Wuhan Institute of Biological Products, Co. Ltd., Jiangxia District, Wuhan, People's Republic of China.
Wuhan Institute of Biological Products, Co. Ltd., Jiangxia District, Wuhan, People's Republic of China
J Virol. 2021 Feb 24;95(6). doi: 10.1128/JVI.01743-20.
Coxsackievirus A5 (CV-A5) has recently emerged as a main hand, foot, and mouth disease (HFMD) pathogen. Following a large-scale vaccination campaign against enterovirus 71 (EV-71) in China, the number of HFMD-associated cases with EV-71 was reduced, especially severe and fatal cases. However, the total number of HFMD cases remains high, as HFMD is also caused by other enterovirus serotypes. A multivalent HFMD vaccine containing 4 or 6 antigens of enterovirus serotypes is urgently needed. A formaldehyde-inactivated CV-A5 vaccine derived from Vero cells was used to inoculate newborn Kunming mice on days 3 and 10. The mice were challenged on day 14 with a mouse-adapted CV-A5 strain at a dose that was lethal for 14-day-old suckling mice. Within 14 days postchallenge, groups of mice immunized with three formulations, empty particles (EPs), full particles (FPs), and a mixture of the EP and FP vaccine candidates, all survived, while 100% of the mock-immunized mice died. Neutralizing antibodies (NtAbs) were detected in the sera of immunized mice, and the NtAb levels were correlated with the survival rate of the challenged mice. The virus loads in organs were reduced, and pathological changes and viral protein expression were weak or not observed in the immunized mice compared with those in alum-inoculated control mice. Another interesting finding was the identification of CV-A5 dense particles (DPs), facilitating morphogenesis study. These results demonstrated that the Vero cell-adapted CV-A5 strain is a promising vaccine candidate and could be used as a multivalent HFMD vaccine component in the future. The vaccine candidate strain CV-A5 was produced with a high infectivity titer and a high viral particle yield. Three particle forms, empty particles (EPs), full particles (FPs), and dense particles (DPs), were obtained and characterized after purification. The immunogenicities of EP, FP, and the EP and FP mixture were evaluated in mice. Mouse-adapted CV-A5 was generated as a challenge strain to infect 14-day-old mice. An active immunization challenge mouse model was established to evaluate the efficacy of the inactivated vaccine candidate. This animal model mimics vaccination, similar to immune responses of the vaccinated. The animal model also tests protective efficacy in response to the vaccine against the disease. This work is important for the preparation of multivalent vaccines against HFMD caused by different emerging strains.
柯萨奇病毒 A5 (CV-A5) 近期已成为手足口病 (HFMD) 的主要病原体。在中国大规模开展肠道病毒 71 型 (EV-71) 疫苗接种后，EV-71 相关 HFMD 病例，尤其是重症和致死病例数量有所减少。然而，HFMD 总病例数仍然居高不下，因为 HFMD 还可由其他肠道病毒血清型引起。因此，急需研发包含 4 种或 6 种肠道病毒血清型抗原的多价 HFMD 疫苗。本研究使用从 Vero 细胞中衍生的甲醛灭活 CV-A5 疫苗，在第 3 天和第 10 天对新生昆明小鼠进行接种。在第 14 天，用可适应于小鼠的 CV-A5 株对已免疫小鼠进行攻毒，攻毒剂量对 14 日龄乳鼠具有致死性。在攻毒后 14 天内，用三种制剂（空颗粒（EP）、全颗粒（FP）和 EP 和 FP 疫苗候选物的混合物）免疫的小鼠均存活，而 100%的模拟免疫小鼠死亡。免疫小鼠血清中检测到中和抗体（NtAb），且 NtAb 水平与攻毒后小鼠的存活率相关。与铝佐剂接种的对照小鼠相比，免疫小鼠的器官病毒载量降低，病理变化和病毒蛋白表达较弱或不明显。另一个有趣的发现是鉴定出 CV-A5 致密颗粒（DPs），这有助于形态发生研究。这些结果表明，Vero 细胞适应的 CV-A5 株是一种有前途的疫苗候选物，未来可作为多价 HFMD 疫苗的组成部分。候选疫苗株 CV-A5 以高感染滴度和高病毒颗粒产量生产。在纯化后获得并表征了三种颗粒形式：空颗粒（EP）、全颗粒（FP）和致密颗粒（DPs）。在小鼠中评估了 EP、FP 和 EP 和 FP 混合物的免疫原性。生成适应于小鼠的 CV-A5 作为攻毒株，感染 14 日龄小鼠。建立主动免疫攻毒小鼠模型，以评估灭活候选疫苗的功效。该动物模型模拟了疫苗接种，类似于接种疫苗后的免疫反应。该动物模型还测试了针对该疾病的疫苗的保护效力。这项工作对于针对不同新兴株引起的 HFMD 的多价疫苗的制备很重要。
