The porcine circovirus type 2 (PCV2) capsid (Cap) protein and porcine parvovirus (PPV) VP2 protein have been studied in vaccines to control postweaning multisystemic wasting syndrome (PMWS). Virus-like particle (VLP) vaccines are nonreplicative vectors that deliver epitopes and induce immune responses. However, most VLP vaccines are recombinant proteins expressed in eukaryotic systems and are expensive and complex. In this study, the full-length PCV2-Cap and PPV-VP2 proteins were expressed in Escherichia coli, which self-assembled into VLPs. The highly soluble proteins were purified using Ni-chelating affinity chromatography. The proteins self-assembled into VLPs of ∼20 nm (Cap VLP) and 25 nm (VP2 VLP) in diameter. The immunogenicities of Cap VLP and VP2 VLP were determined in piglets coinfected with PPV and PCV2 postimmunization. The results suggested that Cap VLP and VP2 VLP did not antagonize each other. The combined vaccine induced stronger humoral and cellular immune responses and provided the best protection against PPV and PCV2 coinfection. On a farm containing PMWS-infected pigs, the combined Cap VLP and VP2 VLP vaccine significantly improved piglet growth indices; the average daily weight gains were significantly higher than those of the Cap VLP vaccine and nonimmunized groups. Thus, Cap and VP2 protein expression in E. coli is feasible for large-scale VLP vaccine production. The combined vaccine may be a promising candidate vaccine for better preventing PMWS-associated diseases coinfected with PCV2 and PPV.

中文翻译：

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针对猪细小病毒和2型猪圆环病毒的病毒样颗粒疫苗可减少断奶后多系统消耗综合症相关的临床症状。

已在疫苗中研究了猪圆环病毒2型（PCV2）衣壳（Cap）蛋白和猪细小病毒（PPV）VP2蛋白，以控制断奶后多系统消耗综合症（PMWS）。病毒样颗粒（VLP）疫苗是传递表位并诱导免疫反应的非复制型载体。但是，大多数VLP疫苗是在真核系统中表达的重组蛋白，价格昂贵且复杂。在这项研究中，全长PCV2-Cap和PPV-VP2蛋白在大肠杆菌中表达，它会自动组装成VLP。使用镍螯合亲和色谱法纯化高可溶性蛋白。蛋白质自组装成直径约20 nm（Cap VLP）和25 nm（VP2 VLP）的VLP。在免疫后PPV和PCV2共感染的仔猪中测定了Cap VLP和VP2 VLP的免疫原性。结果表明，Cap VLP和VP2 VLP没有相互对抗。联合疫苗可诱导更强的体液和细胞免疫反应，并提供针对PPV和PCV2合并感染的最佳保护。在含有PMWS感染猪的农场中，Cap VLP和VP2 VLP组合疫苗显着改善了仔猪的生长指数。平均每日体重增加显着高于Cap VLP疫苗和非免疫组。因此，Cap和VP2蛋白在大肠杆菌对于大规模VLP疫苗生产是可行的。联合疫苗可能是一种有前途的候选疫苗，可以更好地预防与PCV2和PPV共同感染的PMWS相关疾病。