Tribbles pseudokinase 3 promotes enterovirus A71 infection via dual mechanisms

Enterovirus A71 (EV-A71) is the main pathogen causing hand, foot and mouth disease (HFMD) in children and occasionally associated with neurological diseases such as aseptic meningitis, brainstem encephalitis (BE) and acute flaccid paralysis. We report here that cellular pseudokinase tribbles 3 (TRIB3) facilitates the infection of EV-A71 via dual mechanisms. In one hand, TRIB3 maintains the metabolic stability of scavenger receptor class B member 2 (SCARB2), the bona fide receptor of EV-A71, to enhance the infectious entry and spreading of the virus. On the other hand, TRIB3 facilitates the replication of EV-A71 RNA in a SCARB2-independent manner. The critical role of TRIB3 in EV-A71 infection and pathogenesis was further demonstrated in vivo in mice. In comparison to wild-type C57BL/6 mice, EV-A71 infection in TRIB3 knockdown mice (Trib3+/-) resulted in significantly lower viral loads in muscular tissues and reduced lethality and severity of clinical scores and tissue pathology. In addition, TRIB3 also promoted the replication of coxsackievirus B3 (CVB3) and coxsackievirus A16 (CVA16) in vitro. In conclusion, our results suggest that TRIB3 is one of key host cellular proteins required for the infection and pathogenesis of EV-A71 and some other human enteroviruses and may thus be a potential therapeutic target for combating the infection of those viruses.

The EV71 2A protease occupies the central cleft of SETD3 and disrupts SETD3-actin interaction

SETD3 is an essential host factor for the replication of a variety of enteroviruses that specifically interacts with viral protease 2A. However, the interaction between SETD3 and the 2A protease has not been fully characterized. Here, we use X-ray crystallography and cryo-electron microscopy to determine the structures of SETD3 complexed with the 2A protease of EV71 to 3.5 Å and 3.1 Å resolution, respectively. We find that the 2A protease occupies the V-shaped central cleft of SETD3 through two discrete sites. The relative positions of the two proteins vary in the crystal and cryo-EM structures, showing dynamic binding. A biolayer interferometry assay shows that the EV71 2A protease outcompetes actin for SETD3 binding. We identify key 2A residues involved in SETD3 binding and demonstrate that 2A's ability to bind SETD3 correlates with EV71 production in cells. Coimmunoprecipitation experiments in EV71 infected and 2A expressing cells indicate that 2A interferes with the SETD3-actin complex, and the disruption of this complex reduces enterovirus replication. Together, these results reveal the molecular mechanism underlying the interplay between SETD3, actin, and viral 2A during virus replication.

Hyperglycemia facilitates EV71 replication: Insights into miR-206-mediated regulation of G3BP2 promoting EV71 IRES activity

Background: Neurotropic virus infections actively manipulate host cell metabolism to enhance virus neurovirulence. Although hyperglycemia is common during severe infections, its specific role remains unclear. This study investigates the impact of hyperglycemia on the neurovirulence of enterovirus 71 (EV71), a neurovirulent virus relying on internal ribosome entry site (IRES)-mediated translation for replication. Methods: Utilizing hSCARB2-transgenic mice, we explore the effects of hyperglycemia in EV71 infection and elucidate the underlying mechanisms. Results: Remarkably, administering insulin alone to reduce hyperglycemia in hSCARB2-transgenic mice results in a decrease in brainstem encephalitis and viral load. Conversely, induced hyperglycemia exacerbates neuropathogenesis, highlighting the pivotal role of hyperglycemia in neurovirulence. Notably, miR-206 emerges as a crucial mediator induced by viral infection, with its expression further heightened by hyperglycemia and concurrently repressed by insulin. The use of antagomiR-206 effectively mitigates EV71-induced brainstem encephalitis and reduces viral load. Mechanistically, miR-206 facilitates IRES-driven virus replication by repressing the stress granule protein G3BP2. Conclusions: Novel therapeutic approaches against severe EV71 infections involve managing hyperglycemia and targeting the miR-206-stress granule pathway to modulate virus IRES activity.

Construction of an infectious clone for enterovirus A89 and mutagenesis analysis of viral infection and cell binding

Enterovirus A89 (EV-A89) is an unconventional strain belonging to the Enterovirus A species. Limited research has been conducted on EV-A89, leaving its biological and pathogenic properties unclear. Developing reverse genetic tools for EV-A89 would help to unravel its infection mechanisms and aid in the development of vaccines and anti-viral drugs. In this study, an infectious clone for EV-A89 was successfully constructed and recombinant enterovirus A89 (rEV-A89) was generated. The rEV-A89 exhibited similar characteristics such as growth curve, plaque morphology, and dsRNA expression with parental strain. Four amino acid substitutions were identified in the EV-A89 capsid, which were found to enhance viral infection. Mechanistic studies revealed that these substitutions increased the virus's cell-binding ability. Establishing reverse genetic tools for EV-A89 will significantly contribute to understanding viral infection and developing anti-viral strategies.IMPORTANCEEnterovirus A species contain many human pathogens and have been classified into conventional cluster and unconventional cluster. Most of the research focuses on various conventional members, while understanding of the life cycle and infection characteristics of unconventional viruses is still very limited. In our study, we constructed the infectious cDNA clone and single-round infectious particles for the unconventional EV-A89, allowing us to investigate the biological properties of recombinant viruses. Moreover, we identified key amino acids residues that facilitate EV-A89 infection and elucidate their roles in enhancing viral binding to host cells. The establishment of the reverse genetics system will greatly facilitate future study on the life cycle of EV-A89 and contribute to the development of prophylactic vaccines and anti-viral drugs.

Identification of fangchinoline as a broad-spectrum enterovirus inhibitor through reporter virus based high-content screening

Hand, foot, and mouth disease (HFMD) is a common pediatric illness mainly caused by enteroviruses, which are important human pathogens. Currently, there are no available antiviral agents for the therapy of enterovirus infection. In this study, an excellent high-content antiviral screening system utilizing the EV-A71-eGFP reporter virus was developed. Using this screening system, we screened a drug library containing 1042 natural compounds to identify potential EV-A71 inhibitors. Fangchinoline (FAN), a bis-benzylisoquinoline alkaloid, exhibits potential inhibitory effects against various enteroviruses that cause HFMD, such as EV-A71, CV-A10, CV-B3 and CV-A16. Further investigations revealed that FAN targets the early stage of the enterovirus life cycle. Through the selection of FAN-resistant EV-A71 viruses, we demonstrated that the VP1 protein could be a potential target of FAN, as two mutations in VP1 (E145G and V258I) resulted in viral resistance to FAN. Our research suggests that FAN is an efficient inhibitor of EV-A71 and has the potential to be a broad-spectrum antiviral drug against human enteroviruses.

Rapid detection of four major HFMD-associated enteroviruses by multiplex HiFi-LAMP assays

Hand, foot, and mouth disease (HFMD) caused by various enteroviruses is a major public health concern globally. Human enterovirus 71(EVA71), coxsackievirus A16 (CVA16), coxsackievirus A6 (CVA6), and coxsackievirus A10 (CVA10) are four major enteroviruses responsible for HFMD. Rapid, accurate, and specific point-of-care (POC) detection of the four enteroviruses is crucial for the prevention and control of HFMD. Here, we developed two multiplex high-fidelity DNA polymerase loop-mediated isothermal amplification (mHiFi-LAMP) assays for simultaneous detection of EVA71, CVA16, CVA6, and CVA10. The assays have good specificity and exhibit high sensitivity, with limits of detection (LOD) of 11.2, 49.6, 11.4, and 20.5 copies per 25 μL reaction for EVA71, CVA16, CVA6, and CVA10, respectively. The mHiFi-LAMP assays showed an excellent clinical performance (sensitivity 100.0%, specificity 83.3%, n = 47) when compared with four singleplex RT-qPCR assays (sensitivity 93.1%, specificity 100%). In particular, the HiFi-LAMP assays exhibited better performance (sensitivity 100.0%, specificity 100%) for CVA16 and CVA6 than the RT-qPCR assays (sensitivity 75.0-92.3%, specificity 100%). Furthermore, the mHiFi-LAMP assays detected all clinical samples positive for the four enteroviruses within 30 min, obviously shorter than about 1-1.5 h by the RT-qPCR assays. The new mHiFi-LAMP assays can be used as a robust point-of-care testing (POCT) tool to facilitate surveillance of HFMD at rural and remote communities and resource-limited settings.

Cordycepin Inhibits Enterovirus A71 Replication and Protects Host Cell from Virus-Induced Cytotoxicity through Adenosine Action Pathway

Enterovirus A71 (EV-A71) infection typically causes mild illnesses, such as hand-foot-and-mouth disease (HFMD), but occasionally leads to severe or fatal neurological complications in infants and young children. Currently, there is no specific antiviral treatment available for EV-A71 infection. Thus, the development of an effective anti-EV-A71 drug is required urgently. Cordycepin, a major bioactive compound found in Cordyceps fungus, has been reported to possess antiviral activity. However, its specific activity against EV-A71 is unknown. In this study, the potency and role of cordycepin treatment on EV-A71 infection were investigated. Results demonstrated that cordycepin treatment significantly reduced the viral load and viral ribonucleic acid (RNA) level in EV-A71-infected Vero cells. In addition, EV-A71-mediated cytotoxicity was significantly inhibited in the presence of cordycepin in a dose-dependent manner. The protective effect can also be extended to Caco-2 intestinal cells, as evidenced by the higher median tissue culture infectious dose (TCID50) values in the cordycepin-treated groups. Furthermore, cordycepin inhibited EV-A71 replication by acting on the adenosine pathway at the post-infection stage. Taken together, our findings reveal that cordycepin could be a potential antiviral candidate for the treatment of EV-A71 infection.

Enterovirus A71 does not meet the uncoating receptor SCARB2 at the cell surface

Enterovirus A71 (EV-A71) infection involves a variety of receptors. Among them, two transmembrane protein receptors have been investigated in detail and shown to be critical for infection: P-selectin glycoprotein ligand-1 (PSGL-1) in lymphocytes (Jurkat cells), and scavenger receptor class B member 2 (SCARB2) in rhabdomyosarcoma (RD) cells. PSGL-1 and SCARB2 have been reported to be expressed on the surface of Jurkat and RD cells, respectively. In the work reported here, we investigated the roles of PSGL-1 and SCARB2 in the process of EV-A71 entry. We first examined the expression of SCARB2 in Jurkat cells, and detected it within the cytoplasm, but not on the cell surface. Further, using PSGL-1 and SCARB2 knockout cells, we found that although both PSGL-1 and SCARB2 are essential for virus infection of Jurkat cells, virus attachment to these cells requires only PSGL-1. These results led us to evaluate the cell surface expression and the roles of SCARB2 in other EV-A71-susceptible cell lines. Surprisingly, in contrast to the results of previous studies, we found that SCARB2 is absent from the surface of RD cells and other susceptible cell lines we examined, and that although SCARB2 is essential for infection of these cells, it is dispensable for virus attachment. These results indicate that a receptor other than SCARB2 is responsible for virus attachment to the cell and probably for internalization of virions, not only in Jurkat cells but also in RD cells and other EV-A71-susceptible cells. SCARB2 is highly concentrated in lysosomes and late endosomes, where it is likely to trigger acid-dependent uncoating of virions, the critical final step of the entry process. Our results suggest that the essential interactions between EV-A71 and SCARB2 occur, not at the cell surface, but within the cell.

Advances in anti-EV-A71 drug development research

BACKGROUND

Enterovirus A71 (EV-A71) is capable of causing hand, foot and mouth disease (HFMD), which may lead to neurological sequelae and even death. As EV-A71 is resistant to environmental changes and mutates easily, there is still a lack of effective treatments or globally available vaccines.

AIM OF REVIEW

For more than 50 years since the HFMD epidemic, related drug research has been conducted. Progress in this area can promote the further application of existing potential drugs and develop more efficient and safe antiviral drugs, and provide useful reference for protecting the younger generation and maintaining public health security.

KEY SCIENTIFIC CONCEPTS OF REVIEW

At present, researchers have identified hundreds of EV-A71 inhibitors based on screening repurposed drugs, targeted structural design, and rational modification of previously effective drugs as the main development strategies. This review systematically introduces the current potential drugs to inhibit EV-A71 infection, including viral inhibitors targeting key sites such as the viral capsid, RNA-dependent RNA polymerase (RdRp), 2C protein, internal ribosome entry site (IRES), 3C proteinase (3Cpro), and 2A proteinase (2Apro), starting from each stage of the viral life cycle. Meanwhile, the progress of host-targeting antiviral drugs and their development are summarized in terms of regulating host immunity, inhibiting autophagy or apoptosis, and regulating the cellular redox environment. In addition, the current clinical methods for the prevention and treatment of HFMD are summarized and discussed with the aim of providing support and recommendations for the treatment of enterovirus infections including EV-A71.

VP1 codon deoptimization and high-fidelity substitutions in 3D polymerase as potential vaccine strategies for eliciting immune responses against enterovirus A71

Enterovirus A71 (EV-A71) can induce severe neurological complications and even fatal encephalitis in children, and it has caused several large outbreaks in Taiwan since 1998. We previously generated VP1 codon-deoptimized (VP1-CD) reverse genetics (rg) EV-A71 viruses (rgEV-A71s) that harbor a high-fidelity (HF) 3D polymerase. These VP1-CD-HF rgEV-A71s showed lower replication kinetics in vitro and decreased virulence in an Institute of Cancer Research (ICR) mouse model of EV-A71 infection, while still retaining their antigenicity in comparison to the wild-type virus. In this study, we aimed to further investigate the humoral and cellular immune responses elicited by VP1-CD-HF rgEV-A71s to assess the potential efficacy of these EV-A71 vaccine candidates. Following intraperitoneal (i.p.) injection of VP1-CD-HF rgEV-A71s in mice, we observed a robust induction of EV-A71-specific neutralizing IgG antibodies in the antisera after 21 days. Splenocytes isolated from VP1-CD-HF rgEV-A71s-immunized mice exhibited enhanced proliferative activities and cytokine production (IL-2, IFN-γ, IL-4, IL-6, and TNF-α) upon re-stimulation with VP1-CD-HF rgEV-A71, as compared to control mice treated with adjuvant only. Importantly, administration of antisera from VP1-CD-HF rgEV-A71s-immunized mice protected against lethal EV-A71 challenge in neonatal mice. These findings highlight that our generated VP1-CD-HF rgEV-A71 viruses are capable of inducing both cellular and humoral immune responses, supporting their potential as next-generation EV-A71 vaccines for combating EV-A71 infection.IMPORTANCEEV-A71 can cause severe neurological diseases and cause death in young children. Here, we report the development of synthetic rgEV-A71s with the combination of codon deoptimization and high-fidelity (HF) substitutions that generate genetically stable reverse genetics (rg) viruses as potential attenuated vaccine candidates. Our work provides insight into the development of low-virulence candidate vaccines through a series of viral genetic editing for maintaining antigenicity and genome stability and suggests a strategy for the development of an innovative next-generation vaccine against EV-A71.

A novel mucosal bivalent vaccine of EV-A71/EV-D68 adjuvanted with polysaccharides from Ganoderma lucidum protects mice against EV-A71 and EV-D68 lethal challenge

BACKGROUND

Human enteroviruses A71 (EV-A71) and D68 (EV-D68) are the suspected causative agents of hand-foot-and-mouth disease, aseptic meningitis, encephalitis, acute flaccid myelitis, and acute flaccid paralysis in children. Until now, no cure nor mucosal vaccine existed for EV-A71 and EV-D68. Novel mucosal bivalent vaccines are highly important for preventing EV-A71 and EV-D68 infections.

METHODS

In this study, formalin-inactivated EV-A71 and EV-D68 were used as antigens, while PS-G, a polysaccharide from Ganoderma lucidum, was used as an adjuvant. Natural polysaccharides have the characteristics of intrinsic immunomodulation, biocompatibility, low toxicity, and safety. Mice were immunized intranasally with PBS, EV-A71, EV-D68, or EV-A71 + EV-D68, with or without PS-G as an adjuvant.

RESULTS

The EV-A71 + EV-D68 bivalent vaccine generated considerable EV-A71- and EV-D68-specific IgG and IgA titres in the sera, nasal washes, saliva, bronchoalveolar lavage fluid, and feces. These antibodies neutralized EV-D68 and EV-A71 infectivity. They also cross-neutralized infections by different EV-D68 and EV-A71 sub-genotypes. Furthermore, compared with the PBS group, EV-A71 + EV-D68 + PS-G-vaccinated mice exhibited an increased number of EV-D68- and EV-A71-specific IgA- and IgG-producing cells. In addition, T-cell proliferative responses, and IFN-γ and IL-17 secretion in the spleen were substantially induced when PS-G was used as an adjuvant with EV-A71 + EV-D68. Finally, in vivo challenge experiments demonstrated that the immune sera induced by EV-A71 + EV-D68 + PS-G conferred protection in neonate mice against lethal EV-A71 and EV-D68 challenges as indicated by the increased survival rate and decreased clinical score and viral RNA tissue expression. Taken together, all EV-A71/EV-D68 + PS-G-immunized mice developed potent specific humoral, mucosal, and cellular immune responses to EV-D68 and EV-A71 and were protected against them.

CONCLUSIONS

These findings demonstrated that PS-G can be used as a potential adjuvant for EV-A71 and EV-D68 bivalent mucosal vaccines. Our results provide useful information for the further preclinical and clinical development of a mucosal bivalent enterovirus vaccine against both EV-A71 and EV-D68 infections.

Inhibition of lysosome-tethered Ragulator-Rag-3D complex restricts the replication of Enterovirus 71 and Coxsackie A16

Enterovirus 71 (EV71) and Coxsackie A16 (CVA16) are two major causative agents of hand, foot, and mouth disease (HFMD) in young children. However, the mechanisms regulating the replication and pathogenesis of EV71/CVA16 remain incompletely understood. We performed a genome-wide CRISPR-Cas9 knockout screen and identified Ragulator as a mediator of EV71-induced apoptosis and pyroptosis. The Ragulator-Rag complex is required for EV71 and CVA16 replication. Upon infection, the Ragulator-Rag complex recruits viral 3D protein to the lysosomal surface through the interaction between 3D and RagB. Disruption of the lysosome-tethered Ragulator-Rag-3D complex significantly impairs the replication of EV71/CVA16. We discovered a novel EV71 inhibitor, ZHSI-1, which interacts with 3D and significantly reduces the lysosomal tethering of 3D. ZHSI-1 treatment significantly represses replication of EV71/CVA16 as well as virus-induced pyroptosis associated with viral pathogenesis. Importantly, ZHSI-1 treatment effectively protects against EV71 infection in neonatal and young mice. Thus, our study indicates that targeting lysosome-tethered Ragulator-Rag-3D may be an effective therapeutic strategy for HFMD.

Coxsackievirus A6 2C protein antagonizes IFN-β production through MDA5 and RIG-I depletion

IMPORTANCE

Coxsackievirus A6 (CV-A6) is a major emerging pathogen associated with atypical hand, foot, and mouth disease and can cause serious complications such as encephalitis, acute flaccid paralysis, and neurorespiratory syndrome. Therefore, revealing the associated pathogenic mechanisms could benefit the control of CV-A6 infections. In this study, we demonstrate that the nonstructural 2CCV-A6 suppresses IFN-β production, which supports CV-A6 infection. This is achieved by depleting RNA sensors such as melanoma differentiation-associated gene 5 and retinoic acid-inducible gene I (RIG-I) through the lysosomal pathway. Such a function is shared by 2CEV-A71 and 2CCV-B3 but not 2CCV-A16, suggesting the latter might have an alternative way to promote viral replication. This study broadens our understanding of enterovirus 2C protein regulation of the RIG-I-like receptor signaling pathway and reveals a novel mechanism by which CV-A6 and other enteroviruses evade the host innate immune response. These findings on 2C may provide new therapeutic targets for the development of effective inhibitors against CV-A6 and other enterovirus infections.

Application value of EV/EV71/CA16-SAT detection in children with hand-foot-mouth disease

The objective of this work was to explore the application value of a new type of fluorescent nucleic acid isothermal amplification (SAT) to detect EV/EV71/CA16-SAT in children with hand-foot-mouth disease (HFMD). For this purpose, from March 2017 to September 2019, Chengdu Children's Specialized Hospital collected throat swabs from children with clinical manifestations of hand, foot and mouth disease, and used SAT technology to screen and detect universal enterovirus (EV) nucleic acid (There were 1860 children with EV-RNA) positive. Patients who are EV-RNA positive at any time: first use the same throat swab specimen to detect EV71/CA16-RNA; secondly, collect venous blood and use the colloidal gold method to detect IgM antibodies in EV71/CA16 serum. The patients with positive EV71/CA16-RNA or EV71/CA16-IgM (or both) were repeated the above two methods 2 weeks and 4 weeks after standard treatment for review and comprehensive analysis. Results showed that 763 cases were enrolled for the first time: 59.76% were male and 40.24% were female; the age ranged from 1 month to 13 years, of which 69.06% were from 1 to 4 years old; CA16-RNA positive 56.23%, EV71-RNA positive 21.89%, CA16/EV71 -RNA were all positive in 1.57%; CA16-IgM was positive in 64.48%, EV71-IgM was positive in 54.26%, and CA16/EV71-IgM were both positive in 18.74%. After 2 weeks, 722 cases were reexamined: 26.73% were positive for CA16-RNA, 7.89% were positive for EV71-RNA, 0.28% were both positive for CA16/EV71-RNA; 66.21% were positive for CA16-IgM, 51.52% were positive for EV71-IgM, and IgM were all positive in 17.73%. Four weeks later, 489 cases were reexamined: among them, CA16-RNA positive 5.73% of which were positive for EV71 color RNA (0.005%), and 12.68% of them were all positive for EV71lym. The strategy of combining SAT technology and colloidal gold method to detect EV/EV71/CA16 nucleic acid (RNA) and serum IgM antibody in children HFMD can improve the early detection rate and accuracy of HFMD; According to the comprehensive analysis of the detection results of children with HFMD at the early stage, 2 weeks and 4 weeks of the present study, it is suggested that EV/EV71/CA16-SAT nucleic acid detection can be used to judge the prognosis, follow-up treatment, set isolation time, return students to school, and community management in children with HFMD. and prevention and control have more clinical application value.

Molecular epidemiology and phylodynamic analysis of enterovirus 71 in Beijing, China, 2009-2019

BACKGROUND

Enterovirus 71(EV71)-associated hand, foot and mouth disease (HFMD) decreased dramatically in Beijing from 2009 to 2019. This study was to investigate the epidemiological characteristics, evolutionary dynamics, geographic diffusion pathway, and other features of EV71 in Beijing, China.

METHODS

We conducted a retrospective study of EV71-associated HFMD and its causative agent in Beijing, China, from 2009 to 2019. Phylogenetic and phylogeographic methods based on the EV71 genome were used to determine the evolution features, origin, and spatiotemporal dynamics. Positive selection sites in the VP1 gene were identified and exhibited in the tertiary structure. Bayesian birth-death skyline model was used to estimate the effective reproductive number (Re).

RESULTS

EV71-associated HFMD decreased greatly in Beijing. From 2009 to 2019, EV71 strains prevalent in Beijing shared high homology in each gene segment and evolved with a rate of 4.99*10- 3 substitutions per site per year. The genetic diversity of EV71 first increased and peaked in 2012 and then decreased with fluctuations. The time to the most recent common ancestor (TMRCA) of EV71 in Beijing was estimated around 2003 when the EV71 strains were transmitted to Beijing from east China. Beijing played a crucial role in seeding EV71 to central China as well. Two residues (E145Q/G, A293S) under positive selection were detected from both the VP1 dataset and the P1 dataset. They were embedded within the loop of the VP1 capsid and were exposed externally. Mean Re estimate of EV71 in Beijing was about 1.007.

CONCLUSION

In recent years, EV71 was not the primary causative agent of HFMD in Beijing. The low Re estimate of EV71 in Beijing implied that strategies for preventing and controlling HFMD were performed effectively. Beijing and east China played a crucial role in disseminating EV71 to other regions in China.

The Upf1 protein restricts EV-A71 viral replication

Enterovirus A71 (EV-A71) is transmitted through the respiratory tract, gastrointestinal system, and fecal-oral routes. The main symptoms caused by EV-A71 are hand, foot, and mouth disease (HFMD) or vesicular sore throat. Upf1 (Up-frameshift protein 1) was reported to degrade mRNA containing early stop codons, known as nonsense-mediated decay (NMD). Upf1 is also involved in the NMD mechanism as a host factor detrimental to viral replication. In this study, we dissected the potential roles of Upf1 in the EV-A71-infected cells. Upf1 was virulently down-regulated in three different EV-A71-infected cells, RD, Hela, and 293T, implying that Upf1 is a host protein unfavorable for EV-A71 replication. Knockdown of Upf1 protein resulted in increased viral RNA expression and production of progeny virus, and conversely, overexpression of Upf1 protein resulted in decreased viral RNA expression and production of progeny virus. Importantly, we observed increased RNA levels of asparagine synthetase (ASNS), one of the indicator substrates for the NMD mechanism, which indirectly suggests that EV-A71 infection of cells suppresses NMD activity in the host. The results shown in this study are useful for subsequent analysis of the relationship between the NMD/Upf1 mechanism and other picornaviruses, which may lead to the development of anti-picornavirus drugs.

An enterovirus A71 virus-like particle with replaced loops confers partial cross-protection in mice

Enterovirus A71 (EV-A71), coxsackievirus A16 (CV-A16), and CV-A10 belong to the main prevailing types causing hand-foot-and-mouth disease. Since EV-A71 monovalent vaccine does not confer cross-protection, developing a multivalent vaccine is essential. In this study, a trivalent chimeric virus-like particle of EV-A71 (EV-A71-VLPCHI3) was constructed based on EV-A71-VLP backbone by replacing the corresponding surface loops with CV-A16 VP1 G-H, CV-A10 VP1 B-C and E-F loops, which are critical for immunogenic neutralization. The baculovirus-insect cell expression system was employed for EV-A71-VLPCHI3 production. EV-A71-VLPCHI3 was purified by sucrose density gradient and observed by transmission electron microscopy. The immunogenicity and protective efficacy of EV-A71-VLPCHI3 were evaluated in mice. Our results revealed that EV-A71-VLPCHI3 had a similar morphology to inactivated EV-A71 particles and could induce specific IgG antibodies against EV-A71, CV-A16 and CV-A10 in mice. More importantly, EV-A71-VLPCHI3 enhanced cross-reactive protection against CV-A16 and CV-A10, by 20 % and 40 %, compared to inactivated EV-A71 counterparts, respectively. In conclusion, the successful construction of EV-A71-VLPCHI3 suggested that loop-dependent heterologous protection could be transferred by loops replacement on the surface of viral capsid. This strategy may also supplement the development of multivalent vaccines against other infectious viral diseases.

Neutralization of African enterovirus A71 genogroups by antibodies to canonical genogroups

Enterovirus 71 (EV-A71) is a major public health problem, causing a range of illnesses from hand-foot-and-mouth disease to severe neurological manifestations. EV-A71 strains have been phylogenetically classified into eight genogroups (A to H), based on their capsid-coding genomic region. Genogroups B and C have caused large outbreaks worldwide and represent the two canonical circulating EV-A71 subtypes. Little is known about the antigenic diversity of new genogroups as compared to the canonical ones. Here, we compared the antigenic features of EV-A71 strains that belong to the canonical B and C genogroups and to genogroups E and F, which circulate in Africa. Analysis of the peptide sequences of EV-A71 strains belonging to different genogroups revealed a high level of conservation of the capsid residues involved in known linear and conformational neutralization antigenic sites. Using a published crystal structure of the EV-A71 capsid as a model, we found that most of the residues that are seemingly specific to some genogroups were mapped outside known antigenic sites or external loops. These observations suggest a cross-neutralization activity of anti-genogroup B or C antibodies against strains of genogroups E and F. Neutralization assays were performed with diverse rabbit and mouse anti-EV-A71 sera, anti-EV-A71 human standards and a monoclonal neutralizing antibody. All the batches of antibodies that were tested successfully neutralized all available isolates, indicating an overall broad cross-neutralization between the canonical genogroups B and C and genogroups E and F. A panel constituted of more than 80 individual human serum samples from Cambodia with neutralizing antibodies against EV-A71 subgenogroup C4 showed quite similar cross-neutralization activities between isolates of genogroups C4, E and F. Our results thus indicate that the genetic drift underlying the separation of EV-A71 strains into genogroups A, B, C, E and F does not correlate with the emergence of antigenically distinct variants.

Identification of Critical Amino Acids of Coxsackievirus A10 Associated with Cell Tropism and Viral RNA Release during Uncoating

Coxsackievirus A10 (CV-A10) is a prevailing causative agent of hand-foot-mouth disease, necessitating the isolation and adaptation of appropriate strains in cells allowed for human vaccine development. In this study, amino acid sequences of CV-A10 strains with different cell tropism on RD and Vero cells were compared. Various amino acids on the structural and non-structural proteins related to cell tropism were identified. The reverse genetic systems of several CV-A10 strains with RD+/Vero- and RD+/Vero+ cell tropism were developed, and a set of CV-A10 recombinants were produced. The binding, entry, uncoating, and proliferation steps in the life cycle of these viruses were evaluated. P1 replacement of CV-A10 strains with different cell tropism revealed the pivotal role of the structural proteins in cell tropism. Further, seven amino acid substitutions in VP2 and VP1 were introduced to further investigate their roles played in cell tropism. These mutations cooperated in the growth of CV-A10 in Vero cells. Particularly, the valine to isoleucine mutation at the position VP1-236 (V1236I) was found to significantly restrict viral uncoating in Vero cells. Co-immunoprecipitation assays showed that the release of viral RNA from the KREMEN1 receptor-binding virions was restricted in r0195-V1236I compared with the parental strain r0195 (a RD+/Vero+ strain). Overall, this study highlights the dominant effect of structural proteins in CV-A10 adaption in Vero cells and the importance of V1236 in viral uncoating, providing a foundation for the mechanism study of CV-A10 cell tropism, and facilitating the development of vaccine candidates.

Targeting HNRNPA2B1 inhibits enterovirus 71 replication in SK-N-SH cells

OBJECTIVE

To investigate the effect of heterogeneous nuclear ribonucleoprotein A2B1 (HNRNPA2B1) on the replication of enterovirus 71 (EV-71) in SK-N-SH cells.

METHODS

The mRNA and protein expression of HNRNPA2B1 in SK-N-SH cells were detected by real-time quantitative PCR (qRT-PCR) and western blotting (WB), respectively. WB was used to detect HNRNPA2B1 protein expression in the nucleus and cytosol. The localization of HNRNPA2B1 protein in the nucleus and cytosol was detected by immunofluorescence (IF). The expression of HNRNPA2B1 was inhibited by small interfering RNA (si-HNRNPA2B1). Viral RNA, viral structural protein VP1, and viral titer were detected by qRT-PCR, WB, and viral dilution counting, respectively.

RESULTS

EV-71 infection significantly upregulates the expression of HNRNPA2B1 in SK-N-SH cells. EV-71 infection promotes HNRNPA2B1 nucleus-cytoplasm redistribution. Down-regulation of HNRNPA2B1 expression significantly inhibited EV-71 replication.

CONCLUSION

HNRNPA2B1 protein redistributed from nucleus to cytoplasm and is highly expressed in the cytoplasm during EV-71 infection. Inhibition of HNRNPA2B1 levels effectively inhibits EV-71 replication in SK-N-SH cells.

Molecular evolutionary dynamics of enterovirus A71, coxsackievirus A16 and coxsackievirus A6 causing hand, foot and mouth disease in Thailand, 2000-2022

Hand, foot and mouth disease (HFMD) is a public health threat worldwide, particularly in the Asia-Pacific region. Enterovirus A71 (EV-A71), coxsackievirus A16 (CVA16), and CVA6 are the major pathogens causing HFMD outbreaks in several countries, including Thailand. We retrieved 385 VP1 nucleotide sequences, comprising 228 EV-A71, 33 CVA16, and 124 CVA6, deposited in the databases between 2000 and 2022 for molecular evolutionary characterization using Bayesian phylogeny. All EV-A71 identified belonged to genotype B, subgenotypes B4, and B5, and to genotype C, subgenotypes C1, C2, C4a, C4b, and C5. The analyzes demonstrated these viruses' co-circulation and subgenotypic changes throughout the past two decades. The CVA16 was grouped in genotype B1, predominantly subgenotype B1a, and the CVA6 was grouped in subgenotype D3, clades 1-4. The tMRCA of EV-A71 genotypes B and C, CVA16 B1, and CVA6 D3 dated 1993.79, 1982.62, 1995.86, and 2007.31, respectively, suggesting that the viruses were likely introduced and cryptically circulated in Thailand before the HFMD cases were recognized. We demonstrated these viruses' fluctuation and cyclical pattern throughout the two decades of observation. This study provided insight into evolutionary dynamics concerning molecular epidemiology and supported the selection of current genotype-matched vaccines, vaccine development, and implementation.

The neuropathological mechanism of EV-A71 infection attributes to inflammatory pryoptosis and viral replication via activating the hsa_circ_0045431/ hsa_miR_584/NLRP3 regulatory axis

Neuropathological damage has been considered to be the main cause of death from EV-A71 infection, but the underlying mechanism has not been elucidated. Pyroptosis, a new form of inflammatory programmed cell death, has been verified to be involved in the pathogenesis of various viruses. circRNAs are a novel type of endogenous noncoding RNA gaining research interest in recent years, especially their special roles in the process of virus infection. Thus, in this study, we combined EV-A71, pyroptosis and circRNA to find a breakthrough in the pathogenesis of EV-A71 infection. Firstly, whether EV-A71 infection leaded to pyroptosis formation was examined by a series detection of cell death, cell viability, LDH release, caspase 1 activity, the expression levels of pyroptosis-related molecules and the concentrations of IL-1β and IL-18. Secondly, high-throughput sequencing of circRNAs was carried out to excavate the circRNA-miRNA-mRNA regulatory axis which might be associated with pyroptosis formation. Finally, the gain- and loss-of-functional experiments were further conducted to identify their functions. Our results showed that EV-A71 infection caused pyroptosis formation in SH-SY5Y cells. The circRNA sequencing analyzed the differentially expressed circRNAs and their possible functions. It was found that the hsa_circ_0045431/hsa_miR_584/NLRP3 regulatory axis might be involved in pyroptosis formation during EV-A71 infection. Then, hsa_circ_0045431 sponged hsa_miR_584 and hsa_miR_584 directly targeted NLRP3 were validated by IF, dual-luciferase, qRT-PCR and WB assays. Functional experiments were performed to further uncover that the up-regulation of hsa_circ_0045431 and NLRP3 promoted the inflammatory pyroptosis and viral replication, while the up-regulation of hsa_miR_584 suppressed the inflammatory pyroptosis and viral replication, and vice versa. Collectively, our study demystified that EV-A71 infection induced pyroptosis formation by activating hsa_circ_0045431/hsa_miR_584/NLRP3 regulatory axis, which could further effect viral replication. These findings provided novel insights into the pathogenesis of EV-A71 infection, and meanwhile revealed that the hsa_circ_0045431/ hsa_miR_584/NLRP3 regulatory axis can serve as a potential biological therapeutic target for EV-A71 infection.

VP2 residue N142 of coxsackievirus A10 is critical for the interaction with KREMEN1 receptor and neutralizing antibodies and the pathogenicity in mice

Coxsackievirus A10 (CVA10) has recently emerged as one of the major causative agents of hand, foot, and mouth disease. CVA10 may also cause a variety of complications. No approved vaccine or drug is currently available for CVA10. The residues of CVA10 critical for viral attachment, infectivity and in vivo pathogenicity have not been identified by experiment. Here, we report the identification of CVA10 residues important for binding to cellular receptor KREMEN1. We identified VP2 N142 as a key receptor-binding residue by screening of CVA10 mutants resistant to neutralization by soluble KREMEN1 protein. The receptor-binding residue N142 is exposed on the canyon rim but highly conserved in all naturally occurring CVA10 strains, which provides a counterexample to the canyon hypothesis. Residue N142 when mutated drastically reduced receptor-binding activity, resulting in decreased viral attachment and infection in cell culture. More importantly, residue N142 when mutated reduced viral replication in limb muscle and spinal cord of infected mice, leading to lower mortality and less severe clinical symptoms. Additionally, residue N142 when mutated could decrease viral binding affinity to anti-CVA10 polyclonal antibodies and a neutralizing monoclonal antibody and render CVA10 resistant to neutralization by the anti-CVA10 antibodies. Overall, our study highlights the essential role of VP2 residue N142 of CVA10 in the interactions with KREMEN1 receptor and neutralizing antibodies and viral virulence in mice, facilitating the understanding of the molecular mechanisms of CVA10 infection and immunity. Our study also provides important information for rational development of antibody-based treatment and vaccines against CVA10 infection.

Research progress on pathogenic and therapeutic mechanisms of Enterovirus A71

In recent years, enterovirus A71 (EV-A71) infection has become a major global public health problem, especially for infants and young children. The results of epidemiological research show that EV-A71 infection can cause acute hand, foot, and mouth disease (HFMD) and complications of the nervous system in severe cases, including aseptic pediatric meningoencephalitis, acute flaccid paralysis, and even death. Many studies have demonstrated that EV-A71 infection may trigger a variety of intercellular and intracellular signaling pathways, which are interconnected to form a network that leads to the innate immune response, immune escape, inflammation, and apoptosis in the host. This article aims to provide an overview of the possible mechanisms underlying infection, signaling pathway activation, the immune response, immune evasion, apoptosis, and the inflammatory response caused by EV-A71 infection and an overview of potential therapeutic strategies against EV-A71 infection to better understand the pathogenesis of EV-A71 and to aid in the development of antiviral drugs and vaccines.

Potential of a bivalent vaccine for broad protection against enterovirus 71 and coxsackie virus 16 infections causing hand, foot, and mouth disease

Hand, foot, and mouth disease (HFMD) is a highly contagious viral infection that is mainly caused by enterovirus 71 (EV71) and coxsackievirus 16 (CVA16). As there are no specific therapeutics for HFMD, the development of a bivalent vaccine is required to cover a broad range of infections. In this study, the effectiveness of novel monovalent and bivalent vaccines targeting EV71 C4a and CVA16 was investigated for their ability to prevent viral infections in neonatal human scavenger receptor class B member 2 (hSCARB2) transgenic mice. As hSCARB2 serves as a key viral receptor for EV71, these transgenic mice are susceptible to EV71 strains and facilitate viral binding, internalization, and uncoating processes. Antisera prepared by vaccine immunization were transferred to 2-day-old hSCARB2 transgenic mice, which were then infected with EV71 C4a or CVA16 virus. The antisera generated by each monovalent or bivalent vaccine effectively protected against EV71 C4a and CVA16 infections. The examination of tissue damage and viral contents in various organs indicated that both monovalent and bivalent antisera reduced EV71 C4a viral load in the brainstem, and no significant tissue damage was observed. During CVA16 infection, the monovalent and bivalent antisera significantly reduced viral contents in both the brainstem and muscles. These results suggest that passive immunity by monovalent and bivalent antisera can effectively protect against EV71 C4a and CVA16 infections. Thus, the development of a bivalent vaccine that can provide broad protection against both CV and EV infections may be a promising strategy in preventing HFMD.

The effects of SCARB2 and SELPLG gene polymorphisms on EV71 infection in hand, foot and mouth disease

The same viral infection in different hosts may result in varying levels of clinical symptoms, which is related to the genetic background of the host itself. A total of 406 common cases and 452 severe cases of enterovirus 71 (EV71) infection in Yunnan Province were selected as the research subjects, and SNaPshot technology was used to detect genetic polymorphisms for 25 Tag single-nucleotide polymorphisms (TagSNPs) in the selectin P ligand (SELPLG) and scavenger receptor class B member 2 (SCARB2) genes. Our results demonstrate that SCARB2 polymorphisms (rs74719289, rs3733255 and rs17001551) are related to the severity of EV71 infection (A vs G: OR 0.330; 95% CI 0.115 - 0.947; T vs C: OR 0.336; 95% CI 0.118 - 0.958; and A vs G: OR 0.378; 95% CI 0.145 - 0.984). The SELPLG polymorphisms were not significantly different between common cases and severe cases. Therefore, we conclude that the SCARB2 gene has a protective effect on the course of hand, foot and mouth disease caused by EV71 infection and that SCARB2 gene mutations can reduce the severity of the disease.

Molecular epidemiology and clinical characteristics of enteroviruses associated HFMD in Chengdu, China, 2013-2022

OBJECTIVES

This study aims to investigate molecular epidemiology and clinical characteristics of enterovirus associated hand-foot-mouth disease (HFMD) in Chengdu, China, 2013-2022. Monitoring the molecular epidemiology and clinical features of HFMD for up to 10 years may provide some ideas for future protection and control measures.

METHODS

We conducted a retrospective analysis of the medical records of all patients with laboratory-confirmed HFMD-related enterovirus infection at the West China Second University Hospital from January 2013 to December 2022. We described the characteristics in serotype, age, sex distribution and hospitalization of enterovirus infection cases using data analysis and graphic description.

RESULTS

A total of 29,861 laboratory-confirmed cases of HFMD-related enterovirus infection were reported from 2013 to 2022. There was a significant reduction in the number and proportion of EV-A71 cases after 2016, from 1713 cases (13.60%) in 2013-2015 to 150 cases (1.83%) in 2017-2019. During the COVID-19 pandemic, EV-A71 cases even disappeared. The proportion of CV-A16 cases decreased from 13.96% in 2013-2015 to 10.84% in 2017-2019 and then to 4.54% in 2020-2022. Other (non-EV-A71 and non-CV-A16) serotypes accounted for 95.45% during 2020-2022, with CV-A6 accounting for 50.39% and CV-A10 accounting for 10.81%. Thus, CV-A6 and CV-A10 became the main prevalent serotypes. Furthermore, There was no significant difference in the enterovirus prevalence rate between males and females. The hospitalization rate of EV-A71 patients was higher that of other serotypes. In general, the proportion of HFMD hospitalizations caused by other pathogens except for EV-A71, CV-A16, CV-A10 and CV-A16 was second only to that caused by EV-A71. The proportion of children over 4 years old infected with enterovirus increased.

CONCLUSION

The incidence of HFMD associated with enterovirus infection has decreased significantly and CV-A6 has been the main pathogen of HFMD in Chengdu area in recent years. The potential for additional hospitalizations for other untested enterovirus serotypes suggested that attention should also be paid to the harms of infections with unknown enterovirus serotypes. Children with HFMD were older. The development of new diagnostic reagents and vaccines may play an important role in the prevention and control of enterovirus infection.

miR-342-5p targets CTNNBIP1 to promote enterovirus 71 replication

OBJECTIVE

The aim of this research was to explore the role of miR-342-5p in EV71 replication.

METHODS

Peritoneal injection of EV71 (107 TCID50/mL) at 50, 100, and 150 μL was conducted to infect 12-day-old suckling mice (n = 10 per group), and clinical scores and survival rates were recorded during a 6-day trial duration and followed by transcriptome sequencing of collected spinal cord tissues. The differential miRNAs and target genes of the infected and uninfected EV71 mice were analyzed. The miR-342 and CTNNBIP1 binding sites were detected using a dual luciferase reporter assay. Cell viability was detected by CCK-8. RT-qPCR, Western blot, immunofluorescence, and immunohistochemistry assays were conducted to detect VP1 protein levels.

RESULTS

Transcriptome sequencing analyses know that the Wnt pathway played a role in EV71 infection, and the CTNNBIP1 gene in this pathway was the target gene of miR-342-5p. Whether in HMC3 cells or in the spinal cord tissue from the suckling mice, high levels of miR-342-5p markedly promoted EV71 VP1 mRNA and protein expression, elevated TNF-α, IL-6, and IL-10 levels, and inhibited IFN-β levels. In addition, highly expressed miR-342-5p destroyed neuronal structure in spinal cord tissues and reduced the number of glial cells. Highly expressed CTNNBIP1 blocked the promotion of miR-342-5p in EV71 replication, and inhibited TNF-α, IL-6, and IL-10 levels, whereas elevated IFN-β levels. This mechanism is that miR-342-5p can target the CTNNBIP1 3' UTR region, inhibit its expression and reduce its binding to CTNNB1, thus enhancing the interaction between CTNNB1 and TCF4 and activating the Wnt pathway-mediated type I interferon response.

CONCLUSION

In nerve cells and tissues, the overexpression of miR-342-5p promoted the replication of EV71 and attenuated the innate immune response to antiviral disease via Wnt/CTNNB1 signaling pathway.

SHFL inhibits enterovirus A71 infection by triggering degradation of viral 3Dpol protein via the ubiquitin-proteasome pathway

Enterovirus A71 (EV-A71) is a highly contagious virus that poses a major threat to global health, representing the primary etiological agent for hand-foot and mouth disease (HFMD) and neurological complications. It has been established that interferon signaling is critical to establishing a robust antiviral state in host cells, mainly mediated through the antiviral effects of numerous interferon-stimulated genes (ISGs). The host restriction factor SHFL is a novel ISG with broad antiviral activity against various viruses through diverse underlying molecular mechanisms. Although SHFL is widely acknowledged for its broad-spectrum antiviral activity, it remains elusive whether SHFL inhibits EV-A71. In this work, we validated that EV-A71 triggers the upregulation of SHFL both in cell lines and in a mouse model. Knockdown and overexpression of SHFL in EVA71-infected cells suggested that this factor could markedly suppress EV-A71 replication. Our findings further revealed an intriguing mechanism of SHFL that it could interact with the nonstructural proteins 3Dpol of EV-A71 and promoted the degradation of 3Dpol through the ubiquitin-proteasome pathway. Furthermore, the zinc-finger domain and the 36 amino acids (164-199) of SHFL were crucial to the interaction between SHFL and EV-A71 3Dpol . Overall, these findings broadened our understanding of the pivotal roles of SHFL in the interaction between the host and EV-A71.

MicroRNA expression profile of human umbilical vein endothelial cells in response to coxsackievirus A10 infection reveals a potential role of miR-143-3p in maintaining the integrity of the blood-brain barrier

Coxsackievirus A10 (CV-A10) has been one of the main etiologies of hand, foot, and mouth disease (HFMD) epidemics in recent years and can cause mild to severe illness and even death. Most of these severe and fatal cases were closely associated with neurological impairments, but the potential mechanism of neuropathological injury triggered by CV-A10 infection has not been elucidated. MicroRNAs (miRNAs), implicated in the regulation of gene expression in a post-transcriptional manner, play a vital role in the pathogenesis of various central nervous system (CNS) diseases; therefore, they serve as diagnostic biomarkers and are emerging as novel therapeutic targets for CNS injuries. To gain insights into the CV-A10-induced regulation of host miRNA-processing machinery, we employed high-throughput sequencing to identify differentially expressed miRNAs in CV-A10-infected human umbilical vein endothelial cells (HUVECs) and further analyzed the potential functions of these miRNAs during CV-A10 infection. The results showed that CV-A10 infection could induce 189 and 302 significantly differentially expressed miRNAs in HUVECs at 24 and 72 hpi, respectively, compared with the uninfected control. Moreover, the expression of four selected miRNAs and their relevant mRNAs was determined to verify the sequencing data by quantitative reverse transcription-polymerase chain reaction (RT-qPCR) methods. After that, gene target prediction and functional annotation revealed that the targets of these dysregulated miRNAs were mostly enriched in cell proliferation, signal transduction, cAMP signalling pathway, cellular response to interleukin-6, ventral spinal cord interneuron differentiation, negative regulation of glial cell differentiation, neuron migration, positive regulation of neuron projection development, etc., which were primarily involved in the processes of basic physiology, host immunity, and neurological impairments and further reflected vital regulatory roles of miRNA in viral pathogenicity. Finally, the construction of a miRNA-regulated network also suggested that the complex regulatory mechanisms mediated by miRNAs might be involved in viral pathogenesis and virus-host interactions during CV-A10 infection. Furthermore, among these dysregulated miRNAs, miR-143-3p was demonstrated to be involved in the maintenance of blood-brain barrier (BBB) integrity.

Enterovirus 71 enters human brain microvascular endothelial cells through an ARF6-mediated endocytic pathway

Infection of the central nervous system caused by enterovirus 71 (EV71) remains the main cause of death in hand-foot-and-mouth disease. However, the mechanism responsible for how EV71 breaks through the blood-brain barrier to infect brain cells has yet to be elucidated. By performing a high-throughput small interfering RNA (siRNA) screening and validation, we found that the infection of human brain microvascular endothelial cells (HBMECs) by EV71 was independent of the endocytosis pathways mediated by caveolin, clathrin, and macropinocytosis but dependent on ADP-ribosylation factor 6 (ARF6), a small guanosinetriphosphate (GTP)-binding protein of the Ras superfamily. The specific siRNA targeting ARF6 markedly inhibited HBMECs susceptibility to EV71. EV71 infectivity was inhibited by NAV-2729, a specific inhibitor of ARF6, in a dose-dependent manner. The subcellular analysis demonstrated the co-localization of the endocytosed EV71 and ARF6, while knockdown of ARF6 with siRNA remarkably influenced EV71 endocytosis. By immunoprecipitation assays, we found a direct interaction of ARF6 with EV71 viral protein. Furthermore, ARF1, another small GTP-binding protein, was also found to participate in ARF6-mediated EV71 endocytosis. Murine experiments demonstrated that NAV-2729 significantly alleviated mortality caused by EV71 infection. Our study revealed a new pathway by which EV71 enters the HBMECs and provides new targets for drug development.

Variant enterovirus A71 found in immune-suppressed patient binds to heparan sulfate and exhibits neurotropism in B-cell-depleted mice

Enterovirus A71 (EV-A71) causes hand, foot, and mouth disease outbreaks with neurological complications and deaths. We previously isolated an EV-A71 variant in the stool, cerebrospinal fluid, and blood of an immunocompromised patient who had a leucine-to-arginine substitution on the VP1 capsid protein, resulting in increased heparin sulfate binding. We show here that this mutation increases the virus's pathogenicity in orally infected mice with depleted B cells, which mimics the patient's immune status, and increases susceptibility to neutralizing antibodies. However, a double mutant with even greater heparin sulfate affinity is not pathogenic, suggesting that increased heparin sulfate affinity may trap virions in peripheral tissues and reduce neurovirulence. This research sheds light on the increased pathogenicity of variant with heparin sulfate (HS)-binding ability in individuals with decreased B cell immunity.

Identification of specific and shared epitopes at the extreme N-terminal VP1 of Coxsackievirus A4, A2 and A5 by monoclonal antibodies

Hand, foot and mouth disease (HFMD) is caused by a variety of serotypes in species A of the Enterovirus genus, including recently re-emerged Coxsackievirus A2 (CV-A2), CV-A4 and CV-A5. For development of diagnostic reagents, for surveillance, and the development of multivalent vaccines against HFMD, the antigenicity of HFMD-associated enteroviruses warrants investigation. The purified virions of CV-A4 were inoculated into Balb/c mice and hybridomas were obtained secreting monoclonal antibodies (mAbs) directed against CV-A4 and cross-reacting with other closely related species A enteroviruses. The mAbs were characterized by ELISA, Western blotting and in vitro neutralizing assays. The majority of mAbs was non-neutralizing, with only 2% of the mAbs neutralizing CV-A4 specifically. Most of mAbs bound to linear VP1 epitopes of CV-A4. Interestingly, four types of mAbs were obtained which bound specifically to CV-A4 or were broadly to CV-A4/-A2, CV-A4/-A5 and CV-A4/-A2/-A5, respectively. Mapping with overlapping or single-amino-acid mutant peptides revealed that the four types of mAbs all bound to the first 15 amino acids at the N-terminus of the VP1. This region of picornaviruses is functionally important as it is involved in uncoating and releasing of viral RNA into the cytosol. The binding footprints of four type mAbs are composed of conserved and variable residues and are different from each other. The newly discovered broadly cross-reactive mAbs reflect the high homology of CV-A4/ CV-A2/CV-A5. The results also demonstrate that it is possible and beneficial to develop the diagnostic reagents to detect rapidly the main pathogens of enteroviruses associated with HFMD cause by CV-A4/CV-A2/CV-A5.

Evolutionary and Genetic Recombination Analyses of Coxsackievirus A6 Variants Associated with Hand, Foot, and Mouth Disease Outbreaks in Thailand between 2019 and 2022

Coxsackievirus (CV)-A6 infections cause hand, foot, and mouth disease (HFMD) in children and adults. Despite the serious public health threat presented by CV-A6 infections, our understanding of the mechanisms by which new CV-A6 strains emerge remains limited. This study investigated the molecular epidemiological trends, evolutionary dynamics, and recombination characteristics of CV-A6-associated HFMD in Thailand between 2019 and 2022. In the HFMD patient samples collected during the 4-year study period, we identified enterovirus (EV) RNA in 368 samples (48.7%), of which CV-A6 (23.7%) was the predominant genotype, followed by CV-A4 (6%), EV-A71 (3.7%), and CV-A16 (3.4%). According to the partial viral protein (VP) 1 sequences, all these CV-A6 strains belonged to the D3 clade. Based on the viral-RNA-dependent RNA polymerase (RdRp) gene, four recombinant forms (RFs), RF-A (147, 84.5%), RF-N (11, 6.3%), RF-H (1, 0.6%), and newly RF-Y (15, 8.6%), were identified throughout the study period. Results from the similarity plot and bootscan analyses revealed that the 3D polymerase (3Dpol) region of the D3/RF-Y subclade consists of sequences highly similar to CV-A10. We envisage that the epidemiological and evolutionarily insights presented in this manuscript will contribute to the development of vaccines to prevent the spread of CV-A6 infection.

Genetic and Cross Neutralization Analyses of Coxsackievirus A16 Circulating in Taiwan from 1998 to 2021 Suggest Dominant Genotype B1 can Serve as Vaccine Candidate

Coxsackievirus A16 (CVA16) is well known for causing hand-foot-and-mouth disease (HFMD) and outbreaks were frequently reported in Taiwan in the past twenty years. The epidemiology and genetic variations of CVA16 in Taiwan from 1998 to 2021 were analyzed in this study. CVA16 infections usually occurred in early summer and early winter, and showed increased incidence in 1998, 2000-2003, 2005, 2007-2008, and 2010 in Taiwan. Little or no CVA16 was detected from 2017 to 2021. CVA16 infection was prevalent in patients between 1 to 3 years old. A total of 69 isolates were sequenced. Phylogenetic analysis based on the VP1 region showed that CVA16 subgenotype B1 was dominantly isolated in Taiwan from 1998 to 2019, and B2 was identified only from isolates collected in 1999 and 2000. There was a high frequency of synonymous mutations in the amino acid sequences of the VP1 region among CVA16 isolates, with the exception of position 145 which showed positive selection. The recombination analysis of the whole genome of CVA16 isolates indicated that the 5'-untranslated region and the non-structural protein region of CVA16 subgenotype B1 were recombined with Coxsackievirus A4 (CVA4) and enterovirus A71 (EVA71) genotype A, respectively. The recombination pattern of subgenotype B2 was similar to B1, however, the 3D region was similar to EVA71 genotype B. Cross-neutralization among CVA16 showed that mouse antisera from various subgenotypes viruses can cross-neutralize different genotype with high neutralizing antibody titers. These results suggest that the dominant CVA16 genotype B1 can serve as a vaccine candidate for CVA16.

Enterovirus 71 VP1 promotes 5-HT release by upregulating the expression of ERICH3 and methyltransferase ZC3H13: VP1 promotes 5-HT release by ERICH3 and ZC3H13 upregulation

BACKGROUND AND AIM

The effect of structural viral protein 1 (VP1) on neurological damage caused by enterovirus 71 (EV71) infection is unclear. This study aimed to explore the transcriptome changes in EV infected patients and the role of VP1 on the cell secretion pathway of neuron cells.

METHODS

In our cohort, EV infected patients were enrolled, and RNA-seq analysis was used to evaluate the distinct transcript patterns of cerebrospinal fluid (CSF). The EV71 VP1-overexpressing vector (pEGFP-c3-VP1) was generated and transfected into neuron cells. The relationship between Glutamate Rich 3 (ERICH3) and methyltransferase Zinc Finger CCCH-Type Containing 13 (ZC3H13) and their effect on the serotonin (5-HT) release of neuron cells were explored using small interfering RNA. The expression of ERICH3 and ZC3H13 and concentration of 5-HT were determined using real-time PCR, Western blot, and ELISA, respectively.

RESULT

The expression of ERICH3 and ZC3H13 were significantly upregulated in EV infected patients with neurological symptoms compared to those without (P<0.05). The ERICH3 gene had many N6-methyladenosine (m6A) binding sites that can be regulated by m6A modification. Further, the expression of ERICH3 and ZC3H13 were elevated significantly in EV71-VP1 overexpressing neuron cells (P<0.05). Moreover, ERICH3 or ZC3H13 deficiency could significantly downregulate the release of 5-HT in VP1-overexpressing cells (P<0.05). Nonetheless, ERICH3 expression was significantly suppressed when ZC3H13 was silenced in neuron cells and vice versa (P<0.05).

CONCLUSIONS

EV71-VP1 can promote 5-HT release by upregulating the expression of ERICH3 and ZC3H13. 5-HT might be a novel therapeutic target for EV71 infection-induced fatal neuronal damage.

EV71 3C protease cleaves host anti-viral factor OAS3 and enhances virus replication

The global spread of enteroviruses (EVs) has become more frequent, severe and life-threatening. Intereron (IFN) I has been proved to control EVs by regulating IFN-stimulated genes (ISG) expression. 2'-5'-oligoadenylate synthetases 3 (OAS3) is an important ISG in the OAS/RNase L antiviral system. The relationship between OAS3 and EVs is still unclear. Here, we reveal that OAS3, superior to OAS1 and OAS2, significantly inhibited EV71 replication in vitro. However, EV71 utilized autologous 3C protease (3Cpro) to cleave intracellular OAS3 and enhance viral replication. Rupintrivir, a human rhinovirus 3C protease inhibitor, completely abolished the cleavage of EV71 3Cpro on OAS3. And the proteolytically deficient mutants H40G, E71A, and C147G of EV71 3Cpro also lost the ability of OAS3 cleavage. Mechanistically, the Q982-G983 motif in C-terminal of OAS3 was identified as a crucial 3Cpro cutting site. Further investigation indicated that OAS3 inhibited not only EV71 but also Coxsackievirus B3 (CVB3), Coxsackievirus A16 (CA16), Enterovirus D68 (EVD68), and Coxsackievirus A6 (CA6) subtypes. Notably, unlike other four subtypes, CA16 3Cpro could not cleave OAS3. Two key amino acids variation Ile36 and Val86 in CA16 3Cpro might result in weak and delayed virus replication of CA16 because of failure of OAS and 3AB cleavage. Our works elucidate the broad anti-EVs function of OAS3, and illuminate a novel mechanism by which EV71 use 3Cpro to escape the antiviral effect of OAS3. These findings can be an important entry point for developing novel therapeutic strategies for multiple EVs infection.

[Investigation of Virulence Variation of Enterovirus 71 Strains during Thermal Adaptive Evolution]

Objective

To study the virulence variation of enterovirus 71 (EV71) during thermal adaptive evolution, providing references for the prevention and control of the EV71-related hand, foot and mouth disease.

Methods

Parental strains and thermal-adapted strains originating from EV71 sibling strains (lineage #100 and #101) were used for plaque assay validation, CCK-8 cytotoxicity experiment, and host proteomics studies after Vero cell infection. Plaque morphology and cell inhibition rate of the viral strains were obtained. Mass spectrometry was used to examine and analyze the functions of proteins that were differential expressed in the host cells.

Results

Plaque morphology variation was found only in the heat-adapted strain of lineage #101. Increase in cell inhibition rate was observed in all the thermal-adapted strains, but the amount of increase varied in different strains. According to the results of clustering analysis and principal component analysis, after infection of Vero cells, the host cell protein profile of the heat-adapted strains was similar to that of the parental strains and the host cell protein profile of cold-adapted strains was similar to that of cell-adapted strains. It showed that 500 kinds of proteins presented inter-group difference in their expression, with 239 kinds being up-regulated proteins and 261 being down-regulated. The function of the up-regulated proteins were related to post-translational protein modification, while the functions of the down-regulated proteins were related to SRP-dependent cotranslational protein translocation/targeting to membrane and retrograde protein transport.

Conclusion

Virulence variations of enterovirus 71 may accompany thermal adaptive evolution, but its mechanism of action still awaits further investigation.

Role of Non-Coding RNA in Neurological Complications Associated With Enterovirus 71

Enterovirus 71 (EV71) is the main pathogenic virus that causes hand, foot, and mouth disease (HFMD). Studies have reported that EV71-induced infections including aseptic meningitis, acute flaccid paralysis, and even neurogenic pulmonary edema, can progress to severe neurological complications in infants, young children, and the immunosuppressed population. However, the mechanisms through which EV71 causes neurological diseases have not been fully explored. Non-coding RNAs (ncRNAs), are RNAs that do not code for proteins, play a key role in biological processes and disease development associated with EV71. In this review, we summarized recent advances concerning the impacts of ncRNAs on neurological diseases caused by interaction between EV71 and host, revealing the potential role of ncRNAs in pathogenesis, diagnosis and treatment of EV71-induced neurological complications.

Type I Interferon-Induced TMEM106A Blocks Attachment of EV-A71 Virus by Interacting With the Membrane Protein SCARB2

Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CV-A16) are the main causative agents of hand, foot and mouth disease (HFMD) worldwide. Studies showed that EV-A71 and CV-A16 antagonize the interferon (IFN) signaling pathway; however, how IFN controls this viral infection is largely unknown. Here, we identified an IFN-stimulated gene, Transmembrane Protein 106A (TMEM106A), encoding a protein that blocks EV-A71 and CV-A16 infection. Combined approaches measuring viral infection, gene expression, and protein interactions uncovered that TMEM106A is required for optimal IFN-mediated viral inhibition and interferes with EV-A71 binding to host cells on the receptor scavenger receptor class B member 2 (SCARB2). Our findings reveal a new mechanism contributing to the IFN-mediated defense against EV-A71 and CV-A16 infection and provide a potential strategy for HFMD treatment by using the antiviral role of TMEM106A against enterovirus.

Life-Threatening Enterovirus 71 Encephalitis in Unrelated Children with Autosomal Dominant TLR3 Deficiency

PURPOSE

Enterovirus A71 (EV71) causes a broad spectrum of childhood diseases, ranging from asymptomatic infection or self-limited hand-foot-and-mouth disease (HFMD) to life-threatening encephalitis. The molecular mechanisms underlying these different clinical presentations remain unknown. We hypothesized that EV71 encephalitis in children might reflect an intrinsic host single-gene defect of antiviral immunity. We searched for mutations in the toll-like receptor 3 (TLR3) gene. Such mutations have already been identified in children with herpes simplex virus encephalitis (HSE).

METHODS

We sequenced TLR3 and assessed the impact of the mutations identified. We tested dermal fibroblasts from a patient with EV71 encephalitis and a TLR3 mutation and other patients with known genetic defects of TLR3 or related genes, assessing the response of these cells to TLR3 agonist poly(I:C) stimulation and EV71 infection.

RESULTS

Three children with EV71 encephalitis were heterozygous for rare mutations-TLR3 W769X, E211K, and R867Q-all of which were shown to affect TLR3 function. Furthermore, fibroblasts from the patient heterozygous for the W769X mutation displayed an impaired, but not abolished, response to poly(I:C). We found that TLR3-deficient and TLR3-heterozygous W769X fibroblasts were highly susceptible to EV71 infection.

CONCLUSIONS

Autosomal dominant TLR3 deficiency may underlie severe EV71 infection with encephalitis. Human TLR3 immunity is essential to protect the central nervous system against HSV-1 and EV71. Children with severe EV71 infections, such as encephalitis in particular, should be tested for inborn errors of TLR3 immunity.

Enterovirus A71 Induces Neurological Diseases and Dynamic Variants in Oral Infection of Human SCARB2-Transgenic Weaned Mice

Enterovirus A71 (EV-A71) and many members of the Picornaviridae family are neurotropic pathogens of global concern. These viruses are primarily transmitted through the fecal-oral route, and thus suitable animal models of oral infection are needed to investigate viral pathogenesis. An animal model of oral infection was developed using transgenic mice expressing human SCARB2 (hSCARB2 Tg), murine-adapted EV-A71/MP4 virus, and EV-A71/MP4 virus with an engineered nanoluciferase gene that allows imaging of viral replication and spread in infected mice. Next-generation sequencing of EV-A71 genomes in the tissues and organs of infected mice was also performed. Oral inoculation of EV-A71/MP4 or nanoluciferase-carrying MP4 virus stably induced neurological symptoms and death in infected 21-day-old weaned mice. In vivo bioluminescence imaging of infected mice and tissue immunostaining of viral antigens indicated that orally inoculated virus can spread to the central nervous system (CNS) and other tissues. Next-generating sequencing further identified diverse mutations in viral genomes that can potentially contribute to viral pathogenesis. This study presents an EV-A71 oral infection murine model that efficiently infects weaned mice and allows tracking of viral spread, features that can facilitate research into viral pathogenesis and neuroinvasion via the natural route of infection. IMPORTANCE Enterovirus A71 (EV-A71), a positive-strand RNA virus of the Picornaviridae, poses a persistent global public health problem. EV-A71 is primarily transmitted through the fecal-oral route, and thus suitable animal models of oral infection are needed to investigate viral pathogenesis. We present an animal model of EV-A71 infection that enables the natural route of oral infection in weaned and nonimmunocompromised 21-day-old hSCARB2 transgenic mice. Our results demonstrate that severe disease and death could be stably induced, and viral invasion of the CNS could be replicated in this model, similar to severe real-world EV-A71 infections. We also developed a nanoluciferase-containing EV-A71 virus that can be used with this animal model to track viral spread after oral infection in real time. Such a model offers several advantages over existing animal models and can facilitate future research into viral spread, tissue tropism, and viral pathogenesis, all pressing issues that remain unaddressed for EV-A71 infections.

[Genetic characterization analysis of the whole genome sequence of Coxsackievirus A8 associated with hand, foot and mouth disease in China]

Objective: To study the genomic sequence of Coxsackievirus A8 (CV-A8) associated with hand, foot and mouth disease (HFMD) from 2013 to 2018 in China and to analyze the genetic evolution of each coding region of the full-length genome. Methods: The genome sequences of 11 CV-A8 strains isolated from patients with HFMD in different regions of China from 2013 to 2018 were determined. Sequence alignment and genetic evolution analysis were performed by Sequencher 5.0 and MEGA 7.0 software, etc. Results: Sequence alignment showed that the genome length of 11 CV-A8 strains ranged from 7 393 bp to 7 400 bp. There was no base insertion or deletion in the coding region compared with the prototype strain, but there were individual base insertion or deletion in the non-coding region. The nucleotide and amino acid similarities in the VP1 region of 11 CV-A8 strains were 78.3%-98.6% and 92.6%-99.7%, respectively, and the nucleotide and amino acid sequences identities with the CV-A8 prototype strain were 78.3%-98.2% and 92.6%-99.7%, respectively. Based on the phylogenetic analysis of VP1 region sequences, the CV-A8 can be divided into five genotypes: A, B, C, D and E. The 11 CV-A8 strains in this study belonged to genotypes C (1 strain), D (2 strains) and E (8 strains). The nucleotide and amino acid similarities of 11 CV-A8 full-length genomes were 81.3%-98.8% and 95.9%-99.5%, respectively. The phylogenetic tree of the P2 region showed that the eight E genotypes CV-A8 had the closest evolutionary distance with CV-A4, CV-A14, and CV-A16. The phylogenetic tree of the P3 region showed that the eight E genotypes CV-A8 had a close evolutionary distance with CV-A5, CV-A16, CV-A14 and CV-A4. Conclusions: The 11 CV-A8 stains in this study showed significant intra-genotype diversity in capsid region and recombinant diversity in non-capsid region which indicated that CV-A8 quasispecies were still undergoing dynamics variation. CV-A8 may become an important pathogen of HFMD and the monitoring of CV-A8 needs to be further strengthened.

Relationship between polymorphism of receptor SCARB2 gene and clinical severity of enterovirus-71 associated hand-foot-mouth disease

BACKGROUND

To investigate the relationship between polymorphism of scavenger receptor class B member 2 (SCARB2) gene and clinical severity of enterovirus (EV)-71 associated hand-foot-mouth disease (HFMD).

METHODS

Among the 100 recruited cases, 56 were in the severe HFMD group (case group) and 44 were in the general HFMD group (control group). By screening functional single nucleotide polymorphisms (SNPs) and hot SNPs, and performing SNP site optimization, some SNP sites of SCARB2 gene were selected for analysis. Genotyping was performed using a MassArray platform. PLINK software was used for statistical processing and analysis of the correlation differences between the mutant genotypes in the severe and general HFMD groups. The relationship between the SNPs and clinical severity of enterovirus (EV)-71 associated HFMD was assessed.

RESULTS

28 SNPs in SCARB2 were selected by site optimization. Then three loci were not in agreement with the minor allele frequency (MAF) in the 1000 Han Chinese in Beijing (CHB) dataset. Another three loci could not be detected. Nine loci were not suitable for further analysis (MAF < 0.01 and Hardy-Weinberg [HWE] P < 0.001). A total of 13 sites were subsequently analyzed. Through Fisher analysis, the frequency of the rs6812193 T allele was 0.134 and 0.034 in the severe and general HFMD groups, respectively (P 0.023 < 0.05, odds ratio [OR] 4.381 > 1). Logistic regression analysis of rs6812193 T alleles between the severe and general HFMD groups, respectively (P 0.023 < 0.05, OR 4.412 > 1, L95 1.210 > 1). Genotype logistic regression analysis of the rs6812193 alleles CT + TT versus CC gave an OR of 4.56 (95% confidence interval [95% CI] 1.22-17.04, P = 0.012).

CONCLUSION

The rs6812193 T allele was a susceptibility SNP for SHFMD, and the rs6812193 polymorphism might be significantly associated with the susceptibility to EV-71 infection.

Chimeric enterovirus 71 virus-like particle displaying conserved coxsackievirus A16 epitopes elicits potent immune responses and protects mice against lethal EV71 and CA16 infection

Hand-foot-and-mouth disease (HFMD) is an infectious disease of infants and young children frequently caused by the enterovirus A species, mainly enterovirus 71 (EV71) and coxsackievirus A16 (CA16). In this study, we prepared the EV71 virus-like particle (EV71-VLP) and its chimeras using recombinant baculovirus (Bac-P1-3CD) co-expressing EV71 P1 (under polyhedrin promoter) and 3CD (under CMV-IE promoter) proteins in Sf9 cells. EV71-VLP chimera ChiEV71(1E)-VLP or ChiEV71(4E)-VLP displayed single CA16 PEP71 epitope in VP1 or four conserved CA16 neutralizing epitopes (PEP71 in VP1, aa136-150 in VP2, aa176-190 in VP3 and aa48-62 in VP4) by substitution of the corresponding regions of EV71 structure proteins, respectively. In mice, EV71-VLP and its chimeras elicited similar EV71-specific IgG and neutralizing antibody (NAb) titers compared to inactivated EV71. Expectedly, vaccination of ChiEV71(1E)-VLP or ChiEV71(4E)-VLP resulted in significantly increased CA16-specific IgG and NAb production and improved cross-protection against CA16 infection compared to EV71-VLP. Interestingly, the VLPs induced potent cellular immune responses and significantly decreased Th2 type (IL-4 and IL-10) cytokines secretion in the splenocytes of immunized mice compared to inactivated EV71 or inactivated CA16. Neonatal mice born to dams immunized with the chimeric VLPs or neonatal mice passively transferred with sera of immunized mice were completely protected from lethal EV71 challenge and partially protected from lethal CA16 infection. Our study provides a novel bivalent or multivalent vaccine strategy to prevent EV71 and related-enterovirus infections.

The inhibition of enterovirus 71 induced apoptosis by Durvillaea antarctica through P53 and STAT1 signaling pathway

The infection of enterovirus 71 (EV71) resulted in hand, foot, and mouth disease and may lead to severe nervous system damage and even fatalities. There are no effective drugs to treat the EV71 virus and it is crucial to find novel drugs against it. Polysaccharide isolated from Durvillaea antarctica green algae has an antiviral effect. In this study, D. antarctica polysaccharide (DAPP) inhibited the infection of EV71 was demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), reverse transcription polymerase chain reaction, flow cytometry, and western blot. MTT assay showed that DAPP had no toxicity on Vero cells at the concentration 250 μg/ml. Furthermore, DAPP significantly reduced the RNA level of EV71 in a dose-dependent manner. Moreover, DAPP inhibited the Vero cells apoptosis induced by EV71 via the P53 signaling pathway. Meanwhile, the expression of signal transducer and activator of transcription 1 and mammalian target of rapamycin were increased and the proinflammatory cytokines were significantly inhibited by DAPP. Taken together, these results suggested that DAPP could be a potential pharmaceutical against the infection of EV71 virus.

Sporadic hand, foot, and mouth disease cases associated with non-C4 enterovirus 71 strains in Xiamen, China, from 2009 to 2018

Enterovirus 71 (EV71) has caused large hand, foot, and mouth disease (HFMD) epidemics among young children, and EV71 infection is the leading cause of severe HFMD cases and deaths. In mainland China, the prevalence and risk factors of non-C4 EV71 strains are still unclear. In this study, we monitored non-C4 strains over a 10-year HFMD epidemiological surveillance period in Xiamen. The 5’UTR and VP1 coding region of EV71 strains were amplified by RT-nested PCR and sequenced. Thirty-two non-C4 EV71 strains were identified during 2009-2018. This study provides important information about the prevalence of EV71 in China that will be applicable for development of vaccines and diagnostic reagents as well as establishment of policies for HFMD prevention and control.

Virus Shedding in Patients With Hand, Foot and Mouth Disease Induced by EV71, CA16 or CA6: Systematic Review and Meta-analysis

BACKGROUND

As the highly contagious hand, foot and mouth disease (HFMD) spreads rapidly among children, isolation is the most effective way to control its spread. However, studies on the duration of virus shedding of the HFMD-related enterovirus and a reasonable quarantine period for HFMD patients are inconsistent.

METHODS

We undertook a systematic review and meta-analysis evaluating the viral shedding of patients with HFMD caused by Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) and coxsackievirus A6.

RESULTS

A total of 17 observational studies evaluating 626 participants were included. In the first 5 weeks after onset, the pooled virus positive rate in specimens of EV71-related patients decreased from 0.79 (P < 0.001 for heterogeneity) to 0.38 (P < 0.001 for heterogeneity). The positive rate of CVA16 was reduced from 0.91 (P < 0.001 for heterogeneity) to 0.29 (P < 0.001 for heterogeneity). The positive rates of CVA16 and coxsackievirus A6 were approximately 50% in the third week after onset, while a 50% positive rate appeared in the fourth week in EV71 related cases.

CONCLUSIONS

We found the positive rates of virus shedding were still high among the patients released from quarantine, and the duration of viral shedding was inconsistent among HFMD patients caused by different serotypes. Our findings provide comprehensive evidence for a possible flexible quarantine period according to the serotype.

Pathogenesis Study of Enterovirus 71 Using a Novel Human SCARB2 Knock-In Mouse Model

Enterovirus 71 (EV71) can cause a severe hand-foot-mouth disease in children. However, the precise mechanism of EV71-associated disease, particularly the neuropathogenesis and pulmonary disorder, is still not fully understood because no suitable animal models are available. The human scavenger receptor class B, member 2 (hSCARB2), is a cellular receptor for EV71. Here, we generated a novel knock-in (KI) mouse model using the CRISPR/Cas9 system to insert the hSCARB2 gene into the mouse Rosa26 locus to study the pathogenesis of EV71. The hSCARB2 KI mice infected with clinical isolates of EV71 showed neurological symptoms, such as ataxia, paralysis, and death. Viral replication was detected in mainly astrocytes and a limited number of neurons and microglia, accompanied by gliosis. Vascular leakage and alveoli filled with erythrocytes were detected, suggesting that edema and hemorrhage, which are observed in human patients, also occurred in EV71-infected KI mice. In addition, proinflammatory cytokines and chemokines were significantly increased in the serum of infected KI mice. These pathological features of the KI mice after infection resembled those of EV71 encephalomyelitis in humans. Therefore, our KI mouse model is suitable to study the pathogenesis of EV71 and is of great significance for development of antiviral drugs and vaccines to treat or prevent EV71 infection.IMPORTANCE Enterovirus 71 (EV71) is associated with severe hand-foot-mouth disease. Recently, outbreaks of EV71 infection with high mortality have been reported in the Asia-Pacific region, posing a great challenge for global public health. To date, the precise mechanism of EV71-induced disease, particularly the neuropathogenesis and respiratory disorders, is still not fully understood because no suitable animal models are available. Human scavenger receptor class B, member 2 (hSCARB2), has been identified as a cellular receptor for EV71. Here, we introduce a novel CRISPR/Cas9-mediated hSCARB2 knock-in (KI) mouse model for the study of EV71 pathogenesis, which is of great significance for the development of antiviral drugs and vaccines.

[Etiological characteristics of hand, foot and mouth disease in Yangzhou from 2015 to 2019]

To understand the prevalence and etiological characteristics of hand, foot and mouth disease(HFMD) in Yangzhou, so as to provide scientific basis for prevention and control of HFMD. HFMD cases from six sentinel hospitals in Yangzhou from January 2015 to December 2019 were taken as the subject of study. The epidemiological data of HFMD were analyzed by descriptive epidemiology method, the enterovirus were detected using RT-PCR method and the etiological characteristics were analyzed. The data were collected by Excel 2007 and statistically analyzed by SPSS22.0 software. A total of 1 151 positive cases were detected from all 2 129 HFMD clinical specimens collected in Yangzhou from 2015 to 2019, with a total positive rate of 54.06%, including 148 cases of EV71(6.95%), 382 cases of CA16(17.94%) and 621 cases of other enterovirus(29.17%). The difference of positive rate in different years(χ²=99.28, P<0.05), different months(χ²=92.09, P<0.05) and different districts(χ²=71.39, P<0.05)was statistically significant. Each subtype of enterovirus showed alternating prevalence in different years. The peak period of detection rate was from April to September (720 cases, 62.55%). The reported incidence for males was higher than females, with the male-female ratio of 1.58∶1 and children under six (971 cases, 84.36%) as the major attacked population. There were obvious seasonal, regional and population characteristics of HFMD in Yangzhou City from 2015 to 2019. It reminds us that surveillance of HFMD should be continually implemented, more attention should be paid to the prevention and control of key population in high-risk seasons, and the booming HFMD cases caused by other enterovirus should be emphasized especially.