Foot-and-mouth disease virus (FMDV), the most acid-unstable virus among picornaviruses, tends to disassemble into pentamers at pH values slightly below neutrality. However, the structural integrity of intact virion is one of the most important factors that influence the induction of a protective antibody response. Thus, improving the acid stability of FMDV is required for the efficacy of vaccine preparations. According to the previous studies, a single substitution or double amino acid substitutions (VP1 N17D, VP2 H145Y, VP2 D86H, VP3 H142D, VP3 H142G, and VP1 N17D + VP2 H145Y) in the capsid were introduced into the full-length infectious clone of type O FMDV vaccine strain O/HN/CHN/93 to develop seed FMDV with improved acid stability. After the transfection into BSR/T7 cells of constructed plasmids, substitution VP1 N17D or VP2 D86H resulted in viable and genetically stable FMDVs, respectively. However, substitution VP2 H145Y or VP1 N17D + VP2 H145Y showed reverse mutation and additional mutations, and substitution VP3 H141G or VP3 H141D prevented viral viability. We found that substitution VP1 N17D or VP2 D86H could confer increased acid resistance, alkali stability, and thermostability on FMDV O/HN/CHN/93, whereas substitution VP1 N17D was observed to lead to a decreased replication ability in BHK-21 cells and mildly impaired virulence in suckling mice. In contrast, substitution VP2 D86H had no negative effect on viral infectivity. These results indicated that the mutant rD86H carrying substitution VP2 D86H firstly reported by us could be more adequate for the development of inactivated FMD vaccines with enhanced acid stability.

中文翻译：

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具有增强的酸稳定性的工程可行的口蹄疫病毒有助于开发改进的疫苗。

口蹄疫病毒（FMDV）是在小核糖核酸病毒中最酸不稳定的病毒，在pH值略低于中性的情况下，往往会分解为五聚体。然而，完整的病毒体的结构完整性是影响诱导保护性抗体应答的最重要因素之一。因此，疫苗制剂的功效需要提高FMDV的酸稳定性。根据先前的研究，衣壳中的单取代或双氨基酸取代（VP1 N17D，VP2 H145Y，VP2 D86H，VP3 H142D，VP3 H142G和VP1 N17D + VP2 H145Y）被引入到O型FMDV疫苗株O / HN / CHN / 93可开发出具有改善的酸稳定性的种子FMDV。将构建好的质粒转染到BSR / T7细胞后，取代VP1 N17D或VP2 D86H分别导致可行的和遗传稳定的FMDV。但是，替代VP2 H145Y或VP1 N17D + VP2 H145Y显示出反向突变和其他突变，替代VP3 H141G或VP3 H141D阻止了病毒的生存能力。我们发现，取代VP1 N17D或VP2 D86H可以赋予FMDV O / HN / CHN / 93更高的耐酸性，碱稳定性和热稳定性，而观察到取代VP1 N17D则导致BHK-21细胞复制能力下降，且轻度乳鼠的毒力受损。相反，替代VP2 D86H对病毒感染性没有负面影响。这些结果表明，我们首次报道的携带取代VP2 D86H的rD86H突变体可能更适合开发具有增强的酸稳定性的灭活的FMD疫苗。