CTSB and infection: After 24 h post-infection, our results revealed that treatment with chemical inhibitors of cathepsins resulted in a significant increase in MTB intracellular survival (P < 0.001) in M1 macrophages, with a 10-fold increased survival when using CtsB inhibitors and approximately 5-fold increased survival when using CtsS and CtsL inhibitors (Fig. 3A, left).