# Immunopathogenesis of Severe Fever with Thrombocytopenia Syndrome: Core Driving Role of Cytokine Storm

## TL;DR

This paper explains how a cytokine storm caused by the SFTS virus leads to severe illness and suggests possible treatments targeting immune responses.

## Contribution

The paper highlights the central role of cytokine storm in SFTS progression and reviews potential immunotherapies targeting immune dysregulation.

## Key findings

- SFTSV inhibits the host's type I interferon response, promoting immune evasion and viral replication.
- Cytokine storm disrupts immune balance, leading to vascular damage and multi-organ failure in SFTS.
- Targeting cytokine pathways with therapies like tocilizumab and JAK inhibitors may improve SFTS outcomes.

## Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is a newly discovered tick-borne disease caused by SFTS virus (SFTSV) infection. Patients present with high fever, thrombocytopenia, and multiple organ dysfunction, with a high mortality rate and a lack of specific treatment, all of which indicate that research on the deterioration mechanism and treatment of this disease is urgent. Currently, multiple studies have indicated that cytokine storm is one of the core factors contributing to the deterioration of the disease. SFTSV inhibits the host’s type I interferon response through its non-structural protein NSs, thereby promoting immune evasion and viral replication. Extensive viral stimulation leads to dysfunction and abnormal polarization of immune cells (including monocytes, macrophages, dendritic cells, T cells, and B cells), triggering the massive release of pro-inflammatory factors(such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β)), anti-inflammatory factors (such as interleukin-10 (IL-10)), and chemokines(such as interferon-gamma inducible protein 10 (IP-10), monocyte chemoattractant protein-1 (MCP-1), and interleukin-8 (IL-8)). This cytokine storm exacerbates the imbalance between pro-inflammatory and anti-inflammatory factors, as well as immune paralysis, leading to vascular endothelial damage, microthrombosis, and ultimately, multi-organ failure, which determines the clinical outcome. Simultaneously, specific cytokines and immune cell phenotypes can serve as biomarkers for disease severity and prognosis. In terms of treatment, this article further summarizes the intervention strategies targeting the aforementioned immune links, including intravenous immunoglobulin (IVIG), tocilizumab (targeting the IL-6 receptor), inhibitors of Janus kinase (JAK) and nuclear factor-kappa B (NF-κB) signaling pathways, interferon, neutralizing antibodies, and other immunotherapy methods. By analyzing the dynamic changes and mechanisms of cytokine storm in the course of SFTS, and summarizing current potential immunotherapy methods, this article aims to provide a theoretical framework for the future treatment of SFTS.