We read with great interest a review that provides a systematic evaluation of the most recent in vitro and in vivo investigations targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cell entry, although authors showed that SARS-CoV-2 has five structural proteins including the S (spike), M (membrane), N (nucleocapsid), and E (envelope) proteins, and the HE (hemagglutinin esterase) in fig. 2 (Seyedpour et al., 2021). However, based on the scientific evidence which is described in this letter, SARS-CoV-2 lacks HE so it cannot be considered as a structural protein in SARS-CoV-2 (Chan et al., 2020; Mittal et al., 2020; Zandi et al., 2021).

Recently a novel coronavirus called SARS-CoV-2 causes coronavirus disease 2019 (COVID-19) as a global pandemic (Navand et al., 2020). SARS-CoV-2 is considered the seventh human coronavirus. Coronaviruses belong to Coronaviridae family which are classified in four genera: alpha-, beta-, gamma-, and delta-coronaviruses. In coronaviruses, only some beta-coronaviruses contain HE (Chan et al., 2020). There are five subgenera Embecovirus, Sarbecovirus, Merbecovirus, Nobecovirus, and Hibecovirus in beta-coronavirus genus. Both SARS-CoV and SARS-CoV-2 are members of beta-coronaviruses of Sarbecovirus, MERS-CoV is a beta-coronavirus of Merbecovirus, although OC43-CoV and HKU1-CoV are beta-coronaviruses of the Embecovirus (Committee ICoToVE, 2020; Frutos et al., 2021; Zhang et al., 2021).

The genome of coronaviruses is 26–32 kb in length. The genome of SARS-CoV-2 codes four structural proteins: S, E, M, N, and several accessory proteins: ORF3a, 3b, 6, 7a, 7b, 8, 9b, 9c, and 10. SARS-CoV-2 does not contain HE gene (Chan et al., 2020; Zhang et al., 2021). However, other beta-coronaviruses such as HKU1-CoV and OC43-CoV of Embecovirus subgenera bear HE gene and can encode HE (Hulswit et al., 2019).

In conclusion, SARS-CoV-2 as a beta-coronavirus of Sarbecovirus lacks HE and encodes four structural proteins thus HE cannot be used as a drug target against COVID-19.

我们非常感兴趣地阅读了一篇综述，该综述对针对严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 细胞进入的最新体外和体内研究进行了系统评估，尽管作者表明 SARS-CoV-2 有五个结构蛋白包括 S（刺突）、M​​（膜）、N（核衣壳）和 E（包膜）蛋白，以及图 1 中的 HE（血凝素酯酶）。2（Seyedpour 等人，  2021 年）。然而，根据这封信中描述的科学证据，SARS-CoV-2 缺乏 HE，因此不能将其视为 SARS-CoV-2 中的结构蛋白（Chan 等人，  2020 年；Mittal 等人，  2020 年） ；赞迪等人，  2021 年）。

最近，一种名为 SARS-CoV-2 的新型冠状病毒导致 2019 年冠状病毒病 (COVID-19) 成为全球大流行病 (Navand et al.,  2020 )。SARS-CoV-2 被认为是第七种人类冠状病毒。冠状病毒属于冠状病毒科，分为四个属：α-、β-、γ-和δ-冠状病毒。在冠状病毒中，只有一些β-冠状病毒含有HE（Chan et al.,  2020）。β-冠状病毒属中有五个亚属Embecovirus、Sarbecovirus、Merbecovirus、Nobecovirus和Hibecovirus。SARS-CoV 和 SARS-CoV-2 都是 Sarbecovirus 的 β 冠状病毒的成员，MERS-CoV 是 Merbecovirus 的 β 冠状病毒，尽管 OC43-CoV 和 HKU1-CoV 是 Embecovirus 的 β 冠状病毒（ICoToVE 委员会，  2020; Frutos 等人，  2021 年；张等人，  2021）。

冠状病毒的基因组长度为 26-32 kb。SARS-CoV-2 的基因组编码四种结构蛋白：S、E、M、N 和几种辅助蛋白：ORF3a、3b、6、7a、7b、8、9b、9c 和 10。 SARS-CoV-2不含 HE 基因 (Chan et al.,  2020 ; Zhang et al.,  2021 )。然而，其他 β 冠状病毒如 Embecovirus 亚属的 HKU1-CoV 和 OC43-CoV 带有 HE 基因并且可以编码 HE（Hulswit 等人，  2019 年）。

总之，SARS-CoV-2 作为 Sarbecovirus 的 β 冠状病毒缺乏 HE 并编码四种结构蛋白，因此 HE 不能用作针对 COVID-19 的药物靶点。