(416) Antibody Recruiting Small Molecules as Immune Probes

Introduction/Rationale: Immunotherapies that enhance the immune response may offer a novel approach for eliminating mycobacteria infections. Our collaborative team synthesized and characterized the first antibody-recruiting small molecule (ARM) for mycobacteria. ARMs are bispecific molecules that attach haptens to pathogenic cells and recruit endogenous, anti-hapten antibodies that promote immunity. The core component to our ARMs is trehalose, which integrates into the bacterial membrane via a conserved pathway and displays the hapten, DNP, for antibody binding. Tre-DNP incorporation increases antibody recruitment, phagocytosis, and killing by macrophages.

Methods: We hypothesized that antibody-dependent Fc receptor (FcR) signaling promotes macrophage phagolysosome (PL) fusion, which we tested by measuring colocalization of Lysotracker-labeled lysosomes and CMFDA-stained bacteria. To further enhance ARM incorporation and antibody recruitment, we developed second-generation ARMs using a two-step click conjugation approach.

Results: Macrophages that ingested ARM-labeled and opsonized mycobacteria exhibited greater PL fusion compared to the controls. Preliminary data indicated that these ARMs achieved improved incorporation and antibody recruitment compared with the one-step approach.

Conclusion: Ongoing studies are testing whether greater antibody recruitment or different haptens promote a stronger immune response. A mechanistic understanding of how Tre-DNP enhances the immune response toward mycobacteria could lead to further refinement of this immunotherapeutic strategy.