Development of Aspergillus cell surface-targeting antibodies as novel theranostics

This project aims to develop a new class of targeted biologics as novel antifungal agents that neutralise key enzymes present in the fungal cell wall. We aim to develop antibodies that recognise cell surface glycoproteins of the major filamentous pathogen, Aspergillus fumigatus. Life-threatening invasive aspergillosis infections are initiated by germination of inhaled spores and invasion of lung tissue by fungal mycelium. Early in infection the hydrophobin-rich layer of the A. fumigatus conidia is shed and new cell wall is synthesised as the germling emerges from the conidia. This is a very active period of growth and in vivo transcript profiling has highlighted upregulation of several cell-wall associated genes including key genes encoding wall-localised carbohydrate remodelling enzymes. This overarching hypothesis that cell-wall glycoproteins are credible antifungal drug targets was strengthened by the recent finding that a glucan-transglucosidase is essential for A. fumigatus growth. This project will develop antibodies, by screening human binding site phage display libraries, for binders against cell surface-exposed epitopes, present in pre-selected cell-wall enzymes. For Aspergillus it is hoped that binding alone may compromise, through steric hindrance, the activity of these enzymes and this in turn may impair growth and/or the generation of a robust cell wall. A functional bio-assay, to rank enzyme neutralisation, will be included as well as more typical biochemical screens used to determine specificity and affinity of binders. The antifungal activity of our lead candidates will be tested using ex vivo models with macrophage cell lines and primary cells, and in vivo infection models Galleria mellonella larvae and murine model of aspergillosis. Furthermore, we believe our anti-Aspergillus domains hold enormous promise as a targeting element capable of being engineered into Chimearic Antigen Receptors T-cells (CAR-Ts). CAR-T approaches are revolutionising the treatment of "difficult to treat" cancers where patient T-cells are removed, engineered to recognise the cancer (display binding sites) and returned to the patient to deliver long-lived cell killing with a cure possible for patients. CAR-T is now also being considered for life-threatening, systemic fungal infections. Interestingly, our initial interrogation of the Aspergillus genome has indicated that we may be able to "find" proteins and epitopes that could have significant cross reactivity between fungal pathogenic species. Therefore, a pan-fungal therapeutic may also be possible and/or antibodies isolated as potential therapeutic leads may be useful (pan) fungal-specific diagnostic tools (theranostics).