SFTS Patients Research Articles

Nucleocapsid protein-specific IgM antibody responses in the disease progression of severe fever with thrombocytopenia syndrome

ObjectivesSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that is caused by the SFTS virus (SFTSV) and has a high fatality rate. SFTSV-specific antibody profiles among patients with different clinical outcomes are yet to be described. The nucleocapsid protein (NP) is the most immunogenic viral antigen of the SFTSV. This study, therefore, sought to determine NP-specific antibody responses among SFTS patients with different disease progressions. MethodsIn the present study, 43 patients with confirmed SFTS were enrolled in our cohort, and 9 of them deceased. The clinical presentations and key laboratory parameters associated with SFTS fatality were also recorded. Serum samples from each patient were collected every 2 days during their hospitalization. NP-specific IgM and IgG responses as well as Gn or Gc-specific IgM responses were examined by enzyme-linked immunosorbent assay (ELISA), whereas, the dynamic viral loads of SFTSV RNA were quantified via real-time reverse transcription polymerase chain reaction (RT-PCR). ResultsFirst, 77% of patients generated positive NP-specific IgM antibody responses within two weeks since illness onset, defined as ‘N-specific IgM-positive patients’, while the rest of the patients were termed as ‘N-specific IgM-delayed patients’. Only 17% of the patients generated NP-specific IgG responses. The absence of NP-specific humoral responses was strongly associated with a high risk of fatality and severity of SFTS. IgM-positive patients had significantly lower levels of viral loads, less disturbed coagulopathy, and hepatic and cardiac damage compared to IgM-delayed patients. Moreover, compared to severe or fatal SFTS patients, mild SFTS patients had significantly higher magnitudes of NP-specific IgM responses, but not NP-specific IgG, Gn-specific IgM, or Gc-specific IgM responses. The abundance of NP-specific IgM responses negatively correlated with viral loads, coagulation disturbances, and hepatic injuries among SFTS patients. ConclusionsOur data highlight distinct humoral profiles of NP-specific IgM responses among SFTS patients with different disease progressions and clinical outcomes.

The proportion, origin and pro-inflammation roles of low density neutrophils in SFTS disease

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is a novel emerging viral infectious disease. We explored the percentage, origins and functional roles of low density neutrophils (LDNs), one of the neutrophils subsets, in SFTS.MethodsThe LDNs and normal density neutrophils (NDNs) from blood of SFTS and normal volunteers which were collected separately. The percentage, origins and the phagocytic capability of SFTS viral (SFTSV) of LDNs were investigated by flow cytometry and real time PCR. The capacity of LDNs to secrete cytokines and to damage endothelial cells was assessed by ELISA and flow cytometry.ResultsWe observed that the proportion of LDNs increased dramatically compared with the healthy donors and became the dominant circulating neutrophil population in SFTS patients. Interestingly, the NDNs from the normal donors could switch to LDNs under the SFTS environment. Moreover, SFTSV load in LDNs was significantly higher than that of NDNs in the severe SFTS patients. In addition, the LDNs secreted much higher levels of pro-inflammatory cytokines than NDNs in SFTS and could induce endothelial cell injury.ConclusionThe NDNs can be converted to LDNs. This conversion mechanism could become the source of LDNs. The LDNs in severe SFTS patient could engulf more SFTSV and exhibit pro-inflammation functions.Trial registrationThe Ethics Committee of Tongji Medical College, Huazhong University of Science and Technology (IORG No: IORG0003571) gave a final APPROVAL for the study.

Extensive severe fever with thrombocytopenia syndrome virus contamination in surrounding environment in patient rooms

ObjectivesSevere fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease in Korea and China. Although there is previous evidence of person-to-person transmission via direct contact with body fluids, the role of environmental contamination by SFTS virus (SFTSV) in healthcare settings has not been established. We therefore investigated the contamination of the healthcare environment by SFTSV. MethodsWe investigated the possible contamination of hospital air and surfaces with SFTSV transmission by collecting air and swabbing environmental surface samples in two hospitals treating six SFTS patients between March and September 2017. The samples were tested using real-time RT-PCR for SFTS M and S segments. ResultsOf the six SFTS patients, four received mechanical ventilation and three died. Five rooms were occupied by those using mechanical ventilation or total plasma exchange therapy in isolation rooms without negative pressure and one room was occupied by a patient bedridden due to SFTS. SFTSV was detected in 14 (21%) of 67 swab samples. Five of 24 swab samples were obtained from fomites including stethoscopes, and 9 of 43 were obtained from fixed structures including doorknobs and bed guardrails. Some samples from fixed structures such as television monitors and sink tables were obtained in areas remote from the patients. SFTSV RNA was not detected in five air samples from three patients' rooms. ConclusionsOur data suggest that SFTSV contamination was extensive in surrounding environments in SFTS patients' rooms. Therefore, more strict isolation methods and disinfecting procedures should be considered when managing SFTS patients.

Kinetics of viral load and cytokines in severe fever with thrombocytopenia syndrome

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease in China, Japan, and Korea, which is characterized by high fever, thrombocytopenia, and high mortality. It is hypothesized that a cytokine storm plays an important role in the pathophysiology of SFTS. However, limited data have been published on the detailed kinetics of the viral load and cytokine profiles throughout the course of this disease. ObjectivesWe investigated the patterns of changes in cytokines and viral load in SFTS patients. Study designDuring the admission period of patients, RNA was extracted from plasma and quantified by reverse transcription polymerase chain reaction. In addition, cytokine bead arrays were performed for the 18 cytokines and chemokines selected for testing. ResultsThe median time from admission to the negative conversion of SFTS viremia was 17.0 days. When censored patients were found to be negative for viral load at discharge, the median duration of viral shedding was 13.0 days (95% CI, 5.4–20.6). Interferon (IFN)-α, interleukin (IL)-10, and IFN-γ-induced protein (IP)-10 concentrations significantly increased in the early course of disease and then decreased during the hospital stay. However, the concentrations of tumor necrosis factor-α, IL-1β, IL-12p40, IL-13, IL-17A, Regulated on Activation and Normally T-cell Expressed and Secreted (RANTES), and vascular endothelial growth factor (VEGF) increased during the late course of disease. Initial IP-10 levels during hospital days 1–4 were the most significantly correlated with initial viral load (r = 0.88, P < .01). ConclusionSFTS viremia persisted until weeks 2–3 and was highly correlated with initial plasma IP-10 levels. In addition, IFN-α, IL-10, and IP-10 were associated with the initial cytokine storm in SFTS.

Severe Fever with Thrombocytopenia Syndrome Virus Infection Associated with Hemophagocytic Lymphohistiocytosis as Poor Prognostic Factor

BackgroundSevere fever with thrombocytopenia (SFTS) is an emerging infectious disease caused by a novel bunyavirus designated SFTS virus (SFTSV) with a high fatality rate. Hemophagocytic lymphohistiocytosis (HLH) is an immune-mediated life-threatening disease triggered by infections, neoplasms and noninfectious inflammatory diseases. A few HLH associated with SFTSV were reported. According to the diagnostic criteria of HLH, 11 patients with SFTS were reviewed.MethodsDuring last 2 years (2015–2016), 11 SFTS patients were diagnosed at the Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine, Wonju, South Korea. Clinical features were analyzed using diagnostic criteria of 2004-HLH trial. We described if the prognosis of SFTSV-infected patients was associated with clinical features of HLH.ResultsOf 11 patients, four patients were fulfillled the diagnostic criteria of 2004-HLH trial (five of eight criteria). Two patients were fulfilled the four criteria. Five patients were fulfilled three or less criteria. Three of six patients who fulfilled four or more criteria were died. There was no mortality in five patients who fulfilled three or less criteria. Hemophagocytosis in bone marrow (BM) was observed in all six patients who were taken BM study.ConclusionIn SFTS, HLH was severe clinical feature and it might be associated with poor prognosis.Disclosures All authors: No reported disclosures.

Development and validation of a real-time reverse transcriptase PCR assay for sensitive detection of SFTSV.

Severe fever with thrombocytopenia syndrome bunyavirus (sftsv) is an emerging tick-borne rna virus recently identified as the pathogen that causes severe fever with thrombocytopenia syndrome (sfts) in china. the existing commercial nucleic acid testing (comnat) assay with a relatively high claimed limit of quantitative detection (loqd) is not capable of sensitive detection and quantitation of sftsv. Thus, a new real-time reverse transcriptase (rt)-pcr assay with improved sensitivity is needed for clinical diagnosis; it could also be used to screen blood donors if necessary. We developed a new sftsv rt-pcr nat assay (newnat). About 129 plasma samples from 93 suspected sfts patients with typical clinical symptoms were tested using an anti-sftsv total antibody elisa and both comnat and newnat. The test performance of the two nat assays was evaluated and compared. The newnat had a lower limit for quantitative testing compared to comnat. Twelve samples were comnat negative but newnat positive. Out of 35 suspected sfts patients who were comnat negative and anti-sftsv total antibody negative, four tested positive by the newnat assay and one of these four seroconverted within 2-4 days after testing newnat positive. A high correlation was observed between the cts of the newnat and comnat assays. The newnat assay was sensitive for quantitative detection of sftsv and may be applicable to clinical diagnosis and studies of the need for blood donor screening.

The analysis of clinical features and prognosis factors in patients with severe fever with thrombocytopenia syndrome

Objective To explore the influence of clinical indicators in patients with thrombocytopenia syndrome (SFTS) with severe fever on disease development and prognosis. Methods The SFTS patients who were admitted to the Department of Infection Diseases of Wuhan Union Hospital between April 1, 2015 and October 30, 2015 were included. Among 164 patients with SFTS, there were 136 cases recovered and 28 cases died. Clinical date including clinical manifestations and laboratory test index were collected and retrospectively analyzed. The correlation between the prognosis and clinical indicators were analyzed with the Spearman correlation analysis, the discriminatory power of clinical dates were tested with the area under the receiver-operating characteristic curve. Results The average age of died patients in the study was (64.5±9.1), which increased significantly(t=-3.609, P<0.01) compared with recovered patients with (56.9±10.2). Laboratory results suggest all patients had a drop in white blood cell and platelet count; almost all patients had a drop in serum calcium levels, and a rise in aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase (CK), activated partial thromboplastin time (APTT), D-dimmer levels. The nucleic acid quantification of SFTSV suggests death patients (5.83±0.98) lg TCID50/mL was significantly higher than the recovered patients (3.96±1.08) lg TCID50/mL, with statistical difference (t=-8.49, P<0.01). Conclusions Age, the nucleic acid quantification of SFTSV, CK and APTT are factors can be used to predict prognosis of SFTS. Key words: Severe fever with thrombocytopenia syndrome; Novel bunyavirus; Prognosis

Score risk model for predicting severe fever with thrombocytopenia syndrome mortality

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging epidemic infectious disease with high mortality in East Aisa, especially in China. To predict the prognosis of SFTS precisely is important in clinical practice.MethodsFrom May 2013 to November 2015, 233 suspected SFTS patients were tested for SFTS virus using RT-PCR. Cox regression model was utilized to comfirm independent risk factors for mortality. A risk score model for mortality was constructed based on regression coefficient of risk factors. Log-rank test was used to evaluate the significance of this model.ResultsOne hundred seventy-four patients were confirmed with SFTS, of which 40 patients died (23%). Baseline age, serum aspartate aminotransferase (AST) and serum creatinine (sCr) level were independent risk factors of mortality. The area under ROC curve (AUCs) of these parameters for predicting death were 0.771, 0.797 and 0.764, respectively. And hazard ratio (HR) were 1.128, 1.002 and 1.013, respectively. The cutoff value of the risk model was 10. AUC of the model for predicting mortality was 0.892, with sensitivity and specificity of 82.5 and 86.6%, respectively. Log-rank test indicated strong statistical significance (×2 = 88.35, p < 0.001).ConclusionsThis risk score model may be helpful to predicting the prognosis of SFTS patients.

The prospective evaluation of viral loads in patients with severe fever with thrombocytopenia syndrome

BackgroundSevere fever with thrombocytopenia syndrome (SFTS), caused by novel bunyavirus (SFTSV) is a potentially fatal disease that was first identified in China. Person to person transmission through contact with blood or body fluids was considered as an important infection route. ObjectivesThe study is designed to investigate the longitudinal viral loads following SFTSV infection and to identify factors affecting viral shedding in SFTS patients. MethodsA prospective, observational study was performed on 208 laboratory-confirmed SFTSV infected patients in Xinyang, Henan Province. Sequential serum samples were collected on admission and during the hospitalization for quantification of SFTSV RNA by real-time RT-PCR. ResultsThe viral RNA was undetectable in 55.6% of the patients on admission into the hospital, becoming detectable in most cases until three days and attained maximum level on six days after disease onset. This was followed by an obvious decrease thereafter, but maintained detectable for over 20 days. Viral load was independently predictable of severe disease outcome throughout the hospitalization. Viral load of >107copies/mL was predictable of fatal outcome. The serum levels of PLT, WBC, LDH, AST and CK were significantly associated with viral loads level. ConclusionsThe diagnosis of SFTSV infection based on PCR test should be performed at least three days after disease onset. Peaking viral loads were attained around six days after disease, posing a highest risk of human-to-human transmission.

Bone marrow findings in severe fever with thrombocytopenia syndrome: prominent haemophagocytosis and its implication in haemophagocytic lymphohistiocytosis

AimsSevere fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease caused by the SFTS virus; primary manifestations are fever, thrombocytopenia, leukopenia and gastrointestinal symptoms. Before an aetiological diagnosis is...

Simultaneous detection of IgG antibodies associated with viral hemorrhagic fever by a multiplexed luminex-based immunoassay (TECH1P.855)

Abstract Viral hemorrhagic fevers (VHFs) are worldwide diseases caused by several kinds of viruses. With the emergence of new viruses, advanced diagnostic methods are urgently needed for identification of VHFs. Based on Luminex xMAP technology, a rapid, sensitive, multi-pathogen and high-throughput method which could simultaneously detect hemorrhagic fever viruses (HFVs) specific IgG antibodies was developed. Recombinant antigens of nine HFVs were produced and purified from a prokaryotic expression system and the influence of the coupling amount was investigated. Cross-reactions among antigens and their rabbit immune sera were evaluated. Serum samples collected from 51 laboratory confirmed hemorrhagic fever with renal syndrome (HFRS) patients, 43 confirmed SFTS patients and 88 healthy donors were analyzed. Results showed that recombinant nucleocapsid protein of the five viruses belonging to the genus Hantavirus, had serological cross-reactivity with their corresponding rabbit immune sera, but not apparent with immune sera of other four viruses. Evaluation of this new method with clinical serum samples showed 98.04% diagnostic sensitivity for HFRS, 90.70% for SFTS detection and the specificity was ranging from 66.67% to 100.00%. The multiplexed luminex-based immunoassay has firstly been established in our study, which provides a potentially reliable diagnostic tool for IgG antibody detection of VHFs. Corresponding author: Prof. Dr. Dexin Li; Email: lidx@chinacdc.cn

Comprehensive Multiplex One-Step Real-Time TaqMan qRT-PCR Assays for Detection and Quantification of Hemorrhagic Fever Viruses

BackgroundViral hemorrhagic fevers (VHFs) are a group of animal and human illnesses that are mostly caused by several distinct families of viruses including bunyaviruses, flaviviruses, filoviruses and arenaviruses. Although specific signs and symptoms vary by the type of VHF, initial signs and symptoms are very similar. Therefore rapid immunologic and molecular tools for differential diagnosis of hemorrhagic fever viruses (HFVs) are important for effective case management and control of the spread of VHFs. Real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) assay is one of the reliable and desirable methods for specific detection and quantification of virus load. Multiplex PCR assay has the potential to produce considerable savings in time and resources in the laboratory detection.ResultsPrimers/probe sets were designed based on appropriate specific genes for each of 28 HFVs which nearly covered all the HFVs, and identified with good specificity and sensitivity using monoplex assays. Seven groups of multiplex one-step real-time qRT-PCR assays in a universal experimental system were then developed by combining all primers/probe sets into 4-plex reactions and evaluated with serial dilutions of synthesized viral RNAs. For all the multiplex assays, no cross-reactivity with other HFVs was observed, and the limits of detection were mainly between 45 and 150 copies/PCR. The reproducibility was satisfactory, since the coefficient of variation of Ct values were all less than 5% in each dilution of synthesized viral RNAs for both intra-assays and inter-assays. Evaluation of the method with available clinical serum samples collected from HFRS patients, SFTS patients and Dengue fever patients showed high sensitivity and specificity of the related multiplex assays on the clinical specimens.ConclusionsOverall, the comprehensive multiplex one-step real-time qRT-PCR assays were established in this study, and proved to be specific, sensitive, stable and easy to serve as a useful tool for rapid detection of HFVs.

Simultaneous detection of IgG antibodies associated with viral hemorrhagic fever by a multiplexed Luminex-based immunoassay

Viral hemorrhagic fevers (VHFs) are worldwide diseases caused by several kinds of viruses. With the emergence of new viruses, advanced diagnostic methods are urgently needed for identification of VHFs. Based on Luminex xMAP technology, a rapid, sensitive, multi-pathogen and high-throughput method which could simultaneously detect hemorrhagic fever viruses (HFVs) specific IgG antibodies was developed. Recombinant antigens of nine HFVs including Hantaan virus (HTNV), Seoul virus (SEOV), Puumala virus (PUUV), Andes virus (ANDV), Sin Nombre virus (SNV), Crimean-Congo hemorrhagic fever virus (CCHFV), Rift Valley fever virus (RVFV), Severe fever with thrombocytopenia syndrome bunyavirus (SFTSV) and dengue virus (DENV) were produced and purified from a prokaryotic expression system and the influence of the coupling amount was investigated. Cross-reactions among antigens and their rabbit immune sera were evaluated. Serum samples collected from 51 laboratory confirmed hemorrhagic fever with renal syndrome (HFRS) patients, 43 confirmed SFTS patients and 88 healthy donors were analyzed. Results showed that recombinant nucleocapsid protein of the five viruses belonging to the genus Hantavirus, had serological cross-reactivity with their corresponding rabbit immune sera, but not apparent with immune sera of other four viruses. Evaluation of this new method with clinical serum samples showed 98.04% diagnostic sensitivity for HFRS, 90.70% for SFTS detection and the specificity was ranging from 66.67% to 100.00%. The multiplexed Luminex-based immunoassay has firstly been established in our study, which provides a potentially reliable diagnostic tool for IgG antibody detection of VHFs.

Clinical progression and predictors of death in patients with severe fever with thrombocytopenia syndrome in China

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease of which the clinical progression and factors related to death are still unclear. ObjectiveTo identify the clinical progression of SFTS and explore predictors of fatal outcome throughout the disease progress. Study designA prospective study was performed in a general hospital located in Xinyang city during 2011–2013. Confirmed SFTS patients were recruited and laboratory parameters that were commonly evaluated in clinical practice were collected. The clinical progression was determined based on analysis of dynamic profiles and Friedman's test. At each clinical stage, the laboratory features that could be used to predict fatal outcome of SFTS patients were identified by stepwise discriminant analysis. ResultsTotally 257 survivors and 54 deceased SFTS patients were recruited and the data of 11 clinical and laboratory parameters along their entire disease course were consecutively collected. Three clinical stages (day 1–5 post onset, day 6–11 post onset and day 12 to hospital discharge) were determined based on distinct clinical parameters evaluations. Multivariate discriminant analysis at each clinical stage disclosed the indicators of the fatal outcome as decreased platelet counts at early stage, older age and increased AST level at middle stage, and decreased lymphocyte percentage and increased LDH level at late stage. ConclusionsThe significant indicators at three clinical stages could be used to assist identifying the patients with high risk of death. This knowledge might help to perform supportive treatment and avoid fatality.

Severe Fever with Thrombocytopenia Virus Glycoproteins Are Targeted by Neutralizing Antibodies and Can Use DC-SIGN as a Receptor for pH-Dependent Entry into Human and Animal Cell Lines

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel bunyavirus that recently emerged in China. Infection with SFTSV is associated with case-fatality rates of up to 30%, and neither antivirals nor vaccines are available at present. Development of antiviral strategies requires the elucidation of virus-host cell interactions. Here, we analyzed host cell entry of SFTSV. Employing lentiviral and rhabdoviral vectors, we found that the Gn/Gc glycoproteins (Gn/Gc) of SFTSV mediate entry into a broad range of human and animal cell lines, as well as human macrophages and dendritic cells. The Gn/Gc proteins of La Crosse virus (LACV) and Rift Valley Fever Virus (RVFV), other members of the bunyavirus family, facilitated entry into an overlapping but not identical range of cell lines, suggesting that SFTSV, LACV, and RVFV might differ in their receptor requirements. Entry driven by SFTSV Gn/Gc was dependent on low pH but did not require the activity of the pH-dependent endosomal/lysosomal cysteine proteases cathepsins B and L. Instead, the activity of a cellular serine protease was required for infection driven by SFTSV and LACV Gn/Gc. Sera from convalescent SFTS patients inhibited SFTSV Gn/Gc-driven host cell entry in a dose-dependent fashion, demonstrating that the vector system employed is suitable to detect neutralizing antibodies. Finally, the C-type lectin DC-SIGN was found to serve as a receptor for SFTSV Gn/Gc-driven entry into cell lines and dendritic cells. Our results provide initial insights into cell tropism, receptor usage, and proteolytic activation of SFTSV and will aid in the understanding of viral spread and pathogenesis.

Early diagnosis of novel SFTS bunyavirus infection by quantitative real-time RT-PCR assay

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease recently identified to be caused by a novel bunyavirus (SFTSV). The clinical diagnosis is urgently needed to differentiate the disease from other infections. ObjectiveTo develop a sensitive quantitative real-time RT-PCR assay for rapid detection of SFTSV viral RNA and evaluate potential use for clinical diagnosis of SFTS. Study designPrimers and probes were designed to target the L, M, and S segments of SFTSV, and standard curves were established based on serial dilutions of in vitro transcribed viral RNA or viral RNA extracts. The serum samples collected from 70 laboratory confirmed SFTS patients, 114 non-SFTS patients, and 400 healthy donors were analyzed. ResultsBased on three optimized primer–probe sets to detect L, M, S genes of SFTSV, the quantitative real-time RT-PCR assay could discriminate SFTSV infection from other vector-borne viral diseases in human with potential detection limit of 10 viral RNA copies/μl or 10 TCID50/ml virus load. Strong linear correlations (r2>0.99) between the Ct values and viral RNA standards over a liner range were obtained. The assay specificity was determined by sequence alignment and experimentally tested on various related viruses. Evaluation of the study method with clinical serum samples showed 98.6% clinical diagnostic sensitivity and over 99% specificity. ConclusionThe quantitative real-time RT-PCR assay established in this study can be used as a reliable method for early diagnosis of SFTSV infection.