Shuizhen He

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.

Development of an IgM-capture ELISA for Coxsackievirus A16 infection

Diagnosis of Coxsackievirus A16 (CA16) infection in China relies mainly on reverse transcription-polymerase chain reaction (RT-PCR) that require expensive equipment and special trained personnel, thus making its wide application in health care settings unlikely. In this study, a novel IgM anti-CA16 assay was developed for the detection of IgM antibodies to CA16 in serum. The responses and diagnostic value of IgM for the CA16 infection were assessed by testing 1970 serum samples. The results showed that sensitivity of IgM test was 84.6% (259/306, 95% CI: 80.1-88.5), and specificity in control subjects and patients with CA16 HFMD was 99.2% (1508/1520, 95% CI: 98.6-99.6) and 90.3% (14/144, 95% CI: 84.2-94.6), respectively. The IgM positive rate reached 56.3% in the sera collected within the first day after onset, increased continuously to 95.3% at day 5 to day 7 after onset, and then reached 100% after more than 8 days. The cross-reaction rate in patients infected with other non-CA16 enteroviruses was 9.7% (14/144). These results suggest that the IgM anti-CA16 assay offers a rapid, convenient, and reliable method to detect acute CA16 infections.

A One-Step, Triplex, Real-Time RT-PCR Assay for the Simultaneous Detection of Enterovirus 71, Coxsackie A16 and Pan-Enterovirus in a Single Tube

The recent, ongoing epidemic of hand, foot, and mouth disease (HFMD), which is caused by enterovirus infection, has affected millions of children and resulted in thousands of deaths in China. Enterovirus 71 (EV71) and coxsackie A16 (CA16) are the two major distinct pathogens for HFMD. However, EV71 is more commonly associated with neurologic complications and even fatalities. Therefore, simultaneously detecting and differentiating EV71 and CA16 specifically from other enteroviruses for diagnosing HFMD is important. Here, we developed a one-step, triplex, real-time RT-PCR assay for the simultaneous detection of EV71, CA16, and pan-enterovirus (EVs) in a single tube with an internal amplification control. The detection results for the serially diluted viruses indicate that the lower limit of detection for this assay is 0.001–0.04 TCID50/ml, 0.02 TCID50/ml, and 0.001 TCID50/ml for EVs, EV71, and CA16, respectively. After evaluating known HFMD virus stocks of 17 strains of 16 different serotypes, this assay showed a favorable detection spectrum and no obvious cross-reactivity. The results for 141 clinical throat swabs from HFMD-suspected patients demonstrated sensitivities of 98.4%, 98.7%, and 100% for EVs, EV71, and CA16, respectively, and 100% specificity for each virus. The application of this one-step, triplex, real-time RT-PCR assay in clinical units will contribute to HFMD surveillance and help to identify causative pathogen in patients with suspected HFMD.

Serial Foodborne Norovirus Outbreaks Associated with Multiple Genotypes

Noroviruses (NoV) have been recognized as an important pathogen associated with acute gastroenteritis worldwide during the past three decades. In the spring of 2012, a series of foodborne outbreaks in tourist groups were reported to Xiamen Center for Disease Control and Prevention, Xiamen, Fujian province, China. Among a total of 268 tourists in 7 groups, the prevalence rate of acute gastroenteritis was 16.0% (43/268). Twenty-three feces or anal swabs were collected for laboratory tests of causative agents, no bacterial pathogen was identified, while 22 of them were positive for NoV RNA. In addition, thirteen NoV fragments were recovered from positive specimens and sequenced, belonging to five genotypes such as GI.3, GI.4, GII.4, GII.6, and GII.14, respectively. However, NoV fragments obtained from locally infected patients showed distinct genotypes. Therefore, epidemiological investigation and laboratory analyses demonstrated that the serial foodborne NoV outbreaks in tourists were co-infection of multiple genotypes induced acute gastroenteritis linked to a restaurant.

A Convenient Nucleic Acid Test on the Basis of the Capillary Convective PCR for the On-Site Detection of Enterovirus 71

The recent and continuing epidemic of enterovirus 71 in China has affected millions of children and resulted in thousands of deaths. Timely diagnosis and management is essential for disease control. Current enterovirus 71 molecular tests require resources that are unavailable for on-site testing. We have developed a simple-to-operate nucleic acid test, the convenient and integrated nucleic acid test, for local medical institutions. It uses a convective PCR for rapid amplification, a dipstick for visual detection of PCR products, and a simple commercial kit for nucleic acid extraction. By using a specially designed reagent and reaction tube containing a dipstick, the amplification and detection processes are well integrated and simplified. Moreover, cross contamination that may be caused by an open-tube detection system can be avoided. On the basis of the convenient and integrated nucleic acid test, an enterovirus 71 assay for on-site testing was developed. After evaluating known hand, foot, and mouth disease virus stocks of 17 strains of 11 different serotypes, this assay showed a favorable detection spectrum and no cross-reactivity. Its clinical performance was established by testing 141 clinical samples and comparing the results with a nested RT-PCR method. The assay showed a clinical sensitivity and specificity of 98.5% and 100%, respectively. Our results suggest that this convenient and integrated nucleic acid test enterovirus 71 assay may serve as an on-site diagnosis tool.

Serological survey of neutralizing antibodies to eight major enteroviruses among healthy population

Human enteroviruses (EVs) are the most common causative agents infecting human, causing many harmful diseases, such as hand, foot, and mouth disease (HFMD), herpangina (HA), myocarditis, encephalitis, and aseptic meningitis. EV-related diseases pose a serious worldwide threat to public health. To gain comprehensive insight into the seroepidemiology of major prevalent EVs in humans, we firstly performed a serological survey for neutralizing antibodies (nAbs) against Enterovirus A71 (EV-A71), Coxsackie virus A16 (CV-A16), Coxsackie virus A6 (CV-A6), Coxsackie virus A10 (CV-A10), Coxsackie virus B3 (CV-B3), Coxsackie virus B5 (CV-B5), Echovirus 25 (ECHO25), and Echovirus 30 (ECHO30) among the healthy population in Xiamen City in 2016, using micro-neutralization assay. A total of 515 subjects aged 5 months to 83 years were recruited by stratified random sampling. Most major human EVs are widely circulated in Xiamen City and usually infect infants and children. The overall seroprevalence of these eight EVs were ranged from 14.4% to 42.7%, and most of them increased with age and subsequently reached a plateau. The co-existence of nAbs against various EVs are common among people ≥ 7 years of age, due to the alternate infections or co-infections with different serotypes of EVs, while most children were negative for nAb against EVs, especially those < 1 year of age. This is the first report detailing the seroepidemiology of eight prevalent EVs in the same population, which provides scientific data supporting further studies on the improvement of EV-related disease prevention and control.

An emerging and expanding clade accounts for the persistent outbreak of Coxsackievirus A6-associated hand, foot, and mouth disease in China since 2013

Enterovirus (EV)-A71 and Coxsackievirus (CV)-A16 have historically been the major pathogens of hand, foot, and mouth disease (HMFD) in China; however, CV-A6， which had previously received little attention, became the predominant pathogen in 2013, and has remained one of the common pathogens since then. In this work, we conducted a molecular epidemiology study of CV-A6-associated HFMD in Xiamen from 2009 to 2015. The data showed CV-A6 pandemics had a certain periodicity rather than occurring randomly. Evolution analysis based on near-complete VP1 nucleotide sequences showed subgenotype D5 lineage 4 strains account for the persistent outbreak of CV-A6-associated HFMD in China since 2013. Alignment analysis revealed eight candidate amino acid substitutions in VP1, which may provide useful information for the research of CV-A6 virulence enhancement. This study contributed to elucidating the circulation patterns and genetic characteristics of CV-A6 in China; however, further surveillance and intervention in CV-A6 epidemics is recommended.

Development and evaluation of rapid point-of-care tests for detection of Enterovirus 71 and Coxsackievirus A16 specific immunoglublin M antibodies.

Two colloidal gold immunochromatographic assays (CGIAs) for detection of EV71- and CA16- immunoglobulin M (IgM) were developed and evaluated. A total of 1465 sera collected from children with hand, foot, and mouth disease (HFMD), non-HFMD patients and healthy children. The sensitivity of IgM CGIA tests for EV71 and CA16 were 97.6% (330/338) and 91.6% (296/323) respectively, compared to those who were viral RNA positive by PCR. Their performances were comparable to those of commercial ELISA kits, with agreement of 98.1% for EV71-IgM and 97.3% for CA16-IgM. In addition, for EV71- and CA16-IgM CGIAs, the results of whole blood samples were 99.6% (248/249) and 100% (191/191) concordant to those with serum samples, respectively. As rapid point-of-care (POC) tests, the two CGIAs were suitable to be used in community clinic units, especially in resource-poor areas and will facilitate the control of HFMD.

Development of multiplex real-time reverse-transcriptase polymerase chain reaction assay for simultaneous detection of Zika, dengue, yellow fever, and chikungunya viruses in a single tube: WU et al.

Zika virus (ZIKV), dengue virus (DENV), chikungunya virus (CHIKV) and yellow fever virus (YFV) share the same mosquito vectors and have similar clinical manifestations early stage of infection. Therefore, simultaneously differentiating these viruses from each other is necessary. We developed a multiplex real‐time reverse‐transcriptase polymerase chain reaction (RT‐PCR) assay for the differentiation of these four viruses in a single tube. The linear range was established by regression analysis, and the R2 value for each virus was ≥0.98, and the 95% lower limit of detection for each virus was as follows (copies/reaction): ZIKV‐Asian, 9; ZIKV‐Africa, 15; CHIKV, 11; DENV‐1, 19; DENV‐2, 13; DENV‐3, 24; DENV‐4, 36; and YFV, 17. Meanwhile, our multiplex real‐time RT‐PCR has a good consistency with the commercial singleplex assay. In summary, the developed assay can be effectively used for the diagnosis of ZIKV, DENV, CHIKV, and YFV infections.