Horsington Jacquelyn, Singanallur Balasubramanian Nagendrakumar, Nfon Charles K, Bittner Hilary, Vosloo Wilna
Australian Centre for Disease Preparedness, Transboundary Disease Mitigation, Commonwealth Scientific and Industrial Research Organisation (CSIRO) Health and Biosecurity, Geelong, VIC, Australia.
Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada.
Front Vet Sci. 2022 Oct 28;9:1027556. doi: 10.3389/fvets.2022.1027556. eCollection 2022.
Over the last 15 years, FMDV serotype A viruses in South-East Asia (A/ASIA/SEA-97 lineage) have diverged into several clusters. Variants from Thailand in 2011-2013 have caused vaccine failures and returned poor r-values (<0.30) to A Iraq 64 (A22) and A Malaysia 97 (A May) vaccine strains. We investigated the protective ability of monovalent and bivalent A Malaysia 97 and A22 Iraq 64 vaccine strains against infection with an A/Asia/SEA-97 variant in pigs. Pigs were challenged with a variant of A/Asia/SEA-97 lineage either 21- or 7- days post-vaccination (V21 or V7) using the heal-bulb challenge. Only one in five pigs were protected in the V21 monovalent vaccine groups. Less severe clinical signs were observed in the A22 IRQ group compared to the A MAY 97 group. In the V21 combination group, 4 out of 5 pigs were protected and viraemia was significantly reduced compared to the monovalent V21 groups. V7 vaccine groups were not protected. The neutralising antibody response was below the detection limit in all groups on the challenge day, showing a poor correlation with protection. There was no evidence that the pigs protected from systemic disease had protective antibody responses sooner than other pigs in the study, implying other immune mechanisms might play a role in protecting these animals. FMDV was detected in the nasal and oral swab samples between 1 and 6 dpc. Viral loads were lower in the nasal swab samples from the V21 combination group than the other groups, but there was no difference in the oral swab samples. Since all unvaccinated controls were euthanised by 6-day post-challenge for ethical reasons, the 'area under the curve (AUC)' method was used to compare the viraemia and virus excretion in different groups. We recommend that for the A/Asia/SEA97 variants, a combination vaccine with A Malaysia 97 and A22 Iraq 64 vaccine strains would be ideal compared to monovalent vaccines.
在过去15年中，东南亚的口蹄疫病毒A型（A/ASIA/SEA - 97谱系）已分化为几个簇。2011 - 2013年来自泰国的变异株导致疫苗失效，且与A伊拉克64（A22）和A马来西亚97（A五月）疫苗株的r值较差（<0.30）。我们研究了单价和双价A马来西亚97和A22伊拉克64疫苗株对猪感染A/Asia/SEA - 97变异株的保护能力。在接种疫苗后21天或7天（V21或V7），使用蹄踵接种法用A/Asia/SEA - 97谱系的一个变异株对猪进行攻毒。在V21单价疫苗组中，每五头猪中只有一头得到保护。与A五月97组相比，A22 IRQ组观察到的临床症状较轻。在V21联合疫苗组中，五头猪中有四头得到保护，与单价V21组相比，病毒血症显著降低。V7疫苗组未得到保护。攻毒当天所有组的中和抗体反应均低于检测限，与保护效果相关性较差。没有证据表明免受全身性疾病影响的猪比研究中的其他猪更早产生保护性抗体反应，这意味着其他免疫机制可能在保护这些动物中发挥作用。在攻毒后1至6天，在鼻拭子和口腔拭子样本中检测到口蹄疫病毒。V21联合疫苗组鼻拭子样本中的病毒载量低于其他组，但口腔拭子样本中没有差异。由于出于伦理原因，所有未接种疫苗的对照组在攻毒后6天被安乐死，因此使用“曲线下面积（AUC）”方法比较不同组的病毒血症和病毒排泄情况。我们建议，对于A/Asia/SEA97变异株，与单价疫苗相比，A马来西亚97和A22伊拉克64疫苗株的联合疫苗将是理想选择。
