Formalin-inactivated EV-D68 particles produced in serum-free HEK293A suspension culture induced specific neutralizing antibody responses, supporting their use as vaccine candidates.
A serum-free HEK293A suspension culture system can successfully propagate EV-D68 to produce full viral particles that induce strong, specific neutralizing immune responses for vaccine development.
Enterovirus D68 (EV-D68) is an emerging pathogen that typically causes respiratory illness but can also lead to acute flaccid myelitis, which has been reported in several outbreaks worldwide. As EV-D68 has been found to be difficult to infect and proliferate in the standard Vero cells, a viable manufacturing process for the development of inactivated EV-D68 vaccine is urgently needed. We performed cell line screening and found that the HEK293A is a suitable host for EV-D68 propagation. The EV-D68 TW2014 (B3) strain was used to develop the EV-D68 production using a serum-free HEK293A (sfHEK293A) suspension system. Two major EV-D68 particles, the empty and full viral particles, were separated by ultracentrifugation and were found to induce low and high neutralizing antibody responses, respectively, in animal studies. To facilitate the mass production of vaccine, a combination of size-exclusion and anion-exchange chromatography was developed to purify EV-D68 particles. High quality, pure EV-D68 particles could be obtained by this simple procedure for vaccine production. Additionally, we found that the EV-D68 MO (B1) and KY (A2) strains could also be propagated in this sfHEK293A cell system, but at a lower 33 °C condition. These three formalin-inactivated EV-D68s were shown to induce EV-D68-specific neutralizing responses and also neutralize a recently circulating strain, but failed to cross-neutralize enterovirus A71 (EV-A71) in sera assay. The combination of EV-D68 and EV-A71 in one vaccination induced the neutralizing responses against both viruses. Our results showed that EV-D68 particles produced from the sfHEK293A suspension culture could be used to prepare EV-D68 vaccine candidates. Purifying the full EV-D68 particles for vaccine production is recommended for inducing a high, specific immune response. Combination of EV-D68 and EV-A71 is beneficial for the development of bivalent enterovirus vaccine.
Shen et al. (Tue,) conducted a other in Enterovirus D68. Formalin-inactivated EV-D68 vaccine candidates was evaluated on Neutralizing antibody responses. Formalin-inactivated EV-D68 particles produced in serum-free HEK293A suspension culture induced specific neutralizing antibody responses, supporting their use as vaccine candidates.