Research Projects

In 2023, the World Health Organization (WHO) reported 10.8 million new Tuberculosis (TB) cases and 1.25 million deaths. Healthcare workers working at TB services and family and close contacts of TB patients are at higher risk of contracting active TB (Baussano et al., Emerg Infect Dis, 17, 2011; Shiferaw et al., PLoS One, 16, 2021). This suggests that more than 50 million people are at high risk of contracting TB. There is only one approved vaccine for TB, which is BCG; however, it has variable and low efficacy in adults (Martinez et al., Lancet Glob Health, 10, 2022). Close contacts of TB patients are usually started on preventive therapy that consists of daily isoniazid and/or rifapentine tablets for several months, and hence encounter similar non-compliance as TB treatment due to the long treatment duration and side effects of antibiotics. We propose to develop a biomaterial-based inhalable bacteriophage product that can emerge as a safe and patient-compliant TB preventive alternative to a long-term antibiotic preventive regimen. Why bacteriophages for prevention? Bacteriophages (phages) are safe and are effective against multidrug-resistant bacteria. Phages are specific to one or a few closely related bacterial species and do not infect the patient's commensal microflora (Cho & Blaser, Nature Reviews: Genetics, 13, 2012), which antibiotics can severely perturb. Mycobacteriophages have been extensively studied, with a vast library of phages. The actinobacteriophage database at PhagesDB.org has around 12600 phages that infect Mycobacterium species. Several of these phages are lytic and can infect Mycobacterium tuberculosis (Mtb). Why porous particles for pulmonary dry powder delivery? For TB, which is spread through aerosols, it would be ideal to have phages present in the lungs of susceptible populations via dry powder delivery to ensure interaction with bacteria before it gets internalized within macrophages and exerts its pathogenesis through granuloma formation. Previous attempts to deliver phages in mice via nebulization have resulted in sub-optimal outcomes (Carrigy et al., Pharm Res, 34, 2017; Carrigy et al., Antimicrob Agents Chemother, 2019). This could be attributed to low phage deposition after nebulization, as only ~15% of nebulized phages deposit in deep lungs (Liu et al., Journal of Aerosol Medicine and Pulmonary Drug Delivery, 29, 2016). Dry powder delivery allows ease of administration, increased patient compliance, low systemic side effects, long-term storage and stability of the drug (Ungaro et al., J Pharm Pharmacol, 64, 2012). However, delivery of phages to the lungs through inhalation is restricted due to their size range (less than 100 nm) as they cannot efficiently deposit in the lungs and are exhaled out. Using polymeric carriers loaded with phages can solve this challenge as they can be designed to deposit in deep lungs and also protect phages from structural damage. For dry powder delivery, polymeric particles must be designed such that their aerodynamic diameter (daero) is 500 nm - 5 µm for deep lung delivery (Edwards et al., Science, 276, 1997). daero is related to the actual sphere diameter d by the formula: (daero = dgeometric*(ρ)^0.5, ρ = density). As porous microparticles have a lower density, they can have large geometric diameters but still be in the right aerodynamic range to deposit in deep lungs. This will prevent phagocytosis by alveolar macrophages and result in a high residence time of phages. Statement of purpose and research questions: The purpose of this proposal is to develop polymeric particle-loaded phage formulations for the prevention of TB in high-risk individuals. The research questions are as follows: • Can the lytic phages be efficiently delivered via biomaterial-based dry powder inhalation? • Are the lytic phages effective in preventing animals from contracting tuberculosis after bacterial challenge? • Are the lytic phages safe and effective after repeated use?