Chit Laa Poh
Sunway University, Malaysia
Title: MicroRNA reduction of enterovirus 71 viral replication attenuates and confers protective immune response in mice
Biography
Biography: Chit Laa Poh
Abstract
The hand, foot, and mouth disease (HFMD) is generally manifested as a subclinical infection, but fatal neurological complications can occur in young children. Epidemiological surveillance in China from 2008-2014 showed that 43.73% of HFMD cases were due to EV-A71. Up to date, there is no WHO-approved vaccine against EV-A71. This study demonstrated a novel miRNA vaccine construct for EV-A71 which decreased viral replication in vitro, whilst conferring a protective immune response in four-week old ICR mice. A vaccine construct was engineered to carry microRNA (miRNA) target sequences let-7a and miR-124a in the EV-A71 genome, allowing endogenous RNA silencing in specific cell types. The viral RNA copy number of the miRNA vaccine strain was much lower in RD (1.2 X 102) and SHSY-5Y cells (7.7 X 10) that expressed let-7a and miR-124a, respectively. The miRNA vaccine construct caused much reduction in plaque number (3.5 x 104 PFU/ml) in the SHSY-5Y cells as compared to the wild type virus (5.0 x 108 PFU/ml). No weight loss and hind limb paralysis were observed in the miRNA vaccine-administered mice (n=5) in comparison to the naïve group of mice (n=5). Significantly elevated systemic levels of IFN-γ and lower levels of pro-inflammatory cytokines TNF-α and IL-6 were detected. Higher CD8+ T cell response was elicited by the miRNA vaccine strain in mice as compared to the inactivated vaccine. The miRNA vaccine construct was able to confer protective immunity against EV-A71 sub-genotypes B3, C3 and C4. Ten serial passage studies to determine the genetic stability of the target sequences let-7a and miR-124a showed that the sequences did not revert to wild type virulence. Overall, the miRNA vaccine construct is an effective attenuation strategy for vaccine development.