EV71 vaccine, a new tool to control outbreaks of hand, foot and mouth disease (HFMD)

Vaccination coverage estimates and utilization patterns of inactivated enterovirus 71 vaccine post vaccine introduction in Ningbo, China

Background

In China, enterovirus 71 (EV71) is the major etiological agents of hand foot mouth disease that poses severe risks to children’s health. Since 2015, three inactivated EV71 vaccines have been approved for use. Previous studies indicated the high willingness of EV71 vaccination in eastern China. However, few studies have assessed coverage and utilization patterns of EV71 vaccine in China.

Methods

Children born during 2012–2018 were sampled and their records were abstracted from Ningbo childhood immunization information management system. Descriptive statistics characterized the study population and assessed coverage and timeliness for EV71 vaccination. Simultaneous administration patterns as well as type of EV71 vaccine used were also evaluated. Bivariate and multivariable analysis was used to examine the relationship of socio-demographic characteristics with vaccination coverage and timeliness.

Results

Of 716,178 children living in Ningbo. One hundred seventy-two thousand two hundred thirty-six received EV71 vaccine with a coverage rate of 24.05% and only 8.61% received vaccination timely. 21.97% of children received the complete two dose EV71 series but only 6.49% completed timely. Vaccination coverage and timeliness increased significantly from 2012 birth cohort to 2018 birth cohort. Relatively higher coverage and timeliness were observed in resident children, Inner districts, high socioeconomic areas and large-scaled immunization clinics. Of 329,569 doses of EV71 vaccine, only 5853(1.78%) doses were administered at the same day as other vaccines.

Conclusions

There is a need for increasing EV71 vaccination coverage and timeliness as well as eliminating disparities among different populations. Our study highlights the importance of simultaneous administration to increasing coverage and timeliness of EV71 vaccination.

Chimeric enterovirus 71 virus-like particle displaying conserved coxsackievirus A16 epitopes elicits potent immune responses and protects mice against lethal EV71 and CA16 infection

Hand-foot-and-mouth disease (HFMD) is an infectious disease of infants and young children frequently caused by the enterovirus A species, mainly enterovirus 71 (EV71) and coxsackievirus A16 (CA16). In this study, we prepared the EV71 virus-like particle (EV71-VLP) and its chimeras using recombinant baculovirus (Bac-P1-3CD) co-expressing EV71 P1 (under polyhedrin promoter) and 3CD (under CMV-IE promoter) proteins in Sf9 cells. EV71-VLP chimera ChiEV71(1E)-VLP or ChiEV71(4E)-VLP displayed single CA16 PEP71 epitope in VP1 or four conserved CA16 neutralizing epitopes (PEP71 in VP1, aa136-150 in VP2, aa176-190 in VP3 and aa48-62 in VP4) by substitution of the corresponding regions of EV71 structure proteins, respectively. In mice, EV71-VLP and its chimeras elicited similar EV71-specific IgG and neutralizing antibody (NAb) titers compared to inactivated EV71. Expectedly, vaccination of ChiEV71(1E)-VLP or ChiEV71(4E)-VLP resulted in significantly increased CA16-specific IgG and NAb production and improved cross-protection against CA16 infection compared to EV71-VLP. Interestingly, the VLPs induced potent cellular immune responses and significantly decreased Th2 type (IL-4 and IL-10) cytokines secretion in the splenocytes of immunized mice compared to inactivated EV71 or inactivated CA16. Neonatal mice born to dams immunized with the chimeric VLPs or neonatal mice passively transferred with sera of immunized mice were completely protected from lethal EV71 challenge and partially protected from lethal CA16 infection. Our study provides a novel bivalent or multivalent vaccine strategy to prevent EV71 and related-enterovirus infections.

COVID-19 vaccines: progress and understanding on quality control and evaluation

The outbreak of COVID-19 has posed a huge threat to global health and economy. Countermeasures have revolutionized norms for working, socializing, learning, and travel. Importantly, vaccines have been considered as most effective tools to combat with COVID-19. As of the beginning of 2021, >200 COVID-19 vaccine candidates, covering nearly all existing technologies and platforms, are being research and development (R&D) by multiple manufacturers worldwide. This has posed a huge obstacle to the quality control and evaluation of those candidate vaccines, especially in China, where five vaccine platforms are deployed in parallel. To accelerate the R&D progress of COVID-19 vaccines, the guidances on R&D of COVID-19 vaccine have been issued by National Regulatory Authorities or organizations worldwide. The Center for Drug Evaluation and national quality control laboratory in China have played a leading role in launching the research on quality control and evaluation in collaboration with relevant laboratories involved in the vaccine R&D, which greatly supported the progression of vaccines R&D, and accelerated the approval for emergency use and conditional marketing of currently vaccine candidates. In this paper, the progress and experience gained in quality control and evaluation of COVID-19 vaccines developed in China are summarized, which might provide references for the R&D of current and next generation of COVID-19 vaccines worldwide.

Immunogenicity and Safety of Inactivated Enterovirus 71 Vaccine in Children Aged 36-71 Months: A Double-Blind, Randomized, Controlled, Non-inferiority Phase III Trial

BACKGROUND

The Sinovac enterovirus 71 (EV71) vaccine has been given to children aged 6-35 months with good safety, immunogenicity, and efficacy. Further exploration is needed for the application of Sinovac EV71 vaccine in older children.

METHODS

A phase III, double-blind, single-center, randomized, controlled, non-inferiority, and bridging-designed trial enrolled 300 participants aged 6-35 months and 600 participants aged 36-71 months. Non-inferiority and superiority analyses were made to determine the immunogenicity of Sinovac EV71 vaccine in older children (Older-S group), comparing with that of control EV71 vaccine in the same age group (Older-C group), or comparing with that of Sinovac EV71 vaccine in younger children (Younger-S group).

RESULTS

The seroconversion rate of anti-EV71 in Older-S group (95.5%) was superior to that of Older-C group (86.0%), and non-inferior to that of Younger-S group (98.5%). For baseline seronegative participants, the geometric mean titer of Older-S group (370.0) was non-inferior to that of Older-C group (296.2) and superior to that of Younger-S group (176.5). Incidence of adverse reactions in Older-S group (47.0%) was similar to that of Older-C group (44.8%), or Younger-S group (49.8%).

CONCLUSIONS

This study showed good safety and immunogenicity of Sinovac EV71 vaccine in children aged 36-71 months.

CLINICAL TRIALS REGISTRATION

NCT03909074.

URL

https://clinicaltrials.gov/ct2/show/NCT03909074?term=NCT03909074&draw=2&rank=1.

Cross-Antigenicity between EV71 Sub-Genotypes: Implications for Vaccine Efficacy

Enterovirus A-71 (EV71) is a global, highly contagkkious pathogen responsible for severe cases of hand-food-mouth-disease (HFMD). The use of vaccines eliciting cross neutralizing antibodies (NTAbs) against the different circulating EV71 sub-genotypes is important for preventing HFMD outbreaks. Here, we tested the cross-neutralizing activities induced by EV71 genotype/sub-genotype A, B0-B4, C1, C2, C4, and C5 viruses using rats. Differences were noted in the cross-neutralization of the 10 sub-genotypes tested but there were generally good levels of cross-neutralization except against genotype A virus, against which neutralization antibody titres (NTAb) where the lowest with NTAbs being the highest against sub-genotype B4. Moreover, NTAb responses induced by C4, B4, C1, and C2 viruses were homogenous, with values of maximum/minimum NTAb ratios (MAX/MIN) against all B and C viruses ranging between 4.0 and 6.0, whereas MAX/MIN values against B3 and A viruses were highly variable, 48.0 and 256.0, respectively. We then dissected the cross-neutralizing ability of sera from infants and children and rats immunized with C4 EV71 vaccines. Cross-neutralizing titers against the 10 sub-genotypes were good in both vaccinated infants and children and rats with the MAX/MIN ranging from 1.8–3.4 and 5.1–7.1, respectively, which were similar to those found in naturally infected patients (2.8). Therefore, we conclude that C4 EV71 vaccines can provide global protection to infants and children against HFMD caused by different sub-genotypes.

In Vitro Characterization of Neutralizing Hen Antibodies to Coxsackievirus A16

Coxsackievirus A16 (CA16) is one of the major causative agents of hand, foot, and mouth disease (HFMD). Children aged <5 years are the most affected by CA16 HFMD globally. Although clinical symptoms of CA16 infections are usually mild, severe complications, such as aseptic meningitis or even death, have been recorded. Currently, no vaccine or antiviral therapy for CA16 infection exists. Single-chain variable fragment (scFv) antibodies significantly inhibit viral infection and could be a potential treatment for controlling the infection. In this study, scFv phage display libraries were constructed from splenocytes of a laying hen immunized with CA16-infected lysate. The pComb3X vector containing the scFv genes was introduced into ER2738 Escherichia coli and rescued by helper phages to express scFv molecules. After screening with five cycles of bio-panning, an effective scFv antibody showing favorable binding activity to proteins in CA16-infected lysate on ELISA plates was selected. Importantly, the selected scFv clone showed a neutralizing capability against the CA16 virus and cross-reacted with viral proteins in EV71-infected lysate. Intriguingly, polyclonal IgY antibody not only showed binding specificity against proteins in CA16-infected lysate but also showed significant neutralization activities. Nevertheless, IgY-binding protein did not cross-react with proteins in EV71-infected lysate. These results suggest that the IgY- and scFv-binding protein antibodies provide protection against CA16 viral infection in in vitro assays and may be potential candidates for treating CA16 infection in vulnerable young children.

Spatial-temporal mapping and risk factors for hand foot and mouth disease in northwestern inland China

Background

Hand foot and mouth disease (HFMD) is becoming one of the common human infectious diseases in China. Previous studies have described HFMD in tropical or coastal areas of Asia-Pacific countries. However, limited studies have thoroughly studied the epidemiology and potential risk factors for HFMD in inland areas with complex environmental conditions.

Methodology/Principal findings

Using the data from 2009 to 2018 on reported cases of Xinjiang Uighur Autonomous Region, we characterized the epidemic features of HFMD. Panel negative binomial model was used to identify climate, geographical and demographic determinants for HFMD incidence. A total of 70856 HFMD cases (average annual incidence: 305 per million persons) were reported in Xinjiang during the 10-year study period, of which 10393 (14.7%) were laboratory-confirmed and 98 (0.1%) were severe. HFMD peaked in summer every year during the study period, and incidence in 2012, 2015, 2016 and 2018 had minor peaks in autumn. After adjusting the school or holiday month, multiple factors were found to affect HFMD epidemiology: urban area being major land cover type (incidence risk ratio, IRR 2.08; 95% CI 1.50, 2.89), higher gross domestic product per capita (IRR 1.14; 95% CI 1.11, 1.16), rise in monthly average temperature (IRR 1.65; 95% CI 1.61, 1.69) and monthly accumulative precipitation (IRR 1.20; 95% CI 1.16, 1.24) predicted increase in the incidence of HFMD; farmland being major land cover type (IRR 0.72; 95% CI 0.64, 0.81), an increase of percentage of the minority (IRR 0.91; 95% CI 0.89, 0.93) and population density (IRR 0.98; 95% CI 0.98, 0.99) were related to a decrease in the incidence of HFMD.

Conclusions/Significance

In conclusion, the epidemic status of HFMD in Xinjiang is characterized by low morbidity and fatality. Multiple factors have significant influences on the occurrence and transmission of HFMD in Xinjiang.

Hand foot and mouth disease (HFMD) is one of the common human infectious disease threating Asia-Pacific countries. To explore the epidemiology and environmental risk factors for HFMD in inland China, we utilized 10-year HFMD surveillance data in Xinjiang Uighur Autonomous Region and combined multiple spatial-temporal statistical analyses. We identified spatial-temporal clusters of HFMD incidence and found that multiple factors could affect HFMD incidence: urban area being major land cover type, higher gross domestic product per capita, rise in monthly average temperature and monthly accumulative precipitation predicted increase in the incidence of HFMD; farmland being major land cover type, an increase of percentage of the minority and population density were related to a decrease in the incidence of HFMD. Our findings facilitate the understanding of HFMD epidemiology and risk factors in different geographic regions, which are crucial for conducting prevention and control strategies of HFMD.

Two cases of hand, foot and mouth disease caused by enterovirus A71 after vaccination

BACKGROUND

Enterovirus A71 (EVA71) is one of the main pathogens causing hand, foot and mouth disease (HFMD). In China, the proportion of cases of HFMD caused by EVA71 is known to be significantly lower following EVA71 vaccination; however, infection with EVA71 can still occur after vaccination.

METHODS

The complete genomic sequences of EVA71-KM18A and KM18B (from two rare cases of EVA71 infection following vaccination) were obtained. Phylogenetic analysis, nucleotide mutation analysis, recombinant analysis and comparative analysis of amino acid mutations were performed.

RESULTS

Phylogenetic analysis determined that the EVA71 strains belonged to the C4a subgenotype. The KM18A and KM18B strains were highly similar to the vaccine strains. For the KM18B strain, there were some obvious homologous recombination signals in the 5'non-coding region, region 2A, region 2C and region 3D. Amino acid mutations were observed in the SP55 (position 729) and 71-6 (position 500) conformational neutralizing epitopes of the KM18A and KM18B strains.

CONCLUSIONS

These amino acid mutations may affect the SP55 and 71-6 conformational neutralizing epitopes and change their spatial conformation, thereby weakening vaccine effectiveness.

Enterovirus A71 Vaccines

Enterovirus A71 (EV-A71) is a major causative agent of hand, foot, and mouth disease (HFMD) and herpangina. Moreover, EV-A71 infection can lead to neurological complications and death. Vaccination is the most efficient way to control virus infection. There are currently three inactivated, whole EV-A71 vaccines licensed by the China NMPA (National Medical Products Administration). Several other types of vaccines, such as virus-like particles and recombinant VP1 (capsid protein), are also under development. In this review, we discuss recent advances in the development of EV-A71 vaccines.

Spatial and Temporal Characteristics of Hand-Foot-and-Mouth Disease and Its Response to Climate Factors in the Ili River Valley Region of China

Background: As the global climate changes, the number of cases of hand-foot-and-mouth disease (HFMD) is increasing year by year. This study comprehensively considers the association of time and space by analyzing the temporal and spatial distribution changes of HFMD in the Ili River Valley in terms of what climate factors could affect HFMD and in what way. Methods: HFMD cases were obtained from the National Public Health Science Data Center from 2013 to 2018. Monthly climate data, including average temperature (MAT), average relative humidity (MARH), average wind speed (MAWS), cumulative precipitation (MCP), and average air pressure (MAAP), were obtained from the National Meteorological Information Center. The temporal and spatial distribution characteristics of HFMD from 2013 to 2018 were obtained using kernel density estimation (KDE) and spatiotemporal scan statistics. A regression model of the incidence of HFMD and climate factors was established based on a geographically and temporally weighted regression (GTWR) model and a generalized additive model (GAM). Results: The KDE results show that the highest density was from north to south of the central region, gradually spreading to the whole region throughout the study period. Spatiotemporal cluster analysis revealed that clusters were distributed along the Ili and Gongnaisi river basins. The fitted curves of MAT and MARH were an inverted V-shape from February to August, and the fitted curves of MAAP and MAWS showed a U-shaped change and negative correlation from February to May. Among the individual climate factors, MCP coefficient values varied the most while MAWS values varied less from place to place. There was a partial similarity in the spatial distribution of coefficients for MARH and MAT, as evidenced by a significant degree of fit performance in the whole region. MCP showed a significant positive correlation in the range of 15–35 mm, and MAAP showed a positive correlation in the range of 925–945 hPa. HFMD incidence increased with MAT in the range of 15–23 °C, and the effective value of MAWS was in the range of 1.3–1.7 m/s, which was positively correlated with incidences of HFMD. Conclusions: HFMD incidence and climate factors were found to be spatiotemporally associated, and climate factors are mostly non-linearly associated with HFMD incidence.

Post-marketing safety surveillance for inactivated Enterovirus 71 vaccines in Jiangsu, China from 2017 to 2019

INTRODUCTION

Two types of enterovirus 71 (EV71) vaccines, manufactured using human diploid (H2) and Vero cells, have been administered in Jiangsu Province, China since 2017. In this study, we evaluated their safety profiles using records collected from the Chinese National Adverse Events Following Immunization (AEFIs) Information System (CNAEFIS) and Electronic Immunization Registries System (EIRS) between 2017 and 2019.

METHODS

Demographic characteristics of the patients, AEFI incidence rates(IRs), symptoms, and time intervals were summarized from the reported AEFI data in the CNAEFIS. Also, the administered doses of the two vaccines were exported from the EIRS to calculate the IRs of AEFIs and thus compare the AEFIs between the two types of EV71 vaccines.

RESULTS

In total, 209, 407, and 344 AEFIs cases following EV71 vaccine administration were reported during 2017, 2018, and 2019, respectively, yielding IRs of 59.2, 48.2, and 54.2 per 100,000 doses, respectively. Fever, irritability, allergic eruptions, fatigue, loss of appetite, redness and induration at the injection site were the most commonly reported AEFIs. No significant differences in rare reactions were found between the two types of EV71 vaccinations. The majority of AEFIs were developed within 30 min to 3 days after administration.

CONCLUSION

EV71 vaccines showed satisfactory safety profiles since their first use 3 years ago in the Jiangsu Province. The AEFI profiles were identical to those in pre-marketing studies; most AEFIs after vaccination were mild and common. More active surveillance studies should be performed to provide more comprehensive post-marketing safety data.

Meteorological Factors and the Transmissibility of Hand, Foot, and Mouth Disease in Xiamen City, China

Background: As an emerging infectious disease, the prevention and control of hand, foot, and mouth disease (HFMD) poses a significant challenge to the development of public health in China. In this study, we aimed to explore the mechanism of the seasonal transmission characteristics of HFMD and to reveal the correlation and potential path between key meteorological factors and the transmissibility of HFMD. Methods: Combined with daily meteorological data such as average temperature, average relative humidity, average wind velocity, amount of precipitation, average air pressure, evaporation capacity, and sunshine duration, a database of HFMD incidence and meteorological factors was established. Spearman rank correlation was used to calculate the correlation between the various meteorological factors and the incidence of HFMD. The effective reproduction number (R eff ) of HFMD was used as an intermediate variable to further quantify the dynamic relationship between the average temperature and R eff . Results: A total of 43,659 cases of HFMD were reported in Xiamen from 2014 to 2018. There was a significantly positive correlation between the average temperature and the incidence of HFMD (r = 0.596, p < 0.001), and a significantly negative correlation between the average air pressure and the incidence of HFMD (r = -0.511, p < 0.001). There was no correlation between the average wind velocity (r = 0.045, p > 0.05) or amount of precipitation (r = 0.043, p > 0.05) and incidence. There was a temperature threshold for HFMD's transmissibility. Owing to the seasonal transmission characteristics of HFMD in Xiamen, the temperature threshold of HFMD's transmissibility was 13.4-18.4°C and 14.5-29.3°C in spring and summer and in autumn and winter, respectively. Conclusions: HFMD's transmissibility may be affected by the average temperature; the temperature threshold range of transmissibility in autumn and winter is slightly wider than that in spring and summer. Based on our findings, we suggest that the relevant epidemic prevention departments should pay close attention to temperature changes in Xiamen to formulate timely prevention strategies before the arrival of the high-risk period.

Regional-level risk factors for severe hand-foot-and-mouth disease: an ecological study from mainland China

Background

Severe hand-foot-and-mouth disease (HFMD) is a life-threatening contagious disease among young children and infants. Although enterovirus A71 has been well acknowledged to be the dominant cause of severe HFMD, there still remain other unidentified risk factors for severe HFMD. Previous studies mainly focused on identifying the individual-level risk factors from a clinical perspective, while rare studies aimed to clarify the association between regional-level risk factors and severe HFMD, which may be more important from a public health perspective.

Methods

We retrieved the clinical HFMD counts between 2008 and 2014 from the Chinese Center for Disease Control and Prevention, which were used to calculated the case-severity rate in 143 prefectural-level cities in mainland China. For each of those 143 cities, we further obtained city-specific characteristics from the China City Statistical Yearbook (social and economic variables) and the national meteorological monitoring system (meteorological variables). A Poisson regression model was then used to estimate the associations between city-specific characteristics (reduced by the principal component analysis to avoid multicollinearity) and the case-severity rate of HFMD. The above analysis was further stratified by age and gender to examine potential modifying effects and vulnerable sub-populations.

Results

We found that the case-severity rate of HFMD varied dramatically between cities, ranging from 0 to 8.09%. Cities with high case-severity rates were mainly clustered in Central China. By relating the case-severity rate to city-specific characteristics, we found that both the principal component characterized by a high level of social and economic development (RR = 0.823, 95%CI 0.739, 0.916) and another that characterized by warm and humid climate (RR = 0.771, 95%CI 0.619, 0.960) were negatively associated with the case-severity rate of HFMD. These estimations were consistent across age and gender sub-populations.

Conclusion

Except for the type of infected pathogen, the case-severity rate of HFMD was closely related to city development and meteorological factor. These findings suggest that social and environmental factors may also play an important role in the progress of severe HFMD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-020-00927-9.

Leading Enterovirus Genotypes Causing Hand, Foot, and Mouth Disease in Guangzhou, China: Relationship with Climate and Vaccination against EV71

(1) Background: Assignment of pathogens to the correct genus, species, and type is vital for controlling infectious epidemics. However, the role of different enteroviruses during hand, foot, and mouth disease (HFMD) epidemics and the major contributing factors remain unknown. (2) Methods: HFMD cases from 2016 to 2018 in Guangzhou, China were collected. The relationship between HFMD cases and genotype frequency, as well as the association between genotype frequency and climate factors, were studied using general linear models. We transformed the genotype frequency to the isometric log-ratio (ILR) components included in the model. Additionally, vaccination rates were adjusted in the climate-driven models. (3) Results: We observed seasonal trends in HFMD cases, genotype frequency, and climate factors. The model regressing case numbers on genotype frequency revealed negative associations with both the ILRs of CAV16 (RR = 0.725, p < 0.001) and EV71 (RR = 0.421, p < 0.001). The model regressing genotype frequency on driven factors showed that the trends for EV71 proportions were inversely related to vaccination rate (%, β = -0.152, p = 0.098) and temperature (°C, β = -0.065, p = 0.004). Additionally, the trends for CVA16 proportions were inversely related to vaccination rate (%, β = -0.461, p = 0.004) and temperature (°C, β = -0.068, p = 0.031). The overall trends for genotype frequency showed that EV71 decreased significantly, while the trends for CVA16 increased annually. (4) Conclusions: Our findings suggest a potential pathway for climate factors, genotype frequency, and HFMD cases. Our study is practical and useful for targeted prevention and control, and provides environmental-based evidence.

Forecast and early warning of hand, foot, and mouth disease based on meteorological factors: Evidence from a multicity study of 11 meteorological geographical divisions in mainland China

BACKGROUND

Hand, foot, and mouth disease (HFMD) is a significant public health issue in China. Early warning and forecasting are one of the most cost-effective ways for HFMD control and prevention. However, relevant research is limited, especially in China with a large population and diverse climatic characteristics. This study aims to identify local specific HFMD epidemic thresholds and construct a weather-based early warning model for HFMD control and prevention across China.

METHODS

Monthly notified HFMD cases and meteorological data for 22 cities selected from different climate zones from 2014 to 2018 were extracted from the National Notifiable Disease Surveillance System and the Meteorological Data Sharing Service System, respectively. A generalized additive model (GAM) based on meteorological factors was conducted to forecast HFMD epidemics. The receiver operator characteristic curve (ROC) was generated to determine the value of optimal warning threshold.

RESULTS

The developed model was solid in forecasting the epidemic of HFMD with all R square (R²) in the 22 cities above 85%, and mean absolute percentage error (MAPE) less than 1%. The warning thresholds varied by cities with the highest threshold observed in Shenzhen (n = 7195) and the lowest threshold in Liaoyang (n = 12). The areas under the curve (AUC) was greater than 0.9 for all regions, indicating a satisfied discriminating ability in epidemics detection.

CONCLUSIONS

The weather-based HFMD forecasting and early warning model we developed for different climate zones provides needed information on occurrence time and size of HFMD epidemics. An effective early warning system for HFMD could provide sufficient time for local authorities to implement timely interventions to minimize the HFMD morbidity and mortality.

Vaccine Hesitancy and Concerns About Vaccine Safety and Effectiveness in Shanghai, China

INTRODUCTION

Rapidly urbanizing communities in middle-income countries could be sources of vaccine hesitancy, and may create hot spots of low vaccination coverage. This study characterizes vaccine hesitancy in Shanghai and identifies disparities in vaccine safety and efficacy concerns by residency status-a marker for recent migration into the city.

METHODS

Parents of children aged ≤18 years from immunization clinics in Shanghai were enrolled in summer 2019, with the data analyzed during winter 2019-2020. The paper questionnaire used the Parental Attitudes towards Childhood Vaccines scale, which included questions about vaccine safety and efficacy concerns. The primary independent variable was residency-whether an individual was a Shanghai local or a recent migrant (i.e., non-local). Linear regression models assessed the relationship between residency and vaccine safety and efficacy concerns.

RESULTS

Among 1,021 participants, 65.4% had local residency, and the remainder were urban non-locals (13.1%) or rural non-locals (21.5%). A majority of parents expressed concerns about vaccine side effects (73.8%), vaccine safety (63.9%), and vaccine effectiveness (52.4%). Compared with locals, rural non-locals were more concerned about vaccine side effects (β=0.26, 95% CI=0.07, 0.46), vaccine safety (β=0.42, 95% CI=0.19, 0.65), and vaccine effectiveness (β=0.37, 95% CI=0.16, 0.58).

CONCLUSIONS

Differences in vaccine hesitancy by residency could lead to geographical and sociodemographic disparities in vaccination coverage and outbreaks of vaccine-preventable disease.

SUPPLEMENT INFORMATION

This article is part of a supplement entitled Global Vaccination Equity, which is sponsored by the Global Institute for Vaccine Equity at the University of Michigan School of Public Health.

Early Evidence of Inactivated Enterovirus 71 Vaccine Impact Against Hand, Foot, and Mouth Disease in a Major Center of Ongoing Transmission in China, 2011-2018: A Longitudinal Surveillance Study

BACKGROUND

Enterovirus 71 (EV71) is a major causative agent of hand, foot, and mouth disease (HFMD), associated with severe manifestations of the disease. Pediatric immunization with inactivated EV71 vaccine was initiated in 2016 in the Asia-Pacific region, including China. We analyzed a time series of HFMD cases attributable to EV71, coxsackievirus A16 (CA16), and other enteroviruses in Chengdu, a major transmission center in China, to assess early impacts of immunization.

METHODS

Reported HFMD cases were obtained from China's notifiable disease surveillance system. We compared observed postvaccination incidence rates during 2017-2018 with counterfactual predictions made from a negative binomial regression and a random forest model fitted to prevaccine years (2011-2015). We fit a change point model to the full time series to evaluate whether the trend of EV71 HFMD changed following vaccination.

RESULTS

Between 2011 and 2018, 279 352 HFMD cases were reported in the study region. The average incidence rate of EV71 HFMD in 2017-2018 was 60% (95% prediction interval [PI], 41%-72%) lower than predicted in the absence of immunization, corresponding to an estimated 6911 (95% PI, 3246-11 542) EV71 cases averted over 2 years. There were 52% (95% PI, 42%-60%) fewer severe HFMD cases than predicted. However, the incidence rate of non-CA16 and non-EV71 HFMD was elevated in 2018. We identified a significant decline in the trend of EV71 HFMD 4 months into the postvaccine period.

CONCLUSIONS

We provide the first real-world evidence that programmatic vaccination against EV71 is effective against childhood HFMD and present an approach to detect early vaccine impact or intended consequences from surveillance data.

Dysregulated autophagy contributes to the pathogenesis of enterovirus A71 infection

Enterovirus A71 (EVA71) infection continues to remain a vital threat to global public health, especially in the Asia–Pacific region. It is one of the most predominant pathogens that cause hand, foot, and mouth disease (HFMD), which occurs mainly in children below 5 years old. Although EVA71 prevalence has decreased sharply in China with the use of vaccines, epidemiological studies still indicate that EVA71 infection involves severe and even fatal HFMD cases. As a result, it remains more fundamental research into the pathogenesis of EVA71 as well as to develop specific anti-viral therapy. Autophagy is a conserved, self-degradation system that is critical for maintaining cellular homeostasis. It involves a variety of biological functions, such as development, cellular differentiation, nutritional starvation, and defense against pathogens. However, accumulating evidence has indicated that EVA71 induces autophagy and hijacks the process of autophagy for their optimal infection during the different stages of life cycle. This review provides a perspective on the emerging evidence that the “positive feedback” between autophagy induction and EVA71 infection, as well as its potential mechanisms. Furthermore, autophagy may be involved in EVA71-induced nervous system impairment through mediating intracranial viral spread and dysregulating host regulator involved self-damage. Autophagy is a promising therapeutic target in EVA71 infection.

Genomic epidemiology of coxsackievirus A16 in mainland of China, 2000-18

Hand, foot, and mouth disease (HFMD), which is a frequently reported and concerning disease worldwide, is a severe burden on societies globally, especially in the countries of East and Southeast Asia. Coxsackievirus A16 (CV-A16) is one of the most important causes of HFMD and a severe threat to human health, especially in children under 5 years of age. To investigate the epidemiological characteristics, spread dynamics, recombinant forms (RFs), and other features of CV-A16, we leveraged the continuous surveillance data of CV-A16-related HFMD cases collected over an 18-year period. With the advent of the EV-A71 vaccine since 2016, which targeted the EV-A71-related HFMD cases, EV-A71-related HFMD cases decreased dramatically, whereas the CV-A16-related HFMD cases showed an upward trend from 2017 to October 2019. The CV-A16 strains observed in this study were genetically related and widely distributed in the mainland of China. Our results show that three clusters (B1a-B1c) existed in the mainland of China and that the cluster of B1b dominates the diffusion of CV-A16 in China. We found that eastern China played a decisive role in seeding the diffusion of CV-A16 in China, with a more complex and variant transmission trend. Although EV-A71 vaccine was launched in China in 2016, it did not affect the genetic diversity of CV-A16, and its genetic diversity did not decline, which confirmed the epidemiological surveillance trend of CV-A16. Two discontinuous clusters (2000-13 and 2014-18) were observed in the full-length genome and arranged along the time gradient, which revealed the reason why the relative genetic diversity of CV-A16 increased and experienced more complex fluctuation model after 2014. In addition, the switch from RFs B (RF-B) and RF-C co-circulation to RF-D contributes to the prevalence of B1b cluster in China after 2008. The correlation between genotype and RFs partially explained the current prevalence of B1b. This study provides unprecedented full-length genomic sequences of CV-A16 in China, with a wider geographic distribution and a long-term time scale. The study presents valuable information about CV-A16, aimed at developing effective control strategies, as well as a call for a more robust surveillance system, especially in the Asia-Pacific region.

Comprehensive analysis of differential expression profiles via transcriptome sequencing in SH-SY5Y cells infected with CV-A16

Coxsackievirus A16 (CV-A16) is one of the viruses that is most frequently associated with hand-foot-and-mouth disease (HFMD). Previous studies have shown that CV-A16 infections are mostly self-limiting, but in recent years, it has been gradually found that CV-A16 infections can also induce neurological complications and eventually cause death in children with HFMD. Moreover, no curative drugs or preventative vaccines have been developed for CV-A16 infection. Therefore, it is particularly important to investigate the mechanism of CV-A16 infection-induced neuropathy. In the current study, transcriptome sequencing technology was used to identify changes in the transcriptome of SH-SY5Y cells infected with CV-A16, which might hide the mechanism of CV-A16-induced neuropathology. The transcriptome profiling showed that 82,406,974, 108,652,260 and 97,753,565 clean reads were obtained in the Control, CV-A16-12 h and CV-A16-24 h groups, respectively. And it was further detected that a total of 136 and 161 differentially expressed genes in CV-A16-12 h and CV-A16-24 h groups, respectively, when compared with Control group. Then, to explore the mechanism of CV-A16 infection, we focused on the common differentially expressed genes at different time points of CV-A16 infection and found that there were 34 differentially expressed genes based on which clustering analysis and functional category enrichment analysis were performed. The results indicated that changes in oxidation levels were particularly evident in the GO term analysis, while only the “Gonadotropin-releasing hormone receptor pathway” was enriched in the KEGG pathway analysis, which might be closely related to the neurotoxicity caused by CV-A16 infection. Meanwhile, the ID2 closely related to nervous system has been demonstrated to be increased during CV-A16 infection. Additionally, the data on differentially expressed non-protein-coding genes of different types within the transcriptome sequencing results were analyzed, and it was speculated that these dysregulated non-protein-coding genes played a pivotal role in CV-A16 infection. Ultimately, qRT-PCR was utilized to validate the transcriptome sequencing findings, and the results of qRT-PCR were in agreement with the transcriptome sequencing data. In conclusion, transcriptome profiling was carried out to analyze response of SH-SY5Y cells to CV-A16 infection. And our findings provide important information to elucidate the possible molecular mechanisms which were linked to the neuropathogenesis of CV-A16 infection.

Prognostic Value of Neutrophil-to-Lymphocyte Ratio in Predicting Death Risk in Patients with Severe Hand, Foot and Mouth Disease

Introduction

Severe hand, foot, and mouth disease (HFMD) may lead to serious complications, which cause child mortality during outbreaks. The aim of this study was to determine whether neutrophil-to-lymphocyte ratio (NLR) can predict death risk in severe HFMD.

Methods

Medical records for 664 severe HFMD patients were retrospectively examined, and NLR was calculated from blood counts. Youden’s index was calculated to determine the optimal NLR cutoff. Uni- and multivariate logistic regression were used to determine death risk factors associated with severe HFMD.

Results

An NLR cutoff value of 2.01 and 2.50 respectively predicted mortality among all 664 severe HFMD and 137 critical HFMD. Among all 664 patients, the multivariate model identified the following as independently associated with death risk: high fever (OR 3.342, 95% CI 1.736–6.432), EV71 infection (OR 3.200, 95% CI 1.529–6.698), fasting glucose (OR 37.343, 95% CI 18.616–74.909), and NLR (>2.01) (OR 2.142, 95% CI 1.125–4.079). Among 137 critical HFMD, EV71 infection (OR 3.441, 95% CI 1.132–10.462), fasting glucose (OR 14.173, 95% CI 4.920–40.827), and NLR (>2.50) (OR 4.166, 95% CI 1.570–11.051) were associated with death risk.

Conclusion

In conclusion, NLR (>2.01) in severe HFMD and NLR (>2.50) in critical HFMD patients may be associated with increased death risk.

Short-term effects of meteorological factors, air pollution, and sunspot on childhood hand, foot, and mouth disease in Tianjin, China: a new time series regression, 2014-2018

This study is aimed at defining the relationship between a set of environmental factors and childhood HFMD and then at estimating the related effect. The 16 environmental factors included meteorological, air pollution, and sunspot. A traditional TSR modified by using susceptible-infectious-recovery models and distribution lag nonlinear model was applied to estimate the short-term effects of daily environmental factors on children HFMD occurrence in 2014-2018 with adjustment of potential confounding factors. A total of 70,027 children aged 0-15 years with HFMD were enrolled. No significant effect was observed for daily sunspot numbers and average visibility. We found positive effects of the ambient average temperature, with an approximately m-shaped curve of the overall cumulative relationship, peaking at 25.6 °C with a relative risk (RR) of 1.45 (95% confidence intervals 1.21-1.73). The largest RR value of hot effect was achieved on the current day and then decreased by 2 days (total group, male group, and scatter group) or 1 day (female group and nursery group), and the effect lasted about 6 to 8 days from the lag 4 or lag 6 day. A greater association of temperature with HFMD for the female group and the scattered group was observed. This study suggests that ambient average temperature might be a risk factor for children HFMD in Tianjin. Further studies are warranted to confirm these findings.

Transcriptome analysis following enterovirus 71 and coxsackievirus A16 infection in respiratory epithelial cells

Enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) are the major pathogens responsible for hand, foot and mouth disease (HFMD), but the mechanism by which these viruses cause disease remains unclear. In this study, we used transcriptome sequencing technology to investigate changes in the transcriptome profiles after infection with EV-A71 and CV-A16 in human bronchial epithelial (16HBE) cells. Using systematic bioinformatics analysis, we then searched for useful clues regarding the pathogenesis of HFMD. As a result, a total of 111 common differentially expressed genes were present in both EV-A71- and CV-A16-infected cells. A trend analysis of these 111 genes showed that 91 of them displayed the same trend in EV-A71 and CV-A16 infection, including 49 upregulated genes and 42 downregulated genes. These 91 genes were further used to conduct GO, pathway, and coexpression network analysis. It was discovered that enriched GO terms (such as histone acetylation and positive regulation of phosphorylation) and pathways (such as glycosylphosphatidylinositol (GPI)-anchor biosynthesis and DNA replication) might be closely associated with the pathogenic mechanism of these two viruses, and key genes (such as TBCK and GPC) might be involved in the progression of HFMD. Finally, we randomly selected 10 differentially expressed genes for qRT-PCR to validate the transcriptome sequencing data. The experimental qRT-PCR results were roughly in agreement with the results of transcriptome sequencing. Collectively, our results provide clues to the mechanism of pathogenesis of HFMD induced by EV-A71 and CV-A16.

Human Antibodies to VP4 Inhibit Replication of Enteroviruses Across Subgenotypes and Serotypes, and Enhance Host Innate Immunity

Hand, foot, and mouth disease (HFMD) is a highly contagious disease that usually affects infants and young children (<5 years). HFMD outbreaks occur frequently in the Asia-Pacific region, and these outbreaks are associated with enormous healthcare and socioeconomic burden. There is currently no specific antiviral agent to treat HFMD and/or the severe complications that are frequently associated with the enterovirus of serotype EV71. Therefore, the development of a broadly effective and safe anti-enterovirus agent is an existential necessity. In this study, human single-chain antibodies (HuscFvs) specific to the EV71-internal capsid protein (VP4) were generated using phage display technology. VP4 specific-HuscFvs were linked to cell penetrating peptides to make them cell penetrable HuscFvs (transbodies), and readily accessible to the intracellular target. The transbodies, as well as the original HuscFvs that were tested, entered the enterovirus-infected cells, bound to intracellular VP4, and inhibited replication of EV71 across subgenotypes A, B, and C, and coxsackieviruses CVA16 and CVA6. The antibodies also enhanced the antiviral response of the virus-infected cells. Computerized simulation, indirect and competitive ELISAs, and experiments on cells infected with EV71 particles to which the VP4 and VP1-N-terminus were surface-exposed (i.e., A-particles that don’t require receptor binding for infection) indicated that the VP4 specific-antibodies inhibit virus replication by interfering with the VP4-N-terminus, which is important for membrane pore formation and virus genome release leading to less production of virus proteins, less infectious virions, and restoration of host innate immunity. The antibodies may inhibit polyprotein/intermediate protein processing and cause sterically strained configurations of the capsid pentamers, which impairs virus morphogenesis. These antibodies should be further investigated for application as a safe and broadly effective HFMD therapy.

Emergent Viral Infections of the CNS

Biological evolution of the microbiome continually drives the emergence of human viral pathogens, a subset of which attack the nervous system. The sheer number of pathogens that have appeared, along with their abundance in the environment, demand our attention. For the most part, our innate and adaptive immune systems have successfully protected us from infection; however, in the past 5 decades, through pathogen mutation and ecosystem disruption, a dozen viruses emerged to cause significant neurologic disease. Most of these pathogens have come from sylvatic reservoirs having made the energetically difficult, and fortuitously rare, jump into humans. But the human microbiome is also replete with agents already adapted to the host that need only minor mutations to create neurotropic/toxic agents. While each host/virus symbiosis is unique, this review examines virologic and immunologic principles that govern the pathogenesis of different viral CNS infections that were described in the past 50 years (Influenza, West Nile Virus, Zika, Rift Valley Fever Virus, Hendra/Nipah, Enterovirus-A71/-D68, Human parechovirus, HIV, and SARS-CoV). Knowledge of these pathogens provides us the opportunity to respond and mitigate infection while at the same time prepare for inevitable arrival of unknown agents.

Molecular characteristics of the VP1 region of enterovirus 71 strains in China

Background

Enterovirus 71 (EV71) is the most commonly implicated causative agent of severe outbreaks of paediatric hand, foot, and mouth disease (HFMD).VP1 protein, a capsid protein of EV71, is responsible for the genotype of the virus and is essential for vaccine development and effectiveness. However, the genotypes of EV71 isolates in China are still not completely clear.

Methods

The VP1 gene sequences of 3712 EV71 virus strains from China, excluding repetitive sequences and 30 known EV71 genotypes as reference strains, between 1986 and 2019 were obtained from GenBank. Phylogenetic tree, amino acid homology, genetic variation and genotype analyses of the EV71VP1 protein were performed with MEGA 6.0 software.

Results

The amino acid identity was found to be 88.33%–100% among the 3712 EV71 strains, 93.47%–100% compared with vaccine strain H07, and 93.04%–100% compared with vaccine strains FY7VP5 or FY-23 K-B. Since 2000, the prevalent strains of EV71 were mainly of the C4 genotype. Among these, the C4a subgenotype was predominant, followed by the C4b subgenotype; other subgenotypes appeared sporadically between 2005 and 2018 in mainland China. The B4 genotype was the main genotype in Taiwan, and the epidemic strains were constantly changing. Some amino acid variations in VP1 of EV71 occurred with high frequencies, including A289T (20.99%), H22Q (16.49%), A293S (15.95%), S283T (15.11%), V249I (7.76%), N31D (7.25%), and E98K (6.65%).

Conclusion

The C4 genotype of EV71 in China matches the vaccine and should effectively control EV71. However, the efficacy of the vaccine is partially affected by the continuous change in epidemic strains in Taiwan. These results suggest that the genetic characteristics of the EV71-VP1 region should be continuously monitored, which is critical for epidemic control and vaccine design to prevent EV71 infection in children.

BNIP3 deletion ameliorated enterovirus 71 infection-induced hand, foot and mouth disease via inhibiting apoptosis, autophagy, and inflammation in mice

Bcl2/adenovirus E1B protein-interacting protein 3 (BNIP3) plays a key role in cellular response to stress by regulating apoptosis and selective autophagy. The present study aimed to determine the effects of BNIP3 on enterovirus (EV) 71 infection-induced hand, foot and mouth disease (HFMD), and the apoptosis, autophagy and inflammatory in mice and SH-SY5Y human neuroblastoma cell line. Neonatal BALB/c mice were injected with EV 71 strain to induce the HFMD. Western blotting and ELISA were used to measure the protein expression and cytokine levels. The BNIP3 mRNA and protein levels in the brain were increased in EV 71-infected mice. By contrast, the BNIP3-knockout (KO) mice with EV 71 infection had higher health score and survival rate. BNIP3 deletion reversed the increase of cleaved-caspase 3, cleaved-caspase 8, Bax, LC3 II and LC3 II/LC3 I levels, and the decrease of Bcl2 and Bcl2/Bax and LC3 I levels in the brain of mice with EV 71 infection. The EV 71 infection-induced increase of tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1, interleukin (IL)-1β, IL-6, interferon (IFN)-α and IFN-γ levels were inhibited in BNIP3-KO mice. BNIP3 knockdown with small interfering RNA (siRNA) inhibited the EV 71 infection-induced the increases of apoptosis, autophagy and inflammatory factors in SH-SY5Y cells. BNIP3 overexpression further facilitated the EV 71 infection-induced increase of these inflammatory factors in SH-SY5Y cells. These results demonstrated that BNIP3 deletion ameliorated EV 71 infection-induced HFMD via inhibiting apoptosis, autophagy and inflammation in mice. BNIP3 may be a therapeutic target for HFMD.

WHO working group meeting to develop WHO Recommendations to assure the quality, safety and efficacy of enterovirus 71 vaccines

Enterovirus A71 (EV71) is one of the major causative agents of hand, foot and mouth disease (HFMD), and is sometimes associated with severe central nervous system syndromes. Vaccines against EV71 infection have been developed or are in development in several countries and few have been licensed in China. In response to requests from some of these countries, WHO convened a working group meeting in Shanghai China from 11 to 12 September 2019 to develop WHO Recommendations to assure the quality, safety and efficacy of EV71 vaccines. Meeting participants included members of the drafting group, experts from vaccine developers, manufacturers, regulators and academia. The epidemiology of EV71, as well as the development, regulation and standardization of EV71 vaccines were reviewed in the meeting. Information on R&D, manufacturing, quality control and standardization of EV71 vaccines was presented by vaccine developers, manufacturers and regulators. Based on their experience, the working group discussed the main principles that would determine WHO's position on quality, safety and efficacy of EV71 vaccines. The working group agreed to develop WHO Recommendations to assure the quality, safety and efficacy of inactivated EV71 vaccines with a scope covering only whole virus inactivated vaccines. Other type of vaccines, such as EV71 virus-like particles (VLPs) will not be covered as they are still at the developmental stage. The outline of the document was agreed and will follow the usual style of WHO recommendations. It was also agreed to submit the draft Recommendations for review and adoption to the WHO ECBS in 2020 following discussion at a WHO informal consultation, which will include NRAs and vaccine manufacturers.

The potential of plant-made vaccines to fight picornavirus

INTRODUCTION

Several Picornaviruses are pathogens that generate serious problems for human and animal health worldwide. Vaccination is an attractive approach to fight against picornaviruses. In this regard, the development of low-cost vaccines is a priority to ensure coverage; especially in developing and low-income countries. In this context, plant-made vaccines are a convenient technology since plant cells are low-cost bioreactors capable of producing complex antigens that preserve their antigenic determinants; moreover, they can serve as biocapsules to achieve oral delivery.

AREAS COVERED

In the present review the advances in the development of plant-made vaccines against picornaviruses are summarized and placed in perspective. The main diseases that have been targeted using this approach include Poliovirus, Food and mouth disease virus, Hepatitis A virus, and Enterovirus 71.

EXPERT OPINION

Several vaccine candidates against picornavirus have been characterized at the preclinical level; with many of them capable of inducing humoral and cellular responses that led to neutralization of pathogens when evaluated in vitro and test animal challenge assays. Plant-made vaccines are a promise to fight picornaviruses; especially in the developing world where limited resources hamper vaccination coverage. A critical analysis of the road ahead for this technology is provided.

Assessing the vaccine effectiveness for hand, foot, and mouth disease in Guangzhou, China: a time-series analysis

Objective: Hand, foot, and mouth disease (HFMD) is an important public health issue in China. Although efficacy has been demonstrated by randomized controlled trials, the evidence for effectiveness of the monovalent Enterovirus 71 (EV71) vaccine against HFMD remains unknown. This study aimed to assess the vaccine effectiveness for HFMD in Guangzhou, China. Methods: Routinely collected vaccination and HFMD surveillance data were captured from the China Information System for Disease Control and Prevention. We estimated the EV71 vaccine effectiveness using spatial ecologic and time-series analysis approaches. Results: A total of 174,002 HFMD cases under 5 years of age were reported to the Guangzhou, China surveillance system from January 2016 to December 2018. A total of 408,664 children completed a two-dose EV71 vaccination series. In an ecologic analysis, a two-dose EV71 vaccination rate above the median conferred lower HFMD risk relative to a vaccination rate below the median (ratio ratio = 0.955, 95% confidence interval (CI): 0.949, 0.962; P < .001). In the time-series approach, 0.9% fewer HFMD cases were associated with a 1% increase in the two-dose EV71 vaccination rate, but without statistical significance (P = .094). However, we detected statistically significant protective associations for HFMD among children 3 years of age (0.9% fewer HFMD cases with a 1% increased vaccination rate; P = .046), and for EV71 (1.4%; P = .012) and "other viruses" (1.3%; P = .002), although not for Coxsackievirus A16 (CVA16). Conclusion: Our findings, based on real-world data, provide evidence of EV71 vaccine effectiveness for preventing EV71 and "other" viruses associated with HFMD. An expanded program of EV71 vaccination is urgently needed.

Development of a pseudovirus-based assay for measuring neutralizing antibodies against Coxsackievirus A10

Coxsackievirus A10 (CV-A10) has recently emerged as a major pathogen of hand, foot, and mouth disease in children worldwide. Currently no effective treatments are available; development of anti-CV-A10 vaccine is a most cost-effective way for CV-A10 prevention. Robust assay to measure neutralizing antibody (NtAb) titres elicited by vaccination would greatly prompt anti-CV-A10 vaccine development. Compare to the traditional neutralization assay based on inhibition of cytopathic effects (herein after referred to as cNT) which is time-consuming and labor-intensive, in this study we developed an efficient high-throughput neutralization antibody assay based on CV-A10 pseudoviruses (herein after referred to as pNT). In the pNT, anti-CV-A10 NtAb titre was negatively corresponded with the relative luminescent unit (RLU) produced by luciferase reporter gene incorporated in pseudovirus genome. As described in this study, the NtAb against CV-A10 could be detected within 10-16 h, anti- CV-A10 NtAb in 67 human serum samples were measured in parallel with pNT and cNT assays, a good correlation (r = 0.83,p < .0001) and good agreement(97%) were shown between cNT and pNT, indicating that the pNT provides a rapid and convenient procedure for measuring NtAb production against anti-CV-A10 NtAb measurement.

Immunization with a fusion protein vaccine candidate generated from truncated peptides of human enterovirus 71 protects mice from lethal enterovirus 71 infections

Background

Prophylactic vaccines are critical in preventing hand, foot, and mouth disease (HFMD) primarily caused by human enterovirus 71 (EV71) infection. Children aged less than 5 years are especially susceptible to EV71 infections. In addition to the development of vaccines containing the inactivated virus, those containing virus-like particles (VLPs) with repeated antigens also constitute an effective preventive strategy for EV71 infections, with safety and productivity advantages. We previously developed a fusion protein composed with truncated peptides of the EV71 capsid protein, which assembled into spherical particles. This study aimed to assess the immunoprotective effects of this fusion protein as a vaccine candidate in a mouse model of EV71 infection.

Methods

To evaluate the protective effect of fusion protein vaccine candidate, neonatal mice born by immunized female mice, as well as normal neonatal mice immunized twice were infected with EV71 virus. Whereafter, the survival rates, clinical scores and viral loads were measured.

Results

The high dosage and booster immunization helped induce specific serum antibodies with high neutralization titers, which were transferred to neonatal mice, thereby facilitating effective resistance towards EV71 infection. An active immune response was also observed in neonatal mice which generated following immunization.

Conclusions

The present results suggest that this fusion protein is a suitable vaccine candidate in treating EV71 infections.

Antiviral Activity of a Llama-Derived Single-Domain Antibody against Enterovirus A71

In the past few decades, enterovirus A71 (EVA71) has caused devastating outbreaks in the Asia-Pacific region, resulting in serious sequelae in infected young children. No preventive or therapeutic interventions are currently available for curing EVA71 infection, highlighting a great unmet medical need for this disease. Here, we showed that one novel single-domain antibody (sdAb), F1, isolated from an immunized llama, could alleviate EVA71 infection both in vitro and in vivo We also confirmed that the sdAb clone F1 recognizes EVA71 through a novel conformational epitope comprising the highly conserved region of VP3 capsid protein by using competitive-binding and overlapping-peptide enzyme-linked immunosorbent assays (ELISAs). Because of the virion's icosahedral structure, we reasoned that adjacent epitopes must be clustered within molecular ranges that may be simultaneously bound by an engineered antibody with multiple valency. Therefore, two single-domain binding modules (F1) were fused to generate an sdAb-in-tandem design so that the capture of viral antigens could be further increased by valency effects. We showed that the tetravalent construct F1×F1-hFc, containing two sdAb-in-tandem on a fragment crystallizable (Fc) scaffold, exhibits more potent neutralization activity against EVA71 than does the bivalent sdAb F1-hFc by at least 5.8-fold. We also demonstrated that, using a human scavenger receptor class B member 2 (hSCARB2) transgenic mouse model, a half dose of the F1×F1-hFc provided better protection against EVA71 infection than did the F1-hFc. Thus, our study furnishes important insights into multivalent sdAb engineering against viral infection and provides a novel strategic deployment approach for preparedness of emerging infectious diseases such as EVA71.

What Does Plant-Based Vaccine Technology Offer to the Fight against COVID-19?

The emergence of new pathogenic viral strains is a constant threat to global health, with the new coronavirus strain COVID-19 as the latest example. COVID-19, caused by the SARS-CoV-2 virus has quickly spread around the globe. This pandemic demands rapid development of drugs and vaccines. Plant-based vaccines are a technology with proven viability, which have led to promising results for candidates evaluated at the clinical level, meaning this technology could contribute towards the fight against COVID-19. Herein, a perspective in how plant-based vaccines can be developed against COVID-19 is presented. Injectable vaccines could be generated by using transient expression systems, which offer the highest protein yields and are already adopted at the industrial level to produce VLPs-vaccines and other biopharmaceuticals under GMPC-processes. Stably-transformed plants are another option, but this approach requires more time for the development of antigen-producing lines. Nonetheless, this approach offers the possibility of developing oral vaccines in which the plant cell could act as the antigen delivery agent. Therefore, this is the most attractive approach in terms of cost, easy delivery, and mucosal immunity induction. The development of multiepitope, rationally-designed vaccines is also discussed regarding the experience gained in expression of chimeric immunogenic proteins in plant systems.

Epidemiological and aetiological characteristics of hand, foot, and mouth disease in Sichuan Province, China, 2011-2017

Hand, foot, and mouth disease (HFMD) remains a threat to the Asia-Pacific region. The epidemiological characteristics and pathogen spectrum of HFMD vary with space and time. These variations are crucial for HFMD interventions but poorly understood in Sichuan Province, China, particularly after the introduction of the EV-A71 vaccine. Using descriptive methods, regression analyses, spatial autocorrelation analysis, and space-time scan statistics, we analysed the epidemiological and aetiological characteristics of HFMD surveillance data in Sichuan Province between 2011 and 2017 to identify spatio-temporal variations. The dominant serotypes of HFMD have changed from enterovirus 71 and coxsackievirus A16 to other enteroviruses since 2013. The seasonal pattern of HFMD showed two peaks generally occurring from April to July and November to December; however, the seasonal pattern varied by prefecture and enterovirus serotype. From 2011 to 2017, spatio-temporal clusters were increasingly concentrated in Chengdu, with several small clusters in northeast Sichuan. The clusters observed in southern Sichuan from 2011 to 2015 disappeared in 2016–2017. These findings highlight the importance of pathogen surveillance and vaccination strategies for HFMD interventions; future prevention and control of HFMD should focus on Chengdu and its vicinity.

Transcriptome sequencing analysis of SH-SY5Y cells infected with EV71 reveals the potential neuropathic mechanisms

Enterovirus A71 (EV71) remains the most common causative agent of hand, foot, and mouth disease (HFMD), and the neurological complications induced by EV71 are usually the leading cause of death in children with HFMD. However, the mechanism of nervous system changes caused by EV71 infection is still unclear. Therefore, in the current study, EV71 was inoculated into the human neuroblastoma cell line SH-SY5Y and subsequent transcriptome sequencing was used to examine the alterations of the transcriptome in infected SH-SY5Y cells. It is expected to determine the underlying mechanism of neurological diseases in response to EV71 infection. As a result, a total of 82,406,974, 112,410,808 and 87,780,371 clean reads were found in the control, EV71-12 h and EV71-24 h groups, respectively. Moreover, 160 and 745 differentially expressed genes were identified in the EV71-12 h and EV71-24 h groups, respectively, as compared to the control group. Next, to further explore the pathogenic mechanism triggered by EV71 infection, we mainly focused on the common differentially expressed genes at different time points of EV71 infection. And it was discovered that there were 95 common differentially expressed genes, which were used to conduct GO and pathway analysis. GO enrichment analysis demarcated related biological processes, molecular functions and cellular components, and KEGG pathway analysis enabled annotations of metabolic pathways and revealed interactions among the significantly enriched pathways. The results showed that the enriched GO term "Nervous system development" and enriched pathway "CCKR signaling map" might be important contributors to EV71-induced neuropathological mechanisms. In addition, we also screened 10 up- and down-regulated non-protein coding genes with significantly different expression in our transcriptome profiling, which suggested that these abnormally regulated non-protein-encoding genes might also play important roles in the pathogenesis of EV71 infection. Eventually, RT-qPCR technology was adopted to validate the transcriptome sequencing data and the experiment demonstrated that the RT-qPCR and transcriptome sequencing results were basically consistent. In summary, this is the first transcriptome analysis of SH-SY5Y cells in response to EV71 infection and provides valuable cues for further exploring the mechanism of nervous system changes caused by EV71 infection.

Functional analyses of mammalian virus 5'UTR-derived, small RNAs that regulate virus translation

Enterovirus A71 (EV-A71¹) RNA contains an internal ribosomal entry site (IRES) to direct cap-independent translation. IRES-dependent translation requires the host's translation initiation factors and IRES-associated trans-acting factors (ITAFs). We previously showed that hnRNP A1, the mRNA stability factor HuR, and the RISC subunit Argonaute 2 (Ago2) are ITAFs that associate with stem loop II (SL-II) of the IRES and promote IRES-dependent translation. By contrast, the mRNA decay factor AUF1 is a negative-acting ITAF that also binds SL-II. Moreover, the small RNA-processing enzyme Dicer produces at least four virus-derived, small RNAs (vsRNAs 1-4) from the EV-A71 5'UTR in infected cells. One of these, vsRNA1, derived from SL-II, inhibits IRES activity via an unknown mechanism. In vitro RNA-binding assays revealed that vsRNA1 can alter association of Ago2, HuR, and AUF1 with SL-II. This presents a possible mechanism by which vsRNA1 could control association of ITAFs with the IRES and modulate viral translation. Here, we describe methods for functional analyses of vsRNA1-mediated regulation of IRES activity. These methods should be applicable to other virus-derived, small RNAs as well.

Enterovirus 71 Infection Shapes Host T Cell Receptor Repertoire and Presumably Expands VP1-Specific TCRβ CDR3 Cluster

Enterovirus 71 (EV71) has become an important public health problem in the Asia-Pacific region in the past decades. EV71 infection might cause neurological and psychiatric complications and even death. Although an EV71 vaccine has been currently approved, there is no effective therapy for treating EV71-infected patients. Virus infections have been reported to shape host T cell receptor (TCR) repertoire. Therefore, understanding of host TCR repertoire in EV71 infection could better the knowledge in viral pathogenesis and further benefit the anti-viral therapy development. In this study, we used a mouse-adapted EV71 (mEV71) model to observe changes of host TCR repertoire in an EV71-infected central nervous system. Neonate mice were infected with mEV71 and mouse brainstem TCRβ repertoires were explored. Here, we reported that mEV71 infection impacted host brainstem TCRβ repertoire, where mEV71 infection skewed TCRβ diversity, changed VJ combination usages, and further expanded specific TCRβ CDR3 clones. Using bioinformatics analysis and ligand-binding prediction, we speculated the expanded TCRβ CDR3 clone harboring CASSLGANSDYTF sequence was capable of binding cleaved EV71 VP1 peptides in concert with major histocompatibility complex (MHC) molecules. We observed that mEV71 infection shaped host TCRβ repertoire and presumably expanded VP1-specific TCRβ CDR3 in mEV71-infected mouse brainstem that integrated EV71 pathogenesis in central nervous system.

Study of integrated protective immunity induced in rhesus macaques by the intradermal administration of a bivalent EV71-CA16 inactivated vaccine

Enterovirus type 71 (EV71) and coxsackievirus A 16 (CA16) are recognized as the major pathogens responsible for human hand-foot-mouth disease. To develop a bivalent EV71-CA16 vaccine, rhesus macaques immunized with two doses of this vaccine via the intradermal route were challenged with EV71 or CA16, and their clinical symptoms, viral shedding, neutralizing antibodies, IFN-γ-specific ELISpots, and tissue viral load were examined longitudinally. Specific immunity against EV71 and CA16 was observed in the macaques, which exhibited controlled proliferation of the EV71 and CA16 viruses and upregulated expression of immune-related genes compared with the controls. Furthermore, broad protection against EV71 and CA16 challenge without immunopathological effects was observed in all the immunized macaques. These studies suggest that the bivalent EV71-CA16 inactivated vaccine was effective against wild-type EV71 or CA16 viral challenge in rhesus macaques.

A 5-year molecular epidemiology survey of human enterovirus 71 before vaccine application in Yunnan Province, China

Enterovirus A71 (EV-A71) infection is known to cause hand, foot, and mouth disease (HFMD). Last year, an inactivated EV-A71 whole virus vaccine was used to prevent this disease in Yunnan, China. To obtain a viral genetic background for evaluating vaccine protection and monitor the adaptive evolution of the virus after the vaccination, a 5-year molecular epidemiology survey was performed before the vaccination. Twenty-six EV-A71 strains were separated from 561 stool specimens of patients with serious HFMD. The whole-genomic sequences of these strains were sequenced. Phylogenetic trees were constructed, and the mutation spectra were analyzed based on these viral sequences. There was no obvious mutation for the circular EV-A71 strains of the same year. Pathogenic EV-A71 strains may arise from a "subgroup" randomly each year. Whole-genomic analyses showed that a hotspot nonsynonymous substitution potentially affecting the immunogenicity of vaccines was found in the 2A gene, but not in genes of the viral capsid proteins, and the genetic diversity of whole viral genomes associated with the incidence of HFMD. Therefore, it will be valuable to monitor the genome-wide changes of EV-A71 to detect the adaptive mutations affecting immunogenicity or perform investigations using genetic diversity as a parameter.

Plant-Produced Anti-Enterovirus 71 (EV71) Monoclonal Antibody Efficiently Protects Mice Against EV71 Infection

Enterovirus 71 (EV71) is the main causative agent of severe hand-foot-mouth disease. EV71 affects countries mainly in the Asia-Pacific region, which makes it unattractive for pharmaceutical companies to develop drugs or vaccine to combat EV71 infection. However, development of these drugs and vaccines is vital to protect younger generations. This study aims to develop a specific monoclonal antibody (mAb) to EV71 using a plant platform, which is a cost-effective and scalable production technology. A previous report showed that D5, a murine anti-EV71 mAb, binds to VP1 protein of EV71, potently neutralizes EV71 in vitro, and effectively protects mice against EV71 infection. Herein, plant-produced chimeric D5 (cD5) mAb, variable regions of murine D5 antibody linked with constant regions of human IgG1, was transiently expressed in Nicotiana benthamiana using geminiviral vectors. The antibody was expressed at high levels within six days of infiltration. Plant-produced cD5 retained its in vitro high-affinity binding and neutralizing activity against EV71. Furthermore, a single dose (10 µg/g body weight) of plant-produced cD5 mAb offered 100% protection against infection in mice after a lethal EV71 challenge. Therefore, our results showed that plant-produced anti-EV71 mAb is an effective, safe, and affordable therapeutic option against EV71 infection.

Characterization of inflammatory cytokine profiles in cerebrospinal fluid of hand, foot, and mouth disease children with enterovirus 71-related encephalitis in Hangzhou, Zhejiang, China

Enterovirus 71 (EV71) is an important etiological agent of hand, foot, and mouth disease (HFMD), which can also lead to severe neurological complications (eg, encephalitis) in young children. Although a series of reports on EV71 infection have been published, the pathogenic mechanism of EV71 infection is still not fully understood.We evaluated the cerebrospinal fluid (CSF) levels of the inflammatory cytokines interleukin (IL)-8, IL-1β, IL-6, IL-10, tumor necrosis factor (TNF)-α, and IL-12p70 in 88 children with EV71-related encephalitis and 19 children with febrile convulsion (FC) with the use of commercial cytometric bead array kits.The levels of IL-8, IL-1β, IL-6, and IL-10 in CSF were significantly higher in encephalitis group when compared with those observed in FC group, while no significant changes were noted in the levels of TNF-α and IL-12p70. In addition, significant and positive correlations among CSF IL-8, IL-1β, IL-6, and IL-10 were observed in encephalitis group. Furthermore, receiver operator characteristic analysis determined a cut-off value of 10.62 pg/mL for IL-6 to discriminate encephalitis patients from FCs with the sensitivity and specificity of 89.8% and 84.2%, respectively. Moreover, logistic regression analyses revealed that IL-6 was an independent predictor of EV71-related encephalitis (odds ratio = 23.241, P < .001).Our results indicate that 4 inflammatory cytokines (IL-8, IL-1β, IL-6, and IL-10) play important roles in the pathogenesis of EV71 infection. IL-6 may be used for the evaluation of EV71-related encephalitis and as a potential therapy candidate for EV71 infection.

Enterovirus-Associated Hand-Foot and Mouth Disease and Neurological Complications in Japan and the Rest of the World

Enteroviruses (EVs) are responsible for extremely large-scale, periodic epidemics in pediatric cohorts, particularly in East and Southeast Asia. Clinical presentation includes a diverse disease spectrum, including hand-foot and mouth disease (HFMD), aseptic meningitis, encephalitis, acute flaccid paralysis, and acute flaccid myelitis. HFMD is predominantly attributable to EV-A types, including the major pathogen EV-A71, and coxsackieviruses, particularly CV-A6, CV-A16, and CV-A10. There have been multiple EV-A71 outbreaks associated with a profound burden of neurological disease and fatal outcomes in Asia since the early 1980s. Efficacious vaccines against EV-A71 have been developed in China but widespread pediatric vaccination programs have not been introduced in other countries. Encephalitis, as a consequence of complications arising from HFMD infection, leads to damage to the thalamus and medulla oblongata. Studies in Vietnam suggest that myoclonus is a significant indicator of central nervous system (CNS) complications in EV-A71-associated HFMD cases. Rapid response in HFMD cases in children is imperative to prevent the progression to a CNS infection; however, prophylactic and therapeutic agents have not been well established internationally, therefore surveillance and functional studies including development of antivirals and multivalent vaccines is critically important to reduce disease burden in pediatric populations.

Severe enterovirus A71 associated hand, foot and mouth disease, Vietnam, 2018: preliminary report of an impending outbreak

Since January 2018, over 53,000 hospitalisations and six deaths due to hand, foot and mouth disease (HFMD) have occurred across Vietnam with most cases from September onward. In a large tertiary referral hospital, Ho Chi Minh City, enterovirus A71 subgenogroup C4 was predominant, while B5 was only sporadically detected. The re-emergence of C4 after causing a severe HFMD outbreak with > 200 deaths in 2011–12 among susceptible young children raises concern of another impending severe outbreak.

Antivirals and vaccines for Enterovirus A71

Enterovirus A71 (EV-A71) is an important emerging virus posing a threat to children under five years old. EV-A71 infection in infants or young children can cause hand-foot-and-mouth disease, herpangina, or severe neurological complications. However, there are still no effective antivirals for treatment of these infections. In this review, we summarize the antiviral compounds developed to date based on various targets of the EV-A71 life cycle. Moreover, development of a vaccine would be the most effective approach to prevent EV-A71 infection. Therefore, we also summarize the development and clinical progress of various candidate EV-A71 vaccines, including inactivated whole virus, recombinant VP1 protein, synthetic peptides, viral-like particles, and live attenuated vaccines.

miR-545 promoted enterovirus 71 replication via directly targeting phosphatase and tensin homolog and tumor necrosis factor receptor-associated factor 6

Enterovirus 71 (EV71) is a small, nonenveloped icosahedral RNA virus and is the predominant causative pathogen of hand-foot-and-mouth disease. Recently, microRNAs (miRNAs) are reported to play important roles in the pathogenesis of EV71 replication. This study investigated the role of miR-545 in the EV71 replication and explored the underlying molecular mechanisms. We showed that miR-545 was upregulated in the EV71-infected human embryonic kidney (HEK) 293 cells and rhabdomyosarcoma (RD) cells. Overexpression of miR-545 promoted the viral replication of EV71 and attenuated the inhibitory effects of EV71 on cell viability in HEK293 and RD cells; while knockdown of miR-545 significantly suppressed the EV71 replication in these two cell lines. Bioinformatics analysis and luciferase reporter assay showed that miR-545 directly targeted the 3'untranslated region of phosphatase and tensin homolog (PTEN) and tumor necrosis factor receptor-associated factor 6 (TRAF6) in HEK293 cells. Furthermore, miR-545 negatively regulated the messenger RNA (mRNA) and protein expression of PTEN and TRAF6. The mRNA and protein expression of PTEN and TRAF6 was also suppressed by EV71 infection, which was attenuated by miR-545 knockdown in HEK293 cells. Overexpression of PTEN and TRAF6 both suppressed the EV71 replication in HKE293 cells, and also attenuated the enhanced effects of miR-545 overexpression on the EV71 replication in HEK293 cells. Collectively, our study for the first time showed that miR-545 had an enhanced effect on the EV71 replication in HEK293 and RD cells. Further mechanistic results indicated that miR-545 promoted EV71 replication at least partly via targeting PTEN and TRAF6.

The 100 top-cited studies on vaccine: a bibliometric analysis

Objective: The objective of this study was to analyze the 100 most cited studies on vaccine.Methods: A comprehensive search of studies on vaccine was performed in the Web of Science Core Collection without year or language restrictions. The 100 top-cited studies were retrieved after screening abstracts or full-texts. The outcomes of bibliometric analysis included citation time, citation density, journal name, impact factor, publication year, article type, category, open access, and country of origin.Results: The citation times for the 100 top-cited studies ranged from 593 to 2406, with a median citation times of 834. The 100 top-cited studies were published in 32 journals, and the journal with the most studies was New England Journal of Medicine (n = 20). They were published between 1969 and 2012, and 4 authors published at least 2 studies as the first author. The USA contributed the most studies (n = 70), followed by Switzerland (n = 4), England (n = 4) and Finland (n = 4). Eighty-one studies were published as Article, while 19 were Review. Eleven studies were about vaccine for therapeutic and 68 studies were about vaccine for prophylactic.Conclusions: This is the first bibliometric analysis to provide a detailed list of the 100 most-cited studies on vaccine and helps to recognize the quality of the works, discoveries, and trends in the field.

Comparative analysis of putative novel microRNA expression profiles induced by enterovirus 71 and coxsackievirus A16 infections in human umbilical vein endothelial cells using high-throughput sequencing

Hand, foot and mouth disease (HFMD) is mainly caused by human enterovirus 71 (EV71) and coxsackievirus A16 (CA16), which circulate alternatively or together in epidemic areas. Although the two viruses exhibit genetic homology, their clinical manifestations have some discrepancies. However, the factors underlying these differences remain unclear. Herein, we mainly focused on the alterations and roles of putative novel miRNAs in human umbilical vein endothelial cells (HUVECs) following EV71 and CA16 infections using high-throughput sequencing. The results identified 247 putative novel, differentially expressed miRNAs, of which only 11 miRNAs presented an opposite trend between the EV71- and CA16-infected samples and were used for target prediction. Gene ontology (GO) and pathway enrichment analysis of the predicted targets displayed the top 15 significant biological processes, molecular functions, cell components and pathways. Subsequently, regulatory miRNA-predicted targets and miRNA-GO and miRNA-pathway networks were constructed to further reveal the complex regulatory mechanisms of the miRNAs during infection. Therefore, our data provide useful insights that will help elucidate the different host-pathogen interactions following EV71 and CA16 infections and may offer novel therapeutic targets for these infections.

Antiviral activity of sophoridine against enterovirus 71 in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Enterovirus 71 (EV71) has a propensity to cause hand-foot-and-mouth disease (HFMD) epidemics associated with neurological sequelae. Unfortunately, no drugs are currently available for the clinical treatment of EV71 infections. Sophoridine (SRI) is one of the most abundant alkaloids in Sophora flavescens Aiton (Leguminosae), which has been used to treat fever, throat inflammation, cancer, and other diseases.

MATERIALS AND METHODS

In this study, we found that SRI inhibits EV71 infection in Vero cells. To study the antiviral activity of SRI, Vero cells were divided into 3 treatment groups based on the timing of SRI dosing: prior to viral adsorption (Group A), during viral adsorption (Group B), and after viral adsorption (Group C). We further revealed the antiviral activity of SRI with the attachment assay and the penetration assay. For Group A, 50% viability of Vero cells was observed at a SRI concentration of 61.39 μg/mL, whereas for Groups B, 50% viability was observed at SRI concentrations of 196.86 μg/mL. Furthermore, 29.7% cell viability was observed even at a SRI concentration of 1000 μg/mL in Groups C. The results show that SRI was highly effective against EV71 when Vero cells were pretreated with SRI for 2 h (Group A). Further researches indicate SRI was highly effective at inhibiting EV71 attachment when the SRI concentrations over 250 μg/mL (P < 0.001).

CONCLUSIONS

We have shown that Vero cell viability increases when SRI is administered prior to viral adsorption. This suggests that SRI has the considerable potential as an antiviral for EV71 disease prevention.

Recombinant lactococcus lactis secreting viral protein 1 of enterovirus 71 and its immunogenicity in mice

OBJECTIVE

To construct recombinant Lactococcus lactis (L. lactis) expressing viral protein 1 (VP1) of enterovirus 71 (EV71) and evaluate its immunogenicity to be used as an oral vaccine in BALB/c mice.

RESULTS

Recombinant L. lactis competent in secreting VP1 (~ 30 kDa) into the extracellular environment with the aid of the signal peptide Usp45 was produced. Enzyme-linked immunosorbent assay showed that significant VP1-specific antibody response including the production of both serum IgG and fecal IgA (p < 0.05) was elicited in BALB/c mice upon oral immunization with recombinant L. lactis. Moreover, in contrast to negative control, recombinant L. lactis induced adequate neutralizing antibodies in mouse sera (p < 0.05) as demonstrated in virus neutralization assay, whereas the presence of neutralizing antibodies in fecal samples was obvious but not significant (p > 0.05).

CONCLUSIONS

Recombinant L. lactis expressing VP1 of EV71 has the potential to be used as an oral vaccine candidate. The findings may provide some preliminary evidences for further development of effective and needle-free EV71 vaccines.