Vaccines and Immunization

Biography

Biography: Isabel Yee

Abstract

Enterovirus 71 (EV-A71) can cause mild hand, foot and mouth infections as well as fatal neurological complications. With concern about EV-A71 virulence, there is urgency for effective vaccines. Recent studies have reported novel vaccines incorporating microRNAs (miRNAs) that can regulate gene expression. A live attenuated vaccine strain was constructed by introducing two microRNA targets, let-7a and miR-124a, into the EV-A71 wild type genome to repress viral replication. The miRNA-bearing vaccine would not replicate in neuronal cells carrying the corresponding miRNA but could replicate in the gastrointestinal tract to act as immunogens. The pathogenicity of the miRNA vaccine strain was evaluated in RD, SHSY-5Y and NTERA-2 cell cultures by plaque counts, tissue culture infectious dose (TCID50) determinations and RNA copy numbers. Following transfection of the miRNA vaccine strain into the three cell lines, RD and SHSY-5Y showed minimal cytopathic effects, as compared to the NTERA-2 cells. The viral RNA copy number of the miRNA vaccine strain was much lower in RD (1.2×102) and SHSY-5Y cells (7.7×10) than the wild type RNA copy number of 3.9×104 and 5.8×104, in the respective cell lines. The TCID50 values indicate that the miRNA vaccine strain was attenuated as much as 6-fold when compared to the wild type. There was much reduction in plaque number (3.5×104 PFU/ml) when compared to the wild type (5.0×108 PFU/ml). Intra peritoneal administration of the miRNA vaccine construct in the murine model triggered a mixed Th1/Th2 response. The IgG subtype analysis of the miRNA antisera showed a strong IgG1 specific antibody response and a comparatively lower IgG2a, IgG2b and IgG3 response. As such, the miRNA strain is an attractive candidate to be developed as a live attenuated vaccine.