Antifungal Efficacy of Caspofungin (MK-0991) in Experimental Pulmonary Aspergillosis in Persistently Neutropenic Rabbits: Pharmacokinetics, Drug Disposition, and Relationship to Galactomannan Antigenemia

The antifungal efficacy, pharmacokinetics, and safety of caspofungin (CAS) were investigated in the treatment and prophylaxis of invasive pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of 1, 3, or 6 mg of CAS/kg of body weight/day (CAS1, CAS3, and CAS6, respectively) or 1 mg of deoxycholate amphotericin B (AMB)/kg/day intravenously for 12 days starting 24 h after endotracheal inoculation. Prophylaxis (CAS1) was initiated 4 days before endotracheal inoculation. Rabbits treated with CAS had significant improvement in survival and reduction in organism-mediated pulmonary injury (OMPI) measured by pulmonary infarct score and total lung weight (P < 0.01). However, animals treated with CAS demonstrated a paradoxical trend toward increased residual fungal burden (log CFU per gram) and increased serum galactomannan antigen index (GMI) despite improved survival. Rabbits receiving prophylactic CAS1 also showed significant improvement in survival and reduction in OMPI (P < 0.01), but there was no effect on residual fungal burden. In vitro tetrazolium salt hyphal damage assays and histologic studies demonstrated that CAS had concentration- and dose-dependent effects on hyphal structural integrity. In parallel with a decline in GMI, AMB significantly reduced the pulmonary tissue burden of A. fumigatus (P ≤ 0.01). The CAS1, CAS3, and CAS6 dose regimens demonstrated dose-proportional exposure and maintained drug levels in plasma above the MIC for the entire 24-h dosing interval at doses that were ≥3 mg/kg/day. As serial galactomannan antigen levels may be used for therapeutic monitoring, one should be aware that profoundly neutropenic patients receiving echinocandins for aspergillosis might have persistent galactomannan antigenemia despite clinical improvement. CAS improved survival, reduced pulmonary injury, and caused dose-dependent hyphal damage but with no reduction in residual fungal burden or galactomannan antigenemia in persistently neutropenic rabbits with invasive pulmonary aspergillosis

Triazole-polyene antagonism in experimental invasive pulmonary aspergillosis: in vitro and in vivo correlation.

Combination antifungal therapy is increasingly used in the treatment of invasive aspergillosis. Whether the interaction between amphotericin B and triazoles is antagonistic against invasive aspergillosis is a controversial issue that is not likely to be resolved through a randomized clinical trial. Here, we found both in vitro and in vivo antagonism between liposomal amphotericin B and ravuconazole in simultaneous treatment of experimental invasive pulmonary aspergillosis in persistently neutropenic rabbits. Bliss independence-based drug-interaction modeling showed significant antagonism in vitro and in vivo, with the observed drug effects being 20%-69% lower than would be expected if the drugs were acting independently. These in vitro and in vivo findings of antagonism were consistent with the findings from Loewe additivity-based drug-interaction modeling. No pharmacokinetic interaction was found. The combination of a triazole and polyene may be antagonistic in the treatment of invasive pulmonary aspergillosis

Compartmentalized Intrapulmonary Pharmacokinetics of Amphotericin B and Its Lipid Formulations

We investigated the compartmentalized intrapulmonary pharmacokinetics of amphotericin B and its lipid formulations in healthy rabbits. Cohorts of three to seven noninfected, catheterized rabbits received 1 mg of amphotericin B deoxycholate (DAMB) per kg of body weight or 5 mg of either amphotericin B colloidal dispersion (ABCD), amphotericin B lipid complex (ABLC), or liposomal amphotericin B (LAMB) per kg once daily for a total of 8 days. Following sparse serial plasma sampling, rabbits were sacrificed 24 h after the last dose, and epithelial lining fluid (ELF), pulmonary alveolar macrophages (PAM), and lung tissue were obtained. Pharmacokinetic parameters in plasma were derived by model-independent techniques, and concentrations in ELF and PAM were calculated based on the urea dilution method and macrophage cell volume, respectively. Mean amphotericin B concentrations ± standard deviations (SD) in lung tissue and PAM were highest in ABLC-treated animals, exceeding concurrent plasma levels by 70- and 375-fold, respectively (in lung tissue, 16.24 ± 1.62 versus 2.71 ± 1.22, 6.29 ± 1.17, and 6.32 ± 0.57 μg/g for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0029]; in PAM, 89.1 ± 37.0 versus 8.92 ± 2.89, 5.43 ± 1.75, and 7.52 ± 2.50 μg/ml for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0246]). By comparison, drug concentrations in ELF were much lower than those achieved in lung tissue and PAM. Among the different cohorts, the highest ELF concentrations were found in LAMB-treated animals (2.28 ± 1.43 versus 0.44 ± 0.13, 0.68 ± 0.27, and 0.90 ± 0.28 μg/ml in DAMB-, ABCD-, and ABLC-treated animals, respectively [P = 0.0070]). In conclusion, amphotericin B and its lipid formulations displayed strikingly different patterns of disposition in lungs 24 h after dosing. Whereas the disposition of ABCD was overall not fundamentally different from that of DAMB, ABLC showed prominent accumulation in lung tissue and PAM, while LAMB achieved the highest concentrations in ELF

Expression of Genes Encoding Innate Host Defense Molecules in Normal Human Monocytes in Response to Candida albicans

Little is known about the regulation and coordinated expression of genes involved in the innate host response to Candida albicans. We therefore examined the kinetic profile of gene expression of innate host defense molecules in normal human monocytes infected with C. albicans using microarray technology. Freshly isolated peripheral blood monocytes from five healthy donors were incubated with C. albicans for 0 to 18 h in parallel with time-matched uninfected control cells. RNA from monocytes was extracted and amplified for microarray analysis, using a 42,421-gene cDNA chip. Expression of genes encoding proinflammatory cytokines, including tumor necrosis factor alpha, interleukin 1 (IL-1), IL-6, and leukemia inhibitory factor, was markedly enhanced during the first 6 h and coincided with an increase in phagocytosis. Expression of these genes returned to near baseline by 18 h. Genes encoding chemokines, including IL-8; macrophage inflammatory proteins 1, 3, and 4; and monocyte chemoattractant protein 1, also were strongly up-regulated, with peak expression at 4 to 6 h, as were genes encoding chemokine receptors CCR1, CCR5, CCR7, and CXCR5. Expression of genes whose products may protect monocyte viability, such as BCL2-related protein, metallothioneins, CD71, and SOCS3, was up-regulated at 4 to 6 h and remained elevated throughout the 18-h time course. On the other hand, expression of genes encoding T-cell-regulatory molecules (e.g., IL-12, gamma interferon, and transforming growth factor β) was not significantly affected during the 18-h incubation. Moreover, genes encoding IL-15, the IL-13 receptor (IL-13Ra1), and CD14 were suppressed during the 18-h exposure to C. albicans. Thus, C. albicans is a potent inducer of a dynamic cascade of expression of genes whose products are related to the recruitment, activation, and protection of neutrophils and monocytes

Combination therapy in treatment of experimental pulmonary aspergillosis: In vitro and in vivo correlations of the concentration- and dose-dependent interactions between anidulafungin and voriconazole by bliss independence drug interaction analysis

We studied the antifungal activity of anidulafungin (AFG) in combination with voriconazole (VRC) against experimental invasive pulmonary aspergillosis (IPA) in persistently neutropenic rabbits and further explored the in vitro and in vivo correlations by using Bliss independence drug interaction analysis. Treatment groups consisted of those receiving AFG at 5 (AFG5 group) and 10 (AFG10 group) mg/kg of body weight/day, VRC at 10 mg/kg every 8 h (VRC group), AFG5 plus VRC (AFG5+VRC group), and AFG10 plus VRC (AFG10+VRC group) and untreated controls. Survival throughout the study was 60% for the AFG5+VRC group, 50% for the VRC group, 27% for the AFG10+VRC group, 22% for the AFG5 group, 18% for the AFG10 group, and 0% for control rabbits (P < 0.001). There was a significant reduction of organism-mediated pulmonary injury, measured by infarct scores, lung weights, residual fungal burdens, and galactomannan indexes, in AFG5+VRC-treated rabbits versus those treated with AFG5 and VRC alone (P < 0.05). In comparison, AFG10+VRC significantly lowered only infarct scores and lung weights in comparison to those of AFG10-treated animals (P < 0.05). AFG10+VRC showed no significant difference in other outcome variables. Significant Bliss synergy was found in vivo between AFG5 and VRC, with observed effects being 24 to 30% higher than expected levels if the drugs were acting independently. These synergistic interactions were also found between AFG and VRC in vitro. However, for AFG10+VRC, only independence and antagonism were observed among the outcome variables. We concluded that the combination of AFG with VRC in treatment of experimental IPA in persistently neutropenic rabbits was independent to synergistic at a dosage of 5 mg/kg/day but independent to antagonistic at 10 mg/kg/day, as assessed by Bliss independence analysis, suggesting that higher dosages of an echinocandin may be deleterious to the combination

Detection of a Molecular Biomarker for Zygomycetes by Quantitative PCR Assays of Plasma, Bronchoalveolar Lavage, and Lung Tissue in a Rabbit Model of Experimental Pulmonary Zygomycosis▿

We developed two real-time quantitative PCR (qPCR) assays, targeting the 28S rRNA gene, for the diagnosis of zygomycosis caused by the most common, clinically significant Zygomycetes. The amplicons of the first qPCR assay (qPCR-1) from Rhizopus, Mucor, and Rhizomucor species were distinguished through melt curve analysis. The second qPCR assay (qPCR-2) detected Cunninghamella species using a different primer/probe set. For both assays, the analytic sensitivity for the detection of hyphal elements from germinating sporangiospores in bronchoalveolar lavage (BAL) fluid and lung tissue homogenates from rabbits was 1 to 10 sporangiospores/ml. Four unique and clinically applicable models of invasive pulmonary zygomycosis served as surrogates of human infections, facilitating the validation of these assays for potential diagnostic utility. For qPCR-1, 5 of 98 infarcted lung specimens were positive by qPCR and negative by quantitative culture (qCx). None were qCx positive only. Among 23 BAL fluid samples, all were positive by qPCR, while 22 were positive by qCx. qPCR-1 detected Rhizopus and Mucor DNA in 20 (39%) of 51 serial plasma samples as early as day 1 postinoculation. Similar properties were observed for qPCR-2, which showed greater sensitivity than qCx for BAL fluid (100% versus 67%; P = 0.04; n = 15). The assay detected Cunninghamella DNA in 18 (58%) of 31 serial plasma samples as early as day 1 postinoculation. These qPCR assays are sensitive and specific for the detection of Rhizopus, Mucor, Rhizomucor, and Cunninghamella species and can be used for the study and detection of infections caused by these life-threatening pathogens