Evaluating macrophage activation in response to phage exposure: Implications for phage therapy

Abstract

Background: Bacteriophages are viruses that infect bacteria and are gaining prominence as therapeutic agents against multidrug-resistant (MDR) pathogens. Beyond their bacteriolytic activity, phages also modulate host immune responses, including macrophage behavior. This study explores both the antimicrobial and immunomodulatory potential of phages, focusing on a novel phage targeting Acinetobacter baumannii. Objectives: This research aimed to (1) isolate and characterize a lytic bacteriophage specific to A. baumannii, and (2) evaluate its immunological effects, alongside other phages, on human macrophages derived from THP-1 monocytes. Methods: Environmental samples were screened to isolate phage AUBFM-AANR01, which underwent characterization including host range testing, one-step growth curve analysis, biofilm disruption assays, and genome sequencing. In parallel, differentiated THP-1 macrophages were exposed to phages to assess cell viability and surface marker expression via flow cytometry. Results: Phage AUBFM-AANR01 exhibited potent lytic activity against A. baumannii, efficient adsorption, moderate burst size, and notable biofilm disruption. Genomic analysis confirmed its placement in the Autographiviridae family without lysogeny or virulence genes. Immunologically, AUBFM-AANR01 suppressed macrophage activation, reducing CD86 and CD68 expression and maintaining cells in a resting or intermediate phenotype. These effects persisted in endotoxin-free preparations, indicating a potential phage-specific immunosuppressive mechanism. Conclusion: AUBFM-AANR01 is a promising candidate for inclusion in phage therapy libraries targeting MDR pathogens. Its immunomodulatory properties suggest potential dual functionality: antimicrobial efficacy and the ability to attenuate macrophage activation. These findings support the integration of phages into immunomodulatory therapeutic strategies.