The most severe form of aspergillosis due to A. fumigatus is invasive aspergillosis which is responsible for a high level of mortality amongst inununocompromised patients. A. fumigatus is an air borne saprophyte, which in comparison to most opportunistic fungal pathogens such as C.albicans, does not colonize the normal host and is not adapted to grow in an human host environment. What makes this fungus such a devastating pathogen ? Studies undertaken in recent years have been directed towards the identification of virulence factors in A. fumigatus. Up to now, reverse genetic studies have not been able to identify a single virulence factor in A. fumigatus. Indeed, if mixed infection has demonstrated different levels of aggressiveness in various strains of A. fumigatus, every strain considered separately, is able to infect and kill immunosuppressed mice, whatever is the clinical or environmental origin of the strain tested. These results suggest that any strain of A. fumigatus can become pathogenic if the normal defence reactions of the host are suppressed. Under these circumstances, the host (and not the fungus) becomes the key trigger of the Aspergillus infection. The host factors which are responsible for the eradication of A. fumigatus in the immunocompetent host and are impaired by the immunosuppressive therapies are poorly understood. Our first attempts in this direction and particularly in the enhancement of a protective immunity in the immunocomprornised host, have lead us to the study of the two major antigens of A. fumigatus, a dipeptidylpeptidase V and a catalase. The biochemical and molecular characterization of these two enzymes will be presented.
Full conference title:
13th Congress of the International Society for Human and Animal Mycology
- ISHAM 13th (1997)