TB Phage therapy: Optimizing delivery methods of mycobacteriophages to target intracellular Mycobacterium tuberculosis

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Abstract Tuberculosis (TB) remains as a major global health problem causing 1.2 million deaths and over 10 million new cases each year. The onset of the HIV epidemic beginning in the late 1980s led to immune suppression in humans and significantly increased the emergence of drug resistance, lengthening treatment duration. Ominously, there are strains of M. tuberculosis, the causative agent of TB, that are resistant to many, if not all, of the currently available TB drugs that are extremely difficult to treat. As an alternative to drugs, mycobacteriophages - viruses that kill M. tuberculosis, have been considered as possible agents to treat tuberculosis. However, previous studies have had limited success in mammalian hosts. The goal of this grant is to elucidate why phage therapy fails to work. We hypothesized that the major obstacle is mycobacteriophages are unable to come into contact with the M. tuberculosis cells that live intracellularly. We propose to develop novel strategies to deliver mycobacteriophages to the intracellular compartments in which M. tuberculosis resides. One approach would be to engineer mycobacteriophage capsid proteins so that we can add macrophage delivery ligands to promote cellular uptake. In addition, we plan to explore the use of a Mycobacterium smegmatis strain as a Trojan horse delivery vector to the intracellular M. tuberculosis. These studies will be enhanced by our ability to generate mycobacteriophages that express fluorescent reporter proteins. In order to deliver the mycobacteriophages to the lungs, the site of intracellular localization, we plan to use spray dried mycobacteriophage powders. We also plan to test the hypothesis that mycobacteriophages may work as an adjunct therapy with existing TB drugs in mouse models.