Type I Interferons Triggered through the Toll-Like Receptor 3-TRIF Pathway Control Coxsackievirus A16 Infection in Young Mice

A mouse model and pathogenesis study for CVA19 first isolated from hand, foot, and mouth disease

ABSTRACTCoxsackievirus A19 (CVA19) is a member of Enterovirus (EV) C group in the Picornaviridae family. Recently, we reported a case of CVA19-infected hand, foot, and mouth disease (HFMD) for the first time. However, the current body of knowledge on the CVA19 infection, particularly the pathogenesis of encephalomyelitis and diarrhoea is still very limited, due to the lack of suitable animal models. Here, we successfully established a CVA19 mouse model via oral route based on 7-day-old ICR mice. Our results found the virus strain could directly infect the neurons, astrocytes of brain, and motor neurons of spinal cord causing neurological complications, such as acute flaccid paralysis. Importantly, viruses isolated from the spinal cords of infected mice caused severe illness in suckling mice, fulfilling Koch's postulates to some extent. CVA19 infection led to diarrhoea with typical pathological features of shortened intestinal villi, increased number of secretory cells and apoptotic intestinal cells, and inflammatory cell infiltration. Much higher concentrations of serum cytokines and more peripheral blood inflammatory cells in CVA19-infected mice indicated a systematic inflammatory response induced by CVA19 infection. Finally, we found ribavirin and CVA19 VP1 monoclonal antibody could not prevent the disease progression, but higher concentrations of antisera and interferon alpha 2 (IFN-α2) could provide protective effects against CVA19. In conclusion, this study shows that a natural mouse-adapted CVA19 strain leads to diarrhoea and encephalomyelitis in a mouse model via oral infection, which provides a useful tool for studying CVA19 pathogenesis and evaluating the efficacy of vaccines and antivirals.

Poly (I: C) inhibits reticuloendothelial virus replication in chicken macrophage-like cells through the activation of toll-like receptor-3 signaling

Reticuloendothelial virus (REV) is widely found in many domestic poultry areas and results in severe immunosuppression of infected chickens. This increases the susceptibility to other pathogens, which causes economic losses to the poultry industry. The aim of our study was to determine whether polyinosinic-polycytidylic acid [Poly (I: C)] treatment could inhibit REV replication in chicken macrophage-like cell line, HD11. We found that Poly (I: C) treatment could markedly inhibit REV replication in HD11 from 24 to 48 h post infection (hpi). Additionally, Poly (I: C) treatment could switch HD11 from an inactive type into M1-like polarization from 24 to 48 hpi. Furthermore, Poly (I: C) treatment promoted interferon-β secretion from HD11 post REV infection. Moreover, Toll-like receptor-3 (TLR-3) mRNA and protein levels in HD11 treated with Poly (I: C) were markedly increased compared to those of HD11 not treated with Poly (I: C). The above results suggested that Poly (I: C) treatment switches HD11 into M1-like polarization to secret more interferon-β and activate TLR-3 signaling, which contributes to block REV replication. Our findings provide a theoretical reference for further studying the underlying pathogenic mechanism of REV and Poly (I: C) as a potential therapeutic intervention against REV infection.

Clinically used JAK inhibitor blunts dsRNA-induced inflammation and calcification in aortic valve interstitial cells

Calcific aortic valve disease (CAVD) is the most prevalent valvulopathy worldwide. Growing evidence supports a role for viral and cell-derived double-stranded (ds)-RNA in cardiovascular pathophysiology. Poly(I:C), a dsRNA surrogate, has been shown to induce inflammation, type I interferon (IFN) responses, and osteogenesis through Toll-like receptor 3 in aortic valve interstitial cells (VIC). Here, we aimed to determine whether IFN signaling via Janus kinase (JAK)/Signal transducers and activators of transcription (STAT) mediates dsRNA-induced responses in primary human VIC. Western blot, ELISA, qPCR, calcification, flow cytometry, and enzymatic assays were performed to evaluate the mechanisms of dsRNA-induced inflammation and calcification. Poly(I:C) triggered a type I IFN response characterized by IFN-regulatory factors gene upregulation, IFN-β secretion, and STAT1 activation. Additionally, Poly(I:C) promoted VIC inflammation via NF-κB and subsequent adhesion molecule expression, and cytokine secretion. Pretreatment with ruxolitinib, a clinically used JAK inhibitor, abrogated these responses. Moreover, Poly(I:C) promoted a pro-osteogenic phenotype and increased VIC calcification to a higher extent in cells from males. Inhibition of JAK with ruxolitinib or a type I IFN receptor blocking antibody blunted Poly(I:C)-induced calcification. Mechanistically, Poly(I:C) promoted VIC apoptosis in calcification medium, which was inhibited by ruxolitinib. Moreover, Poly(I:C) co-operated with IFN-γ to increase VIC calcification by synergistically activating extracellular signal-regulated kinases and hypoxia-inducible factor-1α pathways. In conclusion, JAK/STAT signaling mediates dsRNA-triggered inflammation, apoptosis, and calcification and may contribute to a positive autocrine loop in human VIC in the presence of IFN-γ. Blockade of dsRNA responses with JAK inhibitors may be a promising therapeutic avenue for CAVD.

Enterovirus D68 Protease 2Apro Targets TRAF3 To Subvert Host Innate Immune Responses

Human enterovirus D68 (EV-D68) has received considerable attention recently as a global reemergent pathogen because it causes severe respiratory tract infections and acute flaccid myelitis (AFM). The nonstructural protein 2A protease (2A^pro) of EVs, which functions in the cleavage of host proteins, comprises a pivotal part of the viral immune evasion process. However, the pathogenic mechanism of EV-D68 is not fully understood. In this study, we found that EV-D68 inhibited antiviral type I interferon responses by cleaving tumor necrosis factor receptor-associated factor 3 (TRAF3), which is the key factor for type I interferon production. EV-D68 inhibited Sendai virus (SEV)-induced interferon regulatory factor 3 (IRF3) activation and beta interferon (IFN-β) expression in HeLa and HEK293T cells. Furthermore, we demonstrated that EV-D68 and 2A^pro were able to cleave the C-terminal region of TRAF3 in HeLa and HEK293T cells, respectively. A cysteine-to-alanine substitution at amino acid 107 (C107A) in the 2A^pro protease resulted in the loss of cleavage activity to TRAF3, and mutation of glycine at amino acid 462 to alanine (G462A) in TRAF3 conferred resistance to 2A^pro These results suggest that control of TRAF3 by 2A^pro may be a mechanism EV-D68 utilizes to subvert host innate immune responses.IMPORTANCE Human enterovirus 68 (EV-D68) has received considerable attention recently as a global reemergent pathogen because it causes severe respiratory tract infections and acute flaccid myelitis. The nonstructural protein 2A protease (2A^pro) of EV, which functions in cleavage of host proteins, comprises an essential part of the viral immune evasion process. However, the pathogenic mechanism of EV-D68 is not fully understood. Here, we show for the first time that EV-D68 inhibited antiviral type I interferon responses by cleaving tumor necrosis factor receptor-associated factor 3 (TRAF3). Furthermore, we identified the key cleavage site in TRAF3. Our study may suggest a new mechanism by which the 2A^pro of EV facilitates subversion of host innate immune responses. These findings increase our understanding of EV-D68 infection and may help identify new antiviral targets against EV-D68.

Molecular Pathogenicity of Enteroviruses Causing Neurological Disease

Enteroviruses are single-stranded positive-sense RNA viruses that primarily cause self-limiting gastrointestinal or respiratory illness. In some cases, these viruses can invade the central nervous system, causing life-threatening neurological diseases including encephalitis, meningitis and acute flaccid paralysis (AFP). As we near the global eradication of poliovirus, formerly the major cause of AFP, the number of AFP cases have not diminished implying a non-poliovirus etiology. As the number of enteroviruses linked with neurological disease is expanding, of which many had previously little clinical significance, these viruses are becoming increasingly important to public health. Our current understanding of these non-polio enteroviruses is limited, especially with regards to their neurovirulence. Elucidating the molecular pathogenesis of these viruses is paramount for the development of effective therapeutic strategies. This review summarizes the clinical diseases associated with neurotropic enteroviruses and discusses recent advances in the understanding of viral invasion of the central nervous system, cell tropism and molecular pathogenesis as it correlates with host responses.

Interplays between Enterovirus A71 and the innate immune system

Enterovirus A71 (EV-A71) is a growing threat to public health, particularly in the Asia-Pacific region. EV-A71 infection is most prevalent in infants and children and causes a wide spectrum of clinical complications, including hand-foot-and-mouth disease (HFMD), pulmonary and neurological disorders. The pathogenesis of EV-A71 infection is poorly understood at present. It is likely that viral factors and host immunity, and their interplay, affect the pathogenesis and outcome of EV-A71 infection. The mammalian innate immune system forms the first layer of defense against viral infections and triggers activation of adaptive immunity leading to full protection. In this review, we discuss recent advances in our understanding of the interaction between EV-A71 and the innate immune system. We discuss the role of pattern-recognition receptors (PRRs), including Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), and inflammasomes, in the detection of EV-A71 infection and induction of antiviral immunity. As a counteraction, EV-A71 viral proteins target multiple innate immune pathways to facilitate viral replication in host cells. These novel insights at the virus-host interphase may support the future development of vaccines and therapeutics against EV-A71 infection.

Association of polymorphisms in the vitamin D receptor gene with susceptibility to and severity of hand, foot, and mouth disease caused by coxsackievirus A16

Coxsackievirus A16 (CA16) remains the most common causative agent of hand, foot, and mouth disease (HFMD), and is related to high incidence and critical complications. Vitamin D receptor (VDR) activity might affect the outcome of CA16 infection. Our case-control research aims to evaluate the relationship between VDR polymorphisms in the gene encoding and susceptibility to and severity of HFMD due to CA16. Three single-nucleotide polymorphisms (SNPs) of VDR gene were selected according to functional prediction and linkage disequilibrium, and were examined utilizing the SNPscan method to identify possible associations with HFMD caused by CA16. A significant relationship was found in the HFMD cases of polymorphism rs11574129 (GA vs GG: odds ratio (OR) = 0.068, 95% confidence interval (CI) = 0.007-0.693, P = .023; GA + AA vs GG: OR = 0.322, 95%CI = 0.106-0.984, P = .047), and vitamin D levels in genotype AA were significantly higher than those in genotype GG (P < .05). These results suggest that VDR rs11574129 may influence genetic susceptibility to CA16-associated HFMD.

[Levels of lymphocyte subsets, immunoglobulins, and complement C3 and C4 in children with hand-foot-mouth disease]

OBJECTIVE

To study the clinical value of lymphocyte subsets, immunoglobulins, and complement C3 and C4 in the evaluation of immune status in children with hand-foot-mouth disease (HFMD).

METHODS

A total of 282 children with HFMD were enrolled as the HFMD group, and 130 healthy children were enrolled as the healthy control group. The percentages of peripheral CD3⁺, CD4⁺, and CD8⁺ T lymphocytes, CD19⁺ B lymphocytes, and CD56⁺ natural killer cells were measured. The CD4⁺/CD8⁺ ratio was calculated. The levels of immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin G (IgG), and complement C3 and C4 were measured.

RESULTS

The multivariate analysis showed that compared with the healthy control group, the HFMD group had significantly lower percentages of CD3⁺, CD4⁺, and CD8⁺ T lymphocytes and levels of complement C3 and C4 (P<0.05), as well as significantly higher percentage of CD56⁺ natural killer cells and level of IgG (P<0.05). The individual effect analysis showed that the children aged 0-3 years in the HFMD group had a significantly higher CD4⁺/CD8⁺ ratio than the healthy control group (P<0.05); boys aged 0-3 and ≥3 years in the HFMD group had a significantly higher level of IgM than the healthy control group (P<0.05); boys aged ≥3 years and girls aged 0-3 years in the HFMD group had a significantly lower level of IgA than the healthy control group (P<0.05).

CONCLUSIONS

Cellular and humoral immunity disorders are observed in children with HFMD. The monitoring of lymphocyte subsets and immunoglobulin levels can provide a laboratory basis for immune status assessment in children with HFMD.

ATP1B3 cooperates with BST-2 to promote hepatitis B virus restriction

Increasing evidence indicates ATP1B3, one of the regulatory subunits of Na⁺ /K⁺ -ATPase, is involved in numerous viral propagations, such as HIV and EV71. However, the function and mechanism of ATP1B3 on hepatitis B virus (HBV) propagation is unknown. Here, we demonstrated that ATP1B3 overexpression reduced the quantity of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) in supernatants of HBV expression plasmids cotransfected HepG2 cells. Correspondingly, small interfering RNA and short hairpin RNA mediated ATP1B3 silencing promoted HBsAg and HBeAg expression in the supernatants of HBV expression plasmids transfected HepG2 cells. Mechanically, we reported that ATP1B3 expression could activate nuclear factor-κB (NF-κB) pathway by inducing the expression, phosphorylation, and nuclear import of P65 for the first time. And NF-κB inhibitor (Bay11) impaired the restraint of ATP1B3 on HBV replication. This counteraction effect of Bay11 proved that ATP1B3-induced NF-κB activation was crucial for HBV restriction. Accordingly, we observed that anti-HBV factors interferon-α (IFN-α) and interleukin-6 (IL-6) production were increased in HepG2 cells after the NF-κB activation. It suggested that ATP1B3 suppressed HBsAg and HBeAg by NF-κB/IFN-α and NF-κB/IL-6 axis. Further experiments proved that ATP1B3 overexpression induced anti-HBV factor BST-2 expression by NF-κB/IFN-α axis in HepG2 cells but not HEK293T cells, and ATP1B3 silencing downregulated BST-2 messenger RNA level in HepG2 cells. As an HBV restriction factor, BST-2 cooperated with ATP1B3 to antagonize HBsAg but not HBeAg in HepG2 cells. Our work identified ATP1B3 as a novel candidate of HBV restrictor with unrevealed mechanism and we highlighted it might serve as a potential therapeutic molecule for HBV infection.

Ubiquitination of RIPK1 suppresses programmed cell death by regulating RIPK1 kinase activation during embryogenesis

The ubiquitination status of RIPK1 is considered to be critical for cell fate determination. However, the in vivo role for RIPK1 ubiquitination remains undefined. Here we show that mice expressing RIPK1^K376R which is defective in RIPK1 ubiquitination die during embryogenesis. This lethality is fully rescued by concomitant deletion of Fadd and Ripk3 or Mlkl. Mechanistically, cells expressing RIPK1^K376R are more susceptible to TNF-α induced apoptosis and necroptosis with more complex II formation and increased RIPK1 activation, which is consistent with the observation that Ripk1^K376R/K376R lethality is effectively prevented by treatment of RIPK1 kinase inhibitor and is rescued by deletion of Tnfr1. However, Tnfr1^−/−Ripk1^K376R/K376R mice display systemic inflammation and die within 2 weeks. Significantly, this lethal inflammation is rescued by deletion of Ripk3. Taken together, these findings reveal a critical role of Lys376-mediated ubiquitination of RIPK1 in suppressing RIPK1 kinase activity–dependent lethal pathways during embryogenesis and RIPK3-dependent inflammation postnatally.

RIPK1 integrates signals that drive both NF-κB activation and cell death pathways. Here Zhang et al. generate RIPK1 knock-in mice lacking a major ubiquitination site and demonstrate that this modification is important to suppress cell death during embryogenesis and inflammation postnatally.

Enteroviruses: A Gut-Wrenching Game of Entry, Detection, and Evasion

Enteroviruses are a major source of human disease, particularly in neonates and young children where infections can range from acute, self-limited febrile illness to meningitis, endocarditis, hepatitis, and acute flaccid myelitis. The enterovirus genus includes poliovirus, coxsackieviruses, echoviruses, enterovirus 71, and enterovirus D68. Enteroviruses primarily infect by the fecal-oral route and target the gastrointestinal epithelium early during their life cycles. In addition, spread via the respiratory tract is possible and some enteroviruses such as enterovirus D68 are preferentially spread via this route. Once internalized, enteroviruses are detected by intracellular proteins that recognize common viral features and trigger antiviral innate immune signaling. However, co-evolution of enteroviruses with humans has allowed them to develop strategies to evade detection or disrupt signaling. In this review, we will discuss how enteroviruses infect the gastrointestinal tract, the mechanisms by which cells detect enterovirus infections, and the strategies enteroviruses use to escape this detection.

Innate Immunity Evasion by Enteroviruses Linked to Epidemic Hand-Foot-Mouth Disease

Enterovirus (EV) infections are a major threat to global public health, and are responsible for mild respiratory illness, hand, foot, and mouth disease (HFMD), acute hemorrhagic conjunctivitis, aseptic meningitis, myocarditis, severe neonatal sepsis-like disease, and acute flaccid paralysis epidemic. Among them, HFMD is a common pediatric infectious disease caused by EVs of the family Picornaviridae including EV-A71, coxsackieviruses (CV)-A2, CV-A6, CV-A10, and CV-A16. Due to lack of vaccines and specific antiviral therapeutics, millions of children still suffer from HFMD. Innate immune system detects foreign invaders by means of a relatively limited number of sensors, such as pattern recognition receptors (PRRs) [e.g., retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), Toll-like receptors (TLRs), and NOD-like receptors (NLRs)] and even some secreted functional proteins. However, a range of research, highlighted in this review, suggest that EV-associated with HFMD have evolved different strategies to avoid detection by innate immunity via different proteases (e.g., 2A, 3C, 2C, and 3D). Ongoing efforts to better understand virus-host interactions that control innate immunity and then distill how that influences HFMD development promises to have real-world significance. In this review, we address this complex topic in nine sections including multiple proteins associated with PRR and type I interferon (IFN) signaling. Recognizing how EVs linked to HFMD evade host innate immune system, we also describe the interactions between them and, finally, suggest future directions to better inform drug development and public health.

Elevated sodium chloride drives type I interferon signaling in macrophages and increases antiviral resistance

Type I IFN production and signaling in macrophages play critical roles in innate immune responses. High salt (i.e. high concentrations of NaCl) has been proposed to be an important environmental factor that influences immune responses in multiple ways. However, it remains unknown whether high salt regulates type I IFN production and signaling in macrophages. Here, we demonstrated that high salt promoted IFNβ production and its signaling in both human and mouse macrophages, and consequentially primed macrophages for strengthened immune sensing and signaling when challenged with viruses or viral nucleic acid analogues. Using both pharmacological inhibitors and RNA interference we showed that these effects of high salt on IFNβ signaling were mediated by the p38 MAPK/ATF2/AP1 signaling pathway. Consistently, high salt increased resistance to vesicle stomatitis virus (VSV) infection in vitro. In vivo data indicated that a high-salt diet protected mice from lethal VSV infection. Taken together, these results identify high salt as a crucial regulator of type I IFN production and signaling, shedding important new light on the regulation of innate immune responses.

A Neonatal Murine Model of Coxsackievirus A6 Infection for Evaluation of Antiviral and Vaccine Efficacy

Hand, foot, and mouth disease (HFMD) is a global health concern. Family Picornaviridae members, particularly enterovirus A71 (EVA71) and coxsackievirus A16 (CVA16), are the primary etiological agents of HFMD; however, a third enterovirus A species, CVA6, has been recently associated with epidemic outbreaks. Study of the pathogenesis of CVA6 infection and development of antivirals and vaccines are hindered by a lack of appropriate animal models. We have developed and characterized a murine model of CVA6 infection that was employed to evaluate the antiviral activities of different drugs and the protective efficacies of CVA6-inactivated vaccines. Neonatal mice were susceptible to CVA6 infection via intramuscular inoculation, and the susceptibility of mice to CVA6 infection was age and dose dependent. Five-day-old mice infected with 10^5.5 50% tissue culture infective doses of the CVA6 WF057R strain consistently exhibited clinical signs, including reduced mobility, lower weight gain, and quadriplegia with significant pathology in the brain, hind limb skeletal muscles, and lungs of the infected mice in the moribund state. Immunohistochemical analysis and quantitative reverse transcription-PCR (qRT-PCR) analyses showed high viral loads (11 log₁₀/mg) in skeletal muscle, and elevated levels of interleukin-6 (IL-6; >2,000 pg/ml) were associated with severe viral pneumonia and encephalitis. Ribavirin and gamma interferon administered prophylactically diminished CVA6-associated pathology in vivo, and treatment with IL-6 accelerated the death of neonatal mice. Both specific anti-CVA6 serum and maternal antibody play important roles in controlling CVA6 infection and viral replication. Collectively, these findings indicate that this neonatal murine model will be invaluable in future studies to develop CVA6-specific antivirals and vaccines.IMPORTANCE Although coxsackievirus A6 (CVA6) infections are commonly mild and self-limiting, a small proportion of children may have serious complications, such as encephalitis, acute flaccid paralysis, and neurorespiratory syndrome, leading to fatalities. We have established a mouse model of CVA6 infection by inoculation of neonatal mice with a CVA6 clinical isolate that produced consistent pathological outcomes. Here, using this model of CVA6 infection, we found that high levels of IL-6 were associated with severe viral pneumonia and encephalitis, as in an evaluation of antiviral efficacy in vivo, IL-6 had no protective effect and instead accelerated death in neonatal mice. We demonstrated that, as antiviral drugs, both gamma interferon and ribavirin played important protective roles in the early stages of infection, with increased survival in treated neonatal mice challenged with CVA6. Moreover, active and passive immunization with the inactivated vaccines and anti-CVA6 serum also protected mice against homologous challenge infections.

The immune mechanism of intestinal tract Toll-like receptor in mediating EV71 virus type severe hand-foot-and-mouth disease and the MAPK pathway

Immunological response is thought to play a crucial role in the development of a severe hand-foot-and-mouth disease (HFMD) infection in children, but the mechanisms remain largely unknown. This study was designed to help in elucidating the immunopathological pathways involved in the disease by quantifying Toll-like receptor (TLR) mRNAs, MAPK factors and cytokine levels in children experiencing the disease. A total of 86 enterovirus 71 (EV71)-infected HFMD children (49 with mild and 27 with severe disease), along with 30 healthy children were involved in the study. Peripheral vein blood samples were collected from each individual, and used to isolate peripheral blood mononuclear cells (PBMCs) for mRNA extraction and sera for measuring levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-6 and IL-10. The average expression levels of TLR3, TLR4, TLR7 and TLR8 mRNA in PBMCs of children with severe HFMD were significantly higher than those in the other children, the lowest values were found in the healthy control group (P<0.05). The expression levels of TLR2 and TLR9 mRNA were not significantly different (P>0.05) among the groups. Additionally, the expression levels of TNF-α, IFN-γ, IL-6 and IL-10 in the serum of the children in the severe group were significantly higher than those in the other two groups, and the lowest values were again found in the control group (P<0.05). Pearson correlation analysis showed that the TLR3, TLR4, TLR7 and TLR8 mRNA levels in PBMCs were positively correlated with the TNF-α, IFN-γ, IL-6 and IL-10 levels in the serum (P<0.05). Furthermore, the expression levels of the ERK, JNK and p38 mRNA in PBMCs of children in the severe group were significantly higher than those in the other two groups, with the lowest values being in the control group (P<0.05). Pearson correlation analysis showed that the TLR3, TLR4, TLR7 and TLR8 mRNA levels in PBMCs were positively correlated with ERK, JNK and p38 mRNA levels (P<0.05). The results of our study seem to indicate that the high expression levels of TLR3, TLR4, TLR7 and TLR8 induced in severe EV71 HFMD regulate the expression of cytokines by MAPK signaling pathway and negatively affect the ability of the organism to resolve the infection. Further studies are needed to test the hypothesis that immuno-modulation would be an effective treatment approach in pediatric cases of severe HFMD.

Clinical and Associated Immunological Manifestations of HFMD Caused by Different Viral Infections in Children

Hand, foot, and mouth disease (HFMD), with vesiculae on the hands, feet and mouth, is an infectious disease caused by many viral pathogens. However, the differences of immune response induced by these pathogens are unclear. We compared the clinical manifestations and the levels of immunologic indicators from 60 HFMD patients caused by different viral pathogens to analyze the differences in the immune response. It was shown that Th2 cytokines (IL-4 and IL-10) increased significantly in EV71-infected children; Th1 cytokines (IL-2 and IFN-γ) rose in CA16-infected children; both Th1 and Th2 cytokines elevated in non-EVG-infected children; only individual cytokines (such as IL-10) went up in EVG-infected children. Meanwhile, the antibodies induced by viral infection could not cross-interfere between the different pathogens. These differences might be due to variations in the immune response induced by the individual pathogens or to the pathogenesis of the infections by the individual pathogens.

ATP1B3: a virus-induced host factor against EV71 replication by up-regulating the production of type-I interferons

Enterovirus 71 (EV71) infection can cause severe diseases, and is becoming increasingly common in children. In the current study, we carried out yeast two-hybrid assays to screen human proteins that could interact with 3A protein of EV71. Human β3 subunit of Na⁺/K⁺-ATPase (ATP1B3) protein was demonstrated to interact with the 3A protein of EV71. Although 3A protein had no effect on the expression of ATP1B3, EV71 infection resulted in elevated expression of ATP1B3 in RD cell line, both on messenger RNA (mRNA) and protein levels. Interestingly, knockdown of ATP1B3 could significantly increase the replication of EV71, whereas overexpression of ATP1B3 significantly suppressed the replication of EV71 in RD cells. Furthermore, we demonstrated that the expression of ATP1B3 could induce the production of type-I interferons. Our study demonstrated that ATP1B3 inhibit EV71 replication by enhancing the production of type-I interferons, which could act as a potential therapeutic target in EV71 infection.

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Human ATP1B3 protein was demonstrated to interact with EV71 3A protein.

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We found ATP1B3 can induce the production of type-I IFNs during EV71 infection.

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ATP1B3 can inhibit EV71 replication by up-regulating the production of type-I interferons.

Innate Immunity Evasion by Enteroviruses: Insights into Virus-Host Interaction

Enterovirus genus includes multiple important human pathogens, such as poliovirus, coxsackievirus, enterovirus (EV) A71, EV-D68 and rhinovirus. Infection with EVs can cause numerous clinical conditions including poliomyelitis, meningitis and encephalitis, hand-foot-and-mouth disease, acute flaccid paralysis, diarrhea, myocarditis and respiratory illness. EVs, which are positive-sense single-stranded RNA viruses, trigger activation of the host antiviral innate immune responses through pathogen recognition receptors such as retinoic acid-inducible gene (RIG-I)-likeand Toll-like receptors. In turn, EVs have developed sophisticated strategies to evade host antiviral responses. In this review, we discuss the interplay between the host innate immune responses and EV infection, with a primary focus on host immune detection and protection against EV infection and viral strategies to evade these antiviral immune responses.