Association of interleukin 10 and interferon gamma gene polymorphisms with enterovirus 71 encephalitis in patients with hand, foot and mouth disease

A multiplex SNaPshot assay for the detection of single nucleotide polymorphism associated with clinical severity of enterovirus infections

Non-polio enterovirus infections are known to cause a variety of diseases and neurological complications. It is also known that the severity of these diseases largely differs among individuals with different genotypes and alleles. The Single Nucleotide Polymorphisms (SNPs) within specific genes have a considerable effect on the immune response to enteroviruses and on the outcome of disease, leading to variations in complications and infection susceptibility. Knowing the distribution of such SNPs can be valuable for individual case management and studying epidemiological parameters of enterovirus infections. In this feasibility study, a multiplex version of the primer extension-based technique called the SNaPshot Assay has been developed to examine SNPs in various relevant genes for predicting the clinical severity of enterovirus infections. It is already established that this technique is precise, consistent, scalable, and likely to exhibit high throughput. The multiplex SNaPshot can investigate multiple genetic susceptibility markers simultaneously, and the assay can be used to identify vulnerable populations, understand the epidemiology of infections, and manage the outbreaks of enteroviruses. Based on the literature, 15 SNPs were identified which are suspected for higher susceptibility to the worst outcomes after enterovirus infection and the assay was developed. Blood samples of 100 healthy volunteers were collected and tested for assay feasibility as well as to know the proportions of 15 selected SNPs. After the analysis, seven SNPs have been identified and suggested to be considered for future assays. Based on the pilot test results, it appears that positivity for any three out of the identified seven SNPs might indicate a higher risk, and future studies correlated with clinical studies among patients with and without severe diseases utilizing this assay will provide robust parameters to determine at-risk individuals more accurately.

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.

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.

Association of gene polymorphisms of CD55 with susceptibility to and severity of hand, foot, and mouth disease caused by enterovirus 71 in the Han Chinese population

Hand, foot, and mouth disease (HFMD) caused by enterovirus 71 (EV71) can lead to high morbidity and mortality, and genetic background plays an important role during the disease process. We investigated the association between the single-nucleotide polymorphism (SNP) rs2564978 of the CD55 gene and susceptibility to and severity of HFMD using the SNPs can multiple SNP typing methods. Soluble CD55 (sCD55) expression was significantly lower in the EV71 HFMD group than in the control group and lower in severe cases than in mild cases (P < .001). Moreover, CD55 rs2564978 (C vs T OR = 1.300, 95% CI, 1.120-1.509) was associated with the risk of EV71 infection, and genotype TC was related to the severity of the infection (TC vs TT OR = 4.523, 95% CI, 2.033-10.066). Our results suggest that sCD55 expression and the CD55 polymorphism rs2564978 may influence the susceptibility to and severity of EV71 infection.

The Function and Mechanism of Enterovirus 71 (EV71) 3C Protease

Enterovirus 71 (EV71) is the main pathogen of the hand, foot, and mouth disease. It was firstly isolated from sputum specimens of infants with central nervous system diseases in California in 1969, and has been repeatedly reported in various parts of the world, especially in the Asia-Pacific region. EV71 3C protein is a 183 amino acid cysteine protease that can cleave most structural and non-structural proteins of EV71. Based on the analysis and understanding of EV71 3C protease, it is helpful to study and treat diseases caused by EV71 virus infection. The EV71 3C protease promotes virus replication by cleaving EV71 synthesis or host proteins. Moreover, EV71 3C protease inhibits the innate immune system and causes apoptosis. At present, in order to deal with the damage caused by the EV71, it is urgent to develop antiviral drugs targeting 3C protease. This review will focus on the structure, function, and mechanism of EV71 3C protease.

Predicting Severe Enterovirus 71-Infected Hand, Foot, and Mouth Disease: Cytokines and Chemokines

Enterovirus 71 (EV71) is one of the most common intestinal virus that causes hand, foot, and mouth disease (HFMD) in infants and young children (mostly ≤5 years of age). Generally, children with EV71-infected HFMD have mild symptoms that resolve spontaneously within 7-14 days without complications. However, some EV71-infected HFMD cases lead to severe complications such as aseptic meningitis, encephalitis, acute flaccid paralysis, pulmonary edema, cardiorespiratory complication, circulatory disorders, poliomyelitis-like paralysis, myocarditis, meningoencephalitis, neonatal sepsis, and even death. The mechanism of EV71 pathogenesis has been studied extensively, and the regulation of host immune responses is suspected to aggravate EV71-induced severe complications. Recently, several cytokines or chemokines such as TNF-α, IFN-γ, IL-1β, IL-18, IL-33, IL-37, IL-4, IL-13, IL-6, IL-12, IL-23, IL-27, IL-35, IL-10, IL-22, IL-17F, IL-8, IP-10, MCP-1, G-CSF, and HMGB1 have been reported to be associated with severe EV71 infection by numerous research teams, including our own. This review is aimed at summarizing the pathophysiology of the cytokines and chemokines with severe EV71 infection.

Genetic and Environmental Interaction in Type 1 Diabetes: a Relationship Between Genetic Risk Alleles and Molecular Traits of Enterovirus Infection?

PURPOSE OF REVIEW

We provide an overview of the current knowledge regarding the natural history of human type 1 diabetes (T1D) and the documented associations between virus infections (in particular the enteroviruses) and disease development. We review studies that examine whether T1D-specific risk alleles in genes involved in the function of the immune system can alter susceptibility to virus infections or affect the magnitude of the host antiviral response. We also highlight where the major gaps in our knowledge exist and consider possible implications that new insights gained from the discussed gene-environment interaction studies may bring.

RECENT FINDINGS

A commonality between several of the studied T1D risk variants studied is their role in modulating the host immune response to viral infection. Generally, little support exists indicating that the risk variants increase susceptibility to infection and moreover, they usually appear to predispose the immune system towards a hyper-reactive state, decrease the risk of infection, and/or favor the establishment of viral persistence. In conclusion, although the current number of studies is limited, this type of research can provide important insights into the mechanisms that are central to disease pathogenesis and further describe how genetic and environmental factors jointly influence the risk of T1D development. The latter may provide genetic markers that could be used for patient stratification and for the selection of method(s) for disease prevention.

Association of the Polymorphism of rs1799822 on Carnitine Palmitoyltransferase II Gene with Severe Enterovirus 71 Encephalitis in Chinese Children

Mutations of the CPT2 gene cause CPT2 deficiency and affect the β-oxidation of fatty acids. This study examined the consequence of a polymorphism of rs1799822 in the CPT2 gene with respect to EV71 encephalitis in Chinese children. The study included 406 cases of both mild and severe EV71 infection diagnosed by RT-PCR, together with controls (n = 348). We used an improved multiplex ligation detection reaction technique to detect the polymorphism of rs1799822 in the CPT2 gene. The frequency of the (AG+GG) genotype and G allele in the EV71 infection group and in the severe EV71 encephalitis group was significantly lower than in the control group (p = 0.012 vs. p = 0.005, and p = 0.022 vs. p = 0.006, respectively). The frequency of the (AG+GG) genotype and G allele in the severe EV71 encephalitis group was markedly lower than in the mild EV71 encephalitis group (p = 0.045, p = 0.033). The ATP levels in the blood of the (AG+GG) genotype were distinctly higher than in the AA genotype in mild and severe EV71 encephalitis patients (P = 0.037, P = 0.040). A polymorphism of rs1799822 in the CPT2 gene is associated with the severity of EV71 encephalitis and may be one of the protection factors of severe EV71 encephalitis.

Enterovirus and parechovirus infections in children: differences in clinical presentation, mechanisms for meningitis without pleocytosis and mechanisms involved in the neurological outcome

Enterovirus (EV) and Parechovirus (HPeV) are a frequent cause of infection in children. This review gives an overview of possible causes for differences in clinical presentation. EV and HPeV can cause a meningitis with or without pleocytosis. Different possible mechanisms for meningitis without pleocytosis are given. Little is known about the prognosis and long-term effects of EV and HPeV meningitis in children. Only some studies with a small number of children with EV or HPeV meningitis are reported. The different possible mechanisms involved in the neurological outcome after EV or HPeV meningitis will be discussed.

Polymorphisms in enterovirus 71 receptors associated with susceptibility and clinical severity

OBJECTIVE

To evaluate the association of enterovirus 71 (EV71) susceptibility and clinical severity with polymorphisms in EV71 receptors, including human scavenger receptor class B member 2 (SCARB2), P-selectin glycoprotein ligand-1 (PSGL-1), and annexin II (ANXA2).

METHODS

We enrolled laboratory-confirmed EV71 cases and healthy age- and gender-matched controls in Taiwan from 2000 to 2012. We detected genetic polymorphisms in SCARB2, PSGL-1, and ANXA2 and correlated the results with EV71 susceptibility and severity.

RESULTS

We collected 599 EV71 cases and 98 controls. Among EV71 patients, the male to female ratio was 1.61, and the mean age was 2.99±2.47 years. For clinical severity, 117 (19.6%) had severe central nervous system involvement with or without cardiopulmonary failure. For outcomes, 46 (7.7%) had sequelae, and 14 (2.3%) died. SCARB2 polymorphisms (rs6824953 and rs11097262) were associated with susceptibility to EV71 infection (OR 1.60, 95% CI 1.07-2.39; and OR 1.64, 95% CI 1.09-2.47, respectively). PSGL-1 polymorphisms (rs7137098 and rs8179137) were significantly associated with severe EV71 infection (OR 1.46, 95% CI 1.1-1.96; and OR 1.47, 95% CI 1.07-2.03, respectively).

CONCLUSIONS

SCARB2 polymorphisms (rs6824953 and rs11097262) might be associated with EV71 susceptibility. PSGL-1 polymorphisms (rs7137098 and rs8179137) were associated with severe EV71 infection.

IL-10RA Mutation as a Risk Factor of Severe Influenza-Associated Encephalopathy: A Case Report

Influenza-associated encephalitis and encephalopathy (IAE) is a severe complication of influenza infection with high morbidity and mortality. We present the case of a patient with IL-10RA mutation who developed encephalopathy after influenza infection. A 10-day-old boy developed recurrent fever and anal fistula. Growth failure gradually became apparent. He had been treated with antibiotics and elemental nutrition. However, the patient did not respond to the treatments. At 11 months, he suddenly developed shock with encephalopathy and multiple organ failures. He was then diagnosed with IAE. A cytokine study revealed elevated levels of IL-1 receptor antagonist, IL-2, IL-6, IL-8, IP-10, eotaxin, G-CSF, MCP-1, and IL-10. These cytokines are normally downregulated by IL-10. Genetic testing revealed a IL-10RA mutation at the 3' end of exon 4 (c.537G→A). These findings might reflect an increased risk of severe IAE in patients with IL-10RA mutation.

Sequence analysis-based characterization and identification of neurovirulence-associated variants of 36 EV71 strains from China

Enterovirus 71 (EV71) is the main pathogen of hand-foot-mouth disease (HFMD) and causes several neurological complications. As new strains of EV71 are constantly discovered, it is important to understand the genomic characteristics of the viruses and the mechanism of virulence. Herein, we isolated five strains of EV71 from HFMD patients with or without neurovirulence and sequenced their whole genomes. We then performed whole genome sequence analysis of totally 36 EV71 strains. The phylogenetic analysis of the VP1 region revealed all five isolated strains are clustered into C4a of C4 subgenotype. In addition, by comparing the complete genome sequences of 36 strains, 253 variable amino acid positions were found, 14 of which were identified to be associated with neurovirulence (P < 0.05). Moreover, a similar pattern of amino acid variants combination was identified in four strains without neurovirulence, indicating this type of variant pattern might be associated with avirulence. The strains with neurovirulence appeared to be distinguished from those without neurovirulence by the variants in VP1 and P2 regions, implying VP1 and P2 are the important regions associated with neurovirulence. Indeed, 3-D modeling of VP1 and P2 regions of non-neurovirulent and neurovirulent strains revealed that the different variants resulted in different protein structures and amino acid composition of ligand binding site, which might account for their difference in neurovirulence. In summary, our study reveals 14 variable amino acid positions of VP1, P2 and P3 regions are related to the virulence and that mutations in the capsid proteins of EV71 might contribute to neurovirulence.

Correlation analysis on serum inflammatory cytokine level and neurogenic pulmonary edema for children with severe hand-foot-mouth disease

Objective

This study aims to discuss the correlation between serum inflammatory cytokines and neurogenic pulmonary edema (NPE) in children with severe hand–foot–mouth disease (HFMD).

Methods

A total of 89 patients with severe HFMD were enrolled into this study. These patients were divided into two groups, according to the presence of NPE: central nervous system disease (CNSD) group and NPE group. Serum IL-4, IL-10, IL-6, IL-17, tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) levels were measured in patients by enzyme-linked immunosorbent assay at 1, 3, and 5 days after admission. Furthermore, risk factors for NPE were screened using multivariable logistic regression analysis.

Results

IL-6, TNF-α, IL-10, and interferon-γ (IFN-γ) levels in the NPE group were higher than in the CNSD group. TNF-α, IL-10, and IFN-γ levels reached a peak on the 3rd day of admission. Age, continuous fever, blood sugar, white blood cell count, and IL-10 were risk factors for the occurrence of NPE in severe HFMD.

Conclusion

The dynamic unbalance of inflammatory cytokines is related to the occurrence and progress of NPE.

Association of Interleukin-17F gene polymorphisms with susceptibility to severe enterovirus 71 infection in Chinese children

Enterovirus 71 (EV71) is a single-strand RNA virus that causes hand, foot and mouth disease (HFMD) in infants and young children, leading to neurological complications with significant morbidity and mortality. Unfortunately, the pathogenesis of EV71 infection is not well understood. In this study, we investigated the IL-17F rs1889570 and rs4715290 gene polymorphisms in a Chinese Han population. Severe cases and cases with EV71 encephalitis had a significantly higher frequency of the rs1889570 T/T genotype and T allele. The serum IL-17F levels in rs1889570 T/T and C/T genotypes were also significantly elevated when compared to C/C genotypes. However, there was no significant difference observed in rs4715290 genotype distribution and allele frequency. These findings suggest that IL-17F rs1889570 gene polymorphisms are significantly associated with the susceptibility to severe EV71 infection in Chinese Han children.

Hand, foot and mouth disease: current knowledge on clinical manifestations, epidemiology, aetiology and prevention

For a long time, hand, foot and mouth disease (HFMD) was seen as a mild viral infection characterized by typical clinical manifestations that spontaneously resolved in a few days without complications. In the past two decades, HFMD has received new attention because of evidence that this disease could have clinical, epidemiological and aetiological characteristics quite different from those initially thought. In contrast to previous beliefs, it has been clarified that HFMD can be associated with complications, leading to severe neurological sequelae and, rarely, to death. This finding has led to an enormous number of studies that have indicated that several viruses in addition to those known to be causes of HFMD could be associated with the development of disease. Moreover, it was found that if some viruses were more common in some geographic areas, frequent modification of the molecular epidemiology of the infecting strains could lead to outbreaks caused by infectious agents significantly different from those previously circulating. Vaccines able to confer protection against the most common aetiologic agents in a given country have been developed. However, simultaneous circulation of more than one causative virus and modification of the molecular epidemiology of infectious agents make preparations based on a single agent relatively inadequate. Vaccines with multiple components are a possible solution. However, several problems concerning their development must be solved before adequate prevention of severe cases of HFMD can be achieved.

Oligoadenylate synthetase 3 S381R gene polymorphism is associated with severity of EV71 infection in Chinese children

BACKGROUND

Oligoadenylate synthetase 3 (OAS3) is interferon-induced antiviral enzyme, playing a significant role in the innate immune response. Genetic polymorphism in OAS3 gene has been reported to be a susceptibility factor in many infected diseases, but evidence of its effect on enterovirus 71 (EV71) infection is still lacking.

OBJECTIVES

An attempt study was made to investigate whether genetic polymorphism of OAS3 S381R is associated with the severity of EV71 infection in Chinese children.

STUDY DESIGN

Retrospectively sumed up the clinical onsets and experimental results for 249 cases with EV71 infection (including 151 mild cases and 98 severe cases) and 243 controls. An improved multiplex ligation detection reaction (iMLDR) technique was carried out to analyze polymorphism in OAS3 S381R G/C gene for genetic association analyses. The plasma levels of IFN-γ were determined by enzyme-linked immunosorbent assays.

RESULTS

The distribution of OAS3 S381R CC genotype (73.47%) and C allele (85.20%) in severe cases was markedly higher than in mild cases (45.70%, P < .01; 67.88%, P < .01). The blood IFN-γ levels of severe cases were significantly lower in CC genotype (131.66 ± 10.84 pg/mL) compared to GG (183.37 ± 24.50 pg/mL, p < .01) and GC genotype (168.48 ± 26.57 pg/mL, p < .01).

CONCLUSIONS

Carrying the C allele of the OAS3 S381R gene could be a susceptibility factor in the development of severe EV71 infection in Chinese children.

Cytokines Interleukin 4 (IL-4) and Interleukin 10 (IL-10) Gene Polymorphisms as Potential Host Susceptibility Factors in Virus-Induced Encephalitis

Background

This study aimed to analyze and explore the relationship between the cytokines IL-4 and IL-10 in relation to gene polymorphism and their respective effects on the susceptibility to virus-induced encephalitis.

Material/Methods

From January 2012 to June 2013, 112 patients with virus-induced encephalitis (the case group and 109 healthy individuals (the control group) were recruited for the purposes of this study. The functional variations that IL-4 and IL-10 genes exhibit were detected through the use of a function analysis and selection tool for single-nucleotide polymorphisms (FASTSNP). The genotypes of IL-4 were rs2227283 and IL-4 rs2227288, and the genotypes of IL-10 were rs1800871 and IL-10 rs1800872. These genotypes were respectively assessed using direct sequencing.

Results

IL-4 rs2227283 and IL-10 rs1800871 have no correlation in with risk of virus-induced encephalitis (both P>0.05)

GA and AA genotypes were related to IL-4 rs2227288 and GT, while TT and GT + TT genotypes were related to IL-10 rs1800872. These were highlighted as being risk factors in virus-induced encephalitis (all P<0.05). However, the duration of fever, white blood cell (WBC) count, C-reactive protein (CRP), neutrophils, and lymphocytes and monocytes of virus-induced encephalitis patients with IL-4 rs2227288 and IL-10 rs1800872 all displayed significant differences (all P<0.05). Frequencies of GAGT and CAGT haplotypes were evaluated and deemed to be of statistical significance and subsequently were highlighted as being risk factors in virus-induced encephalitis (all P<0.05).

Conclusions

IL-4 rs2227288 and IL-10 rs1800872 may contribute to an increased risk for virus-induced encephalitis. Through use of direct sequencing, we showed that genotypes of IL-4 rs2227288 and IL-10 rs1800872 may have particular host susceptibility to virus-induced encephalitis.

IL-10-592 polymorphism is associated with IL-10 expression and severity of enterovirus 71 infection in chinese children

BACKGROUND

Enterovirus 71 (EV71) infection results in some severe complications with high mortality and disability in Hand, Foot and Mouth Disease (HFMD) in children. Recent studies have shown that cytokine genetic predispositions have associations with both the development of EV71 infection and severity of HFMD.

OBJECTIVE

This study was designed to investigate whether the IL-10-592 polymorphism is associated with IL-10 levels and disease severity in Chinese children with EV71 infection.

STUDY DESIGN

In patients selected, there were 378 cases with EV71 infection (including 291 mild cases, 70 severe cases and 17 critical cases), as well as 406 health controls. EV71 in serum was tested by RT-PCR, and IL-10-592 genotype was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis techniques.

RESULT

The IL-10-592C allele was observed with higher frequency in patients with critical EV71 infection (70.59%) compared with severe EV71 infection (41.43%, P<0.01), mild EV71 infection (43.81%, P<0.01) and healthy children (44.46%, P<0.01). The blood IL-10 levels of critical cases were significantly higher than severe cases, mild cases, and healthy children. Among all of the four groups, IL-10 levels in patients with genotype AA were significantly lower than those with genotypes AC+CC (t=4.86, P<0.05; t=2.30, P<0.05; t=3.44, P<0.05; t=5.58, P<0.05).

CONCLUSION

IL-10-592C allele is associated with IL-10 expressions and the severity of EV71 infection in Chinese patients.

Association of the OAS3 rs1859330 G/A genetic polymorphism with severity of enterovirus-71 infection in Chinese Han children

The 2'5'-oligoadenylate synthetase (OAS) is an interferon (IFN)-induced protein that plays an important role in the antiviral action of IFN, with OAS3 being one of the four OAS classes (OAS1, OAS2, OAS3, OASL). The effect of OAS on several infectious viral diseases has been reported; however, a study of the effect of OAS3 on enterovirus 71 (EV71) is lacking. The purpose of this study was to evaluate the association of the OAS3 rs1859330 G/A genetic polymorphism with susceptibility and severity of EV71 infection. We investigated 370 Chinese Han children with hand-foot-mouth disease (HFMD) (214 of which were mild cases while 156 were severe). An improved multiplex ligation detection reaction (iMLDR) technique was carried out to examine the genotype. The AA genotype distribution (p = 0.002) and A allele frequency (OR = 1.83, 95% CI 1.32-2.52, p < 0.001) of OAS3 rs1859330 in severe cases were significantly higher than in mild cases. When comparing the different genotypes in EV71-infected patients, there were statistical differences in relation to rash (p = 0.03), oral ulcers (p = 0.005), pathologic reflex (p = 0.003), WBC counts (p = 0.032), CRP (p = 0.024), BG concentrations (p = 0.029), ALT (p = 0.02), and EEG (p = 0.019). However, there were no differences in relation to age, gender, AST, CK-MB, CT/ MRI, as well as some symptoms and signs (e.g. duration of fever (days), headache, convulsions, consciousness disturbance, paralysis, sign of meningeal irritation). In the cerebrospinal fluid (CSF) of severe cases, there were no differences in the levels of white cells, protein, glucose, chloride, lymphocytes and monocytes between the different genotypes. The plasma levels of IFN-γ in EV71-infected patients were significantly higher than in the control group (p < 0.01). IFN-γ concentrations in severe cases were lower in A allele carriers (AA+GA) (118.5 ± 12.6pg/mL) than in GG homozygotes (152.6 ± 56.3pg/mL p < 0.05). These findings suggest that the OAS3 rs1859330 G/A genetic polymorphism is associated with the severity of EV-71 infection, and that the A allele is a risk factor for the development of severe EV71 infection.

Galectin-3 and Its Genetic Variation rs4644 Modulate Enterovirus 71 Infection

Galectin-3, a chimeric type β-galactoside-binding protein, is known to modulate viral infection; however, its role in enterovirus 71 (EV71) infection has not been investigated. We generated galectin-3 null rhabdomyosarcoma (RD) cells and evaluated whether EV71 infection would be affected. In galectin-3 null cells, the released and intracellular EV71 viral loads were suppressed after 24 h of infection, and cell death rates were significantly lower, while cell proliferation remained unaltered. In addition, RD cells expressing a nonsynonymous genetic variant of galectin-3, rs4644 (LGALS3 +191C/A, P64H), produced lower virus titers than those with wild-type galectin-3 (C allele). To clarify whether the in vitro viral load reduction correlates with clinical severity, we enrolled children with laboratory-confirmed EV71 infection. Since hyperglycemia is an indicator of severe EV71 infection in children, 152 of 401 enrolled children had glucose examinations at admission, and 59 subjects had serum glucose levels ≥ 150 mg/dL. In comparison to the rs4644 AA genotype (2.2 ± 0.06 log10 mg/dL), serum glucose levels during EV71 infection were higher in patients with CC (2.4 ± 0.17 log10 mg/dL, p = 0.03) and CA (2.4 ± 0.15 log10 mg/dL, p = 0.02) genotypes, respectively. These findings suggest that the rs4644 AA genotype of galectin-3 might exert a protective effect. In summary, galectin-3 affects EV71 replication in our cellular model and its variant, rs4644, is associated with hyperglycemia in the clinical setting. The underlying mechanism and its potential therapeutic application warrant further investigation.

A functional polymorphism in IFNAR1 gene is associated with susceptibility and severity of HFMD with EV71 infection

Enterovirus 71 (EV71), one of the major pathogens of Hand, foot and mouth disease (HFMD), results in millions of infections and hundreds of deaths each year in Southeast Asia. Biased infection and variable clinical manifestations of EV71 HFMD indicated that host genetic background played an important role in the occurrence and development of the disease. We identified the mRNA profiles of EV71 HFMD patients, which type I interferon (IFN) pathway related genes were down-regulated. Four single nucleotide polymorphisms (SNPs) of type I IFN receptor 1 (IFNAR1) were chosen to analyze their relationships to EV71 infection. We found that genotype GG of promoter variant rs2843710 was associated with the susceptibility and severity to EV71 HFMD. In addition, we assessed the regulatory effects of rs2843710 to IFN stimulated genes (ISGs), and found that the expressions of IFNAR1, OAS1 and MX1 were significantly lower in patients with rs2843710 genotype GG. And rs2843710 allele G showed weaker transcriptional activity compared with allele C. Our study indicated that rs2843710 of IFNAR1 was associated with the susceptibility and severity of EV71 HFMD in Chinese Han populations, acting as a functional polymorphism by regulating ISGs expression, such as OAS1 and MX1.

Association of Chemotactic Chemokine Ligand 5 Polymorphisms with the Risk of Developing Severe Enterovirus 71 Infection

Respiratory damage is a main manifestation of severe Enterovirus 71 (EV71) infection. Polymorphisms of -403G/A (rs2107538), -28C/G (rs2280788), and In1.1T/C (rs2280789) in chemotactic chemokine ligand 5 (CCL5) have linked with many respiratory diseases. In this study, we explored the possible correlation of CCL5 polymorphisms with severe EV71 infection. Blood samples were obtained from 87 children hospitalized for EV71 infection. Fifty-seven healthy children were enrolled as asymptomatic controls. Genotype and allele frequencies were analyzed by logistic regression analysis. There were statistically significant differences in polymorphisms of CCL5 -403G/A and In1.1T/C for dominant model (P = 0.016; P = 0.027) and additive model (P = 0.010; P = 0.019) between patients with severe EV71 infection and asymptomatic controls. With ordinal logistic regression model analysis, statistically significant differences were found between polymorphisms of CCL5 (-403G/A) (P = 0.034) with the severity of EV71 infection after adjusting for age. The frequency of A-C-C haplotype was significantly higher in EV71 infection patients than controls (P = 0.032). These results suggest that CCL5 -403G/A and In1.1T/C polymorphisms may contribute to severe EV71 infection and individuals with haplotype of A-C-C may exhibit higher risk of developing severe EV71 infection. These findings may provide insights into pathogenic and protective mechanisms of severe EV71 infection.

Enterovirus 71 Proteins 2A and 3D Antagonize the Antiviral Activity of Gamma Interferon via Signaling Attenuation

Enterovirus 71 (EV71) infection causes severe mortality involving multiple possible mechanisms, including cytokine storm, brain stem encephalitis, and fulminant pulmonary edema. Gamma interferon (IFN-γ) may confer anti-EV71 activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. This study, investigating the role of IFN-γ in EV71 infection using a murine model, showed that IFN-γ was elevated. Moreover, IFN-γ receptor-deficient mice showed higher mortality rates and more severe disease progression with slower viral clearance than wild-type mice. In vitro results showed that IFN-γ pretreatment reduced EV71 yield, whereas EV71 infection caused IFN-γ resistance with attenuated IFN-γ signaling in IFN regulatory factor 1 (IRF1) gene transactivation. To study the immunoediting ability of EV71 proteins in IFN-γ signaling, 11 viral proteins were stably expressed in cells without cytotoxicity; however, viral proteins 2A and 3D blocked IFN-γ-induced IRF1 transactivation following a loss of signal transducer and activator of transcription 1 (STAT1) nuclear translocation. Viral 3D attenuated IFN-γ signaling accompanied by a STAT1 decrease without interfering with IFN-γ receptor expression. Restoration of STAT1 or blocking 3D activity was able to rescue IFN-γ signaling. Interestingly, viral 2A attenuated IFN-γ signaling using another mechanism by reducing the serine phosphorylation of STAT1 following the inactivation of extracellular signal-regulated kinase without affecting STAT1 expression. These results demonstrate the anti-EV71 ability of IFN-γ and the immunoediting ability by EV71 2A and 3D, which attenuate IFN-γ signaling through different mechanisms.

IMPORTANCE

Immunosurveillance by gamma interferon (IFN-γ) may confer anti-enterovirus 71 (anti-EV71) activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. IFN-γ receptor-deficient mice showed higher mortality and more severe disease progression, indicating the anti-EV71 property of IFN-γ. However, EV71 infection caused cellular insusceptibility in response to IFN-γ stimulation. We used an in vitro system with viral protein expression to explore the novel IFN-γ inhibitory properties of the EV71 2A and 3D proteins through the different mechanisms. According to this study, targeting either 2A or 3D pharmacologically and/or genetically may sustain a cellular susceptibility in response to IFN-γ, particularly for IFN-γ-mediated anti-EV71 activity.

Correlation of an interleukin-4 gene polymorphism with susceptibility to severe enterovirus 71 infection in Chinese children

Enterovirus 71 (EV71) has caused many outbreaks of diseases among children worldwide since it was first reported in 1974, but its mechanism of pathogenesis remains unclear. This study was designed to investigate the possible association of the IL-4 -589C/T gene polymorphism with severity of EV71 infection in Chinese children. The IL-4 -589C/T gene polymorphism was detected in EV71-infected subjects (n = 185), including those with mild cases (n = 102) and severe cases (n = 83) as well as healthy controls (n = 234), using an improved multiplex ligation detection reaction (iMLDR) technique. The plasma levels of IL-4 and IFN-γ were determined by enzyme-linked immunosorbent assays. The presence of the CC genotype (p = 0.022) and the C allele (OR, 2.1; 95 % CI, 1.3-3.6; p = 0.004) was significantly higher in severe cases. Furthermore, the CC genotype and C allele were also more frequently found in cases of EV71 encephalitis (p < 0.05). The plasma levels of IL-4 of the CC (7.9 ± 1.3 pg/mL, p < 0.001) and CT genotype (6.8 ± 2.1 pg/mL, p < 0.01) were significantly elevated compared to those of the TT genotype, but the plasma levels of IFN-γ and the IFN-γ/IL-4 ratio were significantly lower for the CC and CT genotypes than for the TT genotype (p < 0.05). These findings suggest that the IL-4 -589C allele could be a susceptibility factor in the development of EV71 disease in Chinese children.

Association analysis of polymorphisms in OAS1 with susceptibility and severity of hand, foot and mouth disease

Hand, foot and mouth disease (HFMD) is a common childhood illness that mainly affects Asian children under the age of 5 years. Human enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the most common pathogens of HFMD. It is imperative that the susceptible population is screened early and that the severe illness population can be identified via genetic variation detection in children. Four single-nucleotide polymorphisms (SNP) [2'-5'-oligoadenylate synthetase1 (OAS1) rs10774671, selectin P ligand (SELPLG) rs2228315, scavenger receptor class B member 2 (SCARB2) rs41284767 and interleukin 28B (IL28B) rs12979860] were determined by Taqman assays in 333 HFMD samples and 163 control samples. The rs2228315, rs41284767 and rs12979860 polymorphisms did not differ significantly between HFMD patients and the controls, but the prevalence of the rs10774671 polymorphism was significantly different between the control children and children infected with CA16 (GG genotype vs. AA + AG genotype, P < 0.05). Children with the GG genotype were more susceptible to CA16-type HFMD. Furthermore, the rs10774671 genotype distribution was clearly different between children with severe HFMD and those with mild HFMD [P < 0.05, OR 0.240, 95% CI (0.071-0.809)]. HFMD children with the AA+AG genotype were more likely to progress to encephalitis than were those with the GG genotype. Plasma γ-interferon (IFN) expression levels among control children and the mild and severe HFMD children were detected by ELISA. Those with mild HFMD had higher γ-IFN expression levels compared with those with severe HFMD (P < 0.05). In addition, there is a significant correlation between γ-IFN levels and OAS1 rs10774671 SNP, as analysed by linear correlation assay. The GG genotype correlated with higher γ-IFN levels (P < 0.05). In short, the OAS1 rs10774671 SNP GG genotype contributed to CA16 susceptibility and was associated with the development of mild HFMD.

A polymorphism in melanoma differentiation-associated gene 5 may be a risk factor for enterovirus 71 infection

Enterovirus 71 (EV71) infection has a wide variety of clinical manifestations, from no symptoms to fatal disease. Host immune response may be a determinant of disease severity. We investigated the association of polymorphisms in three pattern recognition receptor (PRR) genes-toll-like receptor 3 (TLR3) (rs3775291), retinoic acid-inducible gene I (RIG-I) (rs10813831) and melanoma differentiation-associated gene 5 (MDA5) (rs1990760)-with the severity of EV71 infection. Polymorphisms of candidate genes in 87 EV71-infected patients and 57 asymptomatic controls were detected. Binary logistic regression analysis revealed statistically significant differences in polymorphism of MDA5 (rs1990760) between patients with severe EV71 infection and asymptomatic controls in an additive model (OR 0.424, 95% CI 0.213-0.845, p 0.015) and a dominant model (OR 0.256, 95% CI 0.103-0.635, p 0.003). Polymorphism of MDA5 (rs1990760) (OR 0.399, 95% CI 0.199-0.798, p 0.009) was found to be associated with the severity of EV71 infection with the analysis of ordinal logistic regression. These results indicated the association between MDA5 (rs1990760) polymorphism and an increased risk of a severe EV71 infection in Chinese children, which offers potential for investigating the innate immune mechanism of EV71 infection and identifying at-risk infants, for whom a preventive strategy may reduce the severity of EV71 infection.

Genetic polymorphism of CCL2-2518, CXCL10-201, IL8+781 and susceptibility to severity of Enterovirus-71 infection in a Chinese population

OBJECTIVE

The goal of this study was to examine the relationship between CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphism and severity of Enterovirus 71 (EV71) infection in a Chinese population.

METHODS

A case-control study was conducted to compare the distribution of genotype and genetic frequency of the CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphisms among EV71-infected patients (n = 186), including mild cases (n = 103), severe cases (n = 83) and healthy control subjects (n = 233) with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and analyzed the relationship between the CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphism and the susceptibility to EV71 infection.

RESULTS

No significant differences were found in the distribution of genotype CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T between the healthy control group and EV71-infected patients. However, three SNPs were associated with severity of EV71 infection: the G allele (genotypes AG or GG) in the CCL2-2518A/G (OR 2.34, 95 % CI 1.50-3.65, P < 0.001), the A allele (genotypes AA or AG) in the CXCL10-201A/G (OR 3.60, 95 % CI 1.73-7.47, P < 0.001), and the C allele (genotypes CC or CT) in the IL8+781C/T (OR 2.63, 95 % CI 1.67-4.13, P < 0.001) were more frequent in patients with severe EV71 infection. No significant difference was observed between EV71 encephalitis and severe cases. At the same time, there were significant differences in fever days, WBC, CRP and BG concentration, and CCL2, CXCL10 and IL-8 levels according to the three SNPs among 186 EV71-infected patients, but no significant differences were observed in gender, age, ALT, AST, CK-MB, and CSF evaluations.

CONCLUSION

The G carrier of the CCL2-2518A/G, the A carrier of the CXCL10-201A/G, and the C carrier of the IL8+781C/T were found to be associated with severity of EV71 infection, and could be susceptibility factors in the development of EV71 infection in the Chinese population.

Update of enterovirus 71 infection: epidemiology, pathogenesis and vaccine

Enterovirus 71 (EV71) is a neurotropic human pathogen that is the causative agent of hand foot and mouth disease (HFMD), herpangina and brain stem encephalitis. Recurrent EV71 epidemics of various scales have occurred in the Asia-Pacific region. Several specific cell surface molecules serve as the receptors for EV71. Identification of the receptors is an important step to understand EV71 disease. Cytokines, lymphocytes and monocytes contribute significantly to EV71 pathogenesis. The interaction of EV71 and receptors may be associated with the cytokines immunopathogenesis. Some animal models have been established and aim to explore the pathogenesis of EV71 infections. EV71 antibodies can neutralize or enhance infection at subneutralizing levels. These results are important for EV71 vaccine and therapeutics design. Several clinical trials of human inactivated EV71 vaccine have recently been completed. The purpose of this review is to summarize recent discoveries about the epidemiology and pathogenesis of EV71 and provide insights into human vaccine development.

Association of functional polymorphisms in the MxA gene with susceptibility to enterovirus 71 infection

Myxovirus resistance A (MxA) is an antiviral protein induced by type I interferons α and β (IFN-α and IFN-β) that can inhibit virus replication. We examined whether the MxA polymorphisms were related to the risk and severity of enterovirus 71 (EV71) infection in Chinese populations. The MxA C-123A and G-88T polymorphisms were genotyped in two independent case–control populations in China by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analysis. Multivariate logistic regression analysis was used to calculate adjusted odds ratios (ORs) and 95 % confidence intervals (95 % CIs). MxA messenger RNA was quantified by real-time quantitative PCR in peripheral blood mononuclear cells (PBMCs) from 45 healthy children and 19 patients with EV71 infection. Significantly decreased susceptibility to EV71 infection was observed for the -123A allele and -88T allele carriers, with ORs (95 % CIs) estimated as 0.56 (0.39–0.81) and 0.64 (0.47–0.88), respectively, in the northern population. This association was confirmed in the southern population, with ORs (95 % CIs) estimated as 0.58 (0.38–0.89) and 0.67(0.47–0.95), respectively. The A_-123T_-88 haplotype was also significantly associated with lower risk of EV71 infection in both the northern (OR = 0.62; 95 % CI = 0.44–0.85) and the southern population (OR = 0.63; 95 % CI = 0.43–0.92). Furthermore, we observed higher MxA messenger RNA levels in IFNβ1a-stimulated PBMCs from the -123A or -88T allele carriers compared with that from nocarriers. Our findings suggest that polymorphisms in the MxA promoter may play a role in mediating the susceptibility to EV71 infection in Chinese population.

The Pathogenesis and Prevention of Encephalitis due to Human Enterovirus 71

Human enterovirus 71 (HEV71) has emerged as a major cause of viral encephalitis in Southeast Asia, with increased epidemic activity observed since 1997. This is reflected in a large increase in scientific publications relating directly to HEV71. New research is elucidating details of the viral life cycle, confirming similarities between HEV71 and other enteroviruses. Scavenger receptor B2 (SCARB2) is a receptor for HEV71, although other receptors are likely to be identified. Currently, the only strategies to prevent HEV71-associated disease are early diagnosis and aggressive supportive management of identified cases. As more information emerges regarding the molecular processes of HEV71 infection, further advances may lead to the development of effective antiviral treatments and ultimately a vaccine-protection strategy. The protective efficacies of several inactivated HEV71 vaccines have been confirmed in animal models, suggesting that an effective vaccine may become available in the next decade.