Porcine circovirus type 2 (PCV2) is a pathogenic virus that causes high rates of porcine death, resulting in severe economic losses to the swine industry. In recent years, the prevalence of PCV2d genotype infection in pigs has increased, but most commercially available vaccines were developed against the PCV2a strain and do not ensure complete protection from PCV2d. Here, we first constructed an expression vector for the antigenic ORF2-encoded capsid protein of PCV2d (pLp3050-His₆-tag-capsid). We then utilized Lactobacillus plantarum to express the protein at mucosal sites in orally vaccinated mice. After transducing L. plantarum with pLp3050-His₆-tag-capsid, the expressed protein could be found in cell wall and cell-free supernatant fractions by Western blotting. Using flow cytometry, we found that L. plantarum cells with surface-displayed capsid protein increased with time after SppIP induction. Finally, mice that were orally immunized 18 times with capsid-expressing L. plantarum showed increased levels of capsid-specific sIgA and virus neutralizing activity at mucosal sites, suggesting mucosal immunity had been stimulated by the vaccine. Overall, our findings demonstrate the feasibility and utility of a PCV2d-based vaccine, which may be of great value in porcine agriculture.

中文翻译：

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表达猪圆环病毒2d型（PCV2d）衣壳蛋白作为口服疫苗的植物乳杆菌菌株的构建。

猪圆环病毒2型（PCV2）是一种致病性病毒，可导致很高的猪死亡率，从而给养猪业造成严重的经济损失。近年来，猪中PCV2d基因型感染的患病率增加了，但是大多数商业上可买到的疫苗都是针对PCV2a株开发的，不能确保对PCV2d的完全保护。在这里，我们首先构建了针对PCV2d的ORF2抗原编码的衣壳蛋白（pLp3050-His ₆ -tag-衣壳）的表达载体。然后，我们利用植物乳杆菌在口服疫苗的小鼠的粘膜部位表达蛋白质。用pLp3050-His ₆转导植物乳杆菌后-标签-衣壳，通过蛋白质印迹可在细胞壁和无细胞上清液级分中发现表达的蛋白。使用流式细胞仪，我们发现表面展示衣壳蛋白的植物乳杆菌细胞在SppIP诱导后随时间增加。最后，经口衣壳表达免疫18次小鼠植物乳杆菌在黏膜部位显示出增加的衣壳特异性sIgA和病毒中和活性的水平，提示粘膜免疫已经由疫苗刺激。总体而言，我们的发现证明了基于PCV2d的疫苗的可行性和实用性，这在猪农业中可能具有巨大的价值。