Development of a CD8 co-receptor independent T-cell receptor specific for tumor-associated antigen MAGE-A4 for next generation T-cell-based immunotherapy.

BACKGROUND: The cancer-testis antigen MAGE-A4 is an attractive target for T-cell-based immunotherapy, especially for indications with unmet clinical need like non-small cell lung or triple-negative breast cancer. METHODS: An unbiased CD137-based sorting approach was first used to identify an immunogenic MAGE-A4-derived epitope (GVYDGREHTV) that was properly processed and presented on human leukocyte antigen (HLA)-A2 molecules encoded by the HLA-A*02:01 allele. To isolate high-avidity T cells via subsequent multimer sorting, an in vitro priming approach using HLA-A2-negative donors was conducted to bypass central tolerance to this self-antigen. Pre-clinical parameters of safety and activity were assessed in a comprehensive set of in vitro and in vivo studies. RESULTS: A MAGE-A4-reactive, HLA-A2-restricted T-cell receptor (TCR) was isolated from primed T cells of an HLA-A2-negative donor. The respective TCR-T-cell (TCR-T) product bbT485 was demonstrated pre-clinically to have a favorable safety profile and superior in vivo potency compared with TCR-Ts expressing a TCR derived from a tolerized T-cell repertoire to self-antigens. This natural high-avidity TCR was found to be CD8 co-receptor independent, allowing effector functions to be elicited in transgenic CD4+ T helper cells. These CD4+ TCR-Ts supported an anti-tumor response by direct killing of MAGE-A4-positive tumor cells and upregulated hallmarks associated with helper function, such as CD154 expression and release of key cytokines on tumor-specific stimulation. CONCLUSION: The extensive pre-clinical assessment of safety and in vivo potency of bbT485 provide the basis for its use in TCR-T immunotherapy studies. The ability of this non-mutated high-avidity, co-receptor-independent TCR to activate CD8+ and CD4+ T cells could potentially provide enhanced cellular responses in the clinical setting through the induction of functionally diverse T-cell subsets that goes beyond what is currently tested in the clinic.

Caco-2 cell acquisition of dietary iron(III) invokes a nanoparticulate endocytic pathway.

Dietary non-heme iron contains ferrous [Fe(II)] and ferric [Fe(III)] iron fractions and the latter should hydrolyze, forming Fe(III) oxo-hydroxide particles, on passing from the acidic stomach to less acidic duodenum. Using conditions to mimic the in vivo hydrolytic environment we confirmed the formation of nanodisperse fine ferrihydrite-like particles. Synthetic analogues of these (~ 10 nm hydrodynamic diameter) were readily adherent to the cell membrane of differentiated Caco-2 cells and internalization was visualized using transmission electron microscopy. Moreover, Caco-2 exposure to these nanoparticles led to ferritin formation (i.e., iron utilization) by the cells, which, unlike for soluble forms of iron, was reduced (p=0.02) by inhibition of clathrin-mediated endocytosis. Simulated lysosomal digestion indicated that the nanoparticles are readily dissolved under mildly acidic conditions with the lysosomal ligand, citrate. This was confirmed in cell culture as monensin inhibited Caco-2 utilization of iron from this source in a dose dependent fashion (p<0.05) whilet soluble iron was again unaffected. Our findings reveal the possibility of an endocytic pathway for acquisition of dietary Fe(III) by the small intestinal epithelium, which would complement the established DMT-1 pathway for soluble Fe(II).

Dietary iron does not impact the quality of life of patients with quiescent ulcerative colitis: an observational study.

BACKGROUND: In animal models, excess luminal iron exacerbates colonic inflammation and cancer development. Moreover, in inflammatory bowel disease (IBD) patients with mild to moderate disease activity dietary fortificant iron intake is inversely related to quality of life. Here we sought to determine whether dietary iron intakes were also related to quality of life in IBD patients in remission. METHODS: Forty eight patients with ulcerative colitis (UC), 42 of which had quiescent disease during this observational study, and 53 healthy control subjects completed quality of life questionnaires and 7-day food diaries. For comparative analysis, 34/group were matched and the linear relationship between dietary iron intakes (total, haem, non-haem or fortificant) and EuroQol quality of life measures was investigated. For UC patients the linear relationship between dietary iron intakes and the scores from the disease specific inflammatory bowel disease questionnaire (IBDQ) was also considered. RESULTS: The intake of dietary iron, and its various sub-fractions, were not associated with quality of life (EuroQol) in patients with quiescent disease or in healthy control subjects. The picture was similar for the 42 quiescent UC patients when disease-specific IBDQ was used. However, the 6 patients who relapsed during the study again showed an inverse association between IBDQ and dietary iron intake (p = 0.03). CONCLUSIONS: Our data suggest that dietary iron does not impact on quality of life in quiescent UC patients but support that, once the disease is triggered, luminal iron may be a permissive factor for exacerbation of disease activity resulting in lower quality of life.