Huan Changchao, Fan Mingyu, Cheng Qingru, Wang Xiaobo, Gao Qingqing, Wang Wanbin, Gao Song, Liu Xiufan
Key Laboratory of Avian Bioproducts Development, Ministry of Agriculture, Yangzhou, China.
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Front Microbiol. 2018 Mar 15;9:455. doi: 10.3389/fmicb.2018.00455. eCollection 2018.
Porcine circovirus type 2 (PCV2) commercial vaccines are either inactivated PCV2 isolates or subunit vaccine based on the Cap protein of PCV2. Currently, no live-attenuated vaccines are yet available. Although the predominant circulating subtype worldwide is PCV2b, the emerging PCV2d subtype is also increasingly associated with PCV disease. In this study, piglets were inoculated with a live-attenuated chimeric PCV1-2b vaccine before challenged with PCV2b and PCV2d isolates. Thirty-two piglets were randomly divided into seven groups: negative (sham-vaccinated, sham-challenged), VAC+PCV2b (PCV1-2b vaccinated, PCV2b-challenged), VAC+PCV2d (PCV1-2b vaccinated, PCV2d-challenged), CHAL+PCV2b (sham-vaccinated, PCV2b-challenged), CHAL+PCV2d (sham-vaccinated, PCV2d-challenged), CV+PCV2b (commercial-vaccinated, PCV2b-challenged), and CV+PCV2d (commercial-vaccinated, PCV2d-challenged). The results showed that vaccinated challenged groups demonstrated high levels of anti-PCV2 antibody and reduced PCV2b and PCV2d loads both in serum and nasal swabs compared with the challenge-only groups. PCV2 DNA was detected in the superficial inguinal lymph nodes of only one pig in each of the VAC+PCV2b and VAC+PCV2d groups (group mean values, 10 and 10 genomic copies/g, respectively), which was significantly lower than those in CHAL+PCV2b and CHAL+PCV2d animals (group mean values, 10 and 10 genomic copies/g, respectively; < 0.01). In addition, PCV2 DNA in each of the VAC+PCV2b and VAC+PCV2d groups was significantly lower than those in CV+PCV2b and CV+PCV2d animals (group mean values, 10 and 10 genomic copies/g, respectively; < 0.01), indicating that the live-attenuated PCV1-2b vaccine was more effective than commercial vaccine. The live-attenuated PCV1-2b vaccine was effective in reducing PCV2b/PCV2d viremia, shedding, and tissue viral loads in vaccinated challenged pigs compared with challenge-only piglets, indicating that the PCV1-2b prototype vaccine is a good candidate for a live-attenuated vaccine against both PCV2b and PCV2d subtypes. And we first revealed that the live-attenuated PCV1-2b vaccine could protect piglets from challenge with either PCV2b or PCV2d equivalently.
猪圆环病毒2型（PCV2）商业疫苗要么是灭活的PCV2毒株，要么是基于PCV2 Cap蛋白的亚单位疫苗。目前，尚无减毒活疫苗。尽管全球主要流行的亚型是PCV2b，但新兴的PCV2d亚型也越来越多地与PCV疾病相关。在本研究中，仔猪在受到PCV2b和PCV2d毒株攻击之前接种了一种减毒嵌合PCV1-2b疫苗。32头仔猪被随机分为7组：阴性组（假疫苗接种、假攻毒）、VAC+PCV2b组（接种PCV1-2b疫苗、PCV2b攻毒）、VAC+PCV2d组（接种PCV1-2b疫苗、PCV2d攻毒）、CHAL+PCV2b组（假疫苗接种、PCV2b攻毒）、CHAL+PCV2d组（假疫苗接种、PCV2d攻毒）、CV+PCV2b组（商业疫苗接种、PCV2b攻毒）和CV+PCV2d组（商业疫苗接种、PCV2d攻毒）。结果显示，与仅攻毒组相比，接种攻毒组的抗PCV2抗体水平较高，血清和鼻拭子中的PCV2b和PCV2d载量降低。在VAC+PCV2b组和VAC+PCV2d组中，仅各有一头猪的浅表腹股沟淋巴结中检测到PCV2 DNA（组均值分别为10和10基因组拷贝/g），显著低于CHAL+PCV2b组和CHAL+PCV2d组动物（组均值分别为10和10基因组拷贝/g；P<0.01）。此外，VAC+PCV2b组和VAC+PCV2d组中的PCV2 DNA显著低于CV+PCV2b组和CV+PCV2d组动物（组均值分别为10和10基因组拷贝/g；P<0.01），表明减毒PCV1-2b疫苗比商业疫苗更有效。与仅攻毒的仔猪相比，减毒PCV1-2b疫苗在接种攻毒的猪中能有效降低PCV2b/PCV2d病毒血症、病毒脱落和组织病毒载量，表明PCV1-2b原型疫苗是针对PCV2b和PCV2d亚型的减毒活疫苗的良好候选者。并且我们首次揭示，减毒PCV1-2b疫苗能同等程度地保护仔猪免受PCV2b或PCV2d的攻击。
