Fc-engineered monoclonal antibodies drive antibody-dependent enhancement of Mycobacterium tuberculosis

This study investigates how Fc-engineered antibodies affect Mycobacterium tuberculosis (Mtb) growth through antibody-dependent enhancement (ADE). We engineered 16 Fc variants with two distinct Fab regions (710 and 712), both targeting antigen85B (Ag85B), creating 32 total antibody variants. These variants were comprehensively profiled across five antibody effector functions: antibody-dependent neutrophil phagocytosis (ADNP), antibody-dependent monocyte phagocytosis (ADMP), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent NK cell activation (ADNK), and antibody-dependent complement deposition (ADCD). We also assessed FcγR binding profiles using Luminex multiplex assays. Hierarchical clustering identified six distinct functional groups, enabling selection of a representative panel for downstream Mtb infection studies. Notably, 712 IgG3-RH, the most pro-inflammatory variant activating all tested effector functions, promoted Mtb growth in both human macrophages and bronchoalveolar lavage (BAL) cells. These findings demonstrate that: (1) antibody effector functions are primarily determined by the Fc region but are also influenced by the Fab region, highlighting Fab-Fc crosstalk; (2) 712 variants exhibit greater functionality than 710 variants due to higher Ag85B affinity; and (3) pro-inflammatory IgG3 antibodies may be detrimental in TB, providing a framework for identifying antibody features to avoid in TB vaccine design.