Targeted antifungal liposomes

Abstract

15 Aspergillus species cause pulmonary invasive aspergillosis resulting in nearly a hundred 16 thousand deaths each year. Patients at the greatest risk of developing life-threatening 17 aspergillosis have weakened immune systems and/or various lung disorders. Patients are 18 treated with antifungals such as amphotericin B (AmB), casofungin acetate, or triazoles 19 (itraconazole, voriconazole etc.), but these antifungal agents have serious limitations due to lack 20 of sufficient fungicidal effect and human toxicity. Liposomes with AmB intercalated into the lipid 21 membrane (AmBisomes, AmB-LLs), have several-fold reduced toxicity compared to detergent 22 Importance 41 The fungus Aspergillus fumigatus causes pulmonary invasive aspergillosis resulting in 42 nearly a hundred thousand deaths each year. Patients are often treated with antifungal drugs 43 such as amphotericin B loaded into liposomes, AmB-LLs, but all antifungal drugs including 44 AmB-LLs have serious limitations due to human toxicity and insufficient fungal cell killing. Even 45with the best current therapies, one-year survival among patients with invasive aspergillosis is 46 only 25 to 60%. Hence, there is a critical need for improved antifungal therapeutics. 47Dectin-1 is a mammalian protein that binds to beta-glucan polysaccharides found in 48 nearly all fungal cell walls. We coated AmB-LLs with Dectin-1 to make DEC-AmB-LLs. DEC-49

DectiSomes: Glycan Targeting of Liposomal Drugs Improves the Treatment of Disseminated Candidiasis

“…DectiSomes bind efficiently to in vitro grown C. albicans hyphae. The binding of DEC1-AmB-LLs to C. albicans has not been studied in as much detail (27) as DEC2-AmB-LL binding (26). The binding of rhodamine A tagged DEC1-AmB-LLs and DEC2-AmB-LLs to C. albicans hyphae grown in vitro is compared in Fig.…”

“…Five moles percent of the liposomal lipids in the membrane of AmB-LLs are the lipid, DSPE (distearoyl-sn-glycero-3-phosphoethanolamine) coupled to poly-ethylene glycol (PEG). DSPE inserts in the liposome membrane and presents PEG on the liposome surface (27). AmBisome was first patented and introduced to the clinic before the benefits pegylation were described.…”

“…Liposomes and drugs. We constructed AmB-LLs, DEC1-AmB-LLs, DEC2-AmB-LLs, and BSA-AmB-LLs as described previously (26,27). Dectisomes contain 1 mole percent dectin relative to moles of liposomal lipid.…”

“…AmB is amphiphobic and quite insoluble in aqueous solutions, therefore clinical formulations often include AmB loaded into the non-polar interior of detergent micelles (e.g., AmB-DOC) or intercalated into the bilipid membrane of liposomes (e.g., unpegylated AmBisome or our pegylated version AmB-LLs (26,27)). Current antifungal preparations used in the clinic have the disadvantage that they deliver drug to fungal and host cells alike, and have little specificity for fungal cells.…”

“…We define DectiSomes as liposomes coated with a protein that targets them to a pathogenic cell, thereby increasing drug concentrations in the vicinity of the pathogen and away from host cells (28). We previously made two classes of DectiSomes, DEC1-AmB-LLs and DEC2-AmB-LLs, by coating AmB-LLs with the carbohydrate recognition domains of Dectin-1 (27) or Dectin-2 (26). Dectin-1 (CLEC7A) and Dectin-2 (CLEC4N) are human pathogen receptors expressed on the surface of various leukocytes that recognize fungal betaglucan and alpha-mannan containing oligosaccharides, respectively.…”