In theory, it is possible that SARS-CoV-2 acquired RBD mutations (Fig. 1a) during adaptation to passage in cell culture, as has been observed in studies of SARS-CoV11. The finding of SARS-CoV- like coronaviruses from pangolins with nearly identical RBDs, however, provides a much stronger and more parsimonious explanation of how SARS-CoV-2 acquired these via recombination or mutation19.
理论上说,像在SARS-CoV研究中已经观察到的一样,SARS-CoV-2在细胞培养中由适应性传代(迁移)可能获得RBD变异。穿山甲(体内)类似SARS-CoV冠状病毒的发现为SARS-CoV-2如何通过重组或变异获得(RBD)提供了更有力更简约的解释。
The acquisition of both the polybasic cleavage site and predicted O-linke dglycans also argues against culture-based scenarios. New polybasic cleavage sites have been observed only after prolonged passage of low-pathogenicity avian influenza virus in vitro or in vivo17. Furthermore, a hypothetical generation of SARS-CoV-2 by cell culture or animal passage would have required prior isolation of a progenitor virus with very high genetic similarity, which has not been described. Subsequent generation of a polybasic cleavage site would have then required repeated passage in cell culture or animals with ACE2 receptors similar to those of humans, but such work has also not previously been described. Finally, the generation of the predicted O-linked glycans is also unlikely to have occurred due to cell-culture passage, as such features suggest the involvement of an immune system18.
多碱基切割位点和O-链接聚糖的获得也对通过细胞培养(变异)提出争议。只有在长期低致病性禽流感病毒体内体外长期传代后才观察到多碱基切割位点。此外,细胞培养或动物传代产生SARS-CoV-2的假设需要事先分离出具有非常高遗传相似性的祖病毒,这种(工作)还没有见到记述。一个多碱基切割位点的后续产生需要在细胞培养中或者在具有与人类相似的ACE2受体的动物中反复传代,这类工作以前也没有记述。最后,希望得到的O-链接聚糖也不太可能在细胞培养中发生,因为这种特性需要一个免疫系统的参与。
笔者按:综上所述,此文在详细分析了SARS-CoV-2基因序列后,得出的结论是:究竟新冠病毒的源头是什么目前仍然没有定论,全文并没有否定任何一种可能性的猜测,只是更倾向于不是有意实验室人工合成,但在第三种可能性中却又提出必须检查实验室非故意泄漏的可能性,后面虽然说明细胞培养需要长期的更严格的条件,但同时提到了动物实验的可能性,指出两种情形以前没有记述并不等于没有实验室在做类似的工作。