Preclinical study of a combined host- and pathogen directed approach based on bioactive liposomes and bacteriophages against Mycobacterium abscessus infection

Background and Rationale. We have developed apoptotic body like liposomes (ABL) loaded withselected bioactive lipids able to enhance bactericidal innate immunity against multidrug resistant(MDR) pulmonary infections and to limit inflammatory response. In addition, phage therapy is apromising strategy in the fight against MDR bacteria and may represent an additional therapeutic tool for their management. Hypothesis and objectives. The main goal of this project is the development of a novel combinedhost- and pathogen- directed therapeutic approach, based on bioactive liposomes and phages specific for Mycobacterium abscessus (MA), used as a relevant MDR pathogen in Cystic Fibrosis(CF) patients. Essential methods. ABLs will be loaded with different bioactive lipids, tested on primarymacrophages derived by CF patients or healthy donors, in vitro infected with MA, and evaluated interms of bacterial phagocytosis, phagolysosome maturation, killing, and cytokine production. At thesame time, we will search and purify phages specific for MA and their efficacy will be tested invitro as an example of combined host- and pathogen- directed therapeutic approach. Finally, the best combination of ABL/phages in terms of mycobactericidal activity will be selected andevaluated in vitro in MA infected cells and in vivo in a murine model of chronic MA infection. Preliminary results. Our preliminary results show that primary macrophages from healthy donors, either treated or untreated with CFTR inhibitor INH172, in vitro infected with MA and stimulated with selected ABLs, are able to promote i) bacterial uptake, ii) phagosome acidification, iii) ROS production andiv) intracellular mycobacterial killing. Expected results and their significance. Expected results will consist in the identification and purification of phages specific for MA, which will be associated with selected ABL formulations in order to design a novel host- and pathogen- directed combination therapy. This approach will beuseful against MA infections in patients with CF and will be potentially applicable to MDR infections caused also by other pathogenic bacteria.