| Summary: | 碩士 === 國立成功大學 === 微生物暨免疫學研究所 === 87 === Pseudorabies virus (PrV) is one of the most significant viral pathogens for swine. It causes Aujeszky's disease, which results in severe, even lethal diseases in young pigs, leading to severe financial losses. An other important pathogen is Salmonella choleraesuis, which causes swine paratyphoid. The PrV gp50 glycoprotein mediates adsorption and penetration of PrV and represents a major target for neutralizing antibodies, which may protect mice and swine from the PrV disease. A plasmid encoding the PrV gp50 glycoprotein was used as a DNA vaccine candidate. Attenuated strains of enteropathogenic species, such as Salmonella, represent useful carriers for the delivery of heterologous recombinant antigens to the immune system for eliciting both mucosal and systemic immunities. In our previous study, vaccination with DNA encoding the PrV gp50 under the control of an eukaryotic promoter confers partial protection to mice against PrV challenge. The gp50 plasmid DNA may be delivered by avirulent E. coli strains. In addition, coexpression of prothymosin a (ProTa) enhances the immunogenicity and efficacy of DNA vaccines. In this study, a variety of expression vectors for PrV gp50 and ProTa were constructed in an attempt to explore the feasibility of using attenuated Salmonella as a DNA delivery vehicle for PrV DNA vaccination. Attenuated Salmonella choleraesuis strains transformed with gp50 or ProTa or both plasmids were used for oral vaccination to mice. To compare the efficacy of these oral vaccine vectors, survival rate, antibody production, splenocyte proliferation, and cytotoic T lymphocytes (CTL) of mice were examined.
The results show that mice orally receiving two doses of the recombinant S.C.S.C. containing the gp50 plasmid were protected from PrV challenge. Mice immunized with recombinant S.C.S.C. carrying the gp50 gene developed anti-PrV and anti-Salmonella antibodies, T-cell proliferation to PrV and gp50-specific cytotoxic T lymphocyte responses. Although ProTa enhanced PrV-specific T-cell responses, it did not increase the efficacy of the recombinant S.C.S.C. carrying the gp50 gene. Taken together, these results demonstrate that the PrV gp50 gene delivered through Salmonella by the oral route may be a feasible approach in the development of pseudorabies vaccines.
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