Development of FMD and PRRS DNA Vaccines

Shu-Mei Liang ； Jeng-Jer Shich ； Jun-Jei Sheu ； Ning-Sun Yang

《Journal of Genetics and Molecular Biology》 13卷1期 (2002/03) Pp. 60-61

https://doi.org/10.30047/JGMB.200203.0017

並列摘要

The currently available foot-and-mouth disease vaccines are composed of inactivated virus that have the potential risk of causing an outbreak due to the virus escaped from the inactivation process. We have taken several virus free vaccination approaches including DNA vaccine, subunit vaccine or combination of both to evaluate their immune responses and efficacy.
Several viral protein expression plasmids containing foot-and-mouth disease virus (FMDV) coat protein genes, VP1 or VP4-1, were constructed to express VP1 or polycistronic viral proteins, respectively. These plasmids were constructed to be localized in the cytosol, secreted from the transgenic cells, or bound to cell membrane for evaluation of DNA vaccine-mediated immune responses. Among these three expression systems, a vector expressed VP1 in the cytosol, namely pcDNA3-VP I, produced the lowest amount of humoral responses. However, mice priming with pcDNA3-VP1 followed by boosting with the VP1 peptide conjugate resulted in sera containing high titers of antibodies with neutralizing activities. Moreover, mice immunized with this vaccination approach cleared virus completely from FMDV challenge accompanied by increasing IgG2a titers. We also immunized mice with a polycistronic VP(4-1) cDNA expression vector by the gene gun delivery system and showed that this vector conferred an 80% effect in virus clearance.

Besides FMD outbreaks, porcine reproductive and respiratory syndrome (PRRS) is a rapidly spreading, economically important infectious disease of swine. We found that mice immunized with a DNA expression vector encoded ORF5 gene of PRRSV produced low titers of antibodies. To evaluate whether the effect of DNA vaccination can be enhanced by cytokines, DNA vector encoded cytokines such as interleukin 18 or interleukine-1 converting enzyme was administered and was shown to substantially increase the antibody titers.
In summary, we have developed several molecular strategies for FMD and PRRS vaccines. The results of FMDV study suggest that DNA priming might provide an advantage of enhancing the IgG2a immune responses and facilitate the generation of protective immunity. The results of PRRS study, on the other hand, demonstrated the effect of cytokines in enhancing immune responses. The efficacy of each strategy is being evaluated in the swine system.