but without identifiable tick bites. The diagnosis was made on the basis of massive diarrhea, recurrent shock, and unusual erythema presentation following hospital admission.

SFTSV Gn-Head mRNA vaccine confers efficient protection against lethal viral challenge

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne virus, causing thrombocytopenia and hemorrhagic fever, with a fatality rate ranging from 12% to 30%. SFTSV possesses Gn and Gc glycoproteins, which are responsible for host cell receptor attachment and membrane fusion, respectively, to infect host cells. We have previously reported a protein subunit vaccine candidate (sGn-H-FT) of the SFTSV soluble Gn head region (sGn-H) fused with self-assembling ferritin (FT) nanoparticles, displaying strong protective immunogenicity. In this study, we present messenger RNA (mRNA) vaccine candidates encoding sGn-H or sGn-H-FT, both of which exhibit potent in vivo immunogenicity and protection capacity. Mice immunized with either sGn-H or sGn-H-FT mRNA lipid nanoparticle (LNP) vaccine produced strong total antibodies and neutralizing antibodies (NAbs) against sGn-H. Importantly, NAb titers remained high for an extended period. Finally, mice immunized with sGn-H or sGn-H-FT mRNA LNP vaccine were fully protected from a lethal dose of SFTSV challenge, showing no fatality. These findings underscore the promise of sGn-H and sGn-H-FT as vaccine antigen candidates capable of providing protective immunity against SFTSV infection.

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie bandavirus in aged ferrets

IMPORTANCE

Dabie bandavirus (DBV) is an emerging tick-borne virus that causes severe fever with thrombocytopenia syndrome (SFTS) in infected patients. Human SFTS symptoms progress from fever, fatigue, and muscle pain to the depletion of white blood cells and platelets with fatality rates up to 30%. The recent spread of its vector tick to over 20 states in the United States increases the potential for outbreaks of the SFTS beyond the East Asia. Thus, the development of vaccine to control this rapidly emerging virus is a high priority. In this study, we applied self-assembling ferritin (FT) nanoparticle to enhance the immunogenicity of DBV Gn head domain (GnH) as a vaccine target. Mice immunized with the GnH-FT nanoparticle vaccine induced potent antibody responses and cellular immunity. Immunized aged ferrets were fully protected from the lethal challenge of DBV. Our study describes the GnH-FT nanoparticle vaccine candidate that provides protective immunity against the emerging DBV infection.

Identification and Analysis of a Four-Gene Set for Diagnosing SFTS Virus Infection Based on Machine Learning Methods and Its Association with Immune Cell Infiltration

Severe Fever with thrombocytopenia syndrome (SFTS) is a highly fatal viral infectious disease that poses a significant threat to public health. Currently, the phase and pathogenesis of SFTS are not well understood, and there are no specific vaccines or effective treatment available. Therefore, it is crucial to identify biomarkers for diagnosing acute SFTS, which has a high mortality rate. In this study, we conducted differentially expressed genes (DEGs) analysis and WGCNA module analysis on the GSE144358 dataset, comparing the acute phase of SFTSV-infected patients with healthy individuals. Through the LASSO-Cox and random forest algorithms, a total of 2128 genes were analyzed, leading to the identification of four genes: ADIPOR1, CENPO, E2F2, and H2AC17. The GSEA analysis of these four genes demonstrated a significant correlation with immune cell function and cell cycle, aligning with the functional enrichment findings of DEGs. Furthermore, we also utilized CIBERSORT to analyze the immune cell infiltration and its correlation with characteristic genes. The results indicate that the combination of ADIPOR1, CENPO, E2F2, and H2AC17 genes has the potential as characteristic genes for diagnosing and studying the acute phase of SFTS virus (SFTSV) infection.

Clinical characteristics and outcomes of acute kidney injury in patients with severe fever with thrombocytopenia syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging zoonosis caused by a novel bunyavirus. Until recently, the SFTS related acute kidney injury (AKI) was largely unexplored. This study aimed to investigate the clinical characteristics and outcomes of AKI in patients with SFTS.

Methods

The non-AKI and AKI groups were compared in terms of general characteristics, clinical features, laboratory parameters and cumulative survival rate. The independent risk factors for in-hospital mortality in patients with SFTS were analyzed by multivariate logistic regression to identify the population with poor prognosis.

Results

A total of 208 consecutive patients diagnosed with SFTS were enrolled, including 153 (73.6%) patients in the non-AKI group and 55 (26.4%) patients in the AKI group. Compared with patients without AKI, patients with AKI were older and had a higher frequency of diabetes. Among these laboratory parameters, platelet count, albumin and fibrinogen levels of patients with AKI were identified to be significantly lower than those of patients without AKI, while ALT, AST, ALP, triglyceride, LDH, BUN, uric acid, creatine, Cys-C, β2-MG, potassium, AMY, lipase, CK-MB, TnI, BNP, APTT, thrombin time, D-dimer, CRP, IL-6, PCT and ESR levels were significantly higher in patients with AKI. A higher SFTS viral load was also detected in the AKI patients than in the non-AKI patients. The cumulative survival rates of patients at AKI stage 2 or 3 were significantly lower than those of patients without AKI or at AKI stage 1. However, there was no significant difference in the cumulative survival rates between patients without AKI and those with stage 1 AKI. Univariate and multivariate binary logistic regression analyses demonstrated that stage 2 or 3 AKI was an independent risk factor for in-hospital mortality in patients with SFTS.

Conclusion

AKI is associated with poor outcomes in patients with SFTS, especially patients at AKI stage 2 or 3, who generally have high mortality. Our findings support the importance of early identification and timely treatment of AKI in patients with SFTS.

Study of Viral Coinfection of the Ixodes persulcatus Ticks Feeding on Humans in a Natural Focus of the South of the Far East

The phenomenon of pathogen co-infection detected in a half-fed Ixodes persulcatus tick taken from a human in the south of the Far East was studied. Research was carried out on PEK, Vero, and Vero-E6 cell lines, outbred mice, and chicken embryos using ELISA, PCR, IMFA, plaque formation, and electron microscopy. The tick contained an antigen and a genetic marker of the tick-borne encephalitis virus (TBEV). The patient had post-vaccination antibodies in a titer of 1:200, as a result of which, obviously, an antibody-dependent elimination of TBEV occurred. The tick-borne co-isolate also contained an unknown pathogen (Kiparis-144 virus), which, in our opinion, was a trigger for the activation of chronic infection in suckling white mice. In the laboratory co-isolate, ectromelia virus was present, as evidenced by paw edema during the intradermal infection of mice, characteristic rashes on the chorioallantoic envelope of chicken embryos, and typical plaques on Vero-E6. The Kiparis-144 virus was not pathogenic for white mice and chicken embryos, but it successfully multiplied in the PEK, Vero, and Vero-E6 lines. Viral co-infection was confirmed by electron microscopy. Passaging on mice contributed to an increase in the virulence of the co-isolate, whose titer increased by 10,000 times by the fifth passage, which poses an epidemiological danger.

Risk factors associated with death due to severe fever with thrombocytopenia syndrome in hospitalized Korean patients (2018-2022)

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) has no vaccine or treatment and an extremely high fatality rate. We aimed to analyze and evaluate the risk factors for death associated with SFTS.

METHODS

Among reports from 2018 to 2022, we compared and analyzed 1,034 inpatients aged 18 years or older with laboratory-confirmed SFTS who underwent complete epidemiological investigations.

RESULTS

Most of the inpatients with SFTS were aged 50 years or older (average age, 67.6 years). The median time from symptom onset to death was 9 days, and the average case fatality rate was 18.5%. Risk factors for death included age of 70 years or older (odds ratio [OR], 4.82); agriculture-related occupation (OR, 2.01); underlying disease (OR, 7.20); delayed diagnosis (OR, 1.28 per day); decreased level of consciousness (OR, 5.53); fever/chills (OR, 20.52); prolonged activated partial thromboplastin time (OR, 4.19); and elevated levels of aspartate aminotransferase (OR, 2.91), blood urea nitrogen (OR, 2.62), and creatine (OR, 3.21).

CONCLUSION

The risk factors for death in patients with SFTS were old age; agriculture-related occupation; underlying disease; delayed clinical suspicion; fever/chills; decreased level of consciousness; and elevated activated partial thromboplastin time, aspartate aminotransferase, blood urea nitrogen, and creatine levels.

Effect of intravenous immunoglobulin therapy on the prognosis of patients with severe fever with thrombocytopenia syndrome and neurological complications

Background

Intravenous immunoglobulin (IVIG) has been reported to exert a beneficial effect on severe fever with thrombocytopenia syndrome (SFTS) patients with neurological complications. However, in clinical practice, the standard regime is unclear and there is a lack of evidence from large-scale studies.

Methods

A single-center retrospective study was conducted to determine the influence of IVIG dosage and duration on SFTS patients with neurological complications. The primary outcome was 28-day mortality, and laboratory parameters before and after IVIG treatment were measured. Survival curves were generated using the Kaplan-Meier method and analyzed with the log-rank test according to the median IVIG dosage and IVIG duration. Besides, multivariate Cox regression analysis was performed to examine the association between the independent factors and 28-day mortality in SFTS patients.

Results

Overall, 36 patients (58.06%) survived, while 26 (41.9%) patients died. The median age of the included patients was 70 (55-75) years, and 46.8% (29/62) were male. A significantly higher clinical presentation of dizziness and headache was observed in the survival group. The IVIG duration in the survival group was longer than in the death group (P <0.05). Additionally, the IVIG dosage was higher in the survival group than in the death group, but there was not a statistically significant difference between the two groups (P = 0.066). The mediating effect of IVIG duration was verified through the relationship between IVIG dosage and prognosis using the Sobel test. Univariate analysis revealed that IVIG dosage (HR: 0.98; 95% CI: 0.97-1.00; P = 0.007) and IVIG duration (HR: 0.54; 95% CI: 0.41-0.72; P <0.001) were significantly associated with risk of death. The multivariate analysis generated an adjusted HR value of 0.98 (95% CI: 0.96-1.00; P = 0.012) for IVIG dosage and 0.26 (95% CI: 0.09-0.78; P = 0.016) for dizziness and headache.

Conclusion

Prolonged high-dose IVIG is beneficial to the 28-day prognosis in SFTS patients with neurological complications.

Severe fever with thrombocytopenia syndrome virus replicates in platelets and enhances platelet activation

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) virus (SFTSV) infection causes an emerging hemorrhagic fever in East Asia with a high mortality rate. Thrombocytopenia is a consistent feature of SFTS illness, but the mechanism remains elusive.

OBJECTIVES

We aimed to better understand the role of platelets in the pathophysiology of SFTSV infection, including the development of thrombocytopenia.

METHODS

Using platelets from healthy volunteers and patients with SFTS, we evaluated the functional changes in platelets against SFTSV infection. We investigated the direct effect of glycoprotein VI on platelet-SFTSV interaction by quantitative real-time PCR, molecular docking, surface plasmon resonance spectrometry, flow cytometry, western blot, and platelet functional studies in vitro. Interactions of SFTSV and platelet-SFTSV complexes with macrophages were also determined by scanning electron microscope, quantitative real-time PCR, and flow cytometry.

RESULTS

This study is the first to demonstrate that platelets are capable of harboring and producing SFTSV particles. Structural and functional studies found that SFTSVs bind platelet glycoprotein VI to potentiate platelet activation, including platelet aggregation, adenosine triphosphate release, spreading, clot retraction, coagulation, phosphatidylserine exposure, thrombus formation, and adherence. In vitro mechanistic studies highlighted that the interaction of platelets with human THP-1 cells promoted SFTSV clearance and suppressed cytokine production in macrophages. However, unwanted SFTSV replication in macrophages reciprocally aggravated SFTSV persistence in the circulation, which may contribute to thrombocytopenia and other complications during SFTSV infection.

CONCLUSION

These findings together highlighted the pathophysiological role of platelets in initial intrinsic defense against SFTSV infections, as well as intertwined processes with host immunity, which can also lead to thrombocytopenia and poor prognosis.

High C-reactive protein to lymphocyte ratio predicts mortality outcomes of patients with severe fever with thrombocytopenia syndrome: A multicenter study in China

Severe fever with thrombocytopenia syndrome (SFTS) is a life-threatening infectious disease caused by the SFTS virus (SFTSV). This study aimed to evaluate the predictive power of C-reactive protein to lymphocyte ratio (CLR) and establish an early-warning model for SFTS mortality. We retrospectively analyzed hospitalized SFTS patients in six clinical centers from May 2011 to 2022. The efficacy of CLR prediction was evaluated by the receiver operating characteristic (ROC) analysis. A nomogram was established and validated. Eight hundred and eighty-two SFTS patients (median age 64 years, 48.5% male) were enrolled in this study, with a mortality rate of 17.8%. The area under the ROC curve (AUC) of CLR was 0.878 (95% confidence interval [CI]: 0.850-0.903, p < 0.001), which demonstrates high predictive strength. The least absolute shrinkage and selection operator regression selected seven potential predictors. Multivariate logistic regression analysis determined three independent risk factors, including CLR, to construct the nomogram. The performance of the nomogram displayed excellent discrimination and calibration, with significant net benefits in clinical uses. CLR is a brand-new predictor for SFTS mortality. The nomogram based on CLR can serve as a convenient tool for physicians to identify critical SFTS cases in clinical practice.

CD8+ T cells mediate antiviral response in severe fever with thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by a novel Bunyavirus, has gradually become a threatening infectious disease in rural areas of Asia. Studies have identified a severe cytokine storm and impaired humoral immune response in SFTS. However, the cellular immune response to SFTS virus (SFTSV) infection remains largely unknown. Here we report that SFTS patients had a cytokine storm accompanied by high levels of chemokines. CD8⁺ T cells in peripheral blood mononuclear cells of SFTS patients exhibited a more activated phenotype and enhanced the antiviral responses. They increased the expression of CD69 and CD25, secreted a higher level of IFN-γ and granzyme, and had a stronger proliferative ability than in healthy controls. In convalescent SFTS patients, the expression of CD69 and CD25 on CD8⁺ T cells was reduced. In addition, we found the ratio and cellularity of CD14⁺ CD16⁺ intermediate monocytes were increased in peripheral blood of SFTS patients. Both the expression of C-X-C motif chemokine ligand 10 (CXCL10) on CD14⁺ CD16⁺ intermediate monocytes and the expression of C-X-C motif chemokine receptor 3 (CXCR3) on CD8⁺ T cells increased dramatically in SFTS patients. Our studies reveal a potential pathway that CD8⁺ T cells rapidly activate and are mostly recruited by intermediate monocytes through CXCL10 in SFTSV infection. Our results may be of clinical relevance for further treatment and discharge instructions in SFTSV infections.

Virus-host interactions during tick-borne bunyavirus infection

The Bunyavirales order is the largest grouping of RNA viruses, comprising emerging and re-emerging human, plant and animal pathogens. Bunyaviruses have a global distribution and many members of the order are transmitted by arthropods. They have evolved a plethora of mechanisms to manipulate the regulatory processes of the infected cell to facilitate their own replicative cycle, in hosts of disparate phylogenies. Interest in virus-vector interactions is growing rapidly. However, current understanding of tick-borne bunyavirus cellular interaction is heavily biased to studies conducted in mammalian systems. In this short review, we summarise current understandings of how tick-borne bunyaviruses utilise major cellular pathways (innate immunity, apoptosis and RNAi responses) in mammalian or tick cells to facilitate virus replication.

Associated microbiota and treatment of severe fever with thrombocytopenia syndrome complicated with infections

The purpose of this study is to assess the incidence and management of co-infections in hospitalized severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) patients. We retrospectively evaluated the microbiological database records of the SFTS patients in the first affiliated hospital of Anhui Medical University from January 1, 2018, to December 1, 2021. According to the obtained results, co-infections including pulmonary infection, bloodstream infection, biliary tract infection, urinary tract infection, and abdominal infection were observed in SFTS patients. The incidence rate of fungal infections was found to be high in SFTS patients. Furthermore, we suggest that old age people should be evaluated for the risk of fungal infection. In comparison to the non-infection group, patients in the co-infection group were more likely to get mechanical ventilation, antibacterial treatment, antifungal treatment, and blood product therapy (p < 0.001), with a significantly longer length of stay (p < 0.05). In SFTS patients, the most prevalent strains were Aspergillus fumigatus, Aspergillus flavus, Candida, Klebsiella pneumonia, and Escherichia coli. In this investigation, 66.2% (106/160) of patients were given antibiotics, most often Piperacillin/tazobactam or minocycline. 15.6% (25/160) of patients were treated with antifungal drugs: 13.1% (21/160) with voriconazole. Patients with SFTS Associated Pulmonary Aspergillosis (SAPA) received active antifungal treatment, but the mortality rate was still 23.5% (8/34). Only 6 of the 11 patients with SFTS Associated Candidiasis were treated with antifungal drugs with no mortality. Due to the high frequency of fungal pulmonary infection in SFTS patients, more standardized fungal detection program should be strengthened.

Severe Fever with Thrombocytopenia Syndrome Virus Infection, Thailand, 2019-2020

Infection with severe fever with thrombocytopenia syndrome (SFTS) virus, which can cause hemorrhagic febrile illness, is often transmitted by ticks. We identified 3 patients with SFTS in or near Bangkok, Thailand. Our results underscore a need for heightened awareness by clinicians of possible SFTS virus, even in urban centers.

Cyclophilin A causes severe fever with thrombocytopenia syndrome virus-induced cytokine storm by regulating mitogen-activated protein kinase pathway

Introduction

Severe fever with thrombocytopenia syndrome (SFTS) has become a global threat to public health since its first report in China in 2009. However, the pathogenesis of SFTS virus (SFTSV) in humans remains unclear. Also, there are no effective therapeutics for SFTS. Cyclophilin A (CyPA) regulates protein folding and trafficking involved in various viral infectious diseases, but its role in SFTSV infection has not been elucidated.

Methods

We detected plasma CyPA levels in 29 healthy subjects and 30 SFTS patients by ELISA. In THP-1 cells and normal human peripheral blood mononuclear cells (PBMCs), SFTSV-induced extracellular CyPA (eCyPA) was also detected by ELISA. In THP-1, the effects of CyPA on Mitogen-activated protein kinase (MAPK) pathway and NF-κB were determined by Western blot. We validated the interaction between CypA and CD147 by human recombinant CyPA (hrCyPA) and the CD147 inhibitor. Effects of CyPA inhibitor Cyclosporine A (CsA) on cytokines and SFTSV replication in THP-1 cells was also detected. 8-week-old Interferon-α/β Receptor (IFNAR) knockout (IFNAR-/-) C57BL/6 mice were divided into mock group, 10⁶TCID₅₀ SFTSV (Untreated) group and 10⁶TCID₅₀ SFTSV+CsA (CsA-treated) group. The changes of body weight, animal behavior and survival time of each group were recorded. Blood samples were collected from tail vein regularly. After death, the liver, spleen, lung, kidney and brain were collected for pathological HE staining and SFTSV-NP immunohistochemical staining.

Results

Compared to healthy subjects and SFTS patients in the febrile phase of the disease, plasma CyPA levels in SFTS patients at the multi-organ dysfunction (MOD) phase showed significantly elevated (P < 0.01). Extracellular CyPA activates the MAPK pathway by binding to CD147 in THP-1 infected with SFTSV. CsA inhibits the pro-inflammatory and promoting replication effects of CyPA after SFTSV infection in vitro. In vivo, CsA can prolong the survival time and delay the weight loss of SFTSV mice. CsA reduces multi-organ dysfunction in IFNAR-/- mice infected with SFTSV.

Discussion

Our results indicate that CyPA is associated with SFTSV-induced cytokine storm, which can be a potential target for SFTS therapy.

Pathogens in Ixodes persulcatus and Ixodes ricinus ticks (Acari, Ixodidae) in Karelia (Russia)

Ixodid ticks (Acarina, Ixodidae) are vectors of dangerous human infections. The main tick species that determine the epidemiological situation for tick-borne diseases in northern Europe are Ixodes ricinus and Ixodes persulcatus. In recent years, significant changes in the number and distribution of these species have been observed, accompanied by an expansion of the sympatric range. This work summarizes the data of long-term studies carried out in Karelia since 2007 on the infection of I. persulcatus and I. ricinus ticks with various pathogens, including new viruses with unclear pathogenic potential. As a result, tick-borne encephalitis virus (TBEV, Siberian genotype), Alongshan virus, several representatives of the family Phenuiviridae, Borrelia afzelii, Borrelia garinii, Ehrlichia muris, Candidatus Rickettsia tarasevichiae and Candidatus Lariskella arthropodarum were identified. Data were obtained on the geographical and temporal variability of tick infection rates with these main pathogens. The average infection rates of I. persulcatus with TBEV and Borrelia burgdorferi sensu lato were 4.4% and 23.4% and those of I. ricinus were 1.1% and 11.9%, respectively. We did not find a correlation between the infection rate of ticks with TBEV, B. burgdorferi s.l. and Ehrlichia muris/chaffeensis with the sex of the vector. In general, the peculiarities of the epidemiological situation in Karelia are determined by the wide distribution and high abundance of I. persulcatus ticks and by their relatively high infection rate with TBEV and B. burgdorferi s.l. in most of the territory, including the periphery of the range.

Analysis of risk factors associated with fatal outcome among severe fever with thrombocytopenia syndrome patients from 2015 to 2019 in Shandong, China

To better understand the progression of severe fever with thrombocytopenia syndrome (SFTS), identify early predictors of mortality, and improve the cure rate, the present study aimed to analyze the demographic feature, clinical characteristics, and laboratory parameters of patients with SFTS and to explore the risk factors associated with fatal outcome. We retrospectively analyzed demographic feature, clinical characteristics, and laboratory parameters of 216 laboratory-confirmed SFTS patients in Shandong province between January 2015 and December 2019. Univariate analysis was used to assess the relevance between these factors and fatal outcome. Factors with P < 0.05 in univariate analysis were further analyzed using multivariable logistic regression analysis to identify the independent risk factors for mortality of SFTS. Age, five complications (including CNS symptoms, pulmonary infection, heart failure, arrhythmia, and bleeding events), and ten abnormal laboratory parameters (including serum viral load, blood platelet, ALT, AST, LDH, CK, CK-MB, Cr, serum Ca²⁺, and APTT) were statistically significant by univariate analysis. These factors were further analyzed by multivariable logistic regression analysis, and the results indicated that coma, pulmonary infection, high viral load, and prolonged APTT were associated with fatal outcome in SFTS patients. Our study identified four independent risk factors associated with fatal outcome for SFTS patients. The results were hoped to provide help for active treatment of SFTS. However, the identification of risk factors is not absolutely associated with fatal outcome. Patients' risk should be assessed by dynamic observation of the changes in risk factor indicators.

Serum proteomics of severe fever with thrombocytopenia syndrome patients

BACKGROUND

Dabie bandavirus, also termed as severe fever with thrombocytopenia syndrome virus (SFTSV), was first isolated in China in 2010. At this time, the virus was found to have spread to South Korea, Japan, and other countries. A high case fatality rate is reported for SFTS, ranging from 12-50% within various sources. Several omics for clinical studies among SFTS patients as well as studies of cultured SFTSV have attempted to characterize the relevant molecular biology and epidemiology of the disease. However, a global serum proteomics analysis among SFTS patients has not yet been reported to date.

METHODS

In the current study, we evaluated comparative serum proteomics among SFTS patients (eight recovered patients and three deceased patients) with the goal of identifying the protein expression patterns associated with the clinical manifestations of SFTS.

RESULTS

The proteomic results in the current study showed that the coagulation factor proteins, protein S and protein C, were statistically significantly downregulated among the deceased patients. Downregulation of the complement system as well as prolonged neutrophil activation were also observed. Additionally, the downstream proteins of tumour necrosis factor alpha, neutrophil-activating cytokine, and interleukin-1β, an inflammatory cytokine, were overexpressed.

CONCLUSIONS

Thrombocytopenia and multiple organ failure are the major immediate causes of death among SFTS patients. In this study, serum proteomic changes related to thrombocytopenia, abnormal immune response, and inflammatory activation were documented in SFTS patients. These findings provide useful information for understanding the clinical manifestations of SFTS.

A CRISPR-Cas12a-based diagnostic method for multiple genotypes of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) infection is commonly reported in countries of Northeast Asia including China, Japan and South Korea. The majority of the SFTS patients are elderly and the average fatality rate is more than 10%. A rapid and sensitive diagnostic method to monitor and prevent SFTSV transmission remains an urgent clinical challenge. In this study, we developed a molecular diagnostic technique for detection of SFTSV using the CRISPR-Cas12a system combined with reverse transcription recombinase polymerase amplification (RT-RPA). Using this method, we successfully diagnosed SFTSV infections with the reaction time of 50 min from blood plasma without cross-reactivity to other viruses, supporting its application for rapid and sensitive diagnosis of SFTS.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by Dabie bandavirus, also known as SFTSV, and reported in countries of Northeast Asia including China, Japan and South Korea. The average fatality rate is more than 10% and reported to increase with age. Currently, no vaccines or targeted treatments for SFTS are available and only symptomatic therapy is offered. Thus, SFTSV diagnosis at early stages is critical for successful therapeutic outcomes. In this study, we developed a molecular diagnostic technique for detection of SFTSV using the CRISPR-Cas12a system combined with reverse transcription recombinase polymerase amplification (RT-RPA). Using this method, we successfully diagnosed SFTSV infections under isothermal conditions with the reaction time of 50 min from blood plasma.

Dabie bandavirus Nonstructural Protein Interacts with Actin to Induce F-Actin Rearrangement and Inhibit Viral Adsorption and Entry

Dabie bandavirus (DBV) is an emerging Bandavirus that causes multiorgan failure with a high fatality rate in humans. While many viruses can manipulate the actin cytoskeleton to facilitate viral growth, the regulation pattern of the actin cytoskeleton and the molecular mechanisms involved in DBV entry into the host cells remain unclear. In this study, we demonstrate that expression of nonstructural protein (NSs) or infection with DBV induces actin rearrangement, which presents a point-like distribution, and this destruction is dependent on inclusion bodies (IBs). Further experiments showed that NSs inhibits viral adsorption by destroying the filopodium structure. In addition, NSs also compromised the viral entry by inhibiting clathrin aggregation on the cell surface and capturing clathrin into IBs. Furthermore, NSs induced clathrin light chain B (CLTB) degradation through the K48-linked ubiquitin proteasome pathway, which could negatively regulate clathrin-mediated endocytosis, inhibiting the viral entry. Finally, we confirmed that this NSs-induced antiviral mechanism is broadly applicable to other viruses, such as enterovirus 71 (EV71) and influenza virus, A/PR8/34 (PR8), which use the same clathrin-mediated endocytosis to enter host cells. In conclusion, our study provides new insights into the role of NSs in inhibiting endocytosis and a novel strategy for treating DBV infections. IMPORTANCEDabie bandavirus (DBV), a member of the Phenuiviridae family, is a newly emerging tick-borne pathogen that causes multifunctional organ failure and even death in humans. The actin cytoskeleton is involved in various crucial cellular processes and plays an important role in viral life activities. However, the relationship between DBV infection and the actin cytoskeleton has not been described in detail. Here, we show for the first time the interaction between NSs and actin to induce actin rearrangement, which inhibits the viral adsorption and entry. We also identify a key mechanism underlying NSs-induced entry inhibition in which NSs prevents clathrin aggregation on the cell surface by hijacking clathrin into the inclusion body and induces CLTB degradation through the K48-linked ubiquitination modification. This paper is the first to reveal the antiviral mechanism of NSs and provides a theoretical basis for the search for new antiviral targets.

Overview of the immunological mechanism underlying severe fever with thrombocytopenia syndrome (Review)

Severe fever with thrombocytopenia syndrome (SFTS) has been acknowledged as an emerging infectious disease that is caused by the SFTS virus (SFTSV). The main clinical features of SFTS on presentation include fever, thrombocytopenia, leukocytopenia and gastrointestinal symptoms. The mortality rate is estimated to range between 5-30% in East Asia. However, SFTSV infection is increasing on an annual basis globally and is becoming a public health problem. The transmission cycle of SFTSV remains poorly understood, which is compounded by the pathogenesis of SFTS not being fully elucidated. Since the mechanism underlying the host immune response towards SFTSV is also unclear, there are no effective vaccines or specific therapeutic agents against SFTS, with supportive care being the only realistic option. Therefore, it is now crucial to understand all aspects of the host-virus interaction following SFTSV infection, including the antiviral states and viral evasion mechanisms. In the present review, recent research progress into the possible host immune responses against SFTSV was summarized, which may be useful in designing novel therapeutics against SFTS.

Clinical laboratory parameters and fatality of Severe fever with thrombocytopenia syndrome patients: A systematic review and meta-analysis

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease with high case fatality rate. Unfortunately, no vaccine or antiviral specifically targeting SFTS virus (SFTSV) are available for the time being. Our objective was to investigate the association between clinical laboratory parameters and fatality of SFTS patients.

Methods

The systematic review was conducted in accordance with The Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. We searched (from inception to 24th February 2022) Web of Science, PubMed, National Knowledge Infrastructure databases and Wan Fang Data for relevant researchers on SFTS. Studies were eligible if they reported on laboratory parameters of SFTS patients and were stratified by clinical outcomes. A modified version of Newcastle-Ottawa scale was used to evaluate the quality of included studies. Standardized mean difference (SMD) was used to evaluate the association between laboratory parameters and outcomes. The between-study heterogeneity was evaluated quantitatively by standard Chi-square and the index of heterogeneity (I2). Heterogeneity was explored by subgroup and sensitivity analyses, and univariable meta-regression. Publication bias was determined using funnel plots and Egger’s test.

Results

We identified 34 relevant studies, with over 3300 participants across three countries. The following factors were strongly (SMD>1 or SMD<-0.5) and significantly (P<0.05) associated mortality: thrombin time (TT) (SMD = 1.53), viral load (SMD = 1.47), activated partial-thromboplastin time (APTT) (SMD = 1.37), aspartate aminotransferase (AST) (SMD = 1.19), lactate dehydrogenase (LDH) (SMD = 1.13), platelet count (PLT) (SMD = -0.47), monocyte percentage (MON%) (SMD = -0.47), lymphocyte percentage (LYM%) (SMD = -0.46) and albumin (ALB) (SMD = -0.43). Alanine aminotransferase, AST, creatin phosphokinase, LDH, PLT, partial-thromboplastin time and viral load contributed to the risk of dying of SFTS patients in each subgroup analyses. Sensitivity analysis demonstrated that the results above were robust.

Conclusions/significance

The abnormal levels of viral load, PLT, coagulation function and liver function, significantly increase the risk of SFTS mortality, suggesting that SFTS patients with above symptoms call for special concern.

The Endless Wars: Severe Fever With Thrombocytopenia Syndrome Virus, Host Immune and Genetic Factors

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging arboviral infectious disease with a high rate of lethality in susceptible humans and caused by severe fever with thrombocytopenia syndrome bunyavirus (SFTSV). Currently, neither vaccine nor specific antiviral drugs are available. In recent years, given the fact that both the number of SFTS cases and epidemic regions are increasing year by year, SFTS has become a public health problem. SFTSV can be internalized into host cells through the interaction between SFTSV glycoproteins and cell receptors and can activate the host immune system to trigger antiviral immune response. However, SFTSV has evolved multiple strategies to manipulate host factors to create an optimal environment for itself. Not to be discounted, host genetic factors may be operative also in the never-ending winning or losing wars. Therefore, the identifications of SFTSV, host immune and genetic factors, and their interactions are critical for understanding the pathogenic mechanisms of SFTSV infection. This review summarizes the updated pathogenesis of SFTS with regard to virus, host immune response, and host genetic factors to provide some novel perspectives of the prevention, treatment, as well as drug and vaccine developments.

The value of cystatin C in evaluating the severity and prognosis of patients with severe fever with thrombocytopenia syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) is a novel emerging viral infectious disease. We explore the value of cystatin C (CysC) level in the evaluation of disease severity and prognosis in patients with SFTS.

Methods

254 patients with SFTS were enrolled in this study. According to the classification and the outcome of the disease, the patients were divided into the general group and the severe group, the severe patients were divided into the fatal group and the non-fatal group. We compared the laboratory indexes by univariate and multivariate logistic regression analysis to explore the severity and prognostic risk factors of SFTS disease, ROC curve and Kaplan–Meier survival analysis curve were drawn to analyze the independent risk factors and the predictive value of disease severity and prognosis.

Results

Univariate analysis showed that the CysC level in severe group and fatal group was significantly higher than general group and non-fatal group (P < 0.05), respectively. Multivariate logistic regression showed that the CysC level was an independent risk factor for severe and death in SFTS patients, and it can effectively predict the risk of severe (AUC = 0.711, 95% CI: 0.645–0.777) and death (AUC = 0.814, 95% CI: 0.737–0.89). The risk of death in patients with cystatin C ≥ 1.23 mg/L was 5.487 times higher than that in patients with cystatin C < 1.23 mg/L.

Conclusions

The CysC level have good predictive value for disease severity and prognosis in patients with SFTS.

Trial registration Not applicable