Quantitation of Enterovirus A71 Empty and Full Particles by Sedimentation Velocity Analytical Ultracentrifugation.

The enterovirus A71 (EV71) inactivated vaccine is an effective intervention to control the spread of the virus and prevent EV71-associated hand, foot, and mouth disease (HFMD). It is widely administered to infants and children in China. The empty particles (EPs) and full particles (FPs) generated during production have different antigenic and immunogenic properties. However, the antigen detection methods currently used were established without considering the differences in antigenicity between EPs and FPs. There is also a lack of other effective analytical methods for detecting the different particle forms, which hinders the consistency between batches of products. In this study, we analyzed the application of sedimentation velocity analytical ultracentrifugation (SV-AUC) in characterizing the EPs and FPs of EV71. Our results showed that the proportions of the two forms could be quantified simultaneously by SV-AUC. We also determined the repeatability and accuracy of this method and found that both parameters were satisfactory. We assessed SV-AUC for bulk vaccine quality control, and our findings indicated that SV-AUC can be used effectively to analyze the percentage of EPs and FPs and monitor the consistency of the process to ensure the quality of the vaccine.

Immunogenicity and safety of an enterovirus 71 vaccine in children aged 36-71 months: A double-blind, randomised, similar vaccine-controlled, non-inferiority phase III trial.

Background: The enterovirus 71 (EV71) vaccine produced by Wuhan Institute of Biological Products Co., Ltd. (WIBP) (B-EV71) has been given to children aged 6-35 months, and it has shown good safety, immunogenicity and efficacy. However, the administration of EV71 vaccine in children aged 36-71 months, which is another target population, needs further exploration. Methods: We conducted a double-blind, randomised, controlled, non-inferiority phase III clinical trial in children aged 36-71 months, with a further comparison group of children aged 6-35 months in China. Children aged 6-71 months with no history of hand, foot and mouth disease or prior-vaccination of EV71 vaccine were eligible and recruited. Eligible participants aged 36-71 months were randomly assigned (1:1) to receive two doses of the B-EV71 vaccine (Older-B group) or the control EV71 vaccine (C-EV71 vaccine, produced by Institute of Medical Biology, Chinese Academy of Medical Sciences) (Older-C group), administered at a 30-day interval. Eligible participants aged 6-35 months were enrolled consecutively to receive two doses of the B-EV71 vaccine (Younger-B group) at a 30-day interval. Participants, investigators and those assessing outcomes were masked to the vaccine received. Non-inferiority analyses were conducted to compare the immunogenicity of EV71 vaccine in the Older-B group with that in the Older-C and Younger-B groups. Non-inferiority margins were 10% for seroconversion rate differences and 0.5 for geometric mean titre (GMT) ratios. The primary endpoints were the GMT level and seroconversion rate of anti-EV71 neutralising antibody 30 days after the second dose of vaccination. The primary analysis was performed in the per-protocol population. Safety analyses were conducted amongst participants receiving at least one dose of vaccine. This trial was registered at Chinadrugtrials.org.cn (#CTR20192345). Findings: Between June 3 and June 30, 2020, 1600 participants were enrolled and assigned, including 625 participants in the Older-B group, 625 participants in the Older-C group and 350 participants in the Younger-B group. The seroconversion rate of anti-EV71 neutralising antibody in the Older-B group (99.66%; 95% CI: 99.18%-100.00%) was non-inferior to that of the Older-C (99.32%; 95% CI: 98.65%-99.98%) and Younger-B groups (100.00%; 95% CI: 100.00%-100.00%). The differences in seroconversion rates in the Older-B group to those in the Older-C and Younger-B groups were 0.34% (95%CI: -2.17%-2.86%) and -0.34% (95%CI: -2.78%-2.09%). The GMT of the anti-EV71 neutralising antibody in the Older-B group (693.87) was also non-inferior to that in the Older-C (289.37) and Younger-B groups (634.80). The ratios of GMTs in the Older-B group to those in the Older-C and Younger-B groups were 2.67 (95%CI: 2.00-3.00) and 1.00 (95%CI: 0.75-1.00), respectively. The incidence of any adverse event (AE) related to vaccination was similar amongst the three groups (34/625 [5.44%] in the Older-B group, 32/623 [5.14%] in the Older-C group, and 26/349 [7.45%] in the Younger-B group), with only 2 (0.57%) participants having grade 3 AEs in the Younger-B group. Fifteen (0.94%) participants from these three groups had reported serious AEs (SAEs), all of which were unrelated to vaccines. Interpretation: EV71 vaccine produced by WIBP could extend to be administered to children aged 36-71 months against EV71 infection. However, the persistence of vaccine-induced immunities needs to be further investigated. Funding: Hubei Province's young medical talent program (20191229), Hubei Province's young talent program (2021), Hubei Province's young public health talent program (2021); and the Wuhan Institute of Biological Products Co., Ltd.