mRNA expression of proteins related to the early steps in a B-coronavirus infection, excluding AC2, were determined in the small airway epithelium (SAE) of smokers (gray circles) and nonsmokers (white circles.) Expression levels were quantified using RNA sequencing (Illumina HiSeq 2500), and the data values are reported in FPKM (fragments per kilobase of exon per million fragments sequenced.) Only TMPRSS2 expression was modulated by smoking: its expression was significantly increased (p < 0.01) in smokers compared to nonsmokers.