Aspergillus fumigatus, a pathogenic mould causing a wide range of diseases including
aspergillosis, produces a series of toxic substances which appear to act in an additive and/or synergic way on cells.
Aspergillosis generally occurs in immunocompromised hosts or is associated with
organ transplantation. From the muscul skeleton system the vertebrae, ribs and orbit are the most commonly affected, while the joints are less frequent targets. The cytolytic
protein Asp-
hemolysin is one of the toxins produced by Aspergillus fumigatus during
infection. It belongs to the
aegerolysin protein family and shares 43% identity in amino acid sequence with
ostreolysin, a
cytolysin from the mushroom Pleurotus ostreatus. In this work,
ostreolysin was used in an experimental model to study the in vitro effects of
aegerolysin-like
proteins on human chondrocytes and osteoblasts. Immunostaining analyses showed selective binding and clustering of the
protein on chondrocyte membranes, pointing to its association with distinctive membrane microdomains. Consequently,
ostreolysin can induce effective permeabilization of both chondrocytes and osteoblasts. Based on sequence similarities of
ostreolysin and Asp-
hemolysin, their comparable cytolytic effects towards different cells, and similar signs of intoxication in experimental animals, our results indicate that Asp-
hemolysin might be considered as a possible
virulence factor of Aspergillus fumigatus during the
infection of bone and cartilage.