Characterisation of novel-cell-wall LysM-domain proteins LdpA and LdpB from the human pathogenic fungus Aspergillus fumigatus

Aspergillus fumigatus, a filamentous fungus that is ubiquitous in the environment, causes several human pulmonary disorders, including chronic and acute invasive infections and allergic diseases. Lysin motif (LysM) is a small protein domain that binds chitin, a major component of fungal cell wall polysaccharides. Several secreted LysM-domain proteins without catalytic function (LysM effectors) have been identified. They act as virulence factors in plant pathogenic fungi by preventing the immune response induced by chitin; however, LysM proteins in mammalian pathogenic fungi remain largely unexplored. We describe two novel LysM-domain proteins, LdpA and LdpB, in A. fumigatus. Functional analyses of single and double knockouts revealed no significant effects on cell wall chitin content, cell wall integrity, fungal morphology and fungal growth. Fluorescent signals from LdpA-green fluorescent protein (GFP) and LdpB-GFP were observed in cell wall and extracellular matrix. In a mouse model of invasive pulmonary aspergillosis, survival did not differ between Delta ldpA/B and wild-type infection; however, further studies are required to reveal their functions in fungal-host interactions.