Construction and Immunogenicity of a DNA Vaccine Coexpressing GP3 and GP5 of Genotype-1 PRRS virus15 July 2014
DNA vaccines expressing GP3 and GP5 of Genotype-I porcine reproductive and respiratory syndrome (PRRS) virus showed good immunogenicity, and the DNA vaccine expressing both GP3 and GP5 produced better results in this Chinese work in mice, offering the prospect of more effective vaccines for pigs.
The European (EU) genotype of PRRS virus (Genotype-I PRRSV) has recently emerged in China, according to first-named author, Jing-Qiang Ren of the Academy of Military Medical Sciences in Changchun in China and co-authors.
In their paper in BMC Veterinary Research, they explain that the coexistence of Genotype-I and -II PRRSV strains could cause seriously affect PRRSV diagnosis and management. Current vaccines are not able to protect against PRRSV infection completely and have inherent drawbacks. Thus, genetically engineered vaccines, including DNA vaccine and live vector engineered vaccines, have been developed.
This study aimed to determine the enhanced immune responses of mice inoculated with a DNA vaccine coexpressing GP3 and GP5 of a Genotype-I PRRSV.
To evaluate the immunogenicity of GP3 and GP5 proteins from European-type PRRSV, three DNA vaccines, pVAX1-EU-ORF3-ORF5, pVAX1-EU-ORF3 and pVAX1-EU-ORF5, were constructed, which were based on a Genotype-I LV strain (GenBank ID: M96262). BALB/c mice were immunised with the DNA vaccines; delivered in the form of chitosan-DNA nanoparticles.
To increase the efficiency of the vaccine, Quil A (Quillaja) was used as an adjuvant.
GP3 and GP5-specific antibodies, neutralising antibodies and cytokines (IL-2, IL-4, IL-10 and IFN gamma) from the immunized mice sera, and other immune parameters, were examined, including T-cell proliferation responses and subgroups of spleen T-lymphocytes.
The results showed that ORF3 and ORF5 proteins of Genotype-I PRRSV induced GP3 and GP5-specific antibodies that could neutralis the virus. The levels of cytokines IL-2, IL-4, IL-10 and IFN–γ of the experimental groups were significantly higher than those of control groups after booster vaccination (P<0.05).
The production of CD3+CD4+ and CD3+CD8+ T-lymphocyte was also induced. T-lymphocyte proliferation assays showed that the PRRSV LV strain virus could stimulate the proliferation of T-lymphocytes in mice in the experimental group.
Using Quil A as adjuvant, genotype-I PRRSV GP3 and GP5 proteins produced good immunogenicity and reactivity, Renand co-authors concluded. More importantly, they report, better PRRSV-specific neutralising antibody titres and cell-mediated immune responses were observed in mice immunised with the DNA vaccine co-expressing GP3 and GP5 proteins than in those immunised with a DNA vaccine expressing either protein singly.
The results of this study demonstrated that co-immunisation with GP3 and GP5 produced a better immune response in mice.
Ren J-Q., W-C. Sun, H-J. Lu, S-B Wen, J. Jing, F-L. Yan, H. Liu, C-X. Liu1, P-P. Xiao, X. Chen, S-W. Du, R. Du and N-Y. Jin. 2014. Construction and immunogenicity of a DNA vaccine coexpressing GP3 and GP5 of genotype-I porcine reproductive and respiratory syndrome virus. BMC Veterinary Research. 10:128 doi:10.1186/1746-6148-10-128