Comparative study of enterovirus 71 infection of human cell lines

The cell tropism of enterovirus 71 (Enteroviridae) in neuronal, glial and laryngeal cells. The 4643 strain, an enterovirus 71 isolate from a patient in Taiwan, was used to infect three human cell lines representing neuronal cells (SK-N-SH, neuroblastoma), glial cells (U373MG, glioblastoma), and laryngeal cells (HEp-2, larynx epidermoid carcinoma). Immunofluorescent staining and transmission electron microscopy (TEM) were used to detect mature enterovirus 71 4643 virions in these cell lines. The three cell lines were also compared for presence of virus-mediated cytopathic effect (CPE), synthesis of infected cell-specific proteins, viral (-) RNA, and virus replication rate. Virus particles were detected by TEM, and viral replication increased over time, indicating the existence and release of mature viruses from all three infected cell lines. The most severe CPE and the highest viral replication rate were observed in the SK-N-SH cells. Further screening of the infected cell lines by microarray analysis revealed that the neuron growth factor receptor (NGFR) gene was uniquely upregulated in infected SK-N-SH cells, implying that the receptor encoded by this gene may be involved in cell tropism. The data show that neurons are vulnerable to enterovirus 71 4643 infection and are consistent with the clinical observation that enterovirus 71 4643 targets mainly neuronal cells but is also found in many organs in conjunction with an inflammatory reaction.     

人肠道病毒71型感染免疫抑制恒河猴的分析

目的: 通过建立人肠道病毒71型(EV71)感染在免疫抑制恒河猴的动物模型,进一步分析人EV71在免疫抑制动物体内病毒增殖、病理变化以及病毒抗原在不同组织的表达情况。方法: 按照每天15 mg/kg的剂量给8只恒河猴口服环孢菌素A连续7 d后造成其免疫抑制状态,再经呼吸道和消化道感染EV71病毒FY23株,对其进行14 d的临床观察后处死,采集各器官组织进行病毒载量检测,同时对不同的组织进行病理学分析和免疫组化分析。结果: 感染EV71病毒后,免疫抑制组的临床症状、病毒载量、病理分析和免疫组化结果都明显比非免疫抑制组严重,从病毒对机体造成的影响来看呼吸系统感染较消化系统感染明显严重。结论: 本实验分析了人EV71在免疫抑制动物体内病毒增殖的情况,为建立用于EV71疫苗评价的恒河猴动物模型提供了依据,并对未来的EV71疫苗的使用人群范围做出了新的限定。     

Epidemiology of enterovirus types causing neurological disease in Austria 1999–2007: Detection of clusters of echovirus 30 and enterovirus 71 and analysis of prevalent genotypes

Between 1999 and 2007 1,388 stool specimens from patients with acute flaccid paralysis or aseptic meningitis were submitted to the Austrian reference laboratory for poliomyelitis. Samples (201) yielded non‐poliovirus enterovirus in culture. One hundred eighty‐one viruses were available for typing and 78 isolates which remained serologically untyped were further analyzed by CODEHOP‐PCR and sequencing of the VP1 gene and the 5′‐untranslated region (5′‐UTR). Typing revealed an Echovirus 30 outbreak in northwestern Austria in 2000, which was in accordance with the situation in Europe, and no dramatic seasonal changes of Coxsackie viruses were observed. In 2002/2003 a small outbreak of enterovirus 71 (EV71), affected 12 patients in the province of Styria. This virus was identified as genotype C1 and appeared to be genetically distinct from the isolates observed in 2001/2002 in Vienna. In 2004 two unrelated cases occurred in Lower Austria, which were identified as genotype C4, which has been described associated with high mortality most recently in China. In contrast to the situation in Asia the detected EV71 cases were not associated with hand–foot–mouth disease, but with serous meningitis only. This was surprising as a recent publication suggested a reduced neurovirulence of C1 genotype in children in Norway, presumably due to alterations in 5′‐UTR and polymerase gene. However, comparing the 5′‐UTR of the Austrian isolates and established virulent reference strains to the Norwegian isolate and an attenuated EV71 laboratory strain we did not find an indication that the genotype C1 possesses a RNA structure in its 5′‐UTR leading to reduced neurovirulence. J. Med. Virol. 81:317–324, 2009. © 2008 Wiley‐Liss, Inc.     

Responses of IgM for enterovirus 71 infection

A rapid serological assay was developed for detection of specific IgM to enterovirus 71, a human picornavirus that is usually associated with severe central nervous system complications. The sensitivity and specificity of this "in-house" mu-capture enzyme linked-immunosorbent assay was assessed by testing 213 serum samples. With the conventional virus culture as a standard method, the sensitivity and specificity were 91.5 and 93.1%, respectively, for this newly developed immunoassay. This method allows for detection of the IgM responses from the patients either infected by genotype B or genotype C of enterovirus 71. IgM can be detected as early as the second day from the onset of disease. IgM responses exhibit 100% positive rate from enterovirus 71-infected patients with complications, including encephalitis, meningitis, polio-like syndrome, pulmonary edema, and fatal cases. These findings suggest that detection of specific IgM by the use of enzyme linked-immunosorbent assay is a rapid and valuable way for the diagnosis of enterovirus 71 infection.     

Immune responses against enterovirus A71 infection: Implications for vaccine success

Enterovirus A71 (EV‐A71) from the Picornaviridae family is an important emerging pathogen causing hand, foot, and mouth disease (HFMD) outbreaks worldwide. EV‐A71 also caused fatal neurological complications in young children especially in Asia. On the basis of seroepidemiological studies from many Asian countries, EV‐A71 infection is very common. Children of very young age are particularly vulnerable. Large‐scale epidemics that occur every 3 to 4 years are associated with accumulation of an immunologically naive younger population. Capsid proteins especially VP1 with the presence of major B‐ and T‐cell epitopes are the most antigenic proteins. The nonstructural proteins mainly contribute to T‐cell epitopes that induce cross‐reactive immune responses against other enteroviruses. Dominant epitopes and their neutralization magnitudes differ in mice, rabbits, and humans. Neutralizing antibody is sufficient for immune protection, but poorer cellular immunity may lead to severe neurological complications and deaths. Some chemokines/cytokines are consistently found in severely ill patients, for example, IL‐6, IL‐10, IL‐17A, MCP‐1, IL‐8, MIG, IP‐10, IFN‐γ, and G‐CSF. An increase in white cell counts is a risk factor for severe HFMD. Recent clinical trials on EV‐A71 inactivated vaccine showed >90% efficacy and a robust neutralization response that was protective, indicating neutralizing antibody correlates for protection. No protection against other enteroviruses was observed. A comprehensive understanding of the immune responses to EV‐A71 infection will benefit the development of diagnostic tools, potential therapeutics, and subunit vaccine candidates. Future development of a multivalent enterovirus vaccine will require knowledge of correlates of protection, understanding of cross‐protection and memory T‐cell responses among enteroviruses.     

Therapeutic and prevention strategies against human enterovirus 71 infection

Human enterovirus 71 (HEV71) is the cause of hand, foot and mouth disease and associated neurological complications in children under five years of age. There has been an increase in HEV71 epidemic activity throughout the Asia-Pacific region in the past decade, and it is predicted to replace poliovirus as the extant neurotropic enterovirus of highest global public health significance. To date there is no effective antiviral treatment and no vaccine is available to prevent HEV71 infection. The increase in prevalence, virulence and geographic spread of HEV71 infection over the past decade provides increasing incentive for the development of new therapeutic and prevention strategies against this emerging viral infection. The current review focuses on the potential, advantages and disadvantages of these strategies. Since the explosion of outbreaks leading to large epidemics in China, research in natural therapeutic products has identified several groups of compounds with anti-HEV71 activities. Concurrently, the search for effective synthetic antivirals has produced promising results. Other therapeutic strategies including immunotherapy and the use of oligonucleotides have also been explored. A sound prevention strategy is crucial in order to control the spread of HEV71. To this end the ultimate goal is the rapid development, regulatory approval and widespread implementation of a safe and effective vaccine. The various forms of HEV71 vaccine designs are highlighted in this review. Given the rapid progress of research in this area, eradication of the virus is likely to be achieved.     

Partial protection against enterovirus 71 (EV71) infection in a mouse model immunized with recombinant Newcastle disease virus capsids displaying the EV71 VP1 fragment

Enterovirus 71 (EV71) infection may cause severe neurological complications, particularly in young children. Despite the risks, there are still no commercially available EV71 vaccines. Hence, a candidate vaccine construct, containing recombinant Newcastle disease virus capsids that display an EV71 VP1 fragment (NPt-VP1(1-100) ) protein, was evaluated in a mouse model of EV71 infection. Previously, it was shown that this protein construct provoked a strong immune response in vaccinated adult rabbits. That study, however, did not address the issue of its effectiveness against EV71 infection in young animals. In the present study, EV71 viral challenge in vaccinated newborn mice resulted in more than 40% increase in survival rate. Significantly, half of the surviving mice fully recovered from their paralysis. Histological analysis of all of the surviving mice revealed a complete clearance of EV71 viral antigens from their brains and spinal cords. In hind limb muscles, the amounts of the antigens detected correlated with the degrees of tissue damage and paralysis. Findings from this study provide evidence that immunization with the NPt-VP1(1-100) immunogen in a newborn mouse model confers partial protection against EV71 infection, and also highlights the importance of NPt-VP1(1-100) as a possible candidate vaccine for protection against EV71 infections.     

An update on enterovirus 71 infection and interferon type I response

Enteroviruses are members of Pichornaviridae family consisting of human enterovirus group A, B, C, and D as well as nonhuman enteroviruses. Hand, foot, and mouth disease (HFMD) is a serious disease which is usually seen in the Asia‐Pacific region in children. Enterovirus 71 and coxsackievirus A16 are two important viruses responsible for HFMD which are members of group A enterovirus. IFN α and β are two cytokines, which have a major activity in the innate immune system against viral infections. Most of the viruses have some weapons against these cytokines. EV71 has two main proteases called 2A and 3C, which are important for polyprotein processing and virus maturation. Several studies have indicated that they have a significant effect on different cellular pathways such as interferon production and signaling pathway. The aim of this study was to investigate the latest findings about the interaction of 2A and 3C protease of EV71 and IFN production/signaling pathway and their inhibitory effects on this pathway.     

Differences in replication capacity between enterovirus 71 isolates obtained from patients with encephalitis and those obtained from patients with herpangina in Taiwan

The cellular-tropism and biological characteristics of enterovirus 71 (EV71) isolates in Taiwan (TW) were studied. Growth curve experiments were conducted using cell lines that were possibly exhibited pathogenesis, and RT-PCR and sequencing tests were undertaken to amplify the 5' non-coding region (5'-NCR). The encephalitis isolate EV71 TW98NTU2078 was PBMC-tropic, temperature-resistant (Tr) at 40 degrees C, and easier to replicate in HTB-14 (astrocytoma) than the herpangina isolate EV71 TW98NTU1186 (The viral yields were 100-fold higher than those of the herpangina isolate EV71 TW98NTU1186 at 96 hr post infection.). The herpangina isolate EV71 TW98NTU1186 was non-PBMC-tropic, and temperature-sensitive (Ts) at 40 degrees C. The replication of EV71 TW98NTU1186 in HTB-14 was lower. No EV71 isolate infected HTB-37 (human colon adenocarcinoma cells). The encephalitis EV71 isolate exhibited better replication and transmission in PBMCs and astrocytes than did the EV71 isolate without CNS involvement.     

Incidence and case-fatality rates resulting from the 1998 enterovirus 71 outbreak in Taiwan

In 1998, an epidemic of hand-foot-and-mouth disease and herpangina caused by enterovirus 71 occurred in Taiwan, leaving many fatalities and severely handicapped survivors in its wake. The reasons this rather common pathogen would cause such a large-scale epidemic remain unknown. A seroepidemiological survey to elucidate the epidemiological characteristics of this outbreak, including its incidence and case-fatality rates was undertaken. Microneutralization tests for antibodies against enterovirus 71 were used to screen four collections of serum samples: 1) 202 specimens taken from individuals > or = 4 years old in 1994; 2) 245 specimens collected from individuals of all ages in 1997; 3) 1,258 specimens collected from individuals of all ages in 1999; and 4) sera samples from a birth cohort of 81 children who had yearly blood samples taken from 1988-98. After the maternal antibody had declined, the seropositive rates began to increase with age. Approximately half of all children aged 6 years or older were enterovirus 71 seropositive. Significantly higher seropositive rates were noted in 1999 than in 1997, in children aged 0.5-3 years. The incidence of enterovirus 71 infection during the epidemic was estimated to be 13-22%, with the higher rates in younger children. The case-fatality rate was highest (96.96 per 100,000) in infants aged 6-11 months, and declined in older children. The results showed that enterovirus 71 is endemic in Taiwan. The apparent lack of large-scale enterovirus 71 activity in the 3 years before 1998 might have been the prelude to the epidemic's appearance in 1998, and might suggest that enterovirus 71 infection will reappear every few years. The lack of a protective antibody in younger children may account for the high incidence and case-fatality rate in this age group.     

Relationship between serologic response and clinical symptoms in children with enterovirus 71-infected hand-foot-mouth disease

This study aimed to explore the correlation between clinical symptoms, including rash and fever, and serum antibody reaction to enterovirus 71 (EV71) infection in children hospitalized due to hand-foot-mouth disease (HFMD). From May 2014 to July 2014, a total of 547 children hospitalized due to HFMD in Children’s Hospital of Fudan University were enrolled retrospectively. RNA levels of EV71 and CA16 in fecal, serum, and cerebrospinal fluid specimens were measured using quantitative real-time RT-PCR, and EV71-IgM antibody in the serum was detected using immune colloidal gold assays. Of the 547 fecal specimens, 296 were EV71 RNA positive, 109 were CA16 RNA positive, and 8 were positive for both EV71 RNA and CA16 RNA. The total positive rate for either EV71 or CA16 in feces was 72.58% (397/547). Additionally, 544 serum specimens were collected, and 409 were EV71-IgM positive (75.18%). The duration of rash and fever was found to be correlated to the positive rate of serum EV71-IgM, and the positive rate of serum EV71-IgM plus EV71 RNA in feces. The positive rates of serum EV71-IgM and serum EV71-IgM plus EV71 RNA in fecal collected at day 3 of fever were 79.7% and 52.8%, respectively. In conclusion, EV71 and CA16 were found to be the major pathogens responsible for the epidemics of HFMD in children during May to July 2014 in Shanghai, China. There is a close relationship between the positive rate of serum EV71-IgM and the duration of fever and rash.     

肠道病毒71型3C蛋白表达后细胞蛋白质组差异分析

目的 利用蛋白质组学技术研究肠道病毒71型(EV71)编码3c蛋白对宿主细胞蛋白表达的影响.方法 在293T细胞中瞬时过表达EV71 3C蛋白,应用双向荧光差异凝胶电泳(20-DICE)检测3C表达后293T细胞中蛋白的差异.选取表达水平有明显变化的蛋白用Western blot进行验证.结果 在293T细胞中过表达3...     

肠道病毒71型外壳蛋白VP1的可溶性表达、纯化及活性鉴定

目的克隆、表达和鉴定肠道病毒71型（EV71）VP1基因,得到可溶性的蛋白VP1,为制备EV71的抗体和诊断试剂的开发打下基础。方法优化EV71VP1蛋白基因,克隆并构建重组表达质粒pET15b/VP1,转化大肠杆菌BL21。使用Ni2＋亲和层析柱对重组蛋白进行纯化,并用Westernblotting检测目的蛋白。以重组蛋白VP1为抗原,ELISA检测抗原活性。结果重组蛋白在大肠杆菌中可以高效表达,SDS-PAGE显示其相对分子质量为36000,与预计大小一致。ELISA实验证实,重组蛋白具有良好的抗原性。结论本研究成功克隆和表达了EV71VP1蛋白,并得到可溶性的蛋白,对肠道病毒71型诊断试剂的开发有进一步潜在的应用价值。     

RNA interference against enterovirus 71 infection

Enterovirus 71 (EV71) is a highly infectious major causative agent of hand, foot, and mouth disease (HFMD) which could lead to severe neurological complications. There is currently no effective therapy against EV71. In this study, RNA interference (RNAi) is employed as a therapeutic approach for specific viral inhibition. Various regions of the EV71 genome were targeted for inhibition by chemically synthesized siRNAs. Transfection of rhabdomyosarcoma (RD) cells with siRNA targeting the 3'UTR, 2C, 3C, or 3D region significantly alleviated cytopathic effects of EV71. The inhibitory effect was dosage-dependent with a corresponding decrease in viral RNA, viral proteins, and plaque formations by EV71. Viral inhibition of siRNA transfected RD cells was still evident after 48 h. In addition, no significant adverse off-target silencing effects were observed. These results demonstrated the potential and feasibility for the use of siRNA as an antiviral therapy for EV71 infections.     

First detection of enterovirus 71 from an acute flaccid paralysis case with residual paralysis in Iran

In an attempt to determine the types of non-polio enteroviruses (NPEVs) in acute flaccid paralysis (AFP) cases in Iran, we detected enterovirus 71 (EV71) in an AFP case with residual paralysis for the first time. Cell culture detected no enteroviruses, while RT-PCR and subsequent sequencing revealed that the specimen was positive for EV71. EV71 is the causative agent of a variety of diseases from hand, foot and mouth disease to severe neurological complications and is now considered as an important cause of childhood acute flaccid paralysis.     

Genetic and antigenic analyses of enterovirus 71 isolates in Taiwan during 1998–2005

Enterovirus 71 (EV71) infections can lead to devastating clinical outcomes in children, with an increasing number of severe cases worldwide. The genetic and antigenic variability of EV71 strains isolated in Taiwan in 1998-2005 was evaluated using partial nucleotide sequence analysis of the VP1 gene and the neutralisation assay. Phylogenetic analyses revealed that most EV71 isolates from the 1998 epidemic belonged to sub-genogroup C2, with a minority belonging to sub-genogroup B4. Between 1999 and 2003, isolates belonging to sub-genogroup B4 predominated, followed by a change to sub-genogroup C4 in 2004 and 2005. Antibodies raised in rabbits or collected from infected patients were able to neutralise EV71 virus stocks at high dilutions, regardless of the sub-genogroup of the virus being challenged. The presence of phylogenetically distinct yet antigenically similar populations of EV71 in Taiwan is of concern in the context of herd immunity and vaccine development.     

Pathogenesis study of enterovirus 71 infection in rhesus monkeys

Enterovirus 71 (EV71), a major pathogen that is responsible for causing hand-foot-and-mouth disease (HFMD) worldwide, is a member of the Human Enterovirus species A, family Picornaviridae. HFMD that is caused by EV71 is usually characterized by vesicular lesions on the skin and oral mucosa and high morbidity rates in children; additionally, occasional fatal cases have been reported involving brainstem encephalitis and myelitis associated with cardiopulmonary collapse. Although viral pathogenesis in humans is unclear, previous animal studies have indicated that EV71, inoculated via various routes, is capable of targeting and injuring the central nervous system (CNS). We report here the pathogenic process of systemic EV71 infection in rhesus monkeys after inoculation via intracerebral, intravenous, respiratory and digestive routes. Infection with EV71 via these routes resulted in different rates of targeting to and injury of the CNS. Intracerebral inoculation resulted in pulmonary edema and hemorrhage, along with impairment of neurons. However, intravenous and respiratory inoculations resulted in a direct infection of the CNS, accompanied by obvious inflammation of lung tissue, as shown by impairment of the alveoli structure and massive cellular infiltration around the terminal bronchioles and small vessels. These pathological changes were associated with a peak of viremia and dynamic viral distribution in organs over time in the infected monkeys. Our results suggest that the rhesus monkey model may be used to study not only the basic pathogenesis of EV71 viral infections, but also to examine clinical features, such as neurological lesions, in the CNS and pathological changes in associated organs.     

惠州市重症手足口病病原谱及EV71型VP1区基因特征分析

目的分析惠州市手足口病重症病例的病原谱构成,了解惠州市肠道病毒71型分离株的VPl区基因特征．为科学防治手足口病提供科学依据。方法采集300例重症手足口病（HFMD）患者标本,采用实时荧光RT-PCR检测肠道病毒核酸,并对肠道病毒7l型（EV71）和柯萨奇病毒A16型（CoxA16）进行分型检测;选择8株EV71分离株进行VPl区基因全长序列测定,测序结果利用DNASTAR软件进行核苷酸、氨基酸序列分析和同源性比较。并用Mega5．0软件构建亲缘性进化树。结果通过实时荧光RT-PCR特异性检测,EV71阳性结果154份,阳性率为51．33％;CoxAl6阳性结果38份,阳性率为12．67％。测序结果表明,8株EV71之间的VPl基因核苷酸同源性为96．9％～99．2％。氨基酸同源性为99．3％～100％。VPI区基因遗传进化分析表明。8株EV71分离株与c4基因亚型的代表株处于同一分支,均属于C4基因亚型的C4a进化分支。结论惠州市手足口病疫情主要病原EV71病毒均属于C4a基因亚型,与2004年以来的中国大陆EV71病毒流行的基因型一致,未产生明显的抗原漂移及变异。     

人肠道病毒71型VP0蛋白的原核表达及多克隆抗体制备

目的:原核表达并纯化人肠道病毒71型(EV71)VP0蛋白,免疫豚鼠制备多克隆抗体,并鉴定其用于EV71检测的反应性和特异性。方法:PCR方法扩增VP0基因,构建原核表达质粒pET-VP0并转化大肠杆菌,诱导表达并纯化VP0重组蛋白,免疫豚鼠制备抗VP0多克隆抗体,ELISA方法检测抗VP0抗体效价,细胞免疫荧光和Western blot方法鉴定抗体特异性。结果:VP0重组蛋白在大肠杆菌BL21中高效表达,制备的抗VP0抗体效价为1∶106。细胞免疫荧光及Western blot检测结果显示,抗VP0多克隆抗体可以识别原核表达及EV71感染细胞中的VP0蛋白。结论:原核表达了EV71的VP0蛋白并制备出抗VP0多克隆抗体,为EV71的临床诊断、疫苗开发和分子病毒学研究提供了新的研究工具和手段。