Severe fever with thrombocytopenia syndrome virus (SFTSV)-host interactome screen identifies viral nucleoprotein-associated host factors as potential antiviral targets

Genome-wide CRISPR screening identifies LRP1 as an entry factor for SFTSV

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease caused by the SFTS virus (SFTSV), which has high mortality rates and poses a significant threat to public health. To identify potential therapeutic targets against SFTSV, we conduct genome-wide knockout screening, which identifies the previously known host factor CCR2, and reveals prolow-density lipoprotein receptor-related protein 1 (LRP1) as an entry factor for SFTSV. Knockdown or knockout of LRP1 significantly attenuate SFTSV infection in mouse embryonic fibroblasts (MEFs). Additionally, inhibition of LRP1 suppresses SFTSV pseudovirus infection in MEFs, suggesting its role in viral entry. The interaction between the SFTSV glycoprotein Gn and LRP1 via the CLI and CLII domains is revealed by co-IP and surface plasmon resonance (SPR). Moreover, LRP1 antagonists and neutralizing antibodies effectively attenuate SFTSV infection in MEFs. Administration of an LRP1-neutralizing antibody in a lethal male mouse model reduces the viral load, mitigates tissue damage, and improves survival. This study identifies LRP1 as a host entry receptor for SFTSV, providing a target for therapeutic strategy development.

Autoantibody Profiles and Prognostic Significance in Severe Fever With Thrombocytopenia Syndrome (SFTS) Patients

To examine the relationship between autoantibodies, inflammatory cytokines, and coagulation abnormalities in patients with severe fever with thrombocytopenia syndrome (SFTS) and assess their potential as prognostic markers. A total of 105 SFTS patients and 85 healthy controls (HCs) were included. Serum levels of antinuclear antibodies (ANAs), anti-neutrophil cytoplasmic antibodies (ANCAs), anti-endothelial cell antibodies (AECAs), antiphospholipid antibodies (aPLs), as well as inflammatory cytokines and chemokines were measured to evaluate their correlation with prognosis. AECA positivity was found in over 50% of SFTS patients, with higher titers correlating with poor prognosis. AECA levels were associated with hypertension, consciousness disorder, and advanced age. Elevated aPLs were observed and associated with coagulation dysfunction, including prolonged activated partial thromboplastin time (APTT) and thrombin time (TT). Serum levels of inflammatory cytokines and chemokines (IL-1β, IL-6, IL-8, CCL2, and CXCL10) were significantly higher in SFTS patients compared to HCs. Elevated AECA and aPLs, along with a dysregulated cytokine/chemokine profile, were identified as significant prognostic indicators in SFTS, offering potential biomarkers for disease severity. Further research is needed to explore the mechanistic roles of these immune responses and to develop targeted therapies.

Double-Stranded RNA-Based Method for Diagnosing Severe Fever with Thrombocytopenia

Background/Objectives: This study explores the potential of using elevated levels of blood double-stranded RNA (dsRNA) as a diagnostic tool for severe fever with thrombocytopenia syndrome (SFTS) infection. Methods: Blood samples from SFTS patients were collected, dsRNA was purified, and total dsRNA expression was quantitatively analyzed using a spiropyran-based method. Comparative analysis was performed using blood samples from healthy individuals and scrub typhus patients with similar symptoms. Results: The results revealed that individuals infected with SFTS had significantly higher total blood dsRNA levels compared to healthy or scrub typhus controls. The dsRNA-based method also has potential for assessing infection severity based on dsRNA levels. Conclusions: These findings suggest that total dsRNA expression can serve as a quick and convenient method to differentiate SFTS from other non-viral conditions with similar clinical presentations. This method shows promise as a novel diagnostic tool.

The Effect of Tryptophan-to-Tyrosine Mutation at Position 61 of the Nonstructural Protein of Severe Fever with Thrombocytopenia Syndrome Virus on Viral Replication through Autophagosome Modulation

In our prior investigations, we elucidated the role of the tryptophan-to-tyrosine substitution at the 61st position in the nonstructural protein NSsW61Y in diminishing the interaction between nonstructural proteins (NSs) and nucleoprotein (NP), impeding viral replication. In this study, we focused on the involvement of NSs in replication via the modulation of autophagosomes. Initially, we examined the impact of NP expression levels, a marker for replication, upon the infection of HeLa cells with severe fever thrombocytopenia syndrome virus (SFTSV), with or without the inhibition of NP binding. Western blot analysis revealed a reduction in NP levels in NSsW61Y-expressing conditions. Furthermore, the expression levels of the canonical autophagosome markers p62 and LC3 decreased in HeLa cells expressing NSsW61Y, revealing the involvement of individual viral proteins on autophagy. Subsequent experiments confirmed that NSsW61Y perturbs autophagy flux, as evidenced by reduced levels of LC3B and p62 upon treatment with chloroquine, an inhibitor of autophagosome-lysosome fusion. LysoTracker staining demonstrated a decrease in lysosomes in cells expressing the NS mutant compared to those expressing wild-type NS. We further explored the mTOR-associated regulatory pathway, a key regulator affected by NS mutant expression. The observed inhibition of replication could be linked to conformational changes in the NSs, impairing their binding to NP and altering mTOR regulation, a crucial upstream signaling component in autophagy. These findings illuminate the intricate interplay between NSsW61Y and the suppression of host autophagy machinery, which is crucial for the generation of autophagosomes to facilitate viral replication.

Immune escape mechanisms of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), poses a serious threat to global public health, with high fatalities and an increasing prevalence. As effective therapies and prevention strategies are limited, there is an urgent need to elucidate the pathogenesis of SFTS. SFTSV has evolved several mechanisms to escape from host immunity. In this review, we summarize the mechanisms through which SFTSV escapes host immune responses, including the inhibition of innate immunity and evasion of adaptive immunity. Understanding the pathogenesis of SFTS will aid in the development of new strategies for the treatment of this disease.