Enterovirus 71 Neutralizing Antibody Research Articles

Immunogenicity and safety of an inactivated enterovirus 71 vaccine co-administered with measles-mumps-rubella vaccine and live-attenuated Japanese encephalitis vaccine: a phase 4, single-center, randomized controlled trial

ABSTRACT Co-administration of vaccines could be an efficient strategy to increase vaccination uptake and reduce the number of clinic visits. This randomized controlled study aimed to evaluate the immunogenicity and safety of enterovirus 71 (EV71) vaccine co-administered with measles-mumps-rubella (MMR) vaccine and live-attenuated Japanese encephalitis vaccine (LA-JEV). A total of 372 healthy infants were randomly assigned in a 1:1:1 ratio to receive simultaneous administration of EV71 vaccine (dose 1) and MMR on d 0 and EV71 vaccine (dose 2) and LA-JEV on d 30 (Group 1); administration of MMR and LA-JEV on d 0 and 30, respectively (Group 2); or administration of doses 1 and 2 of EV71 vaccine on d 0 and 30, respectively (Group 3). The non-inferiority analysis of the seroconversion for EV71 neutralizing antibody after vaccination was the primary outcome. According to per protocol set, antibody response against EV71, measles, mumps, rubella, and Japanese encephalitis (JE) virus was similar regardless of administration schedule. After vaccination, the seroconversion rate of EV71 neutralizing antibody in Group 1 (107 [97.27%] of 110) was non-inferior to that in Group 3 (109 [97.32%] of 112; difference – 0.05% [95% CI – 5.38 to 5.21]). The incidences of adverse reactions were 62.60% (77/123) in Group 1, 54.84% (68/124) in Group 2, and 37.70% (46/122) in Group 3, and most of them were mild to moderate in severity. No vaccine-related serious adverse events were reported. In total, the co-administration of combined EV71 vaccine with MMR and LA-JEV showed no interference with antibody response and demonstrated good safety profiles.

Interchangeability of two Enterovirus 71 inactivated vaccines in Chinese children: A phase IV, open-label, and randomized controlled trial

BackgroundIn China, three inactivated Enterovirus 71 (EV71) vaccines have been approved. Although the vaccines in an immunization series should be from a single manufacture, children sometimes have to receive EV71 vaccines from more than one manufacturers. The aim of this study was to evaluate the interchangeability and safety of vaccination with EV71 vaccines from two manufacturers among Chinese children. MethodsWe conducted an open label and randomized controlled study among children aged 6–35 months from November 2018 to January 2019. The participants were randomly assigned (1:1:1:1) to receive EV71 vaccines in one of the four different schedules (two using a single vaccine for all doses from one manufacture, and two mixed schedules using vaccines from two manufactures). Blood samples were collected pre-vaccination (Day 0) and one month after the second dose (Day 60) for neutralizing antibody assay. Immunogenicity was assessed in the per-protocol cohort and safety was assessed in the total vaccinated cohort. ResultsA total of 300 children were enrolled and randomized, of whom 89.0% (267/300) were included in the per-protocol cohort for immunogenicity analysis. The seroconversion rates of the EV71 neutralizing antibody in four groups ranged from 98.4% to 100.0%, and were not significantly different among the groups. Compared with other groups, geometric mean titer was higher in group D, in which the participants received Institute of Medical Biology Chinese Academy of Medical Sciences (CAMS) vaccine in the first dose and the Sinovac vaccine in the second dose. Safety profiles were similar among the four groups and no serious adverse events related to the vaccination were reported. ConclusionsInterchangeability of EV71 vaccines from two manufactures to complete an immunization series showed good immunogenicity and safety. The antibody response levels may vary by vaccination sequences of EV71 vaccines from the two manufacturers.Trial registration: ClinicalTrials.govNCT03873740.

A comparative analysis of immunogenicity and safety of an enterovirus 71 vaccine between children aged 3-5 years and infants aged 6-35 months

ABSTRACTBackground: The Sinovac enterovirus 71 (EV71) vaccine has shown good safety, immunogenicity, and efficacy in infants aged 6–35 months, whom are considered as the priority of the target population. However, 3–5 years old children accounted for approximately 30% of HFMD cases and are also worth our attention.Methods: A randomized, double-blind, placebo-controlled, batch-to-batch consistency clinical trial enrolling 1400 participants aged 6–59 months was performed. We pooled the participants receiving three batches of EV71 vaccine together and then stratified them into the 6–35 months and 3–5 years. The non-inferiority analysis of the geometric mean titer (GMT) of EV71 neutralizing antibody post-vaccination was the primary endpoint.Results: In the vaccine group, the GMT of 242 children aged 3–5 years was 132.72 (95% CI, 110.3–159.6), which was non-inferior to that generated in 717 infants aged 6–35 months. Following the vaccination, the incidence of adverse reactions was less frequent in children aged 3–5 years (47.0%) than that found in infants aged 6–35 months (60.1%) (p = 0.0026).Conclusions: Our study indicated that the EV71 vaccine was also safe in children aged 3–5 years, with non-inferior immunogenicity to that in infants aged 6–35 months.

Two models for changes of EV71 immunity in infants and young children

Human enterovirus 71 (EV71) has been associated with outbreaks of hand-foot-and-mouth disease (HFMD) in China. Susceptibility to EV71 is associated with age, but few studies have been accomplished to measure such a relationship. A better understanding of the connection between susceptibility and age is necessary to develop strategies for control of HFMD. In 2010, a survey of an epidemic of EV71 was conducted in a northern city of Jiangsu Province in China. Samples were tested serologically to identify the EV71 neutralizing antibody. Two different mathematical models have now been employed to describe how this antibody varied with age, and parameters in the model were estimated from survey data. Both models depicted the variations in EV71-neutralizing antibody. Seroprevalence was high for neonates but decreased to near zero at 5 months of age. Subsequently, the EV71 antibody levels increased and then remained stable after about 36 months. For models 1 and 2, values for the coefficient of determination (R2) were 0.9458 and 0.9576, and values for root mean square error (RMSE) were 0.0755 and 0.0752, respectively. Model 2, formulated from the characteristics of development of the immune system, was more reliable than model 1, formulated from survey data, because the impact of the survey on the structure of the model was removed. Moreover, model 2 provided the possibility to define the parameters in a biological sense.

Clinical evaluation for batch consistency of an inactivated enterovirus 71 vaccine in a large-scale phase 3 clinical trial

The demonstration of batch-to-batch consistency to confirm the reliability of the manufacturing process has become a mandatory step in vaccine development. This is a post-hoc analysis aimed to provide more solid evidence on the immunogenicity and consistency of 3 consecutive batches of a novel inactivated enterovirus 71 (EV71) vaccine. In total 10 245 healthy Chinese children aged 6–35 months had been recruited and randomized to receive one of 3 batches of EV71 vaccine or placebo according to a two-dose immunization schedule in a phase 3 clinical trial. Blood samples were taken just before and 28 days after vaccinations for serological tests of EV71 neutralizing antibody (NTAb) titer from the subjects. Among them, 7263 (70.9%) subjects with seronegative EV71 NTAb at baseline and the data of serological tests post-vaccination available were included for the analysis. The results showed that EV71 vaccine elicited high geometric mean titers (GMTs) of 407.0 U/mL (95% CI, 373.5–443.6) for batch 1, 468.1 U/mL (95% CI, 432.2–507.0) for batch 2, and 520.6 U/mL (95% CI, 481.2–563.3) for batch 3. The two-sided 95% confidence intervals (CIs) for the GMT ratios between each pair of vaccine batches were all within an interval of [0.67, 1.5]. Subjects who received EV71 vaccines demonstrated significant higher GMTs than those received placebos did (P < 0.001). In terms of incidence of both local and general adverse reactions, no differences were found among 3 vaccine batches and placebos. EV71 vaccine was highly immunogenic in children, and the 3 consecutive batches were well consistent.

Seroprevalence of Human Enterovirus 71 and Coxsackievirus A16 in Guangdong, China, in Pre- and Post-2010 HFMD Epidemic Period

BackgroundHuman Enterovirus 71 and Coxsackie A16 have caused many outbreaks in the last decade in mainland China, resulting in thousands of fatal cases. Seroepidemiology which provides important information to document population immunity is rare in China.Methodology/Principal FindingsA cross sectional study of Enterovirus 71 (EV71) and Coxsackie A16 (CA16) seroprevalence was carried out in Guangdong, China, pre- and post- the 2010 hand, foot and mouth disease (HFMD) epidemic period. The levels of EV71 and CA16 specific antibodies were evaluated by a microneutralization test and the geometric mean titer (GMT) was calculated and compared. Our results indicated frequent infection by EV71 and CA16 in Guangdong before the 2010 epidemic. Only EV71 neutralizing antibody but not CA16 seroprevalence was significantly increased after the 2010 HFMD epidemic. Children less than 3 years old especially those aged 2 years showed the lowest positive rates for EV71 and CA16 NA before epidemic and the most significantly increased EV71 seroprevalence after epidemic. CA16 GMT values declined after the 2010 epidemic.ConclusionsThese results indicate EV71 was the major pathogen of HFMD in Guangdong during the 2010 epidemic. The infection occurs largely in children less than 3 years, who should have first priority to receive an EV71 vaccine.

Protective Efficacy of VP1-Specific Neutralizing Antibody Associated with a Reduction of Viral Load and Pro-Inflammatory Cytokines in Human SCARB2-Transgenic Mice

Hand-foot-mouth diseases (HFMD) caused by enterovirus 71 (EV71) and coxsackievirus 16 (CVA16) in children have now become a severe public health issue in the Asian-Pacific region. Recently we have successfully developed transgenic mice expressing human scavenger receptor class B member 2 (hSCARB2, a receptor of EV71 and CVA16) as an animal model for evaluating the pathogenesis of enterovirus infections. In this study, hSCARB2-transgenic mice were used to investigate the efficacy conferred by a previously described EV71 neutralizing antibody, N3. A single injection of N3 effectively inhibited the HFMD-like skin scurfs in mice pre-infected with clinical isolate of EV71 E59 (B4 genotype) or prevented severe limb paralysis and death in mice pre-inoculated with 5746 (C2 genotype). This protection was correlated with remarkable reduction of viral loads in the brain, spinal cord and limb muscles. Accumulated viral loads and the associated pro-inflammatory cytokines were all reduced. The protective efficacy of N3 was not observed in animals challenged with CVA16. This could be due to dissimilarity sequences of the neutralizing epitope found in CVA16. These results indicate N3 could be useful in treating severe EV71 infections and the hSCARB2-transgenic mouse could be used to evaluate the protective efficacy of potential anti-enterovirus agent candidates.

Incidence Rates of Enterovirus 71 Infections in Young Children during a Nationwide Epidemic in Taiwan, 2008–09

ObjectiveEnterovirus 71 (EV71) is causing life-threatening outbreaks in tropical Asia. In Taiwan and other tropical Asian countries, although nationwide EV71 epidemics occur cyclically, age-specific incidence rates of EV71 infections that are critical to estimate disease burden and design vaccine trials are not clear. A nationwide EV71 epidemic occurred in 2008–09 in Taiwan, which provided a unique opportunity to estimate age-specific incidence rates of EV71 infections.Study DesignWe prospectively recruited 749 healthy neonates and conducted follow-ups from June 2006 to December 2009. Sera were obtained from participants at 0, 6, 12, 24, and 36 months of age for measuring EV71 neutralizing antibody titers. If the participants developed suspected enterovirus illnesses, throat swabs were collected for virus isolation.ResultsWe detected 28 EV71 infections including 20 symptomatic and 8 asymptomatic infections. Age-specific incidence rates of EV71 infection increased from 1.71 per 100 person-years at 0–6 months of age to 4.09, 5.74, and 4.97 per 100 person-years at 7–12, 13–24, and 25–36 months of age, respectively. Cumulative incidence rate was 15.15 per 100 persons by 36 months of age, respectively.ConclusionsRisk of EV71 infections in Taiwan increased after 6 months of age during EV71 epidemics. The cumulative incidence rate was 15% by 36 months of age, and 29% of EV71 infections were asymptomatic in young children.

Seroprevalence of enterovirus 71 and no evidence of crossprotection of enterovirus 71 antibody against the other enteroviruses in kindergarten children in Taipei city

Enterovirus 71 (EV71) infection may cause severe neurological and cardiopulmonary complications, especially in preschool children. This study is to investigate the seroprevalence and seroconversion of EV71, and the crossprotection of EV71 antibody against other enteroviruses among kindergarteners. Overall 228 children in a public kindergarten were enrolled during two academic years, 2006 and 2007, in Taipei, Taiwan and we measured their EV71 neutralizing antibody. When the participants had herpangina; hand, foot and mouth disease (HFMD); febrile illness or respiratory symptoms, throat swabs were sampled and processed for viral culture and enterovirus real-time reverse transcriptase polymerase chain reaction (RT-PCR). Questionnaires, completed by the participants' guardians, surveyed the history of allergy and annual incidence of symptoms related to enterovirus infection. Seropositive rates of EV71 were 20% (32/163) in 2006 and 6% (4/65) in 2007. The rate of EV71 seropositivity increased with age (p < 0.01) in 2006 but it did not differ between genders (p = 0.14). No seroconversion was observed from 2006 to 2007. Herpangina occurred in 64% of children with EV71 seropositivity and 48% of those without EV71 antibodies (p = 0.12). Non-71 enterovirus infection, confirmed by viral study, occurred in 53% (19/36) of the EV71-seropositive children and in 53% (102/192) of EV71-seronegative children (p = 0.89). No participants had EV71 infection during the study period. EV71 did not frequently circulate in Taipei City from September 2006 to June 2008. Presence of EV71 neutralizing antibody was not associated with lower incidence of enterovirus infection caused by non-71 serotypes.

The development and application of a quantitative ELISA detection method for enterovirus 71 antigen

Objective To develop an ELISA method for quantitative determination of enterovirus 71 (EV71) antigen.The method can be applied to detect EV71 antigen contents and analyze the correlation between immunogenicity and immunoprotection.It also can be used for tissue culture infective dose( TCID50 ) assay.Methods A double antibody sandwich ELISA method was developed for quantitative determination of EV71 antigen on the basis of the high-affinity neutralizing monoclonal antibodies ( K8G2 and Y8H2-HRP).This method was compared with microscopic observation for the detection of EV71 TCID50.The correlation was analyzed between the specific activity of EV71 antigen and the EV71 neutralizing antibody titer in immune serum.Results The linear range of this method was 0.125-4.0 U/ml and the R2 value was 0.9911.The reagent did not react with other antigens except EV71 antigen.The recovery ratio of this method was 0.89-1.16.The coefficient of variation was less than 15％.The heat recovery rate was above 85％ when the reagent was in 37℃ for 9 days.There was a good correlation in TCID50 of EV71 between this method and microscopic observation,r=0.990.The specific activity of EV71 antigen had positive correlation with the neutralization titer of immune serum in 21 EV71 strains,r=0.930.Conclusion The quantitative ELISA method for EV71 antigen was developed,which could be used to detect EV71 antigen contents and analyze TCID50.The specific activity of EV71 antigen detected by the method could be used to evaluate the immunoprotection of the vaccine potency test. Key words: Enterovirus 71; Double antibody sandwich ELISA; Specific activity

The Seroprevalence and Seroincidence of Enterovirus71 Infection in Infants and Children in Ho Chi Minh City, Viet Nam

Enterovirus 71 (EV71)-associated hand, foot and mouth disease has emerged as a serious public health problem in South East Asia over the last decade. To better understand the prevalence of EV71 infection, we determined EV71 seroprevalence and seroincidence amongst healthy infants and children in Ho Chi Minh City, Viet Nam. In a cohort of 200 newborns, 55% of cord blood samples contained EV71 neutralizing antibodies and these decayed to undetectable levels by 6 months of age in 98% of infants. The EV71 neutralizing antibody seroconversion rate was 5.6% in the first year and 14% in the second year of life. In children 5–15 yrs of age, seroprevalence of EV71 neutralizing antibodies was 84% and in cord blood it was 55%. Taken together, these data suggest EV71 force of infection is high and highlights the need for more research into its epidemiology and pathogenesis in high disease burden countries.

Seroepidemiology investigation of neutralizing antibody against enterovirus 71 among healthy people in Tianjin

To investigate the latent infection caused by enterovirus 71 (EV71) among healthy people in Tianjin and to provide evidence on prevention and control hand-food and mouth diseases (HFMD). 1611 sera specimens were collected from healthy people in Tianjin while EV71 antibody was detected by neutralization test, and then the results were analyzed statistically. For determining positivity, the cut-point was set at 1:4. The positive rate was 66.79% (1076/1611) for EV71 neutralizing antibody. The lowest positive rate was 32.71% in the 0 - 5 age group while the highest rate was 76.67% in the 16 - 25 age group. Significant difference was seen in the positive rates among different age groups. The lowest positive rate (59.05%) was seen in the city areas while the highest rate (72.35%) was seen in the surrounding counties. 5.71% of the people being tested showed their neutralizing antibody as ≥ 1:256. The difference was statistically significant on positive rates among different areas. We constructed logistic regression models with the EV71 neutralizing antibody positive rate as the dependent variable and age, sex, floating population, area etc. as independent variables. There appeared statistical significances in all the independent variables. Age seemed a risk factor for recessive infection of EV71, and the neutralizing antibody against EV71 might not be kept permanently. In order to prevent and control the HFMD, more attention should be paid to the areas where more floating population were resided.

Development of a high-throughput assay for measuring serum neutralizing antibody against enterovirus 71

Enterovirus 71 (EV71) is the main etiologic agent of hand, foot, and mouth disease (HFMD) and causes frequently severe neurological complications and mortality in young children. The serum neutralizing antibody response is the major indicator of EV71 infection and protective immunity. The current serum neutralization test based on inhibition of cytopathic effect (Nt-CPE) requires manual microscopic examination, which is time-consuming and labor-intensive. In this study, a high-throughput neutralization assay which employs enzyme immunoassay for detecting growth of EV71 in Rhabdomyosarcoma (RD) cells and measuring serum neutralizing antibody (Nt-EIA) against EV71 was developed. RD cells infected with 100 TCID 50 of EV71 for 36–42 h had the best performance and were selected for Nt-EIA. One hundred and twenty human sera (59 negative sera, 61 positive sera) were measured for EV71 neutralization antibody titers by Nt-CPE and Nt-EIA. Neutralization antibody titers against EV71 determined by Nt-EIA had a high sensitivity (100%), specificity (94.9%) and agreement (97.5%) by a qualitative comparison with Nt-CPE. In the quantitative comparison, the correlation coefficient between Nt-EIA and Nt-CPE was 0.91 after log transformation. Overall, the Nt-EIA is a suitable alternative assay for the quantitation of EV71 neutralizing antibody to EV71.