CTSL and COVID-19: (ii) We do not know whether anti–pCTS-L mAbs are protective in other infectious diseases such as coronavirus disease 2019 (COVID-19), although a single-cell meta-analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry genes across tissues revealed a possible role of CTS-L up-regulation in the regulation of SARS-CoV-2 entry into host cells (55).