Ubiquinone-based gene mutation and protein compactness of CoQ5 may contribute to a novel caspofungin resistance mode in Aspergillus flavus from pulmonary aspergillosis.

Invasive pulmonary aspergillosis (IPA), primarily caused by Aspergillus fumigatus and A. flavus, is a life-threatening fungal infection with high mortality rates. This study investigated novel resistance mechanisms to caspofungin (CAS) in clinical Aspergillus isolates with particular focus on genetic alterations in the CoQ5 gene and their functional implications. One hundred and forty-eight Aspergillus isolates from IPA cases were undergone antifungal susceptibility testing, genotyping and phylogenetic analyses, mutations and gene expression studies of Fks1 and CoQ5 genes, and three-dimensional structural analysis of wild-type and mutant CoQ5 proteins. The etiologic agents of IPA comprised A. flavus (72.3%) and A. fumigatus (27.7%). Caspofungin (CAS) resistance was reported in 7.4% of A. flavus and 9.7% of A. fumigatus isolates. Genetic analysis identified a novel mutation in the CoQ5 gene (T371C) resulting in an amino acid substitution (Y102H) in a CAS-resistant A. flavus isolate. Structural modeling suggests this variant may impair protein stability and mitochondrial function, potentially contributing to resistance through indirect mechanisms. The definitive establishment of causality and direct contribution of CoQ5 mutations to caspofungin susceptibility requires further functional validation by employing targeted genetic manipulation and phenotypic validation to directly interrogate the role of the Y102H variant in the resistance mechanism.