TMPRSS2 and pneumonia: This type of pneumonia termed “COVID-19” by the WHO was found to be caused by the SARS-CoV-2 through interaction of the Spike-glycoprotein and the host receptor proteins angiotensin-converting enzyme 2 (ACE2) and the transmembrane protease serine 2 (TMPRSS2), present in the alveolar cells of the lung [82,83].