Foot-and-mouth disease (FMD) is a highly contagious vesicular disease of cloven-hoofed animals, which severely decreases livestock productivity. FMD virus (FMDV), the causative agent, initiates infection by interaction with integrin cellular receptors on pharyngeal epithelium cells, causing clinical signs one to four days after transmission to a susceptible host. However, some Southern African Territories (SAT) viruses have been reported to cause mild or subclinical infections that may go undiagnosed in field conditions and are likely to be more common than previously expected. The studies presented here demonstrate that not all SAT2 viruses are equally virulent in cattle. The two SAT2 viruses, ZIM/5/83 and ZIM/7/83, were both highly attenuated in cattle, as evidenced by the mild clinical signs observed after needle challenge, while two incongruent SAT2 viruses showed significantly different clinical signs in challenged cattle. We then explored the ability of the SAT2 viruses to infect different cell types with defined receptors that are utilised by FMDV and found differences in their ability to lyse cells in culture and to compete in a controlled cell culture environment. The population sequence variation between ZIM/5/83 and ZIM/7/83 revealed multiple sites of single nucleotide variants of low frequency between the predominant virus populations, as could be expected from the genome of an RNA virus. An assessment of the biophysical stability of SAT2 virions during acidification indicated that the SAT2 virus EGY/09/12 was more resilient to acidification than the ZIM/5/83 and ZIM/7/83 viruses; however, whether this difference relates to differences in virulence in vivo is unclear. This study is a consolidated view of the key findings of SAT2 viruses studied over a 14-year period involving many different experiments.

口蹄疫（FMD）是丁香蹄类动物的高度传染性水泡病，严重降低了牲畜的生产力。FMD病毒（FMDV）是病原体，通过与咽上皮细胞上的整合素细胞受体相互作用而开始感染，在传播至易感宿主后一到四天引起临床体征。但是，据报道，某些南部非洲领土（SAT）病毒会引起轻度或亚临床感染，在现场条件下可能无法诊断，而且可能比以前预期的更为普遍。这里介绍的研究表明，并非所有SAT2病毒在牛中都具有同等毒性。牛攻击后，两种SAT2病毒ZIM / 5/83和ZIM / 7/83均在牛中高度减毒，如针刺后观察到的轻度临床体征所证明，而两种不一致的SAT2病毒在受攻击的牛中表现出明显不同的临床体征。然后，我们探索了SAT2病毒用FMDV利用的定义受体感染不同细胞类型的能力，并发现了其溶解培养物中的细胞和在受控细胞培养环境中竞争的能力的差异。ZIM / 5/83和ZIM / 7/83之间的种群序列变异揭示了主要病毒种群之间低频的单核苷酸变异体的多个位点，正如RNA病毒基因组所预期的那样。对酸化过程中SAT2病毒粒子的生物物理稳定性的评估表明，与ZIM / 5/83和ZIM / 7/83病毒相比，SAT2病毒EGY / 09/12对酸化的抵抗力更强。但是，这种差异是否与毒力差异有关体内尚不清楚。这项研究是对SAT2病毒在长达14年的时间内研究的关键发现的综合看法，涉及许多不同的实验。