HER-2 pulsed DC1(H. Lee Moffitt Cancer Center and Research Institute)

Transglutaminase type 2 (TG2) catalyses formation of ε‐(γ‐glutamyl)‐lysine bonds between proteins, including those of the extracellular matrix (ECM). Elevated extracellular TG2 leads to accelerated ECM deposition and reduced clearance that underlies tissue scarring and fibrosis. Many transglutaminase inhibitors exist and allowed for proof‐of‐concept studies in disease models, but their lack of specificity for the TG2 isoform, and/or poor pharmacokinetic/pharmacodynamic properties have limited their clinical application. We sought to develop a high affinity TG2‐specific antibody against extracellular TG2 activity, with characteristics suitable for therapeutic development.

Individual human TG2 domains were used to immunize mice and generate hybridomas. Supernatants were screened for inhibition of recombinant human TG2 activity, with TG2 specificity determined by ELISA.

Thirteen TG2‐specific, hybridoma supernatants inhibited human transamidation activity. Each hybridoma was cloned and the antibody mapped to an epitope in the TG2 core domain, using phage display panning of a TG2 fragment library. Four distinct inhibitory epitopes were determined. The most effective antibodies (AB1, DC1, and BB7) bound to amino acids 313–327 (catalytic core), with an IC50 of approximately 6–7 nM. The antibodies inhibit TG2 in human cells and block ECM accumulation in a primary human proximal tubular epithelial cell model of fibrosis. Only 7 antibodies inhibited rat TG2, all with higher IC50 values.

We identified a preferred inhibitory epitope in human TG2, developed antibodies with required characteristics for clinical development, and established that targeted inhibition of extracellular TG2 transamidation activity is sufficient to modify fibrotic remodelling.

Tumor-infiltrating dendritic cells (DCs) assume varied functional states that impact anti-tumor immunity. To delineate the DC states associated with productive anti-tumor T cell immunity, we compared spontaneously regressing and progressing tumors. Tumor-reactive CD8⁺ T cell responses in Batf3^-/- mice lacking type 1 DCs (DC1s) were lost in progressor tumors but preserved in regressor tumors. Transcriptional profiling of intra-tumoral DCs within regressor tumors revealed an activation state of CD11b⁺ conventional DCs (DC2s) characterized by expression of interferon (IFN)-stimulated genes (ISGs) (ISG⁺ DCs). ISG⁺ DC-activated CD8⁺ T cells ex vivo comparably to DC1. Unlike cross-presenting DC1, ISG⁺ DCs acquired and presented intact tumor-derived peptide-major histocompatibility complex class I (MHC class I) complexes. Constitutive type I IFN production by regressor tumors drove the ISG⁺ DC state, and activation of MHC class I-dressed ISG⁺ DCs by exogenous IFN-β rescued anti-tumor immunity against progressor tumors in Batf3^-/- mice. The ISG⁺ DC gene signature is detectable in human tumors. Engaging this functional DC state may present an approach for the treatment of human disease.