Enhanced immunogenicity to food-and-mouth disease virus in mice vaccination with alphaviral replicon-based DNA vaccine expressing the capsid precursor polypeptide (P1)

Abstract

Recently, alphavirus replicon-based DNA vaccines, also known as suicidal DNA vaccines, have emerged as an important strategy to enhance the potency of DNA vaccines. In this study, two different types of DNA vaccines encoding the capsid precursor polypeptide (P1) of foot-and-mouth disease virus (FMDV) were constructed and the immunogenicity were investigated and compared in mouse model. The first DNA vaccine, pcDP1, is a conventional plasmid DNA vaccine in which P1 was driven directly by a cytomegalovirus promoter. The second DNA vaccine, pSCAP1, is a Semliki Forest virus (SFV) replicon-based DNA vaccine encoding the same antigen. In vitro expression and characterization indicated that two vaccine vectors could correctly produce the P1 antigen. However, pSCAP1 could induce obvious apoptosis of the transfected cells. After immunization in BALB/c mice, the P1-specific ELISA antibodies, neutralizing antibodies, as well as lymphocyte proliferative responses induced by pSCAP1 were significantly higher than those obtained in mice immunized with pcDP1. Notably, mice immunized with the pSCAP1 had the determined ability of clearing virus in their sera after FMDV challenge. These results indicate that the SFV replicon-based DNA vaccine pSCAP1 are more effective than conventional DNA vaccine and it can be considered a promising approach for the development of a safety and efficacious vaccine against FMDV.

A DNA vaccine encoding the FMDV capsid precursor polypeptide P1 and the enhancing effect of bovine herpesvirus 1 VP22 protein as molecular adjuvant

“…However, we found that a DNA vaccine encoding the FMDV P1 protein could induce not only humoral responses but also cell-mediated responses (Yu et al, 2006). At the same time, we demonstrated that vaccination with the DNA vaccine encoding P1 resulted in the clearance of FMDV from the sera of immunized mice challenged by FMDV, while the DNA vaccine encoding the FMDV VP1 protein did not protect animals against the challenge (Yu et al, 2006;Shieh et al, 2001).…”

“…DNA transfection and gene expression were performed according to Yu et al (2006). At 48 hrs after transfection, the plates were fixed with 3.7% formaldehyde in PBS (pH 7.4) and incubated with rabbit polyclonal anti-P1 antiserum.…”

“…Immunization of mice was performed with plasmid pcDP1, pcDBP1, and empty vector pcDNA3.1 (+), separately, according to Yu et al (2006). Serum samples were collected from the retro-orbital plexus of the mice at various time points after immunization to detect P1-specific antibodies and neutralizing antibodies against FMDV.…”

“…The P1-specific antibody responses were determined by ELISA (Yu et al, 2006). The A 630 was measured by an ELISA reader (Labsystems MK3).…”

“…The spleens were removed from the immunized mice and the splenocytes were plated in 96-well flatbottomed plates for MTS assay (Yu et al, 2006). Each splenocytes sample was plated in triplicate.…”