Mild heating of amphotericin B-desoxycholate: effects on ultrastructure, in vitro activity and toxicity, and therapeutic efficacy in severe candidiasis in leukopenic mice.
Heated (20 min at 70 degrees C) amphotericin B-desoxycholate (hAMB-DOC) was further characterized, as was another formulation obtained after centrifugation (60 min, 3000 x g), hcAMB-DOC. Conventional AMB-DOC consisted of individual micelles (approximately 4 nm in diameter) and threadlike aggregated micelles, as revealed by cryo-transmission electron microscopy. For both hAMB-DOC and hcAMB-DOC, pleiomorphic cobweb structures were observed with a mean particle size of approximately 300 nm as determined by laser diffraction. The potent antifungal activity of AMB-DOC against Candida albicans is not reduced by heating. Effective killing of C. albicans (>99.9% within 6 h) was obtained at 0.1 mg/liter with each of the AMB formulations. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, cation release ((86)Rb(+)) from C. albicans of > or =50% was observed at 0.8, 0.4, and 0.4 mg/liter, respectively. After heating of AMB-DOC, toxicity was reduced 16-fold as determined by red blood cell (RBC) lysis. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, hemolysis of > or =50% was observed at 6.4, 102.4, and 102.4 mg/liter, respectively. In contrast, AMB-DOC and its derivates showed similar toxicities in terms of cation release from RBC. For AMB-DOC, hAMB-DOC, and hcAMB-DOC, cation release ((86)Rb(+)) of > or =50% was observed at 1.6, 0.8, and 0.8 mg/liter, respectively. In persistently leukopenic mice with severe invasive candidiasis, higher dosages of both hAMB-DOC and hcAMB-DOC were tolerated than those of conventional AMB-DOC (3 versus 0.8 mg/kg of body weight, respectively), resulting in significantly improved therapeutic efficacy. In conclusion, this new approach of heating AMB-DOC may be of great value for further optimizing the treatment of severe fungal infections.
van Etten
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EW
Department of Medical Microbiology and Infectious Diseases, Erasmus University of Rotterdam, 3000 DR Rotterdam, The Netherlands. vanetten@kmic.fgg.eur.nl
van Vianen
W
W
Roovers
P
P
Frederik
P
P
D000666:Amphotericin B / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D002177:Candidiasis / Q000188:drug therapy*; D002626:Chemistry, Pharmaceutical; D007970:Leukopenia; D051379:Mice; D013696:Temperature
D000935:Antifungal Agents; D000666:Amphotericin B