Modulation of Cystatin F in Human Macrophages Impacts Cathepsin-Driven Killing of Multidrug-Resistant Mycobacterium tuberculosis

Tuberculosis (TB) treatment relies primarily on 70-year-old drugs, and prophylaxis suffers from the lack of an effective vaccine. Among the 10 million people exhibiting disease symptoms yearly, 450,000 have multidrug or extensively drug-resistant (MDR or XDR) TB. A greater understanding of host and pathogen interactions will lead to new therapeutic interventions for TB eradication. One of the strategies will be to target the host for better immune bactericidal responses against the TB causative agent Mycobacterium tuberculosis (Mtb). Cathepsins are promising targets due to their manipulation of Mtb with consequences such as decreased proteolytic activity and improved pathogen survival in macrophages. We recently demonstrated that we could overcome this enzymatic blockade by manipulating protease inhibitors such as cystatins. Here, we investigate the role of cystatin F, an inhibitor that we showed previously to be strongly upregulated during Mtb infection. Our results indicate that the silencing of cystatin F using siRNA increase the proteolytic activity of cathepsins S, L, and B, significantly impacting pathogen intracellular killing in macrophages. Taken together, these indicate the targeting of cystatin F as a potential adjuvant therapy for TB, including MDR and XDR-TB.

Automated summary

TB treatment heavily relies on outdated drugs and lacks an effective vaccine. Understanding the interaction between the host and the pathogen will lead to new therapeutic interventions for TB eradication. Targeting host factors like cathepsins, which manipulate Mycobacterium tuberculosis (Mtb) and impact its survival in macrophages, is a promising strategy. Silencing cystatin F, an upregulated inhibitor during Mtb infection, increases the proteolytic activity of cathepsins and impairs pathogen killing in macrophages. Targeting cystatin F could be a potential adjuvant therapy for TB, including multidrug-resistant and extensively drug-resistant cases.