Phage-mediated TLR2 signaling attenuates intracellular Mycobacterium abscessus survival in macrophages.

The incidence of pulmonary infections caused by M. abscessus (MAB) is on rise globally. Despite susceptible infections, long-term, and combinational treatment, patients respond to MAB therapy only partially with low success rates. In recent years, therapeutic phages have been used in combination with antibiotics to enhance treatments for patients suffering with drug-resistant, chronic, and disseminated mycobacterial infections with favorable clinical outcomes. While phages are commonly recognized for their antimicrobial role through direct lysis of bacteria, expanding body of literature, describing phage interactions with the immune system, indicates that the therapeutic impact of phage may not solely hinge on lytic activity but also on stimulating innate immune responses. In this study, we aimed to uncover phages that work synergistically with macrophage cellular mechanisms, enhancing phagocyte-mediated reduction of intracellular MAB. We discovered phages stimulating TLR2 signaling associated with NLRP3 inflammasome activation, resulting in substantial attenuation of the intracellular pathogen growth. We also uncovered a new phenomenon of intracellular elimination of MAB through fusion of lytic phage vacuoles with bacterial phagosomes. This process is driven by a cellular mechanism triggered by phage exposure to phagocytic cells. New therapeutic characteristics of phage, described in this study, will contribute to future phage-based therapeutic interventions.