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Updated: Sep 23, 2025
Dissecting Innate Immune Signaling in Viral Evasion of Cytokine Production
Published on: March 2, 2014
Chemokine PF4 Inhibits EV71 and CA16 Infections at the Entry Stage
Zhichao Pei1, Hong Wang1, Zhilei Zhao1
1Center of Infectious Diseases and Pathogen Biology, Institute of Virology and AIDS Research, Key Laboratory of Organ Regeneration and Transplantation of The Ministry of Education, The First Hospital of Jilin University, Changchun, China.
Abstract:
Platelet factor 4 (PF4) or the CXC chemokine CXCL4 is the most abundant protein within the α-granules of platelets. Previous studies found that PF4 regulates infections of several viruses, including HIV-1, H1N1, hepatitis C virus (HCV), and dengue virus. Here, we show that PF4 is an inhibitor of enterovirus A71 (EV71) and coxsackievirus A16 (CA16) infections. The secreted form of PF4 from transfected cells or soluble purified PF4 from Escherichia coli, even lacking signal peptide affected secretion, obviously inhibited the propagation of EV71 and CA16. Mechanistically, we demonstrated that PF4 blocked the entry of the virus into the host cells by interactions with VP3 proteins of EV71/CA16 and the interaction with SCARB2 receptor-mediated EV71 and CA16 endocytosis. As expected, the incubation of anti-PF4 antibody with PF4 blocked PF4 inhibition on EV71 and CA16 infections further supported the above conclusion. Importantly, pretreatment of EV71 viruses with PF4 significantly protected the neonatal mice from EV71 lethal challenge and promoted the survival rate of infected mice. PF4 derived from natural platelets by EV71/CA16 activation also presented strong inhibition on EV71 and CA16. In summary, our study identified a new host factor against EV71 and CA16 infections, providing a novel strategy for EV71 and CA16 treatment. IMPORTANCE The virus's life cycle starts with binding to cell surface receptors, resulting in receptor-mediated endocytosis. Targeting the entry of the virus into target cells is an effective strategy to develop a novel drug. EV71 and CA16 are the major pathogens that cause hand, foot, and mouth disease (HFMD) outbreaks worldwide since 2008. However, the treatment of EV71 and CA16 infections is mainly symptomatic because there is no approved drug. Therefore, the underlying pathogenesis of EV71/CA16 and the interaction between host-EV71/CA16 need to be further investigated to develop an inhibitor. Here, we identified PF4 as a potent entry inhibitor of EV71 and CA16 via binding to VP3 proteins of EV71 and CA16 or binding to receptor SCARB2. In the EV71 infection model, PF4 protected mice from EV71 lethal challenge and promoted the survival rate of EV71-infected mice. Our study suggests that PF4 represents a potential candidate host factor for anti-EV71 and CA16 infections.
Insights
Platelet factor 4 (PF4) inhibits enterovirus A71 (EV71) and coxsackievirus A16 (CA16) by blocking viral entry into host cells. This discovery offers a new therapeutic strategy for hand, foot, and mouth disease (HFMD).
Area of Science:
- Virology and Immunology
- Host-pathogen interactions
- Molecular biology
Background:
- Enterovirus A71 (EV71) and coxsackievirus A16 (CA16) are major causes of hand, foot, and mouth disease (HFMD) outbreaks globally.
- Current treatments for EV71 and CA16 infections are primarily symptomatic, with no approved antiviral drugs available.
- Platelet factor 4 (PF4), a protein abundant in platelets, is known to regulate infections by various viruses.
Purpose of the Study:
- To investigate the role of PF4 as a potential inhibitor of EV71 and CA16 infections.
- To elucidate the mechanism by which PF4 affects EV71 and CA16 propagation.
- To evaluate the therapeutic potential of PF4 against EV71 and CA16 in vivo.
Main Methods:
- Assessed the inhibitory effect of secreted and purified PF4 on EV71 and CA16 propagation in vitro.
- Investigated the mechanism of inhibition, focusing on viral entry, interaction with viral VP3 proteins, and receptor SCARB2-mediated endocytosis.
- Utilized anti-PF4 antibodies to confirm the specificity of PF4's inhibitory action.
- Evaluated the protective effect of PF4 against EV71 lethal challenge in a neonatal mouse model.
Main Results:
- PF4 significantly inhibited the propagation of EV71 and CA16.
- PF4 blocked viral entry by interacting with viral VP3 proteins and interfering with SCARB2 receptor-mediated endocytosis.
- Pretreatment of EV71 with PF4 conferred significant protection and improved survival rates in infected neonatal mice.
Conclusions:
- PF4 acts as a potent inhibitor of EV71 and CA16 infections by targeting viral entry.
- PF4's interaction with viral VP3 proteins and the SCARB2 receptor is key to its antiviral mechanism.
- PF4 represents a promising host factor and a potential therapeutic candidate for treating EV71 and CA16 infections.
