Development of Chitosan Particles Loaded with siRNA for Cystatin C to Control Intracellular Drug-Resistant Mycobacterium tuberculosis

The golden age of antibiotics for tuberculosis (TB) is marked by its success in the 1950s of the last century. However, TB is not under control, and the rise in antibiotic resistance worldwide is a major threat to global health care. Understanding the complex interactions between TB bacilli and their host can inform the rational design of better TB therapeutics, including vaccines, new antibiotics, and host-directed therapies. We recently demonstrated that the modulation of cystatin C in human macrophages via RNA silencing improved the anti-mycobacterial immune responses to Mycobacterium tuberculosis infection. Available in vitro transfection methods are not suitable for the clinical translation of host-cell RNA silencing. To overcome this limitation, we developed different RNA delivery systems (DSs) that target human macrophages. Human peripheral blood-derived macrophages and THP1 cells are difficult to transfect using available methods. In this work, a new potential nanomedicine based on chitosan (CS-DS) was efficiently developed to carry a siRNA-targeting cystatin C to the infected macrophage models. Consequently, an effective impact on the intracellular survival/replication of TB bacilli, including drug-resistant clinical strains, was observed. Altogether, these results suggest the potential use of CS-DS in adjunctive therapy for TB in combination or not with antibiotics.The research linked to this work was funded by Fundação para a Ciência e a Tecnologia (FCT) (grant numbers PTDC/SAU-INF/28182/2017 to E.A.; EXPL/SAU-INF/0742/2021 to D.P.; UIDB/04138/2020 to IMed-ULisboa; UIDB/04279/2020 to CIRH; and CEECINST/00070/2021 to Universidade Católica Portuguesa). M.M. is supported by a PhD fellowship from FCT with the reference 2021.07978.BD.