P039

1:Host-Pathogen Interactions Unit, Research Institute for Medicines, Faculty of Pharmacy, University of Lisbon, Portugal; 2:Universidade Católica Portuguesa, Católica Medical School, Center for Interdisciplinary Research in Health, Portugal; 3:Drug Delivery and Immunoengineering Unit, Research Institute for Medicines, Faculty of Pharmacy, University of Lisbon, Portugal

Tuberculosis (TB), primarily caused by Mycobacterium tuberculosis (Mtb), still continues to exert a tremendous burden on public health concerns and deaths worldwide. There is an urgent need for the development of alternative strategies to control the infection. Targeting cathepsins constitutes one of the potential approaches. We demonstrated that Mtb actively manipulates macrophage lysosomal enzymes with consequent decreased proteolytic activity, and increased pathogen intracellular survival. In addition, the overcome of this enzymatic blockade was made through the manipulation of protease inhibitors “cystatins”. Our recent work demonstrated that the manipulation of cystatin F (CstF) in human macrophages using RNA silencing led to increased proteolytic activity of lysosomal cathepsins, improving Mtb intracellular killing. It also revealed the impact of CstF depletion in macrophages during the coinfection of Mtb-infected phagocytes with lymphocytes infected with HIV. Since the in vitro transfection method used is not suitable for a clinical translation here, a different RNA delivery system was developed (DSs) i.e., nanomedicine based on chitosan (Cs-DS). We functionalized the DS with mannose to potentiate the interaction with the mannose receptor (CD206) expressed on macrophages by promoting receptor-ligand interaction, subsequently improving the delivery of siRNA-targeting CstF to the infected macrophage models. The results indicate a more efficient silencing of CstF mRNA, and an effective impact on the intracellular survival of TB bacilli relatively to the conventional previous transfection method and with less toxicity. Overall, the study suggests the potential use of Cs-DS in adjunctive therapy for TB either in combination with or without antibiotics.