The SARS-CoV-2 B.1.617 lineage was identified in October 2020 in India^1,2,3,4,5. Since then, it has become dominant in some regions of India and in the UK, and has spread to many other countries⁶. The lineage includes three main subtypes (B1.617.1, B.1.617.2 and B.1.617.3), which contain diverse mutations in the N-terminal domain (NTD) and the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein that may increase the immune evasion potential of these variants. B.1.617.2—also termed the Delta variant—is believed to spread faster than other variants. Here we isolated an infectious strain of the Delta variant from an individual with COVID-19 who had returned to France from India. We examined the sensitivity of this strain to monoclonal antibodies and to antibodies present in sera from individuals who had recovered from COVID-19 (hereafter referred to as convalescent individuals) or who had received a COVID-19 vaccine, and then compared this strain with other strains of SARS-CoV-2. The Delta variant was resistant to neutralization by some anti-NTD and anti-RBD monoclonal antibodies, including bamlanivimab, and these antibodies showed impaired binding to the spike protein. Sera collected from convalescent individuals up to 12 months after the onset of symptoms were fourfold less potent against the Delta variant relative to the Alpha variant (B.1.1.7). Sera from individuals who had received one dose of the Pfizer or the AstraZeneca vaccine had a barely discernible inhibitory effect on the Delta variant. Administration of two doses of the vaccine generated a neutralizing response in 95% of individuals, with titres three- to fivefold lower against the Delta variant than against the Alpha variant. Thus, the spread of the Delta variant is associated with an escape from antibodies that target non-RBD and RBD epitopes of the spike protein.

SARS-CoV-2 B.1.617 谱系于 2020 年 10 月在印度^{1、2、3、4、5}被确定。从那时起，它在印度和英国的一些地区占据主导地位，并传播到许多其他国家⁶. 该谱系包括三个主要亚型（B1.617.1、B.1.617.2 和 B.1.617.3），它们在 SARS-可能会增加这些变体的免疫逃避潜力的 CoV-2 刺突蛋白。B.1.617.2（也称为 Delta 变体）被认为比其他变体传播得更快。在这里，我们从一名从印度返回法国的 COVID-19 患者身上分离出 Delta 变异株的传染性菌株。我们检查了该菌株对单克隆抗体以及对 COVID-19 康复者（以下称为恢复期个体）或已接种 COVID-19 疫苗的个体血清中存在的抗体的敏感性，然后将该菌株与其他菌株进行比较SARS-CoV-2 毒株。Delta 变体对一些抗 NTD 和抗 RBD 单克隆抗体（包括 bamlanivimab）的中和具有抗性，并且这些抗体显示出与刺突蛋白的结合受损。从症状发作后长达 12 个月的恢复期个体收集的血清对抗 Delta 变体的效力比 Alpha 变体低四倍（B.1.1.7）。来自接受了一剂辉瑞或阿斯利康疫苗的个体的血清对 Delta 变体几乎没有明显的抑制作用。接种两剂疫苗在 95% 的个体中产生了中和反应，针对 Delta 变体的滴度比针对 Alpha 变体的滴度低三到五倍。因此，