CTSB and infection: However, unlike cathepsin B, this protein was not completely absent (CTSC, Fig. 1C) and the decrease in abundance was not significant as assessed by quantitative proteomics analysis (Supplementary Fig 1A and Supplementary Fig 1D), leading us to focus our investigation on cathepsin B. Analysis of transcript abundance using real-time quantitative PCR (RT-qPCR) confirmed that the changes in cathepsin expression during infection were not due to reduced transcription of these proteins (Fig. 1D).