展示生长抑素的猪细小病毒样颗粒构建及其免疫原性

为了获得既可预防猪细小病毒感染又能促进生长的嵌合病毒样颗粒疫苗，以PPV NJ-a株基因组DNA为模板扩增VP2基因片段，在VP2基因N端融合人工合成的4拷贝生长抑素基因，构建杆状病毒转移载体pFast-SS4-VP2。通过转化DH10Bac感受态细胞，pFast-SS4-VP2与穿梭载体Bacmid重组，获得重组Bacmid，命名为rBacmid-SS4-VP2。rBacmid-SS4-VP2转染Sf-9细胞，获得重组病毒rBac-SS4-VP2。SDS-PAGE与Western blotting鉴定可见约68 kDa的rSS4-VP2条带；rBac-SS4-VP2感染细胞IFA检测产生很强的特异性绿色荧光；感染细胞超薄切片电镜观察到大量特征性病毒样颗粒。将重组蛋白分别辅以铝胶、IMS和白油不同佐剂免疫小鼠，通过检测免疫小鼠VP2特异性ELISA抗体、PPV特异性中和抗体、生长抑素的抗体水平及生长激素水平来评价嵌合病毒样颗粒的免疫原性。结果表明，辅以铝胶与IMS佐剂重组蛋白组均产生了与PPV全毒组相似的ELISA抗体与中和抗体反应；重组蛋白免疫组均产生较好的针对生长抑素的抗体反应；免疫小鼠体内生长激素的水平明显升高；其中以铝胶佐剂组产生的各抗体水平最高，白油佐剂组各抗体水平最低。为以后生产安全、有效的颗粒化亚单位疫苗提供了一个新的设计思路，又为应用病毒样颗粒递呈外源肽，从而生产多联亚单位疫苗奠定了基础。

Construction and immunogenicity of recombinant porcine parvovirus-like particles with somatostatin

In order to obtain a virus-like particle vaccine both for porcine parvovirus (PPV) prevention and growth-promotion, VP2 gene of PPV NJ-a strain was amplified with PCR, and four copies of synthetic somatostatin gene were fused to the N-terminal of VP2 gene. The fused gene was cloned into pFast-HT A to construct the recombinant plasmid pFast-SS4-VP2, then the pFast-SS4-VP2 was transformed into DH10Bac competent cells and recombined with shuttle vector Bacmid, followed by identification with blue-white screening and PCR analysis for three cycles, and the positive recombinant was named as rBacmid-SS4-VP2. The positive Sf-9 cells were transfected with rBacmid-SS4-VP2 by Lipofectamine to produce recombinant baculovirus. When the cytopathic effect (CPE) was obvious, the transfected Sf-9 cell was harvested, and the positive recombinant virus was named as rBac-SS4-VP2. The insertion for the target gene into baculovirus genome was confirmed with PCR. SDS-PAGE and Western blotting revealed that the calculated protein of approximately 68 kDa was in the expressed in the insect cells. The Sf-9 cells infected with rBac-SS4-VP2 were stained positive against PPV antibody using the indirect immunofluorescence assay (IFA). Moreover, the virus particle self-assembly was observed under electron microscopy. 90 four-week-old mice were immunized by the recombinant protein coupled with different adjuvants alhydrogel, IMS and oil. VP2-specific ELISA antibodies, PPV-specific neutralizing antibody, somatostatin antibody and growth hormone levels were examined to evaluate the immunogenicity of this virus like particle. Results indicated that mice groups immunized rSS4-VP2 protein with alhydrogel and IMS developed similar humoral immune response comparing with inactived PPV vaccine. Mice group immunized with rSS4-VP2 generated higher level of SS antibody and growth hormone comparing with negative control, mice receiving rSS4-VP2 with alhydrogel developed the highest antibody titre than all other groups, while the oil group developed the lowest antibody level. This study provides not only a new rout for production of safe and effective virus like particle subunit vaccine, but also the foundations for peptide presentation and multivalent subunit vaccine design.