Glycogenomics of the opportunistic fungal pathogen Aspergillus fumigatus

Aspergillus fumigatus is the most common opportunistic fungal pathogen of humans, causing fatal invasive aspergillosis (IA) in immuno-compromised patients. In the proposed project, three putative glycoenzyme genes, mnn9, gpf1 and ncr, have been chosen for further study. All three are predicted to have different roles in enabling the modification of the outer chains of N- or O-glycans. These genes will be cloned and expressed recombinantly in Pichia as well as be knocked-out in Aspergillus. The activity of the enzymes will be assessed by appropriate chromatographic, mass spectrometric or radiometric techniques. The phenotypic outcome of knocking-out these genes will be tested by microscopy, glycomics and virulence tests. In the longer term, identification and analysis of other genes involved in synthesis and transfer of galactofuranose and N-acetylneuraminic acid may prove to be interesting targets for further study. Tangible benefits for immunocompromised patients can be expected due to the development of novel effective therapeutics based on targetting of fungal-specific glycosylation pathways, thus resulting in a lack of side-effects for the patient.

Filamentous fungi are of biotechnological and biomedical relevance due to their production of antibiotics, mycotoxins and allergens or as the causative agents of diseases in immunocompromised patients. Cellular and secreted proteins of fungi are modified with carbohydrates, including so-called N-linked glycans. Our initial goal in this joint project with a group at the Chinese Academy of Sciences was to analyse certain aspects of the structure and biosynthesis of N-linked glycans from Aspergillus fumigatus. Over the period of the project we extended our analyses to comparisons of three Penicillium and three Aspergillus species. Unusual species-specific modifications of the N-linked glycans were determined by mass spectrometry in combination with chromatography. The results show a higher degree of complexity of N-linked glycans of fungi, including epitopes recognised by the human immune system. Longer term our data may enable development of new therapeutics based on targetting of fungal-specific glycosylation pathways, thus resulting in a lack of side-effects for the patient.