Severe fever with thrombocytopenia syndrome virus: a highly lethal bunyavirus

Severe fever with thrombocytopenia syndrome virus induces lactylation of m6A reader protein YTHDF1 to facilitate viral replication

Severe fever with thrombocytopenia syndrome virus (SFTSV), an emerging infectious pathogen with a high fatality rate, is an enveloped tripartite segmented single-stranded negative-sense RNA virus. SFTSV infection is characterized by suppressed host innate immunity, proinflammatory cytokine storm, failure of B-cell immunity, and robust viral replication. m6A modification has been shown to play a role in viral infections. However, interactions between m6A modification and SFTSV infection remain poorly understood. Through MeRIP-seq, we identify m6A modifications on SFTSV RNA. We show that YTHDF1 can bind to m6A modification sites on SFTSV, decreasing the stability of SFTSV RNA and reducing the translation efficiency of SFTSV proteins. The SFTSV virulence factor NSs increases lactylation of YTHDF1 and YTHDF1 degradation, thus facilitating SFTSV replication. Our findings indicate that the SFTSV protein NSs induce lactylation to inhibit YTHDF1 as a countermeasure to host's YTHDF1-mediated degradation of m6A-marked viral mRNAs.

Identification of severe fever with thrombocytopenia syndrome virus isolates in the northwest of Hubei Province, China

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne viral disease that is increasingly affecting human being worldwide. The clinical manifestations and mortality rates of SFTS can vary depending on the geographic region and the specific genotype of the SFTS virus (SFTSV). From July 2022 to August 2023, we collected serum samples from 83 patients with suspected SFTSV infection in the northwest of Hubei Province, China. From which, 13 patients tested positive for SFTSV. Phylogenetic analysis of the SFTSV L, M, and S gene segments was performed using the maximum likelihood method to determine the genetic diversity of the isolates. At least 2 SFTSV genotypes (A and F) were identified in the northwest of Hubei Province. The clinical manifestations and laboratory findings on the first day of admission were investigated. Results showed that bleeding and disturbance of consciousness, and significant elevated AST and APTT, are valuable for assessing the prognosis for SFTS patients. This study disclosed the genomic sequences and genotypes of SFTSV spreading in the northwest of Hubei Province for the first time, providing information of genetically etiology for SFTS in the local district. Furthermore, certain symptoms and/or laboratory findings may indicate adverse clinical outcomes, highlighting the importance of identifying the symptoms and monitoring specific laboratory markers. Future research is needed to investigate the threshold values of these markers and to closely observe the indicative symptoms in order to early identify and timely management of critically ill patients within clinical settings.

MβCD inhibits SFTSV entry by disrupting lipid raft structure of the host cells

Severe fever with thrombocytopenia syndrome virus (SFTSV), recently named as Dabie bandavirus, belongs to the family Phenuiviridae of the order Bunyavirales, is a newly-identified bunyavirus with a case fatality rate of up to 30%, posing a serious threat to public health. Lipid rafts on plasm membranes are important for the entry of enveloped viruses; however, the role of lipid rafts in bunyavirus entry remains unclear. In this study, we found that methyl-beta-cyclodextrin (MβCD), a drug that disrupts cholesterol in lipid rafts of cell membranes, inhibits SFTSV infection. Additionally, there is a back-complementary effect of SFTSV infection upon the addition of cholesterol. Moreover, the concentration of SFTSV particles in lipid rafts during entry directly indicated the role of lipid rafts as a gateway, whereas MβCD could inhibit SFTSV entry by affecting the structure of lipid rafts. In an in vivo study, MβCD also reduced the susceptibility of mice to SFTSV infection. Our results suggest that SFTSV can interact with Talin1 proteins on lipid rafts to enter host cells by endocytosis of lipid rafts and reveal the potential therapeutic value of MβCD for SFTSV infection.

Understanding Viral Haemorrhagic Fevers: Virus Diversity, Vector Ecology, and Public Health Strategies

Viral haemorrhagic fevers encompass a diverse group of severe, often life-threatening illnesses caused by viruses from multiple families, including Arenaviridae, Filoviridae, Flaviviridae, Hantaviridae, Nairoviridae, Peribunyaviridae, and Phenuiviridae. Characterised by fever and haemorrhagic symptoms, these diseases challenge public health systems by overwhelming healthcare facilities, complicating diagnostic processes, and requiring extensive resources for containment and treatment, especially in resource-limited settings. This discussion explores the intricate relationships between VHFs and their transmission vectors-both animal and arthropod-and examines the impact of ecological and geographic factors on disease spread. The primary transmission of VHFs typically occurs through direct contact with infected animals or via bites from haematophagous arthropods, facilitating zoonotic and, at times, human-to-human transmission. With an emphasis on the role of diverse wildlife, domesticated animals, and vectors such as mosquitoes and ticks in the epidemiology of VHFs, there is a recognised need for robust surveillance and strategic public health responses to manage outbreaks. This review discusses the necessity of interdisciplinary approaches that integrate virology, ecology, and public health to enhance diagnostic capabilities, develop vaccines and antivirals, and improve outbreak interventions. Exploring the ecological and biological dynamics of VHFs will help bolster a deeper understanding of these emerging viruses and underpin preparation for future outbreaks. The importance of enhanced global cooperation, continuous research, and collaboration to mitigate the public health threats posed by these complex infections is a central theme, serving as a foundational strategy to reinforce worldwide preparedness and response efforts. Future directions include addressing gaps in vaccine development and tailoring public health strategies to the unique challenges of managing VHFs, such as the rapid mutation rates of viruses, the need for cold chain logistics for vaccine distribution, and socio-economic barriers to healthcare access, in order to ensure readiness for and effective response to emerging threats worldwide.

Comparative analysis of the color change in blue-green inclusions within neutrophils between two patients with different clinical outcomes

Blue-green neutrophilic inclusions (BGNI), also known as "death bodies," are bright green structures observed in the cytoplasm of neutrophils or monocytes and are closely associated with acute liver failure, lactic acidosis, and other serious diseases. Some studies suggested a potential association with phagocytic lipofuscin released by damaged liver cells. The presence of BGNI typically indicated a poor prognosis. We presented two cases. Case 1 was diagnosed with novel bunyavirus infection and exhibited severe hepatic impairment and coagulation dysfunction along with the presence of BGNI in neutrophils. Despite receiving comprehensive symptomatic treatment, the patient's condition rapidly deteriorated leading to eventual demise. Case 2 had severe liver injury caused by wasp stings, and BGNI was observed. Following active treatment measures, the patient eventually achieved recovery. Throughout the disease course of case 1, there was a progressive deepening in color and increase in quantity of BGNI. Conversely, case 2 demonstrated an opposite trend. Based on the comparison of clinical outcomes and variations in color and quantity of BGNI between these two patients, it was found that an increase in the number and deepening of BGNI color corresponded to worsening condition. Conversely, a decrease in quantity and lightening of color indicated improvement. Hence, these findings suggest a possible association between changes in BGNI characteristics and prognosis.

Ultra-rapid detection of nuclear protein of severe fever with thrombocytopenia syndrome virus by colloidal gold immunochromatography assay

In 2009, severe fever with thrombocytopenia syndrome virus (SFTSV), also known as the Dabie bandavirus (DBV), was first discovered in Henan, China. It is a tick-borne zoonotic virus with a fatality rate ranging from 6% to 30%. Currently, we lack safe and effective vaccines or antiviral drugs to treat SFTSV infection. Therefore, the development of a specific, sensitive, and cost-effective detection method is crucial. Using inactivated SFTSV and recombinant SFTSV nucleocapsid protein (SFTSV-NP), we repeatedly immunized mice with different adjuvants and obtained two monoclonal antibodies against SFTSV-NP, which were used to develop a colloidal gold immunochromatographic assay (ICA) rapid test kit for SFTSV. Compared with nucleic acid testing (gold standard), the ICA test strips are 97.67% accurate in testing clinical serum samples (36 cases of clinical serum samples and seven cases of whole blood samples). The test kit was 100% accurate in detecting different SFTSV strains. No false-positive results were generated when detecting other arboviruses. Therefore, our developed SFTSV test kit conveniently, rapidly, and effectively detects SFTSV.

Bunyavirus SFTSV NSs utilizes autophagy to escape the antiviral innate immune response

Severe fever with thrombocytopenia syndrome virus (SFTSV) nonstructural protein (NSs) is an important viral virulence factor that sequesters multiple antiviral proteins into inclusion bodies to escape the antiviral innate immune response. However, the mechanism of the NSs restricting host innate immunity remains largely elusive. Here, we found that the NSs induced complete macroautophagy/autophagy by interacting with the CCD domain of BECN1, thereby promoting the formation of a BECN1-dependent autophagy initiation complex. Importantly, our data showed that the NSs sequestered antiviral proteins such as TBK1 into autophagic vesicles, and therefore promoted the degradation of TBK1 and other antiviral proteins. In addition, the 8A mutant of NSs reduced the induction of BECN1-dependent autophagy flux and degradation of antiviral immune proteins. In conclusion, our results indicated that SFTSV NSs sequesters antiviral proteins into autophagic vesicles for degradation and to escape antiviral immune responses.

Severe fever with thrombocytopenia syndrome (SFTS) in Thailand: using a one health approach to respond to novel zoonosis and its implications in clinical practice

Severe fever with thrombocytopenia syndrome (SFTS), a tick-borne disease caused by Dabie bandavirus (SFTSV) is an emerging infectious disease of substantial concern in East Asia. In 2019, Ongkittikul S et al. reported the first case of SFTS in Thailand. Our report describes a One Health investigation of SFTS zoonosis examining the index case and suspected animal reservoirs using real-time RT-PCR and immunoassays. We add to the report on the first confirmed case of SFTSV infection in a human in Thailand by conducting a limited but informative One Health surveillance study. Dogs and cats tested positive for SFTSV antibody using IgG ELISA. We conclude that domestic dogs and cats might serve as potential reservoirs for SFTSV spread due to their closer proximity to the index case than other non-domestic animals. Notably, we did not detect SFTSV in synanthropic cats or dogs-nor did we detect SFTSV in Rhipicephalus sanguineus ticks-using RT-PCR. We propose that One Health investigations coupling genomic and serologic assays in response to new SFTS cases could play a pivotal role in preventing and managing SFTS among humans and animals in East Asia. As such, we are establishing a collaborative response to SFTS in Thailand through human outbreak investigations that align with principles of One Health, through environmental surveys and animal RT-PCR and immunoassays. Our investigation highlights the importance of coupling RT-PCR with seroprevalence assays as principal elements of One Health surveillance for SFTS in order to shed light on potential animal reservoirs and track emerging zoonosis.

Viruses Identified in Shrews (Soricidae) and Their Biomedical Significance

Shrews (Soricidae) are common small wild mammals. Some species of shrews, such as Asian house shrews (Suncus murinus), have a significant overlap in their habitats with humans and domestic animals. Currently, over 190 species of viruses in 32 families, including Adenoviridae, Arenaviridae, Arteriviridae, Astroviridae, Anelloviridae, Bornaviridae, Caliciviridae, Chuviridae, Coronaviridae, Filoviridae, Flaviviridae, Hantaviridae, Hepadnaviridae, Hepeviridae, Nairoviridae, Nodaviridae, Orthoherpesviridae, Orthomyxoviridae, Paramyxoviridae, Parvoviridae, Phenuiviridae, Picobirnaviridae, Picornaviridae, Polyomaviridae, Poxviridae, Rhabdoviridae, Sedoreoviridae, Spinareoviridae, and three unclassified families, have been identified in shrews. Diverse shrew viruses, such as Borna disease virus 1, Langya virus, and severe fever with thrombocytopenia syndrome virus, cause diseases in humans and/or domestic animals, posing significant threats to public health and animal health. This review compiled fundamental information about shrews and provided a comprehensive summary of the viruses that have been detected in shrews, with the aim of facilitating a deep understanding of shrews and the diversity, epidemiology, and risks of their viruses.

Spatial and Temporal Analysis of Severe Fever with Thrombocytopenia Syndrome in Anhui Province from 2011 to 2023

OBJECTIVE

To analyze the spatial autocorrelation and spatiotemporal clustering characteristics of severe fever with thrombocytopenia syndrome(SFTS) in Anhui Province from 2011 to 2023.

METHODS

Data of SFTS in Anhui Province from 2011 to 2023 were collected. Spatial autocorrelation analysis was conducted using GeoDa software, while spatiotemporal scanning was performed using SaTScan 10.0.1 software to identify significant spatiotemporal clusters of SFTS.

RESULTS

From 2011 to 2023, 5720 SFTS cases were reported in Anhui Province, with an average annual incidence rate of 0.7131/100,000. The incidence of SFTS in Anhui Province reached its peak mainly from April to May, with a small peak in October. The spatial autocorrelation results showed that from 2011 to 2023, there was a spatial positive correlation(P < 0.05) in the incidence of SFTS in all counties and districts of Anhui Province. Local autocorrelation high-high clustering areas are mainly located in the south of the Huaihe River. The spatiotemporal scanning results show three main clusters of SFTS in recent years: the first cluster located in the lower reaches of the Yangtze River, the eastern region of Anhui Province; the second cluster primarily focused on the region of the Dabie Mountain range, while the third cluster primarily focused on the region of the Huang Mountain range.

CONCLUSIONS

The incidence of SFTS in Anhui Province in 2011-2023 was spatially clustered.

Molecular mechanism and structure-guided humanization of a broadly neutralizing antibody against SFTSV

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel tick-borne bunyavirus that causes severe fever with thrombocytopenia syndrome (SFTS), with a high mortality rate of up to 30%. The envelope glycoproteins of SFTSV, glycoprotein N (Gn) and glycoprotein C (Gc), facilitate the recognition of host receptors and the process of membrane fusion, allowing the virus to enter host cells. We previously reported a monoclonal antibody, mAb 40C10, capable of neutralizing different genotypes of SFTSV and SFTSV-related viruses. However, the specific neutralization mechanism is poorly understood. In this study, we elucidated the high-resolution structure of the SFTSV Gn head domain in complex with mAb 40C10, confirming that the binding epitope in the domain I region of SFTSV Gn, and it represented that a novel binding epitope of SFTSV Gn was identified. Through in-depth structural and sequence analyses, we found that the binding sites of mAb 40C10 are relatively conserved among different genotypes of SFTSV and SFTSV-related Heartland virus and Guertu virus, elucidating the molecular mechanism underlying the broad-spectrum neutralizing activity of mAb 40C10. Furthermore, we humanized of mAb 40C10, which is originally of murine origin, to reduce its immunogenicity. The resulting nine humanized antibodies maintained potent affinity and neutralizing activity. One of the humanized antibodies exhibited neutralizing activity at picomolar IC50 values and demonstrated effective therapeutic and protective effects in a mouse infection model. These findings provide a novel target for the future development of SFTSV vaccines or drugs and establish a foundation for the research and development of antibody therapeutics for clinical applications.

Knowledge mapping of severe fever with thrombocytopenia syndrome: a bibliometric analysis

Background

Severe fever with thrombocytopenia syndrome (SFTS), caused by the Dabie bandavirus (DBV), formerly known as the SFTS virus (SFTSV), is characterized by rapid progression, high morbidity, and mortality. This study aims to analyze the current research status, hotspots, and trends of SFTS since 2009 through bibliometrics, focusing on original research and providing valuable references and inspirations for future basic research, prevention and control of SFTS.

Methods

The Web of Science Core Collection (WOSCC) was used to extract global papers on SFTS from 2009 to 2024. VOSviewer and CiteSpace software were also used to process and visualize results.

Results

A total of 760 publications relevant to SFTS were reviewed. Among these publications, the most active country, author, and publication type included China, Liu Wei, and original articles, respectively. Among the institutions, the National Institute of Infectious Diseases emerged as the top publisher. The most frequently used keywords were "China," "Bunyavirus," and "person-to-person transmission." The bibliometric analysis reviewed and summarized the research results in the field of SFTS and demonstrated the research trends in the field. In addition, the study revealed the current research hotspots and predicted the future research frontiers and potential challenges in the field of SFTS, which will provide references for further exploring and investigating the SFTS-related mechanisms and inspire new therapeutic strategies.

Conclusion

Bibliometric visualization provides an overview of research advances, hotspots, and trends regarding SFTS and consolidates existing knowledge. SFTS research is in a phase of rapid development, and the number of annual publications in the field is growing steadily and rapidly. This is laying the groundwork for further research and providing new ideas for clinicians engaged in SFTS-related therapies and researchers working to improve public health. Currently, researchers are focused on elucidating the biology of SFTS, exploring antibodies, delving into pathogenesis, and investigating specific therapies.

A full-length glycoprotein mRNA vaccine confers complete protection against severe fever with thrombocytopenia syndrome virus, with broad-spectrum protective effects against bandaviruses

Highly pathogenic viruses from family Phenuiviridae, which are mainly transmitted by arthropods, have intermittently sparked epidemics worldwide. In particular, tick-borne bandaviruses, such as severe fever with thrombocytopenia syndrome virus (SFTSV), continue to spread in mountainous areas, resulting in an average mortality rate as high as 10.5%, highlighting the urgency and importance of vaccine development. Here, an mRNA vaccine developed based on the full-length SFTSV glycoprotein, containing both the receptor-binding domain and the fusion domain, was shown to confer complete protection against SFTSV at a very low dose by triggering a type 1 helper T cell-biased cellular immune response in rodents. Moreover, the vaccine candidate elicited long-term immunity and protection against SFTSV for at least 5 months. Notably, it provided complete cross-protection against other bandaviruses, such as the Heartland virus and Guertu virus, in lethal challenge models. Further research revealed that the conserved epitopes among bandaviruses within the full-length SFTSV glycoprotein may facilitate broad-spectrum protection mediated by the cellular immune response. Collectively, these findings demonstrate that the full-length SFTSV glycoprotein mRNA vaccine is a promising vaccine candidate for SFTSV and other bandaviruses, and provide guidance for the development of broad-spectrum vaccines from conserved antigens and epitopes.

IMPORTANCE

Tick-borne bandaviruses, such as SFTSV and Heartland virus, sporadically trigger outbreaks in addition to influenza viruses and coronaviruses, yet there are no specific vaccines or therapeutics against them. mRNA vaccine technology has advantages in terms of enabling in situ expression and triggering cellular immunity, thus offering new solutions for vaccine development against intractable viruses, such as bandaviruses. In this study, we developed a novel vaccine candidate for SFTSV by employing mRNA vaccination technology and using a full-length glycoprotein as an antigen target. This candidate vaccine confers complete and durable protection against SFTSV at a notably low dose while also providing cross-protection against Heartland virus and Guertu virus. This study highlights the prospective value of full-length SFTSV-glycoprotein-based mRNA vaccines and suggests a potential strategy for broad-spectrum bandavirus 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.

6-Thioguanine inhibits severe fever with thrombocytopenia syndrome virus through suppression of EGR1

The severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel phlebovirus, recently being officially renamed as Dabie bandavirus, and a causative agent for an emerging infectious disease associated with high fatality. Effective therapeutics and vaccines are lacking and disease pathogenesis is yet to be fully elucidated. In our effort to identify new SFTSV inhibitory molecules, 6-Thioguanine (6-TG) was found to potently inhibit SFTSV infection. 6-TG has been widely used as therapeutic agent since the approval of the Food and Drug Administration in the 1960s. In the current study, we showed that 6-TG was a potent inhibitor of SFTSV infection with 50% effective concentrations (EC50) of 3.465 μM in VeroE6 cells, and 1.848 μM in HUVEC cells. The selectivity index (SI) was >57 in VeroE6 cells and >108 in HUVEC cells, respectively. The SFTSV RNA transcription, protein synthesis, and progeny virions were reduced in a dose dependent manner by the presence of 6-TG in the in vitro infection assay. Further study on the mechanism of the anti-SFTSV activity showed that 6-TG downregulated the production of early growth response gene-1 (EGR1). Using gene silencing and overexpression, we further confirmed that EGR1 was a host restriction factor against SFTSV. Meanwhile, treatment of infected experimental animals with 6-TG inhibited SFTSV infection and alleviated multi-organ dysfunction. In conclusion, we have identified 6-TG as an effective inhibitor of SFTSV replication via the inhibition of EGR1 expression. Further studies are needed to evaluate of 6-TG as a potential therapeutic for treating SFTS.

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.

Increased cTnI Predicts Early Death in Patients with Severe Fever with Thrombocytopenia: A Multicenter Study in North China

Background

Myocardial injury is common in severe fever with thrombocytopenia syndrome (SFTS) patients. Currently, research on the prognostic value of cardiac troponin I (cTnI) for predicting the mortality of SFTS patients, especially death within 7 days is limited.

Methods

Between May 2011 and October 2022, clinical and laboratory data on admission of consecutive SFTS cases were collected from six medical centres in China. The clinical endpoint was in-hospital all-cause death within seven days. Risk factors of myocardial injury and death were analysed using multivariable regression models. Prognostic models were established using Cox regression and performance of indicators was evaluated in terms of calibration, discrimination.

Results

A total of 1379 laboratory-confirmed patients were enrolled, in which 686 subjects were included for analysis. The median age was 66 years, with 48.1% of male. Eighty-seven patients died within seven days and 396 patients diagnosed with myocardial injury during hospitalization. Non-survivors had significant higher levels of cardiac indices than survivors, including cTnI, aspartic transaminase (AST) and lactate dehydrogenase (LDH). Elevated levels of cTnI (HR = 1.058, 95% CI:1.032-1.085), AST (HR = 1.191, 95% CI:1.150-1.234) and LDH (HR = 1.019, 95% CI:1.009-1.029) predicted risk of early in-hospital mortality. cTnI model performed best, with area under curve of 0.850 (0.774-0.926) and concordance index of 0.842, respectively. Statistical differences were found between high and low levels of cTnI for mortality (P<0.001) using 0.35 ng/mL as the optimal cut-off.

Conclusion

The risk of early in-hospital death can be predicted by cTnI. Clinical doctors should remind vigilant concerning the elevation of cardiac enzyme as soon as possible.

Comprehensive meta-analysis of severe fever with thrombocytopenia syndrome virus infections in humans, vertebrate hosts and questing ticks

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonosis caused by the SFTS virus (SFTSV). Understanding the prevalence of SFTSV RNA in humans, vertebrate hosts and ticks is crucial for SFTS control.

METHODS

A systematic review and meta-analysis were conducted to determine the prevalence of SFTSV RNA in humans, vertebrate hosts and questing ticks. Nine electronic databases were searched for relevant publications, and data on SFTSV RNA prevalence were extracted. Pooled prevalence was estimated using a random effects model. Subgroup analysis and multivariable meta-regression were performed to investigate sources of heterogeneity.

RESULTS

The pooled prevalence of SFTSV RNA in humans was 5.59% (95% confidence interval [CI] 2.78-9.15%) in those in close contact (close contacts) with infected individuals (infected cases) and 0.05% (95% CI 0.00-0.65%) in healthy individuals in endemic areas. The SFTSV infection rates in artiodactyls (5.60%; 95% CI 2.95-8.96%) and carnivores (6.34%; 95% CI 3.27-10.23%) were higher than those in rodents (0.45%; 95% CI 0.00-1.50%). Other animals, such as rabbits, hedgehogs and birds, also played significant roles in SFTSV transmission. The genus Haemaphysalis was the primary transmission vector, with members of Ixodes, Dermacentor, and Amblyomma also identified as potential vectors. The highest pooled prevalence was observed in adult ticks (1.03%; 95% CI 0.35-1.96%), followed by nymphs (0.66%; 95% CI 0.11-1.50%) and larvae (0.01%; 95% CI 0.00-0.46%). The pooled prevalence in ticks collected from endemic areas (1.86%; 95% CI 0.86-3.14%) was higher than that in ticks collected in other regions (0.41%; 95% CI 0.12-0.81%).

CONCLUSIONS

Latent SFTSV infections are present in healthy individuals residing in endemic areas, and close contacts with SFTS cases are at a significantly higher risk of infection. The type of animal is linked to infection rates in vertebrate hosts, while infection rates in ticks are associated with the developmental stage. Further research is needed to investigate the impact of various environmental factors on SFTSV prevalence in vertebrate hosts and ticks.

SFTSV nucleoprotein mediates DNA sensor cGAS degradation to suppress cGAS-dependent antiviral responses

Cyclic GMP-AMP synthase (cGAS) is an important DNA pattern recognition receptor that senses double-stranded DNA derived from invading pathogens or self DNA in cytoplasm, leading to an antiviral interferon response. A tick-borne Bunyavirus, severe fever with thrombocytopenia syndrome virus (SFTSV), is an RNA virus that causes a severe emerging viral hemorrhagic fever in Asia with a high case fatality rate of up to 30%. However, it is unclear whether cGAS interacts with SFTSV infection. In this study, we found that SFTSV infection upregulated cGAS RNA transcription and protein expression, indicating that cGAS is an important innate immune response against SFTSV infection. The mechanism of cGAS recognizing SFTSV is by cGAS interacting with misplaced mitochondrial DNA in the cytoplasm. Depletion of mitochondrial DNA significantly inhibited cGAS activation under SFTSV infection. Strikingly, we found that SFTSV nucleoprotein (N) induced cGAS degradation in a dose-dependent manner. Mechanically, N interacted with the 161-382 domain of cGAS and linked the cGAS to LC3. The cGAS-N-LC3 trimer was targeted to N-induced autophagy, and the cGAS was degraded in autolysosome. Taken together, our study discovered a novel antagonistic mechanism of RNA viruses, SFTSV is able to suppress the cGAS-dependent antiviral innate immune responses through N-hijacking cGAS into N-induced autophagy. Our results indicated that SFTSV N is an important virulence factor of SFTSV in mediating host antiviral immune responses.

IMPORTANCE

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne RNA virus that is widespread in East and Southeast Asian countries with a high fatality rate of up to 30%. Up to now, many cytoplasmic pattern recognition receptors, such as RIG-I, MDA5, and SAFA, have been reported to recognize SFTSV genomic RNA and trigger interferon-dependent antiviral responses. However, current knowledge is not clear whether SFTSV can be recognized by DNA sensor cyclic GMP-AMP synthase (cGAS). Our study demonstrated that cGAS could recognize SFTSV infection via ectopic mitochondrial DNA, and the activated cGAS-stimulator of interferon genes signaling pathway could significantly inhibit SFTSV replication. Importantly, we further uncovered a novel mechanism of SFTSV to inhibit innate immune responses by the degradation of cGAS. cGAS was degraded in N-induced autophagy. Collectively, this study illustrated a novel virulence factor of SFTSV to suppress innate immune responses through autophagy-dependent cGAS degradation.

Long-term effects of meteorological factors on severe fever with thrombocytopenia syndrome incidence in eastern China from 2014 to 2020: An ecological time-series study

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease with susceptibility influenced by meteorological factors. However, there is limited understanding of the delayed and interactive impacts of meteorological factors on SFTS incidence.

METHODS

Daily incidence data of SFTS and corresponding meteorological factors for the Jiaodong Peninsula in northeast China were collected from January 1, 2014, to December 31, 2020. Random forest regression model, based on custom search, was performed to compare the importance of meteorological factors. Generalized additive model with quasi-Poisson regression was conducted to examine the nonlinear relationships and interactive effects using penalized spline methods. A distributed lag nonlinear model with quasi-Poisson regression was constructed to estimate exposure-lag effects of meteorological factors.

RESULTS

The most important meteorological factor was weekly mean lowest temperature. The relationship between meteorological factors and SFTS incidence revealed a nonlinear and intricate pattern. Interaction analyses showed that prolonged sunshine duration posed a climatic risk within a specific temperature range for SFTS incidence. The maximum relative risk (RR) observed under extremely low temperature (-4°C) was 1.33 at lag of 15 week, while under extremely high temperature (25°C), the minimum RR was 0.65 at lag of 13 week. The RRs associated with both extremely high and low sunshine duration escalated with an increase in lag weeks.

CONCLUSIONS

This study underscores that meteorological factors exert nonlinear, delayed, and interactive effects on SFTS incidence. These findings highlight the importance of understanding the dependency of SFTS incidence on meteorological factors in particular climates.

Therapeutic plasma exchange combined with ribavirin to rescue critical SFTS patients

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is a zoonotic infectious disease caused by the severe fever with thrombocytopenia syndrome virus (SFTSV). Endemic in East Asia, SFTS is characterized by an exceptionally high mortality rate. Presently, there is no established treatment for SFTS, particularly for patients in critical condition. In this study, we collected and analyzed laboratory and clinical data from 92 critically ill patients with SFTS treated at Weihai Municipal Hospital between 2019 and 2022. We hope that our study will provide some hints for the treatment of critically ill patients with SFTS.

METHODS

A total of 92 critically ill patients with SFTS were included in this study. Of these patients, 45 received treatment with therapeutic plasma exchange (TPE) and ribavirin (referred to as the TPE group), while the remaining patients received only ribavirin (referred to as the non-TPE group). Clinical and laboratory parameters were analyzed retrospectively.

RESULTS

The results showed significant improvements in multiple laboratory parameters following treatment with TPE and ribavirin, including white blood cell and neutrophil count, lactate dehydrogenase, creatine kinase isoenzyme-MB, prothrombin time, activated partial thromboplastin time, D-Dimer, serum sodium and copies of virus genomes. The combination of TPE with ribavirin demonstrated a significant reduction in mortality rates, with a mortality rate of 20.0% in the TPE group compared to 40.4% in the non-TPE group (P = 0.033).

CONCLUSIONS

Our findings suggest that critically ill patients with SFTS who received TPE and ribavirin experienced improvements in both clinical and laboratory parameters. These results indicate that TPE combined with ribavirin may represent a promising novel therapeutic approach for managing critically ill patients with SFTS. However, comparative studies of large sample size or randomized clinical trials are warranted to confirm the effectiveness of this combination therapy in the treatment of severe SFTS cases.

Severe fever with thrombocytopenia syndrome with central nervous system symptom onset: a case report and literature review

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is a natural focal disease transmitted mainly by tick bites, and the causative agent is SFTS virus (SFTSV). SFTS can rapidly progress to severe disease, with multiple-organ failure (MOF) manifestations such as shock, respiratory failure, disseminated intravascular coagulation (DIC) and death, but cases of SFTS patients with central nervous system (CNS) symptoms onset and marked persistent involuntary shaking of the perioral area and limbs have rarely been reported.

CASE PRESENTATION

A 69-year-old woman with fever and persistent involuntary shaking of the perioral area and limbs was diagnosed with SFTS with CNS symptom onset after metagenomic next-generation sequencing (mNGS) of cerebrospinal fluid (CSF) and peripheral blood identified SFTSV. The patient developed a cytokine storm and MOF during the course of the disease, and after aggressive antiviral, glucocorticoid, and gamma globulin treatments, her clinical symptoms improved, her laboratory indices returned to normal, and she had a good prognosis.

CONCLUSION

This case gives us great insight that when patients with CNS symptoms similar to those of viral encephalitis combined with thrombocytopenia and leukopenia are encountered in the clinic, it is necessary to consider the possibility of SFTS involving the CNS. Testing for SFTSV nucleic acid in CSF and blood (mNGS or polymerase chain reaction (PCR)) should be carried out, especially in critically ill patients, and treatment should be given accordingly.

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.

Construction of an early differentiation diagnosis model for patients with severe fever with thrombocytopenia syndrome and hemorrhagic fever with renal syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with a high mortality rate. Differentiating between SFTS and hemorrhagic fever with renal syndrome (HFRS) is difficult and inefficient. Retrospective analysis of the medical records of individuals with SFTS and HFRS was performed. Clinical and laboratory data were compared, and a diagnostic model was developed based on multivariate logistic regression analyzes. Receiver operating characteristic curve analysis was used to evaluate the diagnostic model. Among the 189 patients, 113 with SFTS and 76 with HFRS were enrolled. Univariate analysis revealed that more than 20 variables were significantly associated with SFTS. Multivariate logistic regression analysis revealed that gender, especially female gender (odds ratio [OR]: 4.299; 95% confidence interval [CI]: 1.163-15.887; p = 0.029), age ≥65 years (OR: 16.386; 95% CI: 3.043-88.245; p = 0.001), neurological symptoms (OR: 12.312; 95% CI: 1.638-92.530; p = 0.015), leukopenia (<4.0 × 109/L) (OR: 17.355; 95% CI: 3.920-76.839; p < 0.001), and normal Cr (OR: 97.678; 95% CI: 15.483-616.226; p < 0.001) were significantly associated with SFTS but not with HFRS. The area under the curve of the differential diagnostic model was 0.960 (95% CI: 0.936-0.984), which was significantly better than that of each single factor. In addition, the model exhibited very excellent sensitivity and specificity (92.9% and 85.5%, respectively). In cases where HFRS and SFTS are endemic, a diagnostic model based on five parameters, such as gender, age ≥65 years, neurological symptoms, leukopenia and normal Cr, will facilitate the differential diagnosis of SFTS and HFRS in medical institutions, especially in primary care settings.

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.

Viromes of Haemaphysalis longicornis reveal different viral abundance and diversity in free and engorged ticks

Haemaphysalis longicornis ticks, commonly found in East Asia, can transmit various pathogenic viruses, including the severe fever with thrombocytopenia syndrome virus (SFTSV) that has caused febrile diseases among humans in Hubei Province. However, understanding of the viromes of H. longicornis was limited, and the prevalence of viruses among H. longicornis ticks in Hubei was not well clarified. This study investigates the viromes of both engorged (fed) and free (unfed) H. longicornis ticks across three mountainous regions in Hubei Province from 2019 to 2020. RNA-sequencing analysis identified viral sequences that were related to 39 reference viruses belonging to unclassified viruses and seven RNA viral families, namely Chuviridae, Nairoviridae, Orthomyxoviridae, Parvoviridae, Phenuiviridae, Rhabdoviridae, and Totiviridae. Viral abundance and diversity in these ticks were analysed, and phylogenetic characteristics of the Henan tick virus (HNTV), Dabieshan tick virus (DBSTV), Okutama tick virus (OKTV), and Jingmen tick virus (JMTV) were elucidated based on their full genomic sequences. Prevalence analysis demonstrated that DBSTV was the most common virus found in individual H. longicornis ticks (12.59%), followed by HNTV (0.35%), whereas JMTV and OKTV were not detected. These results improve our understanding of H. longicornis tick viromes in central China and highlight the role of tick feeding status and geography in shaping the viral community. The findings of new viral strains and their potential impact on public health raise the need to strengthen surveillance efforts for comprehensively assessing their spillover potentials.

Severe fever with thrombocytopenia syndrome virus infection shapes gut microbiome of the tick vector Haemaphysalis longicornis

BACKGROUND

Ticks serve as vectors for a diverse array of pathogens, including viruses responsible for both human and livestock diseases. Symbiotic bacteria hold significant potential for controlling tick-borne disease. However, the alteration of tick gut bacterial community in response to pathogen infection has not been analyzed for any tick-borne viruses. Here, the impact of severe fever with thrombocytopenia syndrome virus (SFTSV) infection on bacterial diversity in the gut of Haemaphysalis longicornis is investigated.

METHODS

Unfed tick females were artificially infected with SFTSV. The gut samples were collected and the genomic DNA was extracted. We then investigated alterations in gut bacterial composition in response to SFTSV infection through 16S rRNA gene sequencing.

RESULTS

The study found that a reduction in the number of operational taxonomic units (OTUs) in the tick gut following SFTSV infection. However, there were no significant changes in alpha diversity indices upon infection. Four genera, including Corynebacterium, Arthrobacter, Sphingomonas, and Escherichia, were identified as biomarkers for the tick gut without SFTSV infection. Notably, the predicted correlation network indicated that the biomarkers Sphingomonas and Escherichia exhibited positive correlations within the same subcommunity, which was altered upon viral infection.

CONCLUSIONS

These findings revealed that the change in tick gut bacterial composition upon SFTSV infection and could facilitate the discovery new target for tick-borne viral disease control.

Pathological and virological findings of type I interferon receptor knockout mice upon experimental infection with Heartland virus

Heartland virus (HRTV) causes generalized symptoms, severe shock, and multiple organ failure. We previously reported that interferon-α/β receptor knockout (IFNAR-/-) mice infected intraperitoneally with 1 × 107 tissue culture-infective dose (TCID50) of HRTV died, while those subcutaneously infected with the same dose of HRTV did not. The pathophysiology of IFNAR-/- mice infected with HRTV and the mechanism underlying the difference in disease severity, which depends on HRTV infection route, were analyzed in this study. The liver, spleen, mesenteric and axillary lymph nodes, and gastrointestinal tract of intraperitoneally (I.P.) infected mice had pathological changes; however, subcutaneously (S.C.) infected mice only had pathological changes in the axillary lymph node and gastrointestinal tract. HRTV RNA levels in the mesenteric lymph node, lung, liver, spleen, kidney, stomach, intestine, and blood were significantly higher in I.P. infected mice than those in S.C. infected mice. Chemokine ligand-1 (CXCL-1), tumor necrosis factor (TNF)-α, interleukin (IL)-12, interferon (IFN)-γ, and IL-10 levels in plasma of I.P. infected mice were higher than those of S.C. infected mice. These results indicated that high levels of viral RNA and the induction of inflammatory responses in HRTV-infected IFNAR-/- mice may be associated with disease severity.

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).

A nanoluciferase SFTSV for rapid screening antivirals and real-time visualization of virus infection in mice

BACKGROUND

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne pathogen that causes severe hemorrhagic fever in humans, but no FDA-approved specific antivirals or vaccines are available to treat or prevent SFTS.

METHODS

The plasmids construction and transfection were performed to generate the recombinant SFTSV harboring the nanoluciferase gene (SFTSV-Nluc). Immunostaining plaque assay was performed to measure viral titers, and DNA electrophoresis and Sanger sequencing were performed to evaluate the genetic stability. Luciferase assay and quantitative RT-PCR were performed to evaluate the efficacy of antivirals in vitro. Bioluminescence imaging, titration of virus from excised organs, hematology, and histopathology and immunohistochemistry were performed to evaluate the efficacy of antivirals in vivo.

FINDINGS

SFTSV-Nluc exhibited high genetic stability and replication kinetics similar to those of wild-type virus (SFTSVwt), then a rapid high-throughput screening system for identifying inhibitors to treat SFTS was developed, and a nucleoside analog, 4-FlU, was identified to effectively inhibit SFTSV in vitro. SFTSV-Nluc mimicked the replication characteristics and localization of SFTSVwt in counterpart model mice. Bioluminescence imaging of SFTSV-Nluc allowed real-time visualization and quantification of SFTSV replication in the mice. 4-FlU was demonstrated to inhibit the replication of SFTSV with more efficiency than T-705 and without obvious adverse effect in vivo.

INTERPRETATION

The high-throughput screening system based on SFTSV-Nluc for use in vitro and in vivo revealed that a safe and effective antiviral nucleoside analog, 4-FlU, may be a basis for the strategic treatment of SFTSV and other bunyavirus infections, paving the way for the discovery of antivirals.

FUNDING

This work was supported by grants from the National Key Research and Development Plan of China (2021YFC2300700 to L. Zhang, 2022YFC2303300 to L. Zhang), Strategic Priority Research Program of Chinese Academy of Sciences (XDB0490000 to L. Zhang), National Natural Science Foundation of China (31970165 to L. Zhang, U22A20379 to G. Xiao), the Science and Technology Commission of Shanghai Municipality (21S11903100 to Y. Xie), Hubei Natural Science Foundation for Distinguished Young Scholars (2022CFA099 to L. Zhang).

Regulation of the WNT-CTNNB1 signaling pathway by severe fever with thrombocytopenia syndrome virus in a cap-snatching manner

IMPORTANCE

One of the conserved mechanisms at the stage of genome transcription of segmented negative-strand RNA viruses (sNSVs) is the cap-snatching process, which is vital for sNSVs transcription and provides drugable targets for the development of antivirals. However, the specificity of RNAs snatched by sNSV is still unclear. By transcriptomics analysis of whole blood samples from SFTS patients, we found WNT-CTNNB1 signaling pathway was regulated according to the course of the disease. We then demonstrated that L protein of severe fever with thrombocytopenia syndrome virus (SFTSV) could interact with mRNAs of WNT-CTNNB1 signaling pathway-related gene, thus affecting WNT-CTNNB1 signaling pathway through its cap-snatching activity. Activation of WNT-CTNNB1 signaling pathway enhanced SFTSV replication, while inhibition of this pathway decreased SFTSV replication in vitro and in vivo. These findings suggest that WNT-associated genes may be the substrate for SFTSV "cap-snatching", and indicate a conserved sNSVs replication mechanism involving WNT-CTNNB1 signaling.

Clinical characteristics of perioperative central fever and its relationship with anesthesia

To analyze clinical characteristics and anesthesia-related factors influencing central fever during cranial neurosurgery. 31 central fever cases (observation) and 120 controls (no fever) underwent detailed investigation. Anaesthesia-related variables were analyzed using logistic regression. Observation group exhibited significantly elevated indicators-CSF white blood cells, protein, CRP, severe EEG abnormalities, abnormal imaging, positive meningeal signs, seizures, consciousness disorders, and status epilepticus (P < .05). Anesthesia plans showed no influence (P > .05). pH, PaCO2, PaO2, SaO2, MAP, ICP, CPP, and SjiO2 didn't impact central fever (P > .05). However, high HR, low Da-jvO2, and low CEO2 were independent risk factors (P < .05). Central fever, marked by CNS abnormalities, manifests with distinctive clinical features. Anesthesia plans have limited impact, while elevated HR, low Da-jvO2, and low CEO2 independently contribute to central fever. Understanding these factors is crucial for perioperative care optimization.

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.

Novel nomograms to predict risk and prognosis in hospitalized patients with severe fever with thrombocytopenia syndrome

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging and life-threatening infectious disease caused by SFTS virus. Although recent studies have reported the use of nomograms based on demographic and laboratory data to predict the prognosis of SFTS, no study has included viral load, which is an important factor that influences the prognosis, when compared with other risk factors. Therefore, this study aimed to develop a model that predicts SFTS prognosis before it reaches the critical illness stage and to compare the predictive ability of groups with and without viral load.

Methods

Two hundred patients with SFTS were enrolled between June 2018 and August 2023. Data were sourced from the first laboratory results at admission, and two nomograms for mortality risk were developed using multivariate logistic regression to identify the risk variables for poor prognosis in these patients. We calculated the area under the receiver operating characteristic curve (AUC) for the two nomograms to assess their discrimination, and predictive abilities were compared using net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

Results

The multivariate logistic regression analysis identified four independent risk factors: age, bleeding manifestations, prolonged activated partial thromboplastin time, and viral load. Based on these factors, a final nomogram predicting mortality risk in patients with SFTS was constructed; in addition, a simplified nomogram was constructed excluding the viral load. The AUC [0.926, 95% confidence interval (CI): 0.882-0.970 vs. 0.882, 95% CI: 35 0.823-0.942], NRI (0.143, 95% CI, 0.036-0.285), and IDI (0.124, 95% CI, 0.061-0.186) were calculated and compared between the two models. The calibration curves of the two models showed excellent concordance, and decision curve analysis was used to quantify the net benefit at different threshold probabilities.

Conclusion

Two critical risk nomograms were developed based on the indicators for early prediction of mortality risk in patients with SFTS, and enhanced predictive accuracy was observed in the model that incorporated the viral load. The models developed will provide frontline clinicians with a convenient tool for early identification of critically ill patients and initiation of a better personalized treatment in a timely manner.

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.

Long-Term Detection and Isolation of Severe Fever with Thrombocytopenia Syndrome (SFTS) Virus in Dog Urine

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infection caused by the SFTS virus (SFTSV), with a high fatality rate of approximately 30% in humans. In recent years, cases of contact infection with SFTSV via bodily fluids of infected dogs and cats have been reported. In this study, clinical and virological analyses were performed in two dogs in which SFTSV infection was confirmed for the first time in the Toyama prefecture. Both dogs recovered; however, one was severely ill and the other mildly ill. The amount of the SFTSV gene was reduced to almost similar levels in both dogs. In the dogs' sera, the SFTSV gene was detected at a low level but fell below the detection limit approximately 2 weeks after onset. Notably, the SFTSV gene was detected at levels several thousand times higher in urine than in other specimens from both dogs. Furthermore, the gene was detected in the urine for a long period of >2 months. The clinical signs disappeared on days 1 or 6 after onset, but infectious SFTSV was detected in the urine up to 3 weeks later. Therefore, it is necessary to be careful about contact with bodily fluids, especially urine, even after symptoms have disappeared.

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.

Infection and transovarial transmission of severe fever with thrombocytopenia syndrome virus in Rhipicephalus sanguineus in Hainan Island, China

Severe fever with thrombocytopenia syndrome virus (SFTSV) RNA level increased in female ticks after injection with SFTSV. Furthermore, SFTSV RNA was detected in the eggs and larvae that originated from the virus-infected female ticks.

Roles of interferon induced protein with tetratricopeptide repeats (IFIT) family in autoimmune disease

Interferon-induced tetrapeptide repeat (IFIT) family proteins are an important component of the antiviral immune response. There are four known members of the human IFIT family, namely IFIT1, IFIT2, IFIT3 and IFIT5. More and more evidence shows that IFIT family members are involved in a variety of pathophysiological processes in vivo, regulate the homeostasis and differentiation of a variety of cells including immune cells, and are closely related to a variety of autoimmune diseases, which is expected to become a new therapeutic target. This review reviews the biological roles of different IFIT proteins in various autoimmune diseases, and highlights the potential use of these molecules as biomarkers and prognostic factors in autoimmune diseases, with a view to providing ideas for exploring the diagnosis and treatment of autoimmune diseases.

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.

Rapid and portable bunyavirus SFTSV RNA testing utilizing catalytic hairpin assembly coupled with lateral flow immunoassay

Severe fever with thrombocytopenia syndrome (SFTS) is a prevalent, life-threatening, emergent infectious disease. Currently, reverse transcription-polymerase chain reaction is the gold standard for diagnosing SFTS virus (SFTSV) infection, which requires sophisticated equipment and professional personnel that are frequently unavailable in most SFTS endemic rural areas. Here, we reported a simple, rapid nucleic acid amplification system that combined the catalytic hairpin assembly (CHA) with a lateral flow immunoassay (LFIA) strip-based detection method for SFTSV detection. The detection of SFTSV RNA could be realized by generation of H1-H2 hybrid duplexes labeled with biotin and digoxin, which subsequently added to the LFIA test strips containing streptavidin conjugated with Alexa Fluor 647 as well as anti-digoxin antibodies. Our CHA-based LFIA assay offered high amplification efficiency and specificity with a detection limit of 1 aM. Crucially, this method enabled stable detection of 500 copies/mL of SFTSV within 30 min using clinical serum samples. Therefore, our CHA-based LFIA approach provided a potential useful tool to facilitate early and precise diagnosis of SFTS patients in poorly resourced SFTS endemic areas.IMPORTANCESevere fever with thrombocytopenia syndrome (SFTS) is an emerging and potentially fatal infectious disease prevalent in China. Here we report a simple, rapid nucleic acid amplification system, the catalytic hairpin assembly (CHA) in conjunction with a lateral flow immunoassay (LFIA) strip-based detection method for SFTS virus detection, which demonstrated high amplification efficiency and specificity with limit of detection of 1 aM. Most importantly, we also validate our CHA-based LFIA assay using the clinical serum samples, which was fully compatible with reverse transcription-PCR results. Therefore, our strategy provides a potential useful tool to facilitate early and precise diagnosis of SFTS patients especially in poorly resourced SFTS endemic areas.

Developing and characterizing monoclonal antibodies of Guertu bandavirus nucleoprotein for developing methods of Guertu bandavirus and severe fever with thrombocytopenia syndrome virus detection

Belonging to genus Bandavirus in Phenuiviridae family, Guertu bandavirus (GTV) is a potential pathogen closely related to severe fever with thrombocytopenia syndrome virus (SFTSV) and heartland virus (HRTV) associated with human diseases. Although the medical significance of GTV is not clear, there was serological evidence suggesting past infection with this virus has occurred, indicating its potential threat to human health. So, it is important to prepare for detection of GTV infection so as to control virus transmission and promote disease diagnosis and treatment. This study is aimed at obtaining monoclonal antibodies (mAbs) against GTV nucleoprotein (NP) and evaluating their activities in recognizing viral antigens from genetic-related bandaviruses, SFTSV and HRTV. Eight mAbs were obtained and four of them (22G1, 25C2, 25E2, and 26F8) recognize linear epitopes of GTV NP. The four mAbs showed cross-reactivity to SFTSV but were unable to react with HRTV. Two fine epitopes were identified by the four mAbs, ENP1 (194YNSFRDPLHAAV205) and ENP2 (226GPDGLP231), which are highly conserved in the NPs of GTV and SFTSV but are distinct in HRTV NP. The features of epitopes, including their hydrophilicity, antibody accessibility, flexibility, antigenicity, and spatial locations, were predicted and analyzed, and their potential functional impacts on virus infection and replication and their use for virus detection were discussed. Our results promote the understanding of the molecular basis of GTV and SFTSV NP in inducing antibody responses. The NP-specific mAbs generated in this study are promising fundamental materials for developing viral antigen detection methods for GTV and SFTSV.

Genomic diversity and evolution analysis of severe fever with thrombocytopenia syndrome in East Asia from 2010 to 2022

Background

Conducting an up-to-date analysis on the genomic diversity and evolution patterns of severe fever with thrombocytopenia syndrome virus (SFTSV) is crucial for elucidating the underlying mechanisms of its emergency and pathogenicity, as well as assessing the extent of its threat to public health.

Methods

Complete genome sequences of SFTSV were obtained from GenBank until December 19, 2022. A thorough phylogenetic analysis was conducted using comprehensive bioinformatics methods to estimate the genomic diversity and evolution.

Results

The phylogenetic classification of SFTSV strains yielded seven lineages (A-G) for each genome segment. SFTSV displayed notable variations in evolutionary patterns among different regions and segments, without a linear accumulation of nucleotide substitutions within segments and regions. The comprehensive analysis revealed 54 recombination events and 17 reassortment strains, including the first discovery of recombination events involving sea-crossing and species-crossing. Selection analysis identified three positive sites (2, 671, 1353) in RNA-dependent RNA polymerase, three positive sites (22, 298, 404) in glycoprotein, and two positive sites (9, 289) in nonstructural protein. No positive selection sites were found in nucleoprotein.

Conclusion

Our study unveiled the existence of multiple evolutionary forces influencing SFTSV, contributing to its increasing genetic diversity, which had the potential to modify its antigenicity and pathogenicity. Furthermore, our study highlights the importance of tracking the spread of SFTSV across regions and species.

Advancements in the Worldwide Detection of Severe Fever with Thrombocytopenia Syndrome Virus Infection from 2009 to 2023

Severe fever with thrombocytopenia syndrome (SFTS) is a growing concern as an emerging tick-borne infectious disease originating from the SFTS virus (SFTSV), a recent addition to the Phlebovirus genus under the family of bunyaviruses. SFTS is typically identified by symptoms such as fever, thrombocytopenia, leukopenia, and gastrointestinal problems, accompanied by a potentially high case fatality rate. Thus, early and accurate diagnosis is essential for effective treatment and disease management. This review delves into the existing methodologies for SFTS detection, including pathogenic, molecular, and immunological technologies.

Dabie bandavirus infection induces macrophagic pyroptosis and this process is attenuated by platelets

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infection with a high mortality rate in humans, which is caused by Dabie bandavirus (DBV), formerly known as SFTS virus. Clinical manifestations of SFTS are characterized by high fever, thrombocytopenia, leukopenia, hemorrhage, gastrointestinal symptoms, myalgia and local lymph node enlargement with up to 30% case fatality rates in human. Macrophage depletion in secondary lymphoid organs have important roles in the pathogenic process of fatal SFTS, but its exact cell death mechanism remains largely unknown. Here, we showed for the first time that DBV infection induced macrophagic pyroptosis, as evidenced by swollen cells, pore-forming structures, accumulation of gasdermin D N-terminal (GSDMD-NT) as well as the release of lactate dehydrogenase (LDH) and IL-1β in human macrophages. In addition to the upregulation of pyronecrosis genes, the expressions of pyroptosis-related proteins (GSDMD, caspase-1 and IL-1β) were also elevated. To be noted, platelets were found to play a protective role in DBV-derived pyroptosis. Transcriptome analysis and in vitro studies demonstrated that platelets significantly reduced the gene expressions and protein production of pro-pyroptotic markers and inflammatory cytokines in macrophages, whereas platelets conferred a propagation advantage for DBV. Collectively, this study demonstrates a novel mechanism by which DBV invasion triggers pyroptosis as a host defense to remove replication niches in human macrophages and platelets provide an additional layer to reduce cellular death. These findings may have important implications to the pathogenesis of lethal DBV, and provide new ideas for developing novel therapeutics to combat its infection.

SFTSV infection is associated with transient overproliferation of monoclonal lambda-type plasma cells

The impairment of antibody-mediated immunity is a major factor associated with fatal cases of severe fever with thrombocytopenia syndrome (SFTS). By collating the clinical diagnosis reports of 30 SFTS cases, we discovered the overproliferation of monoclonal plasma cells (MCP cells, CD38⁺cLambda⁺cKappa^-) in bone marrow, which has only been reported previously in multiple myeloma. The ratio of CD38⁺cLambda⁺ versus CD38⁺cKappa⁺ in SFTS cases with MCP cells was significantly higher than that in normal cases. MCP cells presented transient expression in the bone marrow, which was distinctly different from multiple myeloma. Moreover, the SFTS patients with MCP cells had higher clinical severity. Further, the overproliferation of MCP cells was also observed in SFTS virus (SFTSV)-infected mice with lethal infectious doses. Together, SFTSV infection induces transient overproliferation of monoclonal lambda-type plasma cells, which have important implications for the study of SFTSV pathogenesis, prognosis, and the rational development of therapeutics.

Antiviral Activity of Acetylsalicylic Acid against Bunyamwera Virus in Cell Culture

The Bunyavirales order is a large group of RNA viruses that includes important pathogens for humans, animals and plants. With high-throughput screening of clinically tested compounds we have looked for potential inhibitors of the endonuclease domain of a bunyavirus RNA polymerase. From a list of fifteen top candidates, five compounds were selected and their antiviral properties studied with Bunyamwera virus (BUNV), a prototypic bunyavirus widely used for studies about the biology of this group of viruses and to test antivirals. Four compounds (silibinin A, myricetin, L-phenylalanine and p-aminohippuric acid) showed no antiviral activity in BUNV-infected Vero cells. On the contrary, acetylsalicylic acid (ASA) efficiently inhibited BUNV infection with a half maximal inhibitory concentration (IC₅₀) of 2.02 mM. In cell culture supernatants, ASA reduced viral titer up to three logarithmic units. A significant dose-dependent reduction of the expression levels of Gc and N viral proteins was also measured. Immunofluorescence and confocal microscopy showed that ASA protects the Golgi complex from the characteristic BUNV-induced fragmentation in Vero cells. Electron microscopy showed that ASA inhibits the assembly of Golgi-associated BUNV spherules that are the replication organelles of bunyaviruses. As a consequence, the assembly of new viral particles is also significantly reduced. Considering its availability and low cost, the potential usability of ASA to treat bunyavirus infections deserves further investigation.

Serum mAST/ALT ratio had high predictive value for adverse outcome of severe fever with thrombocytopenia syndrome with severe condition

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) usually demonstrates multi-organ injury with a high mortality rate. This study aimed to investigate associations of serum aspartate/alanine aminotransferase (AST)/ALT, cytosolic AST (cAST)/ALT and mitochondrial AST (mAST)/ALT ratios with the prognosis of SFTS patients.

METHODS

A total of 355 confirmed SFTS patients were included. Clinical and laboratory data were compared between survivors and nonsurvivors. Logistic regression analysis was used to assess the independent risk factors for fatality in all patients and those admitted to the intensive care unit (ICU). The predictive values of the risk factors and constructed risk models were evaluated.

RESULTS

Mean age and biochemical parameters were significantly greater in nonsurvivors than in survivors. In ICU patients, the three ratios, high-sensitivity troponin I (hsTnI), creatine kinase (CK), lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) were elevated markedly in nonsurvivors than in survivors. Multivariate logistic regression analysis showed that age, three ratios and α-HBDH were independent risk factors for mortality in all patients. Only the three ratios were independent risk factors for death in ICU patients. Risk Models (M1, M2 and M3) and simplified models (sMs) containing the three ratios respectively had comparatively high predictive values for fatality in all patients with area under ROC curves (AUCs) > 0.85. In ICU patients, mAST/ALT ratio had the highest predictive value, sensitivity and odds ratio (OR) for mortality among three ratios.

CONCLUSION

AST/ALT, cAST/ALT and mAST/ALT ratios were associated with unfavorable clinical outcome of SFTS. The prognostic value of mAST/ALT ratio was higher in severe cases.

DNA virome of ticks in the Northeast and Hubei provinces of China reveals diverse single-stranded circular DNA viruses

BACKGROUND

Ticks are medically important vectors capable of transmitting a variety of pathogens to and between host species. Although the spectrum of tick-borne RNA viruses has been frequently investigated, the diversity of tick-borne DNA viruses remains largely unknown.

METHODS

A total of 1571 ticks were collected from forests and infested animals, and the diversity of the viruses they harbored was profiled using a DNA-specific virome method. The viromic data were phylogenetically analyzed and validated by PCR assays.

RESULTS

Although diverse and abundant prokaryotic viruses were identified in the collected ticks, only eukaryotic DNA viruses with single-stranded circular genomes covering the anelloviruses and circular replication-associated (Rep) protein-encoding single-stranded (CRESS) DNA viruses were recovered from ticks. Anelloviruses were detected only in two tick pools, but CRESS DNA viruses were prevalent across these ticks except in one pool of Dermacentor spp. ticks. Phylogenetic analyses revealed that these tick-borne CRESS DNA viruses were related to viruses recovered from animal feces, tissues and even environmental samples, suggesting that their presence may be largely explained by environmental factors rather than by tick species and host blood meals.

CONCLUSIONS

Based on the results, tick-borne eukaryotic DNA viruses appear to be much less common than eukaryotic RNA viruses. Investigations involving a wider collection area and more diverse tick species are required to further support this speculation.