Network Modeling of Complex Time-Dependent Changes in Patient Adherence to Adjuvant Endocrine Treatment in ER+ Breast Cancer

Early patient discontinuation from adjuvant endocrine treatment (ET) is multifactorial and complex: Patients must adapt to various challenges and make the best decisions they can within changing contexts over time. Predictive models are needed that can account for the changing influence of multiple factors over time as well as decisional uncertainty due to incomplete data. AtlasTi8 analyses of longitudinal interview data from 82 estrogen receptor-positive (ER+) breast cancer patients generated a model conceptualizing patient-, patient-provider relationship, and treatment-related influences on early discontinuation. Prospective self-report data from validated psychometric measures were discretized and constrained into a decisional logic network to refine and validate the conceptual model. Minimal intervention set (MIS) optimization identified parsimonious intervention strategies that reversed discontinuation paths back to adherence. Logic network simulation produced 96 candidate decisional models which accounted for 75% of the coordinated changes in the 16 network nodes over time. Collectively the models supported 15 persistent end-states, all discontinued. The 15 end-states were characterized by median levels of general anxiety and low levels of perceived recurrence risk, quality of life (QoL) and ET side effects. MIS optimization identified 3 effective interventions: reducing general anxiety, reinforcing pill-taking routines, and increasing trust in healthcare providers. Increasing health literacy also improved adherence for patients without a college degree. Given complex regulatory networks’ intractability to end-state identification, the predictive models performed reasonably well in identifying specific discontinuation profiles and potentially effective interventions.

Control, immunoregulation, and expression of innate pulmonary host defenses against Aspergillus fumigatus

The innate host defense system (IHDS) against Aspergillus fumigatus includes dedicated phagocytic cells (peripheral blood monocytes, monocyte derived macrophages, pulmonary alveolar macrophages, neutrophils, myeloid dendritic cells and natural killer cells), cytokines, chemokines, toll-like receptors, and antimicrobial peptides. During the past decade, the advances in the field of the IHDS have been enormous, allowing a better understanding of the immunopharmacological control, immunoregulation, and expression of innate host defense molecules against Aspergillus fumigatus.

Pharmacokinetic and pharmacodynamic modeling of anidulafungin (LY303366): reappraisal of its efficacy in neutropenic animal models of opportunistic mycoses using optimal plasma sampling

The compartmental pharmacokinetics of anidulafungin (VER-002; formerly LY303366) in plasma were characterized with normal rabbits, and the relationships between drug concentrations and antifungal efficacy were assessed in clinically applicable infection models in persistently neutropenic animals. At intravenous dosages ranging from 0.1 to 20 mg/kg of body weight, anidulafungin demonstrated linear plasma pharmacokinetics that fitted best to a three-compartment open pharmacokinetic model. Following administration over 7 days, the mean (+/- standard error of the mean) peak plasma concentration (C(max)) increased from 0.46 +/- 0.02 microg/ml at 0.1 mg/kg to 63.02 +/- 2.93 microg/ml at 20 mg/kg, and the mean area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)) rose from 0.71 +/- 0.04 to 208.80 +/- 24.21 microg. h/ml. The mean apparent volume of distribution at steady state (V(ss)) ranged from 0.953 +/- 0.05 to 1.636 +/- 0.22 liter/kg (nonsignificant [NS]), and clearance ranged from 0.107 +/- 0.01 to 0.149 +/- 0.00 liter/kg/h (NS). Except for a significant prolongation of the terminal half-life and a trend toward an increased V(ss) at the higher end of the dosage range after multiple doses, no significant differences in pharmacokinetic parameters were noted in comparison to single-dose administration. Concentrations in tissue at trough after multiple dosing (0.1 to 10 mg/kg/day) were highest in lung and liver (0.85 +/- 0.16 to 32.64 +/- 2.03 and 0.32 +/- 0.05 to 43.76 +/- 1.62 microg/g, respectively), followed by spleen and kidney (0.24 +/- 0.65 to 21.74 +/- 1.86 and <0.20 to 16.92 +/- 0.56, respectively). Measurable concentrations in brain tissue were found at dosages of > or =0.5 mg/kg (0.24 +/- 0.02 to 3.90 +/- 0.25). Implementation of optimal plasma sampling in persistently neutropenic rabbit infection models of disseminated candidiasis and pulmonary aspergillosis based on the Bayesian approach and model parameters from normal animals as priors revealed a significantly slower clearance (P < 0.05 for all dosage groups) with a trend toward higher AUC(0-24) values, higher plasma concentrations at the end of the dosing interval, and a smaller volume of distribution (P < 0.05 to 0.193 for the various comparisons among dosage groups). Pharmacodynamic modeling using the residual fungal tissue burden in the main target sites as the primary endpoint and C(max), AUC(0-24), time during the dosing interval of 24 h with plasma drug concentration equaling or exceeding the MIC or the minimum fungicidal concentration for the isolate, and tissue concentrations as pharmacodynamic parameters showed predictable pharmacokinetic-pharmacodynamic relationships in experimental disseminated candidiasis that fitted well with an inhibitory sigmoid maximum effect pharmacodynamic model (r(2), 0.492 to 0.819). However, no concentration-effect relationships were observed in experimental pulmonary aspergillosis using the residual fungal burden in lung tissue and survival as parameters of antifungal efficacy. Implementation of optimal plasma sampling in discriminative animal models of invasive fungal infections and pharmacodynamic modeling is a novel approach that holds promise of improving and accelerating our understanding of the action of antifungal compounds in vivo.

Recombinant human macrophage colony-stimulating factor augments pulmonary host defences against Aspergillus fumigatus

The in vivo and ex vivo effects of macrophage colony-stimulating factor (M-CSF) were studied in a profoundly neutropenic rabbit model in order to determine its potential to augment pulmonary host defence against Aspergillus. M-CSF (100-600 microg/kg/d) was administered prophylactically to neutropenic rabbits with pulmonary aspergillosis starting three days pre-inoculation and then throughout neutropenia. Rabbits receiving M-CSF had significantly increased survival (P=0.01) and decreased pulmonary injury, as measured by decreased pulmonary infarction (P=0.004), when compared with untreated controls. Microscopic studies demonstrated greater numbers of activated pulmonary alveolar macrophages (PAMs) in lung tissue of rabbits receiving M-CSF, in comparison to controls (P<0.001). PAMs harvested from rabbits treated with M-CSF had a significantly greater percent phagocytosis of Aspergillus fumigatus conidia than did PAMs from controls (P=0.04). These data indicate that prophylactic administration of M-CSF augments pulmonary host defence against A. fumigatus and suggest a potential role for this cytokine as adjunctive therapy in the treatment of pulmonary aspergillosis in the setting of profound neutropenia.

Dosage-dependent antifungal efficacy of V-echinocandin (LY303366) against experimental fluconazole-resistant oropharyngeal and esophageal candidiasis

V-echinocandin (VER-002; LY303366) is a semisynthetic derivative of echinocandin B and a potent inhibitor of fungal (1, 3)-beta-D-glucan synthase. We studied the antifungal efficacy, the concentrations in saliva and tissue, and the safety of VER-002 at escalating dosages against experimental oropharyngeal and esophageal candidiasis caused by fluconazole-resistant Candida albicans in immunocompromised rabbits. Study groups consisted of untreated controls, animals treated with VER-002 at 1, 2.5, and 5 mg/kg of body weight/day intravenously (i.v.), animals treated with fluconazole at 2 mg/kg/day i.v., or animals treated with amphotericin B at 0.3 mg/kg/day. VER-002-treated animals showed a significant dosage-dependent clearance of C. albicans from the tongue, oropharynx, esophagus, stomach, and duodenum in comparison to that for untreated controls. VER-002 also was superior to amphotericin B and fluconazole in clearing the organism from all sites studied. These in vivo findings are consistent with the results of in vitro time-kill assays, which demonstrated that VER-002 has concentration-dependent fungicidal activity. Esophageal tissue VER-002 concentrations were dosage proportional and exceeded the MIC at all dosages. Echinocandin concentrations in saliva were greater than or equal to the MICs at all dosages. There was no elevation of serum hepatic transaminase, alkaline phosphatase, bilirubin, potassium, or creatinine levels in VER-002-treated rabbits. In summary, the echinocandin VER-002 was well tolerated, penetrated the esophagus and salivary glands, and demonstrated dosage-dependent antifungal activity against fluconazole-resistant esophageal candidiasis in immunocompromised rabbits.

Antimicrobial peptides as potential new antifungals

Ribosomally synthesized natural antimicrobial peptides (AP) and their synthetic derivatives are small, cationic, amphipathic molecules of 12-50 amino acids with unusually broad activity spectra. These peptides kill microorganisms by a common mechanism, which involves binding to the lipid bilayer of biological membranes, forming pores, and ultimately followed by cell lysis. Several AP from mammals, amphibians, insects, plants and their synthetic derivatives demonstrate promising in vitro activity against various pathogenic fungi including azole-resistant Candida albicans strains. In addition to their antimicrobial activity, some AP such as lactoferrin, interact with a variety of host cells and can increase the activity of natural killer and lymphokine activated killer cells. Pretreatment of polymorphonuclear neutrophil leukocytes (PMN) or monocytes with these AP also may upregulate superoxide release. AP as potential new antifungal agents offer some advantages, such as rapid killing of pathogenic fungi and the difficulty to raise mutants resistant to these peptides. AP are limited by their nonselective toxicity, stability, immunogenicity and their costs of production. Potential clinical applications of AP in the future have to be further explored in preclinical and clinical studies to assess their impact as a new class of antifungals.

Correlation between in vitro and in vivo antifungal activities in experimental fluconazole-resistant oropharyngeal and esophageal candidiasis

Oropharyngeal and esophageal candidiasis (OPEC) is a frequent opportunistic mycosis in immunocompromised patients. Azole-resistant OPEC is a refractory form of this infection occurring particularly in human immunodeficiency virus (HIV)-infected patients. The procedures developed by the Antifungal Subcommittee of the National Committee for Clinical Laboratory Standards (NCCLS) are an important advance in standardization of in vitro antifungal susceptibility methodology. In order to further understand the relationship between NCCLS methodology and antifungal therapeutic response, we studied the potential correlation between in vitro susceptibility to fluconazole and in vivo response in a rabbit model of fluconazole-resistant OPEC. MICs of fluconazole were determined by NCCLS methods. Three fluconazole-susceptible (FS) (MIC, </=0.125 microgram/ml) and three fluconazole-resistant (FR) (MIC, >/=64 microgram/ml) isolates of Candida albicans from prospectively monitored HIV-infected children with OPEC were studied. FR isolates were recovered from children with severe OPEC refractory to fluconazole, and FS isolates were recovered from those with mucosal candidiasis responsive to fluconazole. Fluconazole at 2 mg/kg of body weight/day was administered to infected animals for 7 days. The concentrations of fluconazole in plasma were maintained above the MICs for FS isolates throughout the dosing interval. Fluconazole concentrations in the esophagus were greater than or equal to those in plasma. Rabbits infected with FS isolates and treated with fluconazole had significant reductions in oral mucosal quantitative cultures (P < 0.001) and tissue burden of C. albicans in tongue, soft palate, and esophagus (P < 0.001). In comparison, rabbits infected with FR isolates were unresponsive to fluconazole and had no reduction in oral mucosal quantitative cultures or tissue burden of C. albicans versus untreated controls. We conclude that there is a strong correlation between in vitro fluconazole susceptibility by NCCLS methods and in vivo response to fluconazole therapy of OPEC due to C. albicans.

Antifungal activity of splenic, liver and pulmonary macrophages against Candida albicans and effects of macrophage colony-stimulating factor

Disseminated infections due to Candida albicans are frequently encountered in immunocompromised patients. We compared the antifungal activities of macrophages residing in spleen, liver and lungs of rabbits against blastoconidia and pseudohyphae of C. albicans. Splenic adherent cells (SAC), Kupffer cells (KC) and pulmonary alveolar macrophages (PAM) all ingested blastoconidia efficiently. SAC caused significantly more damage to unopsonized pseudohyphae compared with KC (P < 0.01) or PAM (P < 0.001). Incubation of SAC with 15 ng ml(-1) of recombinant human macrophage colony-stimulating factor (M-CSF) at 37 degrees C for 2 days significantly enhanced phagocytosis (P = 0.02) and killing (P = 0.05) of blastoconidia. In contrast, M-CSF had no effect on phagocytic activities of KC or PAM against blastoconidia or on damage caused by any of the macrophages to pseudohyphae of C. albicans. Thus, although all three resident macrophage types ingest blastoconidia efficiently, they differ in their capacity to cause damage to pseudohyphae and in their responsiveness to M-CSF for antifungal activation. M-CSF augments the capacity of SAC to ingest and kill blastoconidia and may therefore have a role in the treatment and prevention of hematogenously disseminated candidiasis.

Antifungal activity of LY303366, a novel echinocandin B, in experimental disseminated candidiasis in rabbits

The safety and antifungal activity of LY303366 (LY), a new broad-spectrum semisynthetic echinocandin, were studied against disseminated candidiasis in persistently neutropenic rabbits. In vitro time-kill assays demonstrated that LY has concentration-dependent fungicidal activity. The pharmacokinetics of LY in the plasma of nonneutropenic rabbits suggested a linear relationship between dose and area under the curve (AUC). The times spent above the MIC during the experimental dosing interval of 24 h were 4 h for LY at 0.1 mg/kg of body weight/day (LY0.1), 8 h for LY at 0.25 mg/kg/day (LY0.25), 12 h for LY at 0.5 mg/kg/day (LY0.5), and 20 h for LY at 1 mg/kg/day (LY1). Antifungal therapy was administered to infected rabbits for 10 days starting 24 h after the intravenous (i.v.) inoculation of 10(3) Candida albicans blastoconidia. Study groups consisted of untreated controls (UCs) and animals treated with amphotericin B (AmB; 1 mg/kg/day i.v.), fluconazole (FLU; 10 mg/kg/day i.v.), and LY0.1, LY0.25, LY0.5, or LY1 i.v. Rabbits treated with LY0.5, LY1, AmB, and FLU had similarly significant clearance of C. albicans from the liver, spleen, kidney, lung, vena cava, and brain in comparison to that for UCs. There was a dose-dependent clearance of C. albicans from tissues in response to LY. Among rabbits treated with LY0.1 there was a significant reduction of C. albicans only in the spleen. In animals treated with LY0.25 there was a significant reduction in all tissues but the brain. By comparison, LY0.5 and LY1 cleared all tissues, including the brain, of C. albicans. These in vivo findings were consistent with the results of in vitro time-kill assays. A dose-dependent effect of altered cell wall morphology was observed among UCs and animals treated with LY0.1, and LY0.25, with a progressive transition from hyphal structure to disrupted yeast forms. Serum creatinine levels were higher and serum potassium levels were lower in AmB-treated rabbits than in UCs and LY- and FLU-treated rabbits. LY0.5 and LY1 were well tolerated, displayed predictable pharmacokinetics in plasma, and had activities comparable to those of AmB and FLU in the treatment of disseminated candidiasis in persistently neutropenic rabbits.

Effects of the hematoregulatory peptide SK&F 107647 alone and in combination with amphotericin B against disseminated candidiasis in persistently neutropenic rabbits

The effects of the hematoregulatory peptide SK&F 107647 were examined in a persistently and profoundly neutropenic rabbit model of disseminated candidiasis in order to determine its potential to enhance resistance against infection and its role as an adjunct to conventional antifungal chemotherapy. In healthy animals, SK&F 107647 elicited a time-dependent increase in CD11b-positive monocytes and neutrophils. When administered to neutropenic rabbits infected with Candida albicans, no significant differences in the number of CFU per gram in any of the tissues tested compared with the number in untreated control rabbits were detected. However, when SK&F 107647 was administered in combination with low doses of amphotericin B, there was a significant reduction in organism burden in the lungs, liver, spleen, and kidneys compared with the burdens in the organs of untreated control animals and in the lungs and kidneys compared with the burdens in the lungs and kidneys of animals treated with amphotericin B alone. These data suggest a potential role for this peptide as adjunctive therapy in combination with conventional antifungal agents in the treatment of disseminated candidiasis in the setting of profound and persistent neutropenia.

Adherence of Candida albicans to bladder mucosa: development and application of a tissue explant assay

In order to study the interactions between Candida species and uroepithelial tissue, a tissue explant assay was developed using bladder mucosa harvested from New Zealand white rabbits. Blastoconidia of Candida albicans, Candida tropicalis and Candida glabrata attached to the uroepithelial tissue in similar quantities. However, there was significantly more adherence to the uroepithelium by pre-germinated C. albicans compared with C. albicans blastoconidia. Furthermore, the amount of uroepithelial tissue injury was directly related to the length of exposure of the tissue to Candida. Thus, this tissue explant assay may provide a useful method for investigating properties related to fungal adherence to transitional uroepithelium and organism-mediated tissue injury.

Increased adherence of fluconazole-resistant isolates of Candida species to explanted esophageal mucosa

The adherence of fluconazole-resistant and fluconazole-susceptible isolates of Candida albicans to explanted rabbit esophageal mucosa was examined in vivo. Among six Candida albicans isolates collected from HIV-infected patients, three fluconazole-resistant (MIC > 64 microg/ml) isolates attached more avidly than three fluconazole-susceptible strains (MIC < or = 0.5 microg/ml) to esophageal mucosa (P < or = 0.05). When three strains each of six different Candida spp. were compared, the more inherently fluconazole-resistant isolates adhered more avidly in the following order: Candida glabrata>Candida krusei>Candida albicans fluconazole-sensitive>Candida tropicalis>Candida parapsilosis. Nonetheless, fluconazole-resistant Candida albicans demonstrated the greatest degree of adherence in comparison to all fluconazole-susceptible Candida albicans (P<0.001) and to all Candida spp. tested (P<0.001). Thus, the refractoriness of esophageal candidiasis in patients infected with fluconazole-resistant isolates may be related to both in vitro drug resistance and increased mucosal adherence.

Interleukin-15 augments superoxide production and microbicidal activity of human monocytes against Candida albicans

Interleukin-15 (IL-15) is a newly described cytokine that shares biological activities with IL-2. We report here results demonstrating the ability of IL-15 to enhance superoxide production and antifungal activity of human monocytes. After 18 and 48 h of treatment with IL-15, human elutriated monocytes manifested enhanced superoxide production in response to either phorbol myristate acetate or opsonized Candida albicans blastoconidia. Similar results were obtained when monocytes were treated with IL-2, but to a lesser extent. Combination studies with IL-15 and IL-2 showed no additive or synergistic effects. Following incubation of monocytes with IL-15 for 18 h, there was no significant increase in mRNA transcripts for components of the NADPH oxidase complex, p40-phox, p47-phox, and gp91-phox, suggesting a posttranscriptional modulation of enhanced superoxide production. Antibodies against the gamma chain of the IL-2 receptor and, to a lesser extent, against the beta chain partially abrogated the IL-15-mediated enhanced superoxide production. Additionally, human monocytes showed enhanced killing activity against C. albicans after 18 h of incubation with IL-15 or IL-2, but this treatment did not enhance the ability of these cells to phagocytose the organism. In addition, the enhanced fungicidal activity seen after 18 h of treatment was no longer detectable after 48 h of cytokine treatment. Culture supernatants from the IL-15-treated monocytes were assayed for the presence of other proinflammatory cytokines. IL-15 treatment did not induce the release of detectable levels of tumor necrosis factor alpha, IL-1beta, or IL-12. Our results indicate that IL-15 upregulates the microbicidal activity of human monocytes against C. albicans.

Specific induction of fibronectin binding activity by hemoglobin in Candida albicans grown in defined media

Fibronectin (FN) is a major component of host extracellular matrix that may play an important role in the initiation and dissemination of Candida albicans infections. Expression of FN binding requires growth of C albicans blastoconidia in complex medium, and the regulation of FN receptor expression is poorly understood. We now demonstrate that hemoglobin is a potent and specific inducer of FN receptor expression and describe a defined medium supplemented with hemoglobin that greatly and stably enhances the binding activity of C. albicans for soluble FN. Enhancement of FN binding by hemoglobin in strain 44807 was concentration dependent and was maximal at 0.1% hemoglobin with 20- to 80-fold enhancement. The hemoglobin-induced FN binding to C. albicans was saturable, with a Kd of 2.7 X 10(-8) M. Enhancement required growth of C. albicans in hemoglobin-containing medium, since simply exposing blastoconidia to hemoglobin in a nongrowing status did not enhance binding. Induction was reversible following removal of hemoglobin from the growth medium and not associated with germination. Inorganic or protein-bound iron was not sufficient for the induction, since other iron-containing proteins or inorganic iron salts were inactive. Growth in the simple medium yeast nitrogen base supplemented with hemoglobin increased cell adhesion to immobilized FN and to cultured monolayers of bovine corneal endothelial cells. These data suggest that hemoglobin may be an important regulator of FN binding activity in C. albicans and thus may play a role in its pathogenesis.

Ex vivo effects of macrophage colony-stimulating factor on human monocyte activity against fungal and bacterial pathogens

The ex vivo effects of macrophage colony-stimulating factor (M-CSF) on antifungal and antibacterial activities of human elutriated monocytes were studied. Cells were isolated prior to the initiation of therapy, on day 3 and at week 7, in six patients with an advanced malignancy receiving M-CSF in a phase I study. Superoxide anion production by monocytes in response to N-formyl methionyl leucyl phenylalanine was enhanced at day 3 of therapy (P = 0.011). In addition, at day 3, fungicidal activity against blastoconidia of Candida albicans was enhanced by M-CSF treatment (P = 0.026), whereas antifungal activity against hyphae of Aspergillus fumigatus was not significantly changed. Bactericidal activity against Staphylococcus aureus was increased at day 3 (P = 0.004). By Northern blot analysis, M-CSF does not upregulate the expression of components of the NADPH-oxidase, the multicomponent enzyme system responsible for generation of superoxide radicals by monocytes. Instead, the predominant effect of M-CSF on circulating monocytes is probably a post-transcriptional effect. In conclusion, these findings suggest that administration of M-CSF to patients may enhance microbicidal activities and thus may provide a useful adjunct to conventional antimicrobial therapy.

Detection and quantitation of the glucuronoxylomannan-like polysaccharide antigen from clinical and nonclinical isolates of Trichosporon beigelii and implications for pathogenicity

Sera from patients with systemic infections caused by the opportunistic fungus Trichosporon beigelii have been shown to cross-react with anticryptococcal antibodies. We quantitatively compared the amounts of antigen produced and examined the expression of O-acetyl epitopes from 35 strains of T. beigelii isolated from deep and superficial infections. By counterimmunoelectrophoresis, 10 of 10 isolates from deep infections were positive for polysaccharide, compared with 7 of 13 isolates from superficial infections (P = 0.02). All 23 strains tested were positive for polysaccharide when screened by immunodot. By enzyme immunoassay, the cross-reactive antigen produced by deep isolates (n = 9) had a mean titer of 1:5,500. In contrast, superficial isolates (n = 22) produced significantly less antigen than the deep isolates (P < 0.001), with a mean titer of 1:700. Isolates from environmental sources (n = 3) were similar to the superficial isolates, with a mean titer of 1:600. The mean concentrations +/- standard errors of cross-reactive polysaccharide released by deep isolates and superficial isolates were 3.09 +/- 0.44 and 1.74 +/- 0.30 micrograms/ml, respectively, when measured by rocket immunoelectrophoresis (P = 0.02). O-Acetyl epitopes were detected on polysaccharide from 8 of 9 strains of T. beigelii isolated from deep sources, while only 2 of 12 superficial isolates expressed detectable O-acetyl epitopes (P = 0.01). Thus, while all isolates of T. beigelii tested were capable of producing glucuronoxylomannan-like cross-reactive antigen, pathogenic isolates produced significantly more antigen than superficial or environmental isolates. Furthermore, significantly more pathogenic isolates than superficial or environmental isolates expressed antigen that was O acetylated.

Response of human polymorphonuclear leukocytes and monocytes to Trichosporon beigelii: host defense against an emerging opportunistic pathogen

To further understand human host defenses against Trichosporon beigelii, functional responses were investigated of polymorphonuclear leukocytes (PMNL) and elutriated human monocytes (EHM) to this opportunistic fungal pathogen. There was significantly less PMNL phagocytosis (P < .001) and killing (P < .001) of T. beigelii isolates than of Candida albicans. However, levels of superoxide anions generated by PMNL in response to T. beigelii and C. albicans were comparable. Pretreatment of PMNL with granulocyte colony-stimulating factor or interferon-gamma (IFN-gamma) did not significantly enhance fungicidal activity. Killing of T. beigelii by EHM also was significantly impaired compared with killing of C. albicans (P < .001). However, pretreatment of EHM with macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or IFN-gamma all resulted in enhanced fungicidal activity. Thus, phagocytosis and killing of T. beigelii by PMNL and EHM are significantly less efficient than that of C. albicans. However, monocytes may be more important in the control of Trichosporon species than previously shown.

Phagocytosis of medically important yeasts by polymorphonuclear leukocytes

Phagocytosis is a critical function of polymorphonuclear leukocytes in the control of mycotic infections. By using a modified fluorescence quenching assay to distinguish between attached and ingested organisms, we determined the percent phagocytosis of several medically important yeasts. The percentages of phagocytosis of serum-opsonized Candida albicans, Candida tropicalis, Candida parapsilosis, and Torulopsis glabrata were all comparable at 37 degrees C. By comparison, there was significantly less phagocytosis of Cryptococcus neoformans and Trichosporon beigelii isolates (P < 0.001). Thus, phagocytosis of C. albicans by polymorphonuclear leukocytes is comparable to that of species other than C. albicans but is significantly greater than that of the basidiomycetous yeasts T. beigelii and C. neoformans.

Dose-dependent antifungal activity and nephrotoxicity of amphotericin B colloidal dispersion in experimental pulmonary aspergillosis

We investigated the safety and efficacy of amphotericin B colloidal dispersion (ABCD) for the treatment of invasive pulmonary aspergillosis in persistently granulocytopenic rabbits. Treatment groups included ABCD in dosages of 1, 5, and 10 mg/kg/day intravenously or conventional desoxycholate amphotericin B (DAmB) at 1 mg/kg/day intravenously. Antifungal activity was directly related to increasing dosage of ABCD as determined by the concentration of Aspergillus fumigatus organisms in lungs and the frequency of hemorrhagic pulmonary lesions. At 5 and 10 mg/kg/day, there was a significant reduction in the tissue burden of A. fumigatus as measured by percent culture-positive lobes and CFU per gram of tissue (P < or = 0.001), whereas at 1 mg/kg/day measured by percent culture-positive lobes and CFU per gram of tissue (P < or = 0.001), whereas at 1 mg/kg/day the tissue burden of A. fumigatus was not significantly different from that in untreated controls. Microbiological clearance was significantly greater at 1 mg of DAmB per kg per day than at 1 mg of ABCD per kg per day (P < or = 0.001). There was no difference in microbiological clearance of bronchoalveolar lavage fluid among the treatment groups as measured by CFU per milliliter. As determined by survival, ABCD at 5.0 mg/kg/day was more effective than DAmB at 1.0 mg/kg/day and ABCD at 10 mg/kg/day. ABCD at 10 mg/kg/day was more nephrotoxic than the lower dosages of ABCD and resulted in higher mortality. Impairment of glomerular filtration developed as a direct function increasing the ABCD dosage (r = 0.77; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Systemically administered antifungal agents. A review of their clinical pharmacology and therapeutic applications

Systemic antifungal agents express great diversity in their pharmacokinetic profiles, mechanisms of action, and toxicities. Understanding the diverse pharmacokinetic properties of systemic antifungals is critical to their appropriate application. Amphotericin B, drug of choice for most invasive mycoses, has unique pharmacokinetic properties, binding initially to serum lipoproteins and redistributing from blood to tissues. Dosing recommendations are based on the specific infection and the status of the host. Lipid formulations of amphotericin B may be able to attenuate some of its toxicities. Flucytosine is a water-soluble, fluorinated pyrimidine that possesses excellent bioavailability. It is administered only in combination with amphotericin B because of frequent development of secondary drug resistance, and is associated with dose-dependent bone marrow suppression. The antifungal azoles are relatively well tolerated, have broad spectrum antifungal activity, and are fungistatic in vitro. Ketoconazole and itraconazole are highly bound to plasma proteins, are extensively metabolised by the liver, and are relatively insoluble in aqueous solution. By comparison, fluconazole is only weakly bound to serum proteins, is relatively stable to metabolic conversion, and is water soluble. Fluconazole penetrates the cerebrospinal fluid well and is approved for primary and suppressive therapy of cryptococcal meningitis in AIDS patients. The echinocandins have a narrow spectrum of antifungal activity, being effective only against Candida spp.

Experimental antifungal chemotherapy in granulocytopenic animal models of disseminated candidiasis: approaches to understanding investigational antifungal compounds for patients with neoplastic diseases

Disseminated candidiasis is the most common life-threatening invasive fungal infection in granulocytopenic patients. A review of recent approaches to pre-clinical laboratory investigation of promising antifungal compounds, which may have potential utility in granulocytopenic patients is presented. A particularly useful strategy is the study of persistently granulocytopenic rabbit models of acute, subacute, and chronic forms of disseminated candidiasis. When the antifungal triazoles (fluconazole, itraconazole, and SCH 39304 [SCH 42427]) were each evaluated for use as preventive, early treatment, or delayed treatment in the different models, the triazoles were consistently more active when used for preventive and early treatment than for delayed treatment. These triazoles were as active as amphotericin B plus flucytosine (AB + FC) when used for early treatment but were less active than AB + FC when used for delayed treatment. Several lipid formulations of amphotericin B demonstrate reduced nephrotoxicity at higher safely achievable dosages in comparison to those of deoxycholate amphotericin B in several models of disseminated candidiasis. When administered to follow non-linear saturable Michaelis-Menten-type plasma pharmacokinetics, the antifungal activity of the echinocandin compound cilofungin was significantly augmented. Thoughtfully designed and carefully conducted laboratory investigations in appropriate animal models of disseminated candidiasis can provide a scientific foundation and guide for development of clinical protocols investigating new approaches to prevention and treatment of invasive candidiasis in granulocytopenic patients.

Disparate effects of interferon-gamma and tumor necrosis factor-alpha on early neutrophil respiratory burst and fungicidal responses to Candida albicans hyphae in vitro

We examined effects of priming with recombinant human interferon-gamma (IFN) or tumor necrosis factor-alpha (TNF) on neutrophil responses to Candida albicans hyphae. Both cytokines increased early superoxide generation after hyphal stimulation. The more pronounced effects of TNF were accompanied by an augmented surface membrane depolarization rate and were insensitive to both pertussis toxin and calcium ion chelation, but were negated by concomitant incubation with puromycin or cycloheximide during priming. IFN augmented hyphal killing despite its only minor enhancement of early respiratory burst responses, but TNF reduced neutrophil fungicidal activity to nearly 40% below those by unprimed control cells even though it enhanced early superoxide responses more dramatically. Though TNF-primed neutrophils killed hyphae at normal initial rates, IFN-primed or even unprimed cells manifested more fungicidal sustained activity. These disparate consequences of cytokine priming on hyphal destruction were paralleled by differences in late generation of potentially candidacidal oxidants, hydrogen peroxide, and hypochlorous acid. IFN added during priming failed to correct TNF-associated functional defects in neutrophil anti-Candida responses. Thus, augmentation of early respiratory burst responses to oxidant-sensitive organisms need not necessarily reflect concomitant salutary effects on microbicidal activity.

Independence of neutrophil respiratory burst oxidant generation from the early cytosolic calcium response after stimulation with unopsonized Candida albicans hyphae

We previously noted differences between neutrophil responses to unopsonized Candida albicans hyphae and responses to other particulate stimuli such as opsonized hyphae or zymosan; these differences include delayed rises in cytosolic calcium [( Ca2+]i), 1,4,5-inositol trisphosphate, and superoxide release and the total absence of early membrane depolarization. Respiratory burst stimulation is required for killing of C. albicans hyphae. Since an early rise in [Ca2+]i may act as a second messenger for burst activation by most agonists, we chelated (Ca2+)i and extracellular Ca2+ [( Ca2+)e] to compare requirements for superoxide responses to hyphae and other stimuli. Intracellular chelation, which ablated early [Ca2+]i rises, eliminated the fMet-Leu-Phe-induced respiratory burst and profoundly reduced that response to opsonized zymosan (by 96.7%), but chelation of both (Ca2+)i and (Ca2+)e only partially inhibited responses to opsonized and unopsonized hyphae (60.5 and 23.3%, respectively; the latter exceeded absolute responses evoked by opsonized zymosan, a 12-fold-more-potent stimulus for unchelated cells). Simultaneous (Ca2+)i and (Ca2+)e chelation further decreased superoxide responses to opsonized zymosan and hyphae (99.4 and 90.4%, respectively) but not to unopsonized hyphae (26.7% inhibition). Though both ingestible (zymosan) and uningestible (hyphae) opsonized particulate stimuli elicited reduced but significant respiratory bursts without early [Ca2+]i rises, the greater superoxide responses and sensitivity to chelation with opsonized zymosan suggest important differences in initiation and/or regulation of responses to these particulate stimuli. In contrast, the respiratory burst elicited by unopsonized hyphae appeared largely Ca2+ independent. If different events mediate neutrophil activation by opsonized and unopsonized hyphae, candidacidal activity in vivo may vary under divergent conditions with specific localized sites of infection.

Effects of recombinant human granulocyte-macrophage colony-stimulating factor on intracellular pH in mature granulocytes

We studied the effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSFrh) on the internal pH of granulocytes using the fluorescent probe BCECF. GM-CSFrh did not directly alter the resting pH of granulocytes isolated from the peripheral blood; however, when the cells were preincubated for 90 minutes with the growth factor and then activated with the chemotactic peptide N-formyl met leu phe (fMLP), they exhibited both an acceleration in the initial rate of acidification and a marked delay in realkalinization. The kinetic changes both in initial acidification and in subsequent realkalinization induced by GM-CSFrh priming were not prevented by protein synthesis inhibitors and were observed in granulocytes harvested from patients with both sex-linked and autosomal recessive chronic granulomatous disease (CGD). By directly quantitating H+ ion secretion, by monitoring the effects of sodium repletion on intracellular pH, and through use of the sodium channel inhibitors amiloride and dimethyl amiloride and the Na+/K+-ATPase inhibitor ouabain, we showed that the altered kinetics of intracellular acidification and alkalinization following fMLP stimulation of GM-CSFrh-primed granulocytes could not be accounted for by changes in transmembrane proton exportation regulated by the Na+/H+ antiport channel. Although the initial acidification following fMLP was abrogated by 2-deoxy-D-glucose in both GM-CSFrh-pretreated and GM-CSFrh-untreated granulocytes, retardation of the subsequent phase of alkalinization was observed in GM-CSFrh-primed cells even after inhibition of both glycolytic and mitochondrial metabolism. Our data indicate that the increased cytosolic acidification following fMLP stimulation in granulocytes "primed" with GM-CSFrh does not result from disordered proton excretion but instead from increased release of intracellular free acid which is only partially coupled to glucose catabolism or to the generation of superoxide anion (O2-).

Induction of signal transduction in human neutrophils by Candida albicans hyphae: the role of pertussis toxin-sensitive guanosine triphosphate-binding proteins

Nonopsonized Candida hyphae elicit from human neutrophils a transient rise in cytosolic calcium concentrations and an oxidative burst without a detectable change in membrane potential. To determine if the signal-transduction pathway used by these organisms is mediated by guanine nucleotide-binding proteins (GNPs), we examined the functional responsiveness of neutrophils pretreated with pertussis toxin (PT). In response to serum-opsonized hyphae or zymosan, the rise in cytosolic calcium, membrane depolarization, and the respiratory burst were only partially abrogated. The transient rise in calcium induced by unopsonized hyphae was, however, completely eliminated in PT-treated neutrophils. Despite total abrogation of the calcium response, PT-treated cells could still mount a respiratory burst in response to these nonopsonized hyphae. Thus, neutrophil signaling by both serum-opsonized particles and nonopsonized hyphae is only partially mediated by PT-sensitive GNPs. Furthermore, the ability of unopsonized hyphae to elicit a respiratory burst without a calcium response suggests these events are separable and confirms the versatility of these organisms as probes for investigating neutrophil activation.

Temporal association of calcium mobilization, inositol trisphosphate generation, and superoxide anion release by human neutrophils activated by serum opsonized and nonopsonized particulate stimuli

We have investigated the involvement of phospholipase C mediated polyphosphoinositide turnover in activation of polymorphonuclear leukocytes by particulate stimuli. Results showed that stimulation of leukocytes with serum opsonized zymosan (ingestible particle), serum opsonized Candida albicans hyphae (noningestible particle), or nonopsonized hyphae was followed by a transient rise in cellular inositol phosphates as has been described for neutrophil activation via the formyl peptide receptor. The kinetics of inositol trisphosphate generation paralleled both the time course of changes in cytosolic calcium concentration and the onset of superoxide anion generation, suggesting that these may be related events.

Cytosolic calcium changes in individual neutrophils stimulated by opsonized and unopsonized Candida albicans hyphae

Previous experiments suggest the critical central role of the neutrophil (PMN) respiratory burst in the prevention and containment of disseminated candidiasis. A rise in cytosolic free calcium concentrations ([Ca2+]i) has been documented as an early event after PMN stimulation which is involved in the subsequent genesis of microbicidal and inflammatory respiratory burst products. [Ca2+]i were therefore determined in individual PMN, loaded with the fluorescent calcium probe fura-2 as they attached to and spread over serum-opsonized or unopsonized Candida albicans hyphae, particles that are too big to be completely ingested. After contact between hyphae and PMN, the PMN rapidly spread over hyphal surfaces. Although both opsonized and unopsonized hyphae stimulated similar magnitudes of peak median increases in PMN [Ca2+]i, the kinetics of responses differed; median [Ca2+]i peaked within 1 min after contact with opsonized hyphae versus 4 min after contact with unopsonized hyphae. Moreover, a detectable calcium transient did not invariably follow contact and spreading of each individual PMN over a hyphal surface. In contrast to patterns seen after stimulation of PMN with opsonized zymosan, in which [Ca2+]i is greatest in the periphagosomal region, there was a more uniform distribution throughout the cytoplasm in PMN stimulated with the noningestable hyphae. These alterations in the early patterns and timing of PMN stimulation may reflect analogous differences in subsequent events which control the efficiency and specificity of microbicidal responses to uningestible hyphae and which also determine whether host tissues are damaged by the generation of toxic PMN activation products.

Unopsonized Candida albicans hyphae stimulate a neutrophil respiratory burst and a cytosolic calcium flux without membrane depolarization

We have defined major differences between events elicited during activation of human neutrophils by opsonized Candida hyphae (noningestible) or zymosan (ingestible) and by unopsonized Candida hyphae (also noningestible). In response to opsonized particles, a transient increase in cytosolic free calcium was initially observed, followed by depolarization in the transmembrane potential and a respiratory burst. Without opsonins, zymosan did not elicit a response from neutrophils. In contrast, unopsonized Candida hyphae elicited a transient increase in cytosolic calcium, as well as triggered a respiratory burst; they did not, however, elicit a depolarization of the neutrophil membrane. Furthermore, the rate of superoxide generation decreased after a prolonged lag period. The calcium flux was also delayed and coincided with the onset of superoxide generation. Thus, our data demonstrate that Candida albicans hyphae activate neutrophils in the absence of added serum components and initiate a neutrophil respiratory burst without an antecedent membrane depolarization.

Comparative activities of UK-49,858 and amphotericin B against Blastomyces dermatitidis infections in mice

UK-49,858, a new antifungal triazole derivative, was compared with amphotericin B in the treatment of pulmonary infections by Blastomyces dermatitidis in male BALB/cByJ mice. Administration of UK-49,858 in daily doses of 25 or 50 mg/kg for 21 days gave 30 and 100% survival rates, respectively. These results compared with 100% mortality in infected controls and 100% survival among mice treated with amphotericin B. UK-49,858 did not eradicate the fungus from the lungs of surviving animals, while amphotericin B effected sterilization of the lungs in 66% of the survivors.

Proteolytic activity of Candida albicans and other yeasts

Clinical isolates of C. albicans (75 strains) and other yeasts (20 strains) were evaluated for their ability to produce a carboxyl acid proteinase in an effort to assess its potential role as a virulence factor. Yeasts were categorized as to the infectious process present in the patient: (1) isolates from patients with invasive disease, (2) isolates from patients with possible invasive disease, (3) isolates from superficially infected patients and (4) isolates from noninfected, colonized patients. Yeasts were grown for 7 days in medium containing bovine serum albumin (BSA) as the sole nitrogen source. The amount of extracellular proteinase was measured at pH 3.2, using BSA as substrate. The majority (97%) of C. albicans isolates produced a detectable proteinase. Some non-C. albicans isolates produced proteinase; however, the amount of activity was generally less than for C. albicans. No correlation was found between the amount of proteolytic activity and the degree of invasiveness of the strains.