Specific detection of enterovirus 71 directly from clinical specimens using real-time RT-PCR hybridization probe assay

Comparative analysis of reverse-transcription-polymerase chain reaction for Aichivirus detection

Aichivirus-A (AiV-A), a member of the Kobuvirus genus of the family Picornaviridae, was first reported in stool samples of patients with non-bacterial gastroenteritis in Aichi Prefecture, Japan, in 1989. AiV has been reported from in various aquatic environments, such as surface water and sewage, can be transmitted via the fecal-oral route through contaminated water. As AiV is known to acute gastroenteritis worldwide, developing methods for AiV detection from contaminated environments and food is required. In the present study, we established an effective polymerase chain reaction (PCR) method to detect AiV. Various real-time reverse transcription (RT)-PCR and conventional PCR methods for AiV detection were compared, and the limit of detection was confirmed by comparing the sensitivity at varied primer concentrations and PCR conditions. The final detection limits were 102 copy/μL in conventional PCR, and 101 copy/μL in the real-time RT-PCR. The optimized method used in this study might aid in detecting AiV contamination.

A review on current diagnostic tools and potential optical absorption spectroscopy for HFMD detection

Hand, Foot, and Mouth Disease (HFMD) is an outbreak infectious disease that can easily spread among children under the age of five. The most common causative agents of HFMD are enterovirus 71 (EV71) and coxsackievirus A16 (CVA16), but infection caused by EV71 is more associated with fatalities due to severe neurological disorders. The present diagnosis methods rely on physical examinations by the doctors and further confirmation by laboratories detection methods such as viral culture and polymerase chain reaction. Clinical signs of HFMD infection and other childhood diseases such as chicken pox, and allergies are similar, yet the genetics and pathogenicity of the viruses are substantially different. Thus, there is an urgent need for an early screening of HFMD using an inexpensive and user-friendly device that can directly detect the causative agents of the disease. This paper reviews current HFMD diagnostic methods based on various target types, such as nucleic acid, protein, and whole virus. This was followed by a thorough discussion on the emerging sensing technologies for HFMD detection, including surface plasmon resonance, electrochemical sensor, and surface enhanced Raman spectroscopy. Lastly, optical absorption spectroscopic method was critically discussed and proposed as a promising technology for HFMD screening and detection.

Optimization of RT-PCR methods for enterovirus detection in groundwater

Enteroviruses (EVs), which belong to the Picornaviridae family, infect individuals asymptomatically or cause mild symptoms (fever, runny nose, cough, skin rash, sneezing, mouth blister). Severe cases can cause various diseases, such as acute hemorrhagic conjunctivitis, aseptic meningitis, or myocarditis, especially in infants. These viruses can be transmitted via the fecal-oral route via contaminated water. In this study, we established a polymerase chain reaction (PCR) method for detecting EVs in water sample using Coxsackievirus B5 (CV-B5) and Echovirus 30 (E-30), which belong to species B of the four species of EVs (EV-A to D). Several methods have been investigated and compared for the detection of EVs, including real-time reverse transcription (RT) polymerase chain reaction and conventional RT-PCR. The most sensitive primer sets were selected, and the PCR conditions were modified to increase sensitivity. We also quantified the detection limits of real-time and conventional RT-PCR. The detection limits of conventional RT-PCR were detected in 105-106 copy/mL for CV-B5 and 106-107 copy/mL for E-30, respectively. This optimized method for detecting EVs is expected to contribute substantially to the investigation of EV outbreaks in water samples.

Evaluation of GeneXpert EV assay for the rapid diagnosis of enteroviral meningitis: a systematic review and meta-analysis

Background

GeneXpert enterovirus Assay is a PCR-based assay for Enterovirus meningitis diagnosis. However, there is currently no research about the performance of GeneXpert enterovirus assay in the diagnosis of enterovirus meningitis. Thus, a systematic review and meta-analysis is significant on the topic.

Methods

Embase, Cochrane Library, Web of Science, and PubMed were systematically reviewed with retrieval types. Some criteria were used to filter the studies. Only studies published in English, that made a comparison between GeneXpert enterovirus assay and RT-PCR, and could be formulated in a 2*2 table, were included. The quality of the included studies was evaluated by QUADAS-2. The effect of the GeneXpert enterovirus assay was assessed by the Sensitivity, Specificity, Positive Likelihood Ratio, Negative Likelihood Ratio, Diagnosis Odds Ratio, and summary receiver operating characteristic (SROC) curve. Publication bias and heterogeneity were evaluated by the Deeks' funnel test and Bivariate Box plot respectively.

Results

7 studies were recruited in the analysis. The Pooled Sensitivity was 0.96 [95% CI (0.94–0.97)], Pooled Specificity was 0.99 [95% CI (0.98–0.99)], Positive Likelihood Ratio was 130.46 [95% CI (35.79–475.58)], Negative Likelihood Ratio was 0.04 [95% CI (0.02–0.10)], and Diagnostic Odds Ratio was 3648.23 (95% CI [963.99–13,806.72)]. In SROC Curve, Area Under Curve (AUC) was 0.9980, and Q*= 0.9849. In Deeks' funnel test, the P-value was 0.807 (P > 0.05), indicating no publication bias. The Bivariate Box plot indicated no evident heterogeneity.

Conclusions

The GeneXpert enterovirus assay demonstrated high diagnostic accuracy in diagnosing enterovirus meningitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00517-3.

Safety and Immunogenicity of a Stable, Cold-Adapted, Temperature-Sensitive/Conditional Lethal Enterovirus A71 in Monkey Study

Enterovirus A71 (EV-A71) and coxsackievirus A16 (CA16) are major etiological agents of hand foot and mouth disease (HFMD) in children, which may result in fatal neurological complications. The development of safe, cost effective vaccines against HFMD, especially for use in developing countries, is still a top public health priority. We have successfully generated a stable, cold-adapted, temperature sensitive/conditional lethal EV-A71 through adaptive culturing in Vero cells at incrementally lower cultivation temperatures. An additional 40 passages at an incubation temperature of 28 °C, and a temperature reversion study at an incubation temperature of 37 °C and 39.5 °C, reveals the virus’s phenotypic and genetic stability at the predefined culture conditions. Six unique mutations (two in noncoding regions and four in nonstructural protein-coding genes) in combination may have contributed to its stable phenotype and inability to fully revert to its original wild phenotype. The safety and immunogenicity of this stable, cold-adapted, temperature sensitive/conditional lethal EV-A71 was performed in six monkeys. None of the inoculated monkeys developed any obvious clinical illness except one which developed a transient spike of fever. No gross postmortem lesion or abnormal histological finding was noted for all monkeys at autopsy. No virus was reisolated although EV-A71 specific RNA was detected in serum samples collected on both day 4 and day 8 postinoculation. Only EV-A71 RNA and viral antigen were detected in the spleen homogenate and peripheral blood mononuclear cells, respectively, collected on day 4. The two remaining monkeys developed good humoral immune response on day 14 and day 30 post-inoculation.

Establishment of Asia-Pacific Network for Enterovirus Surveillance

Enteroviruses (EV), the major pathogens of hand, foot, and mouth disease (HFMD) and herpangina, affect millions of children each year. Most human enteroviruses cause self-limited infections except polioviruses, enterovirus A71 (EV-A71), enterovirus D68 (EV-D68), and several echoviruses (Echo) and coxsackieviruses (CV). Especially, EV-A71 has repeatedly caused large-scale outbreaks in the Asia-Pacific region since 1997. Some Asian countries have experienced cyclical outbreaks of severe EV-A71 infections and initiated development of EV-A71 vaccines. Five EV-A71 vaccine candidates have been clinically evaluated and three of them were approved for marketing in China. However, none of the China-approved products seek marketing approval in other countries. This situation supports a role for collaboration among Asian countries to facilitate clinical trials and licensure of EV-A71 vaccines. Additionally, enterovirus D68 outbreaks have been reported in the US and Taiwan currently and caused severe complications and deaths. Hence, an Asia-Pacific Network for Enterovirus Surveillance (APNES) has been established to estimate disease burden, understand virus evolution, and facilitate vaccine development through harmonizing laboratory diagnosis and data collection. Founded in 2017, the APNES is comprised of internationally recognized experts in the field of enterovirus in Asian countries working to raise awareness of this potentially fatal and debilitating disease. This article demonstrated the summaries of the first expert meeting, 2017 International Workshop on Enterovirus Surveillance and Vaccine Development, held by APNES in Taipei, Taiwan, March 2017.

Development of a highly sensitive real-time nested RT-PCR assay in a single closed tube for detection of enterovirus 71 in hand, foot, and mouth disease

Enterovirus 71 (EV71) is one of the major causative agents of outbreaks of hand, foot, and mouth disease (HFMD). A commercial TaqMan probe-based real-time PCR assay has been widely used for the differential detection of EV71 despite its relatively high cost and failure to detect samples with a low viral load (Ct value > 35). In this study, a highly sensitive real-time nested RT-PCR (RTN RT-PCR) assay in a single closed tube for detection of EV71 in HFMD was developed. The sensitivity and specificity of this assay were evaluated using a reference EV71 stock and a panel of controls consisting of coxsackievirus A16 (CVA16) and common respiratory viruses, respectively. The clinical performance of this assay was evaluated and compared with those of a commercial TaqMan probe-based real-time PCR (qRT-PCR) assay and a traditional two-step nested RT-PCR assay. The limit of detection for the RTN RT-PCR assay was 0.01 TCID₅₀/ml, with a Ct value of 38.3, which was the same as that of the traditional two-step nested RT-PCR assay and approximately tenfold lower than that of the qRT-PCR assay. When testing the reference strain EV71, this assay showed favorable detection reproducibility and no obvious cross-reactivity. The testing results of 100 clinical throat swabs from HFMD-suspected patients revealed that 41 samples were positive for EV71 by both RTN RT-PCR and traditional two-step nested RT-PCR assays, whereas only 29 were EV71 positive by qRT-PCR assay.

Validation and utilization of an internally controlled multiplex Real-time RT-PCR assay for simultaneous detection of enteroviruses and enterovirus A71 associated with hand foot and mouth disease

Background

Hand foot and mouth disease (HFMD) is a disease of public health importance across the Asia-Pacific region. The disease is caused by enteroviruses (EVs), in particular enterovirus A71 (EV-A71). In EV-A71-associated HFMD, the infection is sometimes associated with severe manifestations including neurological involvement and fatal outcome. The availability of a robust diagnostic assay to distinguish EV-A71 from other EVs is important for patient management and outbreak response.

Methods

We developed and validated an internally controlled one-step single-tube real-time RT-PCR in terms of sensitivity, linearity, precision, and specificity for simultaneous detection of EVs and EV-A71. Subsequently, the assay was then applied on throat and rectal swabs sampled from 434 HFMD patients.

Results

The assay was evaluated using both plasmid DNA and viral RNA and has shown to be reproducible with a maximum assay variation of 4.41 % and sensitive with a limit of detection less than 10 copies of target template per reaction, while cross-reactivity with other EV serotypes was not observed. When compared against a published VP1 nested RT-PCR using 112 diagnostic throat and rectal swabs from 112 children with a clinical diagnosis of HFMD during 2014, the multiplex assay had a higher sensitivity and 100 % concordance with sequencing results which showed EVs in 77/112 (68.8 %) and EV-A71 in 7/112 (6.3 %). When applied to clinical diagnostics for 322 children, the assay detected EVs in throat swabs of 257/322 (79.8 %) of which EV-A71 was detected in 36/322 (11.2 %) children. The detection rate increased to 93.5 % (301/322) and 13.4 % (43/322) for EVs and EV-A71, respectively, when rectal swabs from 65 throat-negative children were further analyzed.

Conclusion

We have successfully developed and validated a sensitive internally controlled multiplex assay for rapid detection of EVs and EV-A71, which is useful for clinical management and outbreak control of HFMD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0316-2) contains supplementary material, which is available to authorized users.

SYBR green real-time PCR for the detection of all enterovirus-A71 genogroups

Enterovirus A71 (EV-A71) has recently become an important public health threat, especially in South-East Asia, where it has caused massive outbreaks of Hand, Foot and Mouth disease every year, resulting in significant mortality. Rapid detection of EV-A71 early in outbreaks would facilitate implementation of prevention and control measures to limit spread. Real-time RT-PCR is the technique of choice for the rapid diagnosis of EV-A71 infection and several systems have been developed to detect circulating strains. Although eight genogroups have been described globally, none of these PCR techniques detect all eight. We describe, for the first time, a SYBR Green real-time RT-PCR system validated to detect all 8 EV-A71 genogroups. This tool could permit the early detection and shift in genogroup circulation and the standardization of HFMD virological diagnosis, facilitating networking of laboratories working on EV-A71 in different regions.

How to understand the efficacy measurements for enterovirus type 71 vaccine?

The choice of endpoint was most important for an efficacy vaccine trial. The objective of this paper is to gear toward answering questions about the rationality and scientificity of the primary endpoints choosing, case capturing and diagnosis strategy in our recently reported EV71 vaccine efficacy phase 3 trial. In order to obtain both high sensitivity and specificity in the case detecting, EV71-associated disease had been chosen as primary endpoint, a broad spectrum of clinical symptoms was surveyed, both the real-time RT-PCR and virus isolation were combined for the laboratory diagnosis, and serial specimens since disease onset were collected for assays. Though, the EV71 vaccine efficacy was well measured in the phase 3 trial, several potential factors could also have influences on the cases confirming. More evidence of EV71 vaccine efficacy will be demanded in post-marketing studies in the future.

Epidemiology and etiological characteristics of hand, foot and mouth disease in Huizhou City between 2008 and 2011

To study epidemiological features and etiological characteristics of hand, foot and mouth disease (HFMD), 42,012 cases were investigated from April 2008 to December 2011 in Huizhou, China. The average incidence rate was 21.16 per 10,000. The highest peak of HFMD incidence was detected between April and July each year, accounting for 55.93 % of all reported cases; another peak occurred in October through December, accounting for 24.17 % of the cases. Of the reported cases, 89.75 % were in children less than 4 years old, and there was a slight predominance of HFMD in boys and children living in rural and suburban areas. The major pathogens causing HFMD were enterovirus 71 (EV71) and coxsackievirus A16 (CA16). C4a was the most prominent EV71 subgenotype circulating in Huizhou. This founding provides insight for developing public-health interventions for the control and prevention of HFMD, especially for reducing the risk of HFMD in high-risk individuals by taking precautions against enterovirus infections.

New approaches for enhanced detection of enteroviruses from Hawaiian environmental waters

Health risks associated with sewage-contaminated recreational waters are of important public health concern. Reliable water monitoring systems are therefore crucial. Current recreational water quality criteria rely predominantly on the enumeration of bacterial indicators, while potentially dangerous viral pathogens often remain undetected. Human enteric viruses have been proposed as alternative indicators; however, their detection is often hindered by low viral concentrations present in the environment. Reported here are novel and effective laboratory protocols for viral concentration and highly sensitive and optimized RT-PCR for the efficient detection of enteroviruses, an important enteric virus subset, in Hawaiian environmental waters. Eighteen published enterovirus primer pairs were comparatively evaluated for detection sensitivity. The primer set exhibiting the lowest detection limit under optimized conditions, EQ-1/EQ-2, was validated in a field survey of 22 recreational bodies of water located around the island of Oahu, Hawaii. Eleven sites tested positive for enterovirus, indicating fecal contamination at these locations. As an additional means of viral concentration, shellfish were collected from 9 sample sites and subjected to dissection, RNA extraction, and subsequent RT-PCR. Shellfish tissue from 6 of 9 sites tested positive for enterovirus. The techniques implemented here are valuable resources to aid accurate reflection of microbial contamination in Hawaii’s environmental waters.

Screening and detection of human enterovirus 71 infection by a real-time RT-PCR assay in Marseille, France, 2009-2011

Enterovirus-positive samples diagnosed in Marseille (January 2009 to September 2011) were screened for EV71 by real-time RT-PCR. EV71 was detected in three children below the age of 2 years with no history of overseas travel; two of these cases were associated with severe clinical presentation. Viruses demonstrated genetic similarity to other European genogroup C2 strains. Strain MRS/09/3663 complete sequencing revealed 97.6% identity across the entire genome with a 2008 Singapore isolate, without signs of possible recombination events. To our knowledge, this is the first detection of EV71 infection in Marseille, France, that confirms the current circulation of EV71 in France.

Cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with Enterovirus 71 and Coxsackievirus A 16

OBJECTIVES

To evaluate the cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with EV71 and CA16.

METHODS

Real-time RT-PCR, virus isolation, ELISA and neutralization test were used to detect enteroviruses from clinical specimens and series sera of 79 HFMD patients.

RESULTS

27 EV71, 37 CA16, and 11 other enterovirus-infected patients were identified by RT-PCR. Among EV71 infected patients, anti-EV71 IgM positive ratios were 87.5% during 1-3 days after onset and 100% over 4 days after onset. In CA16 infected patients, the positive ratios were 7.4%, 26.4%, and 62.5% during 1-3 days, 4-6 days, and over 6 days after onset, respectively. Meanwhile, the results of neutralization test showed 18.9% of CA16 infected patients and 11.1% of EV71 infected patients present high cross-neutralization antibody against each other.

CONCLUSIONS

Cross-reactivity of anti-EV71 IgM in patients infected with EV71 and CA16 becomes stronger with the progress of disease. Moreover, high cross-neutralization antibody existing in part of patients suggests that the immune reactivity to EV71 infection can be recalled by CA16, and the immune reactivity to CA16 infection can be recalled by EV71. Therefore, identifying enteroviruses by neutralization test may not be an ideal selection.

Sustained high levels of interleukin-6 contribute to the pathogenesis of enterovirus 71 in a neonate mouse model

Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD) in young children and has been consistently associated with the most severe complications of the disease, including central nervous system inflammation and pulmonary edema. Increasing frequency and amplitude of EV71 outbreaks have raised awareness and concerns worldwide. Previous reports proposed that overwhelming virus replication combined with the induction of massive proinflammatory cytokines is responsible for the pathogenicity of EV71. Specifically, elevated interleukin-6 (IL-6) levels were observed consistently in patients and strongly correlated with disease severity. In this study, we show in the neonate mouse model that sustained high levels of IL-6 produced upon EV71 infection lead to severe tissue damage and eventually death of the animals. Administration of anti-IL-6 neutralizing antibodies after the onset of the clinical symptoms successfully improved the survival rates and clinical scores of the infected hosts. Compared to untreated infected controls, anti-IL-6-treated mice displayed reduced tissue damage, absence of splenic atrophy, and increased immune cell activation. In addition, markedly elevated systemic levels of IL-10 were measured in the protected animals. Furthermore, there was no significant difference in virus titers between anti-IL-6-treated mice and untreated mice, indicating that the anti-IL-6 antibody-mediated protection is independent of the virus load. Our findings thus demonstrate that IL-6 plays a major role in EV71-induced immunopathogenesis. As there is still neither vaccine nor treatment available against EV71, anti-IL-6 antibody treatment represents a potential therapeutic approach to providing protection from the most severe complications of the disease.

Detection of enteroviruses from clinical specimens

Enteroviruses are positive stranded RNA viruses belonging to the genus Enterovirus of the Picornaviridae family. Human enteroviruses are transmitted through the fecal-oral route and have been shown to cause mild to life-threatening diseases. Various diagnostic methods have been developed to detect enteroviruses from clinical specimens but many were impeded by requirements for special reagents, lengthy procedures, low sensitivity or cross-reactivity. This chapter describes rapid and highly sensitive methods of enteroviral detection directly from clinical specimens based on a conventional one-step Reverse Transcription polymerase chain reaction (RT-PCR) and a one-step real-time RT-PCR.

The largest outbreak of hand; foot and mouth disease in Singapore in 2008: the role of enterovirus 71 and coxsackievirus A strains

BACKGROUND

During 2008, Singapore experienced its largest ever outbreak of hand, foot and mouth disease (HFMD), resulting in 29686 cases, including four cases of encephalitis and one fatality.

METHODS

A total of 51 clinical specimens from 43 patients with suspected HFMD at the National University Hospital, Singapore were collected for virus isolation and identification by reverse transcription polymerase chain reaction (RT-PCR) and sequencing.

RESULTS

Enteroviruses were identified in 34 samples (66.7%), with 11 samples (21.6%) being positive for enterovirus 71 (EV71). Other non-EV71 enteroviruses (including coxsackievirus A4, A6, A10, and A16) were identified in 23 samples (45.1%). The most prevalent virus serotypes were CA6, CA10, and EV71. CA6 and CA10 accounted for 35.3% of all HFMD cases, which may explain the high transmissibility and low fatality that characterized this unprecedented epidemic associated with relatively mild disease. Phylogenetic analyses of 10 circulating EV71 strains indicated that they belonged to two subgenogroups, i.e., B5 (80%) and C2 (20%). The VP1 sequences of the 2008 EV71 strains also exhibited continuous mutations during the outbreak, reflecting the relatively high mutation rate of the EV71 capsid protein, which may have implications for future vaccine development.

CONCLUSIONS

A safe and effective vaccine against EV71 is certainly warranted in view of its potential neurovirulence and its role in HFMD epidemics of recurring frequency with resultant fatalities in Asia, as well as other parts of the world.

Performance of detecting IgM antibodies against enterovirus 71 for early diagnosis

Enterovirus 71 (EV71) infection is more likely to induce severe complications and mortality than other enteroviruses. Methods for detection of IgM antibody against EV71 had been established for years, however, the performance of the methods in the very early diagnosis of EV71 infection had not been fully evaluated, which is especially meaningful because of the short incubation period of EV71 infection. In this report, the performance of an IgM anti-EV71 assay was evaluated using acute sera collected from 165 EV71 infected patients, 165 patients infected with other enteroviruses, and more than 2,000 sera from healthy children or children with other infected diseases. The results showed a 90% sensitivity in 20 patients who were in their first illness day, and similar sensitivity remained till 4 days after onset. After then the sensitivity increased to 95% to 100% for more than one month. The specificity of the assay in non-HFMD children is 99.1% (95% CI: 98.6–99.4), similar as the 99.9% specificity in healthy adults. The cross-reaction rate in patients infected with other non-EV71 enteroviruses was 11.4%. In conclusion, the data here presented show that the detection of IgM anti-EV71 by ELISA affords a reliable, convenient, and prompt diagnosis of EV71 infection.

Rapid detection of enterovirus 71 by real-time TaqMan RT-PCR

BACKGROUND

Enterovirus 71 (EV71) is the main etiological agent of Hand, Foot and Mouth Disease (HFMD) and has been associated with neurological complications which resulted in fatalities during recent outbreaks in Asia Pacific region.

OBJECTIVE

Develop a real-time TaqMan RT-PCR for rapid detection of EV71.

STUDY DESIGN

Specific primers and probe were designed based on highly conserved VP1 region of EV71. The sensitivity of the real-time RT-PCR was evaluated with 67 clinical specimens collected from pediatric patients with suspected HFMD.

RESULTS

Our real-time TaqMan RT-PCR showed 100% specificity in detecting EV71 and showed an analytical sensitivity of 5 viral copies. High sensitivity was also achieved in detecting EV71 directly from clinical specimens.

CONCLUSIONS

Real-time TaqMan RT-PCR offers a rapid and sensitive method to detect EV71 from clinical specimens, and will allow quarantine measures to be taken more effectively during outbreaks.

Inhibition of enterovirus 71 in virus-infected mice by RNA interference

Enterovirus 71 (EV71) is the main causative agent of hand, foot, and mouth disease (HFMD) in young children. It is often associated with neurological complications and has caused high mortality levels in recent outbreaks in the Asia Pacific region. Currently, there is no effective antiviral therapy against EV71 infections. In this study, we have evaluated and compared the efficacies of three different forms of small interfering RNAs (siRNAs) in inhibiting EV71 replication in a murine model. We have shown that both synthetic 19-mer siRNAs and plasmid-borne short hairpin RNAs (shRNAs) targeted at the conserved 3D(pol) region were able to inhibit EV71 infections in suckling mice when delivered with or without lipid carrier via the systemic route. The treated mice did not exhibit hind limb paralysis and weight loss, as was observed in untreated mice. EV71 replication was significantly reduced as revealed by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blot. In addition, no evidence of interferon (IFN) induction was detected in the intestinal tissues harvested from the mice as a result of siRNA administration. However, the chemically synthesized 29-mer shRNA did not protect the suckling mice from EV71 infections despite being more potent in the in vitro system. Our results indicate that RNA interference (RNAi) may be a promising therapeutic approach for fighting EV71 infections.

Passive protection against lethal enterovirus 71 infection in newborn mice by neutralizing antibodies elicited by a synthetic peptide

Enterovirus 71 (EV71) infections could lead to high mortalities and neither vaccine nor therapeutic treatment is available. We investigated vaccination with a synthetic peptide SP70 representing a neutralizing linear VP1 epitope of EV71 strain 41 (subgenogroup B4) and passive transfer of anti-SP70 antibodies to protect suckling Balb/c mice against EV71 infectivity. When the mouse anti-SP70 antisera with a neutralizing antibody titer of 1:32 were passively administered to one-day-old suckling mice which had been challenged with a lethal dose of 1000 TCID(50) per mouse, the neutralizing anti-SP70 antibodies were able to confer 80% in vivo protection. In contrast, suckling mice which did not receive any anti-SP70 antisera did not survive the viral challenge at day 21 postinfection. Histological examination and real-time RT-PCR assays revealed viral infiltration in small intestines of EV71-infected mice. Interestingly, anti-SP70 antibodies play a major role in the inhibition of EV71 replication in vivo and significantly reduced the viral titer. In conclusion, EV71-neutralizing antibodies elicited by the synthetic peptide SP70 were able to confer good in vivo passive protection against homologous and heterologous EV71 strains in suckling Balb/c mice.