Update on antifungal therapy

Conazoles

This review provides a historical overview of the analog based drug discovery of miconazole and its congeners, and is focused on marketed azole antifungals bearing the generic suffix “conazole”. The antifungal activity of miconazole, one of the first broad-spectrum antimycotic agents has been mainly restricted to topical applications. The attractive in vitro antifungal spectrum was a starting point to design more potent and especially orally active antifungal agents such as ketoconazole, itraconazole, posaconazole, fluconazole and voriconazole. The chemistry, in vitro and in vivo antifungal activity, pharmacology, and clinical applications of these marketed conazoles has been described.

THTA, a thermotolerance gene of Aspergillus fumigatus

Aspergillus fumigatus grows optimally from 37 to 42 degrees C but can grow at temperatures up to 55 degrees C. To study the genetic basis of thermotolerance and its role in virulence of A. fumigatus, temperature sensitive mutants were isolated. One of the mutants that grew at 42 degrees C but not at 48 degrees C was complemented and the gene, THTA, was identified. Deletion of THTA showed the same temperature sensitivity as the original mutant. THTA encodes a putative protein of 141 kDa with unknown function and the HA-tagged ThtAp accumulated to similar levels in cultures grown at either 37 or 48 degrees C. Southern blot analysis and database searches revealed the presence of THTA-related sequences in several other ascomycetous fungi. No difference in virulence was observed between the deltathtA and wild-type strains. Thus, THTA is essential for growth of A. fumigatus at high temperatures but does not contribute to the pathogenicity of the species.

Antifungal drug therapy in avian species

This article reviews current literature regarding antifungal drugs available for veterinary and human use and those that are in clinical trials. Drugs include the polyenes, amphotericin B and nystatin; flucytosine; and the first generation triazoles. Antifungal agents generally not used in avian medicine or which are being analyzed in clinical trials in people include lipid formulations of amphotericin B and nystatin, voriconazole, echinocandins, and the allylamines. Information about the pharmacology of the triazoles in people is contrasted with known information for these drugs in birds. Extrapolation of efficacy to avian species also is discussed.

Uptake of Aspergillus fumigatus Conidia by phagocytic and nonphagocytic cells in vitro: quantitation using strains expressing green fluorescent protein

Several pathogenic fungal organisms enter eukaryotic cells and manipulate the host cell environment to favor their own growth and survival. Aspergillus fumigatus is a saprophytic fungus that causes invasive lung disease in the immunocompromised host. To determine whether A. fumigatus could enter eukaryotic cells, we studied the uptake of two different GFP-expressing A. fumigatus strains into A549 lung epithelial cells, human umbilical vein endothelial (HUVE) cells, and J774 murine macrophages in vitro. A549 cells internalized 30% of the bound conidia whereas HUVE and J774 cells internalized 50 and 90%, respectively. Conidia within A549 cells remained viable for 6 h; however, 60 to 80% of conidia within J774 cells were killed after only 4 h. Live and heat-killed conidia were internalized to the same extent by A549 cells. After 6 h, almost none of the conidia inside A549 cells had germinated, whereas extracellular conidia had developed germ tubes. Internalization of conidia by A549 cells was a temperature-dependent process and required rearrangement of the underlying host cell cytoskeleton; uptake was inhibited by 75% with 0.5 microM cytochalasin D and by 65% with 5 microM colchicine. Fluorescent labeling of infected A549 cells with rhodamine phalloidin provided visible evidence of cytoskeletal alteration as many of the intracellular conidia were contained in actin-coated phagosomes. These data provide evidence that significant numbers of A. fumigatus conidia can be internalized by nonprofessional phagocytes in vitro and these cells may serve as reservoirs for immune cell evasion and dissemination throughout the host.