The long-term goal of our research is to improve therapy options for individuals suffering from systemic fungal infections. HIV infected individuals are at increased risk for opportunistic fungal infection and current treatment regimens are not optimal. Infection with Cryptococcus neoformans represents a serious problem that results in the potentially fatal disease, cryptococcal meningitis. The antibiotic, amphotericin B (ampB) is active against C. neoformans but serious side effects limit its use. By the same token formulation of this insoluble antibiotic with lipids decreases toxic side effects of the drug, permitting higher doses to be administered. Currently, three different lipid formulations of ampB are approved by the FDA for treatment of systemic fungal infections that are refractory to standard ampB deoxycholate (Fungizone) therapy. During the course of studies of the lipid interaction properties of a unique family of proteins, the amphipathic apolipoproteins, we discovered a method to incorporate ampB into discrete, lipid protein particles, termed Nanodisks. AmpB-Nanodisks possess up to 30 % of their lipid mass as ampB and exist as a homogenous population of disk-shaped particles wherein a phospholipid bilayer containing the ampB is circumscribed by apolipoprotein molecules around the perimeter of the disk. Characterization studies revealed that ampB Nanodisks are stable entities and may be lyophilized and reconstituted without loss of structural integrity. In vitro growth inhibition assays with various pathogenic fungal species revealed that ampB-Nanodisks inhibit 90 % of fungal growth as concentrations far lower than the liposomal formulation of ampB, AmBisome. In the present proposal we plan to optimize the composition, structure, and stability of ampB- Nanodisks, evaluate hypotheses related to the mechanism of the observed enhanced biological activity and determine the in vivo efficacy of ampB-Nanodisks in an animal model of cryptococcosis. We anticipate the results obtained will lead to new treatment options for AIDS related cryptococcal meningitis that offer advantages over existing therapies.
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