Key result
Immunization with 5μg of EV71 C4a-gp41 VLP with alum adjuvant elicited a neutralizing antibody titer of 1:512 against the EV71 C4a virus and induced cross-neutralization against other subtypes.
Why the study?
Enterovirus 71 causes hand-foot-mouth disease with potential severe neurologic complications and mortality in children, prompting efforts to improve the production yield and assess the vaccine potential of recombinant virus-like particles.
Effect estimate: 32-fold increase compared with control after second boosting
p-value: p=<0.01
An optimized baculovirus expression system efficiently produces EV71 virus-like particles that elicit strong humoral immune responses in mice, showing potential as a vaccine candidate.
VLPs induce neutralizing antibodies in preclinical models; leaves open translation to pediatric HFMD prevention.
Enterovirus (EV) 71 is the main pathogen associated with hand-foot-mouth disease (HFMD) and can lead to the disease with severe mortality in children. Since 2009, in the Republic of Korea, an outbreak of EV71 C4a infection with neurologic involvement emerged, where in HFMD involvement was identified and central nervous system complications were reported. In this study, EV71 C4a virus-like particles (VLPs) produced by recombinant technology were generated in a baculovirus expression system. To improve the production yield, EV71 VLP was constructed using the dual promoter system baculovirus P1 and 3CD (baculo-P1-3CD), which harbored both the structural protein-encoding P1 region under the control of the polyhedron promoter and the 3CD protease gene under the regulation of the CMV-IE, lef3, gp41, or chitinase promoters to augment the level of gene transcription. Efficient VLP expression was demonstrated through optimization of incubation time and insect cell type. In addition, to evaluate the potential of VLP as a vaccine candidate, we tested the neutralizing antibodies and total anti-EV71 IgG from the purified EV71 C4a VLP serum. The recombinant EV71 VLP exhibited the morphology of self-assembled VLP, as determined by electron microscopy. Use of baculo-P1-3CD-gp41 led to a high yield (11.3mg/L < 40kDa) of VLPs in High-FiveTM cells at 3 days post-infection. Furthermore, the potential of VLP as a vaccine was evaluated through the neutralizing ability elicited by the purified EV71 VLP after immunization of BALB/c mice, which was shown to induce potent and long-lasting humoral immune responses as evidenced by the cross-neutralization titer. Our results could be used to expedite the developmental process for vaccines under clinical trials and to ensure manufacturing consistency for licensing requirements.
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Kim et al. (2019) studied Enterovirus 71 infection (n=15). EV71 C4a-gp41 VLP vaccine vs. Phosphate-buffered saline (PBS) was evaluated on Neutralizing antibody titer against EV71 C4a virus (32-fold increase compared with control after second boosting, p=<0.01). Immunization with 5μg of EV71 C4a-gp41 VLP with alum adjuvant elicited a neutralizing antibody titer of 1:512 against the EV71 C4a virus and induced cross-neutralization against other subtypes.
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