An Antibody-Recruiting Molecule Enhances Fcγ Receptor-Mediated Uptake and Killing of Mycobacterial Pathogens by Macrophages

Mycobacteria, which include the infectious agents for tuberculosis (TB) and nontuberculous mycobacteria (NTM) disease, pose a critical health challenge due to traits that allow them to evade host immune clearance and Antibiotic action. Toward a novel immunotherapy approach for mycobacteria, we previously reported an antibody-recruiting molecule (ARM) strategy to specifically modify the surface glycans of mycobacteria with exogenous haptens, marking the bacteria for opsonization by endogenous antibodies and enhancing the antibody-mediated immune response. We showed that the ARM, a trehalose-dinitrophenyl conjugate (Tre-DNP), exploited a conserved metabolic pathway to metabolically label the surface of nonpathogenic Mycobacterium smegmatis with DNP, recruited anti-DNP antibodies to the Bacterial surface, and enhanced phagocytosis of the bacteria by THP-1 cells. Here, we extend these findings by investigating the ability of the Tre-DNP ARM strategy to increase macrophage-mediated phagocytosis and killing of different pathogenic mycobacterial species and interrogating mechanisms associated with the outcome. We show that Tre-DNP successfully modified the surface of multiple pathogens, including Mycobacterium tuberculosis and the NTM species Mycobacterium abscessus and Mycobacterium avium, and that phagocytosis and killing of intracellular bacteria by differentiated THP-1 cells is significantly enhanced for all species. Furthermore, we find that enhanced uptake is dependent upon the Fcγ receptor (FcγR) and enhanced killing correlates with sustained production of Reactive Oxygen Species (ROS) and increased phagosome-lysosome fusion. Overall, our data demonstrate that Tre-DNP efficiently promotes ingestion of mycobacteria by human macrophages via the FcγR and enhances host effector responses against the pathogen. Thus, ARMs are tools that can be exploited for the purposes of (i) conducting mechanistic studies on immune recognition and elimination of mycobacterial pathogens and (ii) developing immune-targeting strategies against mycobacterial pathogens.

Fcγ receptor; Mycobacteria; antibodies; antibody-recruiting molecule (ARM); cell labeling; immunotherapy; macrophages; trehalose.