Aspergillus fumigatus is a ubiquitous saprophytic fungus that causes life-threatening disease in immunocompromised individuals. The increasing resistance to current antifungals makes the development of new antifungal drugs an important goal. Our research focuses on inhibiting fungal growth by activating the RNA interference (RNAi) pathway. Activation of the RNAi pathway by dsRNA results in degradation of target mRNA. Therefore this pathway can potentially be exploited to target essential fungal genes leading to their down-regulation, resulting in growth inhibition or death. Major barriers to siRNA entry into the cell are the fungal cell wall and cell membrane. If these obstacles can be overcome a new class of antifungals based on siRNA could be developed.
We assessed the uptake of siRNAs and siRNAs attached to cell-penetrating peptides by A. fumigatus and the model filamentous fungus Neurospora crassa. In a variety of conditions, confocal microscopy reveals siRNAs accumulate in the cell wall of A. fumigatus and cell wall, septa and hyphal tips of N. crassa. To-date, unmodified siRNAs even as small RNAs with chemical modifications (PNA, 2'- fluoro2- deoxy, 2'-O-methyl and/or phosphorothioate linkages) have had no significant impact on growth or target mRNA levels. We are presently testing the efficacy of pooled siRNAs complementary to a variety of short sequences in the target mRNA.
Full conference title:
- MS 2017