Construction Of Eukaryotic Expression Plasmid Of PCV2ORF2Gene And Immune Responses In Mice Immunized With Porcine IL-15

Porcine circovirus type2is associated with many kinds of disease, including Postweaningmultisystemic wasting syndrome (PMWS). Since PMWS was first found in Canada in1991, it hadbeen found all around the world. Although the commercialized vaccine for PCV2had been usedwidely, the infection rate of PCV2was higher in China. It had been one of the most importantdisease that harmed the immune system of swine and caused huge epidemic losses. Because majorvaccine for PCV2a, but PCV2b was popular in the word now, and there were many obvious flawson PCV2proliferation, such as low virus titer, no obvious cytopathic effect and so on. It becamevery difficult to develop classic vaccine of PCV2using cell culture. So PCV2novel vaccine hasbeen a major research direction for PCV2vaccine. Nucleic acid vaccine has been a researchhotspot for PCV2novel vaccine because of its advantages, like simple preparation process, lowcost and so on.In this study, ORF2gene of PCV2b was inserted into the eukaryotic expressionvector--pVAX1, resulting in eukaryotic expression plasmids pVAX1-PCV2-ORF2. The plasmidswere transfected into BHK-21cells and the transient expression of ORF2gene was recognized byspecific anti PCV2monoclonal antibody. The results provided the useful materials for subsequentimmunization in vivo.The experimental mice were divided into5groups, and immunized withPBS(PBS group), pVAX1(vector group), pVAX1-pIL-15(adjuvant group), pVAX1-PCV2-ORF2(single immunized group) and pVAX1-pIL-15with pVAX1-PCV2-ORF2(unite immunized group).The humoral immune response of different groups at different days post-immunization wasdetected by enzyme linked immunosorbent assay and neutralization antibody. And lymphocyteproliferative assay and flow cytometric technique were used to detect the cellular immune response.Finally, the mice in different treatment groups were challenged with PCV2to compare thedifference of the protection rate.The results showed that the general immune responses of the single immunized group micewere higher than the ones of PBS group and vector group. Especially, the mice of unite immunizedgroup had higher immune response than the others. The vaccine of PCV2also had a protectiveeffect against challenge with PCV2in mice. In addition, pIL-15could enhance the protectiveeffect. The results indicated that pIL-15could enhance the immune responses of DNA plasmidencoding the ORF2gene of PCV2, which could induce the cellular immunity, enhance the humoralimmunity and improve the anti-virus capability. Our study provided useful data for researching anovel vaccine against PCV2and shown a new direction.