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T J Walsh

Publications and source records attributed to T J Walsh.

At least 55 records · Page 3Linked to original sources

Invasive candidiasis stimulates hepatocyte and monocyte production of active transforming growth factor beta.

Candida albicans is an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion by C. albicans can influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor beta (TGF-beta) has been documented in mice infected with C. albicans and is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-beta by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-beta1 within inflammatory granulomas, as well as staining for TGF-beta1 and TGF-beta3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-beta observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-beta protein. Human peripheral blood monocytes incubated with C. albicans in vitro release large amounts of biologically active TGF-beta1. The data demonstrate that local production of active TGF-betas by hepatocytes and by infected mononuclear cells is a component of the response to C. albicans infection that most probably contributes to disease progression in the immunocompromised host.

Animals↗

Pharmacokinetics, excretion, and mass balance of 14C after administration of 14C-cholesterol-labeled AmBisome to healthy volunteers.

Amphotericin B (AmB) in small unilamellar liposomes (AmBisome) provides higher plasma concentrations and greater safety than the conventional deoxycholate formulation. The authors compared the disposition of the liposome's drug and cholesterol components by measuring AmB and radioactivity in plasma, urine, and feces for 1 week after a single 2-hour infusion of 14C-cholesterol-labeled AmBisome (2 mg/kg, 1 microgCi/kg) in healthy adults (4 males, 1 female). The plasma profile of 14C-cholesterol differed from that of AmB, lacking an initial rapid disappearance phase, having a lower total clearance, and having a volume of distribution (0.13 L/kg) close to that of the plasma compartment. The biphasic disappearance and long plasma half-life (147 h) of 14C-cholesterol were similar to those of other low-clearance liposomes. This and the low clearance of 14C-cholesterol from the plasma compartment suggest that it served as a liposome marker. The plasma drug-lipid ratio fell during the study, showing that AmB was cleared from plasma more rapidly than cholesterol or liposomes and suggesting that the composition of the liposomes changed over time. 14C-radioactivity was recovered mainly in the feces (9.5% of dose), consistent with the catabolism of cholesterol to bile salts. Combined fecal and renal clearances were < 18% of total clearance, suggesting that most of the liposomal drug and lipid remained in the body 1 week after dosing. Thus, AmBisome remains in the circulation for an extended period of time while releasing AmB, resulting in its markedly altered pharmacokinetic and safety profiles.

Adult↗

Caspofungin: pharmacology, safety and therapeutic potential in superficial and invasive fungal infections.

Invasive fungal infections are important causes of morbidity and mortality in hospitalised patients. Current therapy with amphotericin B and antifungal triazoles has overlapping targets and is limited by toxicity and resistance. The echinocandin lipopeptide caspofungin is the first of a new class of antifungal compounds that inhibit the synthesis of 1,3-beta-D-glucan. This homopolysaccharide is a major component of the cell wall of many pathogenic fungi and yet is absent in mammalian cells. It provides osmotic stability and is important for cell growth and cell division. In vitro, caspofungin has broad-spectrum antifungal activity against Candida and Aspergillus spp. without cross-resistance to existing agents. The compound exerts prolonged post-antifungal effects and fungicidal activity against Candida spp. and causes severe damage of Aspergillus fumigatus at the sites of hyphal growth. Animal models have demonstrated efficacy against disseminated candidiasis and disseminated and pulmonary aspergillosis, both in normal and in immunocompromised animals. Caspofungin possesses favourable pharmacokinetic properties and is not metabolised through the cytochrome P450 (CYP) enzyme system. It showed highly promising antifungal efficacy in Phase II and III clinical trials in immunocompromised patients with oesophageal candidiasis. Caspofungin was effective in patients with invasive aspergillosis intolerant or refractory to standard therapies. Based on its documented antifungal efficacy and an excellent safety profile, caspofungin has been approved recently by the US Food and Drug Administration for the treatment of invasive aspergillosis in patients who are refractory to or intolerant of other therapies (i.e., amphotericin B, lipid formulations of amphotericin B, and/or itraconazole). Phase III clinical trials in patients with candidaemia and in persistently febrile neutropenic patients requiring empirical antifungal therapy are ongoing. This paper reviews the preclinical and clinical pharmacology of caspofungin and its potential role for treatment of invasive and superficial fungal infections in patients.

Animals↗

Antifungal pharmacodynamics: concentration-effect relationships in vitro and in vivo.

The pharmacodynamics of antifungal compounds involve relationships among drug concentrations, time, and antimicrobial effects in vitro and in vivo. Beyond better understanding of a drug's mode of action, characterization of these relationships has important implications for setting susceptibility breakpoints, establishing rational dosing regimens, and facilitating drug development. Important advances have been made in the experimental investigation of pharmacokinetics and pharmacodynamics of antifungal drugs; however, much remains to be learned about specific pathogens and specific sites of infection. Increased incorporation of pharmacokinetic and pharmacodynamic principles in experimental and clinical studies with antifungal agents is an important objective that will benefit the treatment and prophylaxis of life-threatening invasive fungal infections in immunocompromised patients.

Antifungal Agents↗

Cyclosporine A-induced mammary hyperplasia and hyperprolactinemia in New Zealand White rabbits.

PURPOSE: To investigate the potential activity of cyclosporin A (CsA) to induce mammary hyperplasia in New Zealand White (NZW) rabbits. METHODS: Female NZW rabbits were used throughout experiments. To simulate the conditions of immunosuppression, CsA (10 mg/kg of body weight/d) was administered intravenously on a daily basis for 14 days and methylprednisolone (5 mg/kg/d) was administered on the first two days. The CsA (10 mg/kg/d) also was administered without methylprednisolone for 14 days to another cohort of rabbits. Mammary tissue of each rabbit was palpated and serially measured during this treatment period. The CsA was discontinued, and rabbits were monitored for 14 more days during the washout period. Sequential plasma concentrations of prolactin, 17beta-estradiol, and progesterone in each blood sample were determined by use of radioimmunoassay. RESULTS: All NZW rabbits treated with CsA and methylprednisolone for immunosuppression consistently developed striking mammary tissue hyperplasia. At the end of treatment with CsA and methylprednisolone, mammary glands had extensive changes consistent with actively lactating glands. Similar but less extensive hyperplasia developed in response to CsA alone. Plasma concentration of prolactin increased during treatment and decreased during the washout period. Plasma concentration of 17beta-estradiol increased during treatment and continued to increase during the washout period. Plasma progesterone concentration decreased at the end of treatment. On discontinuation of CsA, mammary hyperplasia regressed. CONCLUSIONS: Cyclosporine A, with or without methylprednisolone, induces mammary hyperplasia and hyperprolactinemia in NZW rabbits. This rabbit model may be a reliable in vivo system by which to study immunosuppressant-induced structural and functional changes of mammary glands similar to those observed in humans.

Animals↗

Dissociation of memory and anxiety in a repeated elevated plus maze paradigm: forebrain cholinergic mechanisms.

The effect of intraseptal injection of the cholinergic immunotoxin 192-IgG-saporin on behavior in the elevated plus maze was investigated. A 5-min test-retest paradigm, with minute-by-minute analysis of the first session, was used to evaluate both anxiety and memory in this task. Biochemical analyses revealed a decrease in acetylcholinesterase (AChE) activity in the hippocampus (HPC), septum, and frontal cortex of animals injected with IgG-192 saporin (237.5 ng) when compared with controls. No statistical differences were found between groups in terms of behaviors associated with locomotor activity, conventional measures of anxiety, or ethological behaviors during either session 1 or 2. During test session 2 the controls exhibited decreased exploratory activity and increased indices of anxiety. In contrast, the saporin-treated rats did not exhibit these experience-dependent behavioral changes from session 1 to 2. The minute-by-minute analysis showed a significant decrease in exploratory as well in anxiety associated behaviors during the first session for the control group, but not for the saporin-treated group. These results suggest that the cholinergic innervation of the HPC, the frontal cortex, or both forebrain structures, modulate the initiation of exploratory activity which, results in the acquisition and retention of spatial information, but does not affect the expression of anxiety in the elevated plus-maze.

Acetylcholinesterase↗

High-dose cyclophosphamide in severe aplastic anaemia: a randomised trial.

BACKGROUND: High-dose cyclophosphamide has been proposed as an alternative immunosuppressive agent for treatment of severe aplastic anaemia, with a response rate similar to that with regimens containing antithymocyte globulin (ATG) but neither relapse nor clonal haematological complications. We undertook a phase III, prospective, randomised trial to compare response rates to immunosuppression with either high-dose cyclophosphamide plus cyclosporin or conventional immunosuppression with ATG plus cyclosporin in previously untreated patients. METHODS: Between June, 1997, and March, 2000, 31 patients were enrolled. 15 were assigned cyclophosphamide (1 h intravenous infusion of 50 mg/kg daily for 4 days) and 16 were assigned ATG (40 mg/kg daily for 4 days); both groups received cyclosporin, initially at 12 mg/kg daily with adjustment to maintain concentrations at 200-400 microg/L, for 6 months. The primary endpoint was haematological response (no longer meeting criteria for severe aplastic anaemia). The trial was terminated prematurely after three early deaths in the cyclophosphamide group. Analyses were by intention to treat. FINDINGS: Median follow-up was 21.9 months (range 1-33). There was excess morbidity in the cyclophosphamide group (invasive fungal infections, four cyclophosphamide vs no ATG patients; p=0.043) as well as excess early mortality (three deaths within the first 3 months cyclophosphamide vs no ATG patients; p=0.101). There was no significant difference at 6 months after treatment in the overall response rates among evaluable patients (six of 13 [46%] cyclophosphamide vs nine of 12 [75%] ATG). INTERPRETATION: A longer period of observation will be necessary to assess the secondary endpoints of relapse and late clonal complications as well as disease-free and overall survival. However, cyclophosphamide seems a dangerous choice for treatment of this disorder, given the good results achievable with standard therapy.

Adult↗

Comparative efficacy and distribution of lipid formulations of amphotericin B in experimental Candida albicans infection of the central nervous system.

The central nervous system (CNS) distribution and antifungal efficacy of all 4 approved formulations of amphotericin B (AmB) were investigated in a rabbit model of hematogenous Candida albicans meningoencephalitis. Treatment with AmB deoxycholate (1 mg/kg/day) or liposomal AmB (5 mg/kg/day) yielded the highest peak plasma concentration (C(max)), area under concentration versus time curve from zero to 24 h (AUC(0-24)), and time during dosing level tau Ttau>minimum inhibitory complex (MIC) values and led to complete eradication of C. albicans from brain tissue (P<.05 vs. untreated controls). By comparison, AmB colloidal dispersion and AmB lipid complex (5 mg/kg/day each) were only partially effective (not significant vs. untreated controls). There was a strong correlation of C(max), AUC(0-24), C(max)/MIC, AUC(0-24)/MIC, and Ttau>MIC with clearance of C. albicans from brain tissue (P</=.0002). Although pharmacodynamic parameters derived from the MIC of free AmB were highly predictive of antifungal efficacy, parameters derived from MICs of individual formulations were not predictive. AmB deoxycholate and liposomal AmB had the greatest antifungal efficacy. This activity was concentration and time dependent.

Amphotericin B↗

Practice guidelines for the treatment of candidiasis. Infectious Diseases Society of America.

Infections due to Candida species are the most common of the fungal infections. Candida species produce a broad range of infections, ranging from nonlife-threatening mucocutaneous illnesses to invasive process that may involve virtually any organ. Such a broad range of infections requires an equally broad range of diagnostic and therapeutic strategies. This document summarizes current knowledge about treatment of multiple forms of candidiasis and is the guideline of the Infectious Diseases Society of America (IDSA) for the treatment of candidiasis. Throughout this document, treatment recommendations are scored according to the standard scoring scheme used in other IDSA guidelines to illustrate the strength of the underlying data. The document covers 4 major topical areas. The role of the microbiology laboratory. To a greater extent than for other fungi, treatment of candidiasis can now be guided by in vitro susceptibility testing. The guidelines review the available information supporting current testing procedures and interpretive breakpoints and place these data into clinical context. Susceptibility testing is most helpful in dealing with infection due to non-albicans species of Candida. In this setting, especially if the patient has been treated previously with an azole antifungal agent, the possibility of microbiological resistance must be considered. Treatment of invasive candidiasis. In addition to acute hematogenous candidiasis, the guidelines review strategies for treatment of 15 other forms of invasive candidiasis. Extensive data from randomized trials are really available only for therapy of acute hematogenous candidiasis in the nonneutropenic adult. Choice of therapy for other forms of candidiasis is based on case series and anecdotal reports. In general, both amphotericin B and the azoles have a role to play in treatment. Choice of therapy is guided by weighing the greater activity of amphotericin B for some non-albicans species (e.g., Candida krusei) against the lesser toxicity and ease of administration of the azole antifungal agents. Flucytosine has activity against many isolates of Candida but is not often used. Treatment of mucocutaneous candidiasis. Therapy for mucosal infections is dominated by the azole antifungal agents. These drugs may be used topically or systemically and have been proven safe and efficacious. A significant problem with mucosal disease is the propensity for a small proportion of patients to suffer repeated relapses. In some situations, the explanation for such a relapse is obvious (e.g., relapsing oropharyngeal candidiasis in an individual with advanced and uncontrolled HIV infection), but in other patients the cause is cryptic (e.g., relapsing vaginitis in a healthy woman). Rational strategies for these situations are discussed in the guidelines and must consider the possibility of induction of resistance over time. Prevention of invasive candidiasis. Prophylactic strategies are useful if the risk of a target disease is sharply elevated in a readily identified group of patients. Selected patient groups undergoing therapy that produces prolonged neutropenia (e.g., some bone-marrow transplant recipients) or who receive a solid-organ transplant (e.g., some liver transplant recipients) have a sufficient risk of invasive candidiasis to warrant prophylaxis.

Adult↗

Practice guidelines for diseases caused by Aspergillus. Infectious Diseases Society of America.

Aspergillosis comprises a variety of manifestations of infection. These guidelines are directed to 3 principal entities: invasive aspergillosis, involving several organ systems (particularly pulmonary disease); pulmonary aspergilloma; and allergic bronchopulmonary aspergillosis. The recommendations are distilled in this summary, but the reader is encouraged to review the more extensive discussions in subsequent sections, which show the strength of the recommendations and the quality of the evidence, and the original publications cited in detail. Invasive aspergillosis. Because it is highly lethal in the immunocompromised host, even in the face of therapy, work-up must be prompt and aggressive, and therapy may need to be initiated upon suspicion of the diagnosis, without definitive proof (BIII). Intravenous therapy should be used initially in rapidly progressing disease (BIII). The largest therapeutic experience is with amphotericin B deoxycholate, which should be given at maximum tolerated doses (e.g., 1-1.5 mg/kg/d) and should be continued, despite modest increases in serum creatinine levels (BIII). Lipid formulations of amphotericin are indicated for the patient who has impaired renal function or who develops nephrotoxicity while receiving deoxycholate amphotericin (AII). Oral itraconazole is an alternative for patients who can take oral medication, are likely to be adherent, can be demonstrated (by serum level monitoring) to absorb the drug, and lack the potential for interaction with other drugs (BII). Oral itraconazole is attractive for continuing therapy in the patient who responds to initial iv therapy (CIII). Therapy should be prolonged beyond resolution of disease and reversible underlying predispositions (BIII). Adjunctive therapy (particularly surgery and combination chemotherapy, also immunotherapy), may be useful in certain situations (CIII). Aspergilloma. The optimal treatment strategy for aspergilloma is unknown. Therapy is predominantly directed at preventing life-threatening hemoptysis. Surgical removal of aspergilloma is definitive treatment, but because of significant morbidity and mortality it should be reserved for high-risk patients such as those with episodes of life-threatening hemoptysis, and considered for patients with underlying sarcoidosis, immunocompromised patients, and those with increasing Aspergillus-specific IgG titers (CIII). Surgical candidates would need to have adequate pulmonary function to undergo the operation. Bronchial artery embolization rarely produces a permanent success, but may be useful as a temporizing procedure in patients with life-threatening hemoptysis. Endobronchial and intracavitary instillation of antifungals or oral itraconazole may be useful for this condition. Since the majority of aspergillomas do not cause life-threatening hemoptysis, the morbidity and cost of treatment must be weighed against the clinical benefit. Allergic bronchopulmonary aspergillosis (APBA). Although no well-designed studies have been carried out, the available data support the use of corticosteroids for acute exacerbations of ABPA (AII). Neither the optimal corticosteroid dose nor the duration of therapy has been standardized, but limited data suggest the starting dose should be approximately 0.5 mg/kg/d of prednisone. The decision to taper corticosteroids should be made on an individual basis, depending on the clinical course (BIII). The available data suggest that clinical symptoms alone are inadequate to make such decisions, since significant lung damage may occur in asymptomatic patients. Increasing serum IgE levels, new or worsening infiltrate on chest radiograph, and worsening spirometry suggest that corticosteroids should be used (BII). Multiple asthmatic exacerbations in a patient with ABPA suggest that chronic corticosteroid therapy should be used (BIII). Itraconazole appears useful as a corticosteroid sparing agent (BII). (ABSTRACT TRUNCATED)

Antifungal Agents↗

Interleukin 10 suppresses phagocytic and antihyphal activities of human neutrophils.

We investigated the effects of human interleukin 10 (IL-10) on the antibacterial and antifungal activities of human neutrophils (PMNs) against Staphylococcus aureus and Candida albicans. Incubation of PMNs from healthy volunteers with 20-100 ng/ml of IL-10 at 37 degrees C for 1 h suppressed phagocytosis of serum-opsonized S. aureus (P=0.02) and blastoconidia of C. albicans (P<0.01). In contrast, 2-100 ng/ml of IL-10 had no effect on superoxide anion production upon stimulation with phorbol myristate acetate, N-formylmethionyl leucyl phenylalanine, C. albicans blastoconidia or pseudohyphae; neither did it significantly affect conidiocidal or bactericidal activities of PMNs. However, 20-100 ng/ml of IL-10 significantly decreased PMN-induced damage of C. albicans pseudohyphae (P=0.008). The suppression of phagocytic activity of PMNs against S. aureus and blastoconidia of C. albicans as well as the impairment of PMN-induced hyphal damage may have important implications for understanding the immunosuppressive profile of IL-10 in clinical usage.

Adult↗

Effects of intraseptal zolpidem and chlordiazepoxide on spatial working memory and high-affinity choline uptake in the hippocampus.

Injection of GABA(A)/benzodiazepine receptor ligands into the medial septum (MS) alters the activity of cholinergic neurons that innervate the hippocampus and can produce bidirectional modulation of spatial memory. Recent evidence suggests that two subtypes of the GABA(A) receptor are differentially localized to either GABAergic (alpha(1)/beta(2)/gamma(2)) or cholinergic (alpha(3)/beta(3)/gamma(2)) neurons within the MS. The present studies characterized the dose-related behavioral and neurochemical effects of intraseptal infusions of two benzodiazepine (BDZ) agonists that appear to exhibit different profiles of pharmacological specificity for these receptor subtypes. Male Sprague-Dawley rats were cannulated and then artificial CSF, chlordiazepoxide (CDP: 8 or 12 microg), or zolpidem (4, 8, or 12 microg) was injected into the MS. Spatial working memory was assessed in a delay radial-arm maze task and the activity of cholinergic neurons in the MS was evaluated by high-affinity choline uptake (HA-ChU) in the hippocampus. Intraseptal injection of either CDP or zolpidem produced dose-related impairments in spatial working memory and decreases in hippocampal HAChU. Both BDZ agonists were found to produce retrograde memory deficits and a decrease in HAChU following the highest dose tested (12 microg). However, intraseptal injection of 8 microg of zolpidem produced a behavioral deficit comparable to the high dose of CDP, but did not alter HAChU within the HPC. Although the cholinergic component of the septohippocampal pathway has been shown to be important in modulating hippocampal physiology and spatial memory processes, data from the present experiments suggest that the GABAergic component may also play an important role in the behavioral functions of the septohippocampal pathway.

Animals↗

Impaired acquisition of a Morris water maze task following selective destruction of cerebellar purkinje cells with OX7-saporin.

Spatial learning in the Morris water maze task is believed to be dependent on an intact hippocampal system. However, evidence from human studies and animal experiments suggests a potential cerebellar involvement in spatial processing, place learning, and other types of 'higher-order' cognition. In order to investigate this possibility, intraventricular injections (ICV) of the anti-neuronal immunotoxin OX7-saporin were used to selectively destroy cerebellar Purkinje cells, without affecting other brain areas believed to be critically involved in spatial learning and memory. Bilateral ICV injections of 2 microg OX7-saporin (4 microg total) in adult male rats produced substantial loss of Purkinje cells (56%) throughout the cerebellum without affecting hippocampal morphology or biochemical indices of cholinergic, serotonergic, or catecholaminergic function in the hippocampus, frontal cortex, or striatum. ICV OX7-saporin significantly impaired acquisition and performance of the standard Morris water maze task (though the impairment was less severe than reported in earlier studies that used alternate lesion methods or mutant mice species), but did not alter performance on the cued version of the task, or locomotor activity. In addition, lesioned animals spent significantly less time in the target quadrant on probe trial days 4 and 7 and the average distance to target scores (ADT) were significantly greater than controls on those days. Swim speed was not affected. Based on the specificity of the behavioral and neurobiological alterations, these data support the hypothesis that the cerebellum is involved in spatial processing and place learning.

Adult↗

Concepts in design of comparative clinical trials of antifungal therapy in neutropenic patients.

Fundamental to the successful implementation of antifungal compounds in neutropenic patients is the appropriate design of comparative clinical trials investigating their safety and efficacy. The key elements of comparative clinical trial design include issues of enrollment, stratification, randomization, blinding, administration of study drugs, monitoring of drug toxicity, definitions, and key statistical elements of end points, sample size, and tools for data analysis. The initial selection of compounds and the timing of initiation of antifungal therapy in comparative clinical trials are predicated to a large degree on the in vitro and in vivo activities, plasma pharmacokinetics, profiles of safety and toxicity of the study drugs. Phase I and II studies have a critical role in designing comparative clinical trials of antifungal therapy by providing data on safety, tolerance, and plasma pharmacokinetics of the investigational agent. As new antifungal agents are developed in response to the challenge of invasive fungal infections in immunocompromised patients with cancer, thoughtfully designed and carefully implemented clinical trials will be essential in determining the future utility of these promising compounds.

Antifungal Agents↗

Safety, toxicokinetics and tissue distribution of long-term intravenous liposomal amphotericin B (AmBisome): a 91-day study in rats.

PURPOSE: Amphotericin B in small, unilamellar liposomes (AmBisome) is safer and produces higher plasma concentrations than other formulations. Because liposomes may increase and prolong tissue exposures, the potential for drug accumulation or delayed toxicity after chronic AmBisome was investigated. METHODS: Rats (174/sex) received intravenous AmBisome (1, 4, or 12 mg/kg), dextrose, or empty liposomes for 91 days with a 30-day recovery. Safety (including clinical and microscopic pathology) and toxicokinetics in plasma and tissues were evaluated. RESULTS: Chemical and histopathologic changes demonstrated that the kidneys and liver were the target organs for chronic AmBisome toxicity. Nephrotoxicity was moderate (urean nitrogen [BUN] < or = 51 mg/dl; creatinine unchanged). Liposome-related changes (vacuolated macrophages and hypercholesterolemia) were also observed. Although plasma and tissue accumulation was nonlinear and progressive (clearance and volume decreased, half-life increased with dose and time), most toxic changes occurred early, stabilized by the end of dosing, and reversed during recovery. There were no delayed toxicities. Concentrations in liver and spleen greatly exceeded those in plasma: kidney and lung concentrations were similar to those in plasma. Elimination half-lives were 1-4 weeks in all tissues. CONCLUSIONS: Despite nonlinear accumulation, AmBisome revealed predictable hepatic and renal toxicities after 91 days, with no new or delayed effects after prolonged treatment at high doses that resulted in plasma levels >200 microg/ml and tissue levels >3000 microg/g.

Amphotericin B↗

D-cecropin B: proteolytic resistance, lethality for pathogenic fungi and binding properties.

L-Cecropin B (LCB) is a potent fungicidal peptide that is subject to proteolytic degradation by extracellular enzymes produced by Aspergillus flavus. We hypothesized that D-cecropin B (DCB), containing all D-amino acids, should resist proteolysis while retaining its fungicidal and target specificities. DCB was synthesized by solid phase methods using Fmoc chemistry. In vitro, at pH 6 x 0, DCB was lethal against the germinating conidia of A. flavus (LD90, 25 microM) and A. fumigatus (LD98, 25 microM) and for nongerminating and germinating conidia of Fusarium moniliforme (LD98, 1 x 25 microM) and F. oxysporum (LD95, 2 x 5 microM) at concentrations similar to those previously reported for LCB. It was lethal for Candida albicans with an LD98 at 12 x 5, microM. DCB was not active for the nongerminating conidia of A. fumigatus or A. flavus. Papain, trypsin, pepsin A and Staphylococcus aureus V8 protease degraded LCB but not DCB. Binding assays and circular dichroism showed DCB and LCB bound to cholesterol, ergosterol, beta-1,3-glucan, mannan and chitin. Data show that DCB retains the potent fungicidal properties of the L-form while being resistant to proteolytic enzymes that degrade the latter peptide. This study demonstrates that D-enantiomerization of cecropin B yields a novel fungicidal peptide, which resists proteolytic degradation and is lethal for pathogenic fungi.

Antifungal Agents↗