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The gene encoding phosphoribosylaminoimidazole carboxylase (ADE2) is essential for growth of Cryptococcus neoformans
J R Perfect1, D L Toffaletti, T H Rude
1Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina 27710.
Abstract:
A cryptococcal meningitis model in corticosteroid-treated rabbits was used to assess the requirement for the phosphoribosylaminoimidazole gene (ADE2) for virulence of Cryptococcus neoformans. A wild-type strain (H99), an ade2 auxotroph of H99 (M001), and a randomly selected prototrophic transformant of M001 (M001.1c) which had received the cloned ADE2 cDNA copy were inoculated intrathecally into immunosuppressed rabbits. While M001 was avirulent in the central nervous system model, virulence was completely restored to wild-type pathogenicity in the prototrophic transformant. This study identifies the pathogenic importance of an endogenous adenine pathway in this yeast and confirms that purine biosynthesis is a potential target for antifungal therapy. It also demonstrates that the virulence of C. neoformans can be molecularly changed and detected within a clinically relevant animal model.
Insights
The phosphoribosylaminoimidazole gene (ADE2) is crucial for Cryptococcus neoformans virulence. Restoring ADE2 function in an ade2 mutant fully restored pathogenicity in a rabbit meningitis model, highlighting purine biosynthesis as an antifungal target.
Area of Science:
- Mycology
- Infectious Diseases
- Molecular Biology
Background:
- Cryptococcus neoformans is an opportunistic fungal pathogen causing meningitis.
- The genetic basis of C. neoformans virulence is not fully understood.
- The adenine biosynthesis pathway is essential for many organisms.
Purpose of the Study:
- To investigate the role of the phosphoribosylaminoimidazole gene (ADE2) in Cryptococcus neoformans virulence.
- To assess the potential of purine biosynthesis as a target for antifungal therapies.
- To demonstrate the utility of a clinically relevant animal model for studying fungal virulence.
Main Methods:
- A cryptococcal meningitis model was established in corticosteroid-treated rabbits.
- Intrathecal inoculation was performed using a wild-type C. neoformans strain (H99), an ADE2 auxotroph (M001), and a complemented ADE2 prototroph (M001.1c).
- Virulence was assessed by monitoring the survival and clinical signs in inoculated rabbits.
Main Results:
- The ade2 auxotroph (M001) was avirulent in the immunosuppressed rabbit model.
- Complementation of the ADE2 gene in M001.1c fully restored virulence to wild-type levels.
- The study successfully demonstrated the pathogenic importance of the endogenous adenine pathway.
Conclusions:
- The ADE2 gene and the purine biosynthesis pathway are critical for Cryptococcus neoformans virulence.
- Purine biosynthesis represents a promising target for developing novel antifungal agents.
- This study validates a molecularly tractable animal model for evaluating fungal virulence factors.