Activity of voriconazole, a new triazole, combined with neutrophils or monocytes against Candida albicans: effect of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor

Encapsulated Streptococcus suis impairs optimal neutrophil functions which are not rescued by priming with colony-stimulating factors

The porcine pathogen and zoonotic agent Streptococcus suis induces an exacerbated inflammation in the infected hosts that leads to sepsis, meningitis, and sudden death. Several virulence factors were described for S. suis of which the capsular polysaccharide (CPS) conceals it from the immune system, and the suilysin exhibits cytotoxic activity. Although neutrophils are recruited rapidly upon S. suis infection, their microbicidal functions appear to be poorly activated against the bacteria. However, during disease, the inflammatory environment could promote neutrophil activation as mediators such as the granulocyte colony-stimulating factor granulocyte (G-CSF) and the granulocyte-macrophages colony-stimulating factor (GM-CSF) prime neutrophils and enhance their responsiveness to bacterial detection. Thus, we hypothesized that CPS and suilysin prevent an efficient activation of neutrophils by S. suis, but that G-CSF and GM-CSF rescue neutrophil activation, leading to S. suis elimination. We evaluated the functions of porcine neutrophils in vitro in response to S. suis and investigated the role of the CPS and suilysin on cell activation using isogenic mutants of the bacteria. We also studied the influence of G-CSF and GM-CSF on neutrophil response to S. suis by priming the cells with recombinant proteins. Our study confirmed that CPS prevents S. suis-induced activation of most neutrophil functions but participates in the release of neutrophil-extracellular traps (NETs). Priming with G-CSF did not influence cell activation, but GM-CSF strongly promote IL-8 release, indicating its involvement in immunomodulation. However, priming did not enhance microbicidal functions. Studying the interaction between S. suis and neutrophils-first responders in host defense-remains fundamental to understand the immunopathogenesis of the infection and to develop therapeutical strategies related to neutrophils' defense against this bacterium.

A Review: Antimicrobial Therapy for Human Pythiosis

Human pythiosis is associated with poor prognosis with significant mortality caused by Pythium insidiosum. Antimicrobials’ in vitro and in vivo results against P. insidiosum are inconsistent. Although antimicrobials are clinically useful, they are not likely to achieve therapeutic success alone without surgery and immunotherapy. New therapeutic options are therefore needed. This non-exhaustive review discusses the rationale antimicrobial therapy, minimum inhibitory concentrations, and efficacy of antibacterial and antifungal agents against P. insidiosum. This review further provides insight into the immunomodulating effects of antimicrobials that can enhance the immune response to infections. Current data support using antimicrobial combination therapy for the pharmacotherapeutic management of human pythiosis. Also, the success or failure of antimicrobial treatment in human pythiosis might depend on the immunomodulatory effects of drugs. The repurposing of existing drugs is a safe strategy for anti-P. insidiosum drug discovery. To improve patient outcomes in pythiosis, we suggest further research and a deeper understanding of P. insidiosum virulence factors, host immune response, and host immune system modification by antimicrobials.

Longitudinal multimodal imaging-compatible mouse model of triazole-sensitive and -resistant invasive pulmonary aspergillosis

Invasive pulmonary aspergillosis (IPA) caused by the mold Aspergillus fumigatus is one of the most important life-threatening infections in immunocompromised patients. The alarming increase of isolates resistant to the first-line recommended antifungal therapy urges more insights into triazole-resistant A. fumigatus infections. In this study, we systematically optimized a longitudinal multimodal imaging-compatible neutropenic mouse model of IPA. Reproducible rates of pulmonary infection were achieved through immunosuppression (sustained neutropenia) with 150 mg/kg cyclophosphamide at day −4, −1 and 2, and an orotracheal inoculation route in both sexes. Furthermore, increased sensitivity of in vivo bioluminescence imaging for fungal burden detection, as early as the day after infection, was achieved by optimizing luciferin dosing and through engineering isogenic red-shifted bioluminescent A. fumigatus strains, one wild type and two triazole-resistant mutants. We successfully tested appropriate and inappropriate antifungal treatment scenarios in vivo with our optimized multimodal imaging strategy, according to the in vitro susceptibility of our luminescent fungal strains. Therefore, we provide novel essential mouse models with sensitive imaging tools for investigating IPA development and therapy in triazole-susceptible and triazole-resistant scenarios.

Summary: A novel reproducible longitudinal multimodal imaging-compatible neutropenic mouse model of invasive pulmonary aspergillosis provides increased early fungal detection through novel red-shifted luciferase-expressing triazole-susceptible and -resistant Aspergillus fumigatus strains, and boosted bioluminescence.

Antifungal Drugs Influence Neutrophil Effector Functions

There is a growing body of evidence for immunomodulatory side effects of antifungal agents on different immune cells, e.g., T cells. Therefore, the aim of our study was to clarify these interactions with regard to the effector functions of polymorphonuclear neutrophils (PMN). Human PMN were preincubated with fluconazole (FLC), voriconazole (VRC), posaconazole (POS), isavuconazole (ISA), caspofungin (CAS), micafungin (MFG), conventional amphotericin B (AMB), and liposomal amphotericin B (LAMB). PMN then were analyzed by flow cytometry for activation, degranulation, and phagocytosis and by dichlorofluorescein assay to detect reactive oxygen species (ROS). Additionally, interleukin-8 (IL-8) release was measured by enzyme-linked immunosorbent assay. POS led to enhanced activation, degranulation, and generation of ROS, whereas IL-8 release was reduced. In contrast, ISA-pretreated PMN showed decreased activation signaling, impaired degranulation, and lower generation of ROS. MFG caused enhanced expression of activation markers but impaired degranulation, phagocytosis, generation of ROS, and IL-8 release. CAS showed increased phagocytosis, whereas degranulation and generation of ROS were reduced. AMB led to activation of almost all effector functions besides impaired phagocytosis, whereas LAMB did not alter any effector functions. Independent from class, antifungal agents show variable influence on neutrophil effector functions in vitro Whether this is clinically relevant needs to be clarified.

Immunotherapy of Fungal Infections

Fungal organisms are ubiquitous in the environment. Pathogenic fungi, although relatively few in the whole gamut of microbial pathogens, are able to cause disease with varying degrees of severity in individuals with normal or impaired immunity. The disease state is an outcome of the fungal pathogen's interactions with the host immunity, and therefore, it stands to reason that deep/invasive fungal diseases be amenable to immunotherapy. Therefore, antifungal immunotherapy continues to be attractive as an adjunct to the currently available antifungal chemotherapy options for a number of reasons, including the fact that existing antifungal drugs, albeit largely effective, are not without limitations, and that morbidity and mortality associated with invasive mycoses are still unacceptably high. For several decades, intense basic research efforts have been directed at development of fungal immunotherapies. Nevertheless, this approach suffers from a severe bench-bedside disconnect owing to several reasons: the chemical and biological peculiarities of the fungal antigens, the complexities of host-pathogen interactions, an under-appreciation of the fungal disease landscape, the requirement of considerable financial investment to bring these therapies to clinical use, as well as practical problems associated with immunizations. In this general, non-exhaustive review, we summarize the features of ongoing research efforts directed towards devising safe and effective immunotherapeutic options for mycotic diseases, encompassing work on antifungal vaccines, adoptive cell transfers, cytokines, antimicrobial peptides (AMPs), monoclonal antibodies (mAbs), and other agents.

Enhanced generation of reactive oxygen species by interferon-γ may have contributed to successful treatment of invasive pulmonary aspergillosis in a patient with chronic granulomatous disease

Invasive pulmonary aspergillosis (IPA) is a life-threatening complication of chronic granulomatous disease (CGD), a rare inherited disorder of phagocytes that is characterized by a defect in the production of reactive oxygen species (ROS) caused by mutations in NADPH oxidase 2. Here, we report a case of successful treatment of IPA complicated with CGD by the administration of interferon-γ (IFN-γ) in combination with voriconazole. The patient carried a splice site mutation in the CYBB gene, and the neutrophils could produce a certain amount of ROS. In this case, augmentation of ROS generation in the patient's neutrophils was observed after in vivo IFN-γ treatment, which may be attributable to the induction of a normal CYBB gene in the myeloid progenitor cells. This treatment, in combination with voriconazole, may have contributed to the reversal of IPA in this patient. These results suggest that the in vivo use of IFN-γ may augment ROS generation in CGD neutrophils, thus leading to the successful treatment of severe IPA.

Innate and adaptive antifungal immune responses: partners on an equal footing

Adaptive immunity has long been regarded as the major player in protection against most fungal infections. Mounting evidence suggest however, that both innate and adaptive responses intricately collaborate to produce effective antifungal protection. Dendritic cells (DCs) play an important role in initiating and orchestrating antifungal immunity; neutrophils, macrophages and other phagocytes also participate in recognising and eliminating fungal pathogens. Adaptive immunity provides a wide range of effector and regulatory responses against fungal infections. Th1 responses protect against most forms of mycoses but they associate with significant inflammation and limited pathogen persistence. By contrast, Th2 responses enhance persistence of and tolerance to fungal infections thus permitting the generation of long-lasting immunological memory. Although the role of Th17 cytokines in fungal immunity is not fully understood, they can enhance proinflammatory or anti-inflammatory responses or play a regulatory role in fungal immunity all depending on the pathogen, site/phase of infection and host immunostatus. T regulatory cells balance the activities of various Th cell subsets thereby permitting inflammation and protection on the one hand and allowing for tolerance and memory on the other. Here, recent developments in fungal immunity research are reviewed as means of tracing the emergence of a refined paradigm where innate and adaptive responses are viewed in the same light.

Additive antifungal activity of anidulafungin and human neutrophils against Candida parapsilosis biofilms

OBJECTIVES

To investigate the activities of two newer triazoles and two echinocandins combined with human phagocytes against Candida parapsilosis biofilms.

METHODS

An in vitro model of C. parapsilosis biofilms was used. Biofilms were grown on silicone elastomer discs in 96-well plates at 37°C for 72 h. Biofilms or planktonic cells were incubated with voriconazole, posaconazole, caspofungin or anidulafungin, at clinically relevant concentrations, and human phagocytes (neutrophils or monocytes) alone or in combination with each of the antifungal agents for a further 22 h. Fungal damage induced by antifungal agents and/or phagocytes was determined by XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)2H-tetrazolium-5-carboxanilide] metabolic assay.

RESULTS

Each of the antifungal agents alone and in combination with human phagocytes induced less damage against C. parapsilosis biofilms compared with planktonic cells. No antagonistic interactions between antifungal agents and phagocytes were found. Furthermore, anidulafungin, but not caspofungin, and neutrophils exerted additive activity against C. parapsilosis biofilms.

CONCLUSIONS

Besides a lack of antagonistic interactions between newer antifungal agents and phagocytes, anidulafungin exerts additive immunopharmacological activity against C. parapsilosis biofilms.

Production of IL-6, in contrast to other cytokines and chemokines, in macrophage innate immune responses: effect of serum and fungal (Blastomyces) challenge

Murine peritoneal macrophages, after adherence and establishment in culture in vitro in the presence of medium containing fetal bovine serum (FBS) for 20 h, then cultured for 20 h, produced several cytokines. If, in the second 20 h period, a fungus (heat-killed Blastomyces, HK-Bd) was introduced, a more complex pattern of cytokine (particularly TNF) and chemokine production ensued. The cytokine production, assayed by antibody array and also quantitation in supernatants, was depressed (particularly TNF) by the addition of mouse serum to these cultures, with the exception of IL-6. Macrophages could be cultured in the presence or absence of serum during the initial 20 h adherence and establishment period, enabling study of the effect of serum factors. In the absence of serum, with or without fungal stimulation, cytokine and chemokine production was more restricted, largely to TNF and IL-6. The addition of mouse serum [corrected] resulted in marked depression of TNF and enhancement of IL-6. The combination of HK-Bd and mouse serum resulted in more IL-6 production than either component alone. The enhancement of IL-6 by mouse serum was concentration-dependent and maximal at 8 h. The effects of fungus or serum on macrophage production of cytokines were similar in an outbred and an inbred mouse strain. The larger repertoire of cytokine production in the macrophages that had been cultured longer (20 h+20 h) in serum may be related to maturation of cell receptors. IL-6 production in vivo in response to fungal-serum complexes could affect pathogenesis by opposing the host defense modulation by proinflammatory cytokines or by modulating the destructive effects of inflammation on host tissues.

The effects of fluconazole and cytokines on human mononuclear cells

Candida infections are common infections and fluconazole is one of the most frequently administered antifungal agents in their treatment. The resistance developed against antifungal agents has necessitated the improvement of new treatments. This study focuses on the investigation of the effect of fluconazole and cytokines such as interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF) on chemokine production and anticandidal activity of human monocytes. In the study it was observed that GM-CSF caused an increase in candidacidal activity of monocytes. Anticandidal activity of GM-CSF + IFN-gamma combination was not found to be more effective than GM-CSF or IFN-gamma alone. The presence of cytokine and fluconazole caused an increase in the levels of CCL3 and CCL4 chemokines. Accordingly, it was considered that chemokines could contribute to the efficacy of fluconazole in C. albicans infections. Besides, in order to strengthen the immune system some cytokines might be used in addition to antifungal agents for the treatment.

Antifungal effect of voriconazole on intracellular Candida glabrata, Candida krusei and Candida parapsilosis in human monocyte-derived macrophages

Infections caused by Candida species other than Candida albicans are increasingly common, and decreased susceptibility to azoles has made them more difficult to treat. Since phagocytic killing is important in elimination of Candida infections, intracellular killing of fluconazole-resistant Candida glabrata, Candida krusei and Candida parapsilosis (four strains each) by voriconazole was investigated in human monocyte-derived macrophages (MDMs). MDMs were infected with Candida, and voriconazole was then added. MDMs were lysed at 0, 24 or 48 h after infection, and viable Candida in the lysates enumerated. Compared to the starting inoculum, the number of viable intracellular C. parapsilosis and C. glabrata in untreated MDMs increased to 28,121 and 351 %, respectively, in 48 h. In contrast, the number of C. krusei decreased to 42 %. In MDMs treated with voriconazole, the decrease in viable count was dependent upon drug concentration. At 48 h, C. glabrata was killed only at 5x MIC (P < 0.05), C. krusei was killed at all voriconazole concentrations, while C. parapsilosis was inhibited at 0.5 and 1x MIC and killed at > or = 2.5x MIC (P < 0.05). The data show that intracellular growth and survival of these Candida species in the absence or presence of voriconazole vary markedly. The activity of voriconazole depends on the concentration of the drug and the time of exposure. For the 12 Candida strains studied, regression curves show that the maximum intracellular anticandidal activity of voriconazole was reached at 3.5-5x MIC.

Emerging azole antifungals

Systemic and superficial fungal infections have progressively emerged over the past few decades as an increasing cause of human disease, especially in the immunocompromised host. Control of fungal disease has proved difficult because few risk factors are potentially preventable; the population at highest risk for fungal disease, the immunocompromised patient, has been steadily increasing. There is a clear need for additional safe and effective therapeutic agents for the treatment of systemic fungal disease. A new generation of triazoles that includes voriconazole, posaconazole, ravuconazole and albaconazole has emerged and are presently in different phases of clinical investigation. These new triazoles have demonstrated a broad spectrum of activity, in particular against fungal pathogens previously resistant to previously available antifungals. This review highlights the emerging azole antifungals, both those available and in clinical development, and discusses their prospects for the future.

Immunotherapy for fungal infections

Opportunistic fungal infections are major causes of morbidity and mortality among immunocompromised individuals. Fungi have evolved complex and coordinated mechanisms to survive in the environment and in the mammalian host. Fungi must adapt to "stressors" in the host (including scarcity of nutrients, pH, and reactive oxygen and nitrogen intermediates) in addition to evading host immunity. Knowledge of the immunopathogenesis of fungal infections has paved the way to promising strategies for immunotherapy. These include strategies that increase phagocyte number, activate innate host defense pathways in phagocytes and dendritic cells, and stimulate antigen-specific immunity (e.g., vaccines). Immunotherapy must be tailored to specific immunocompromised states. Challenges exist in bringing promising immunotherapies from the laboratory to clinical trials.

Combination treatment of invasive fungal infections

The persistence of high morbidity and mortality from systemic fungal infections despite the availability of novel antifungals points to the need for effective treatment strategies. Treatment of invasive fungal infections is often hampered by drug toxicity, tolerability, and specificity issues, and added complications often arise due to the lack of diagnostic tests and to treatment complexities. Combination therapy has been suggested as a possible approach to improve treatment outcome. In this article, we undertake a historical review of studies of combination therapy and also focus on recent studies involving newly approved antifungal agents. The limitations surrounding antifungal combinations include nonuniform interpretation criteria, inability to predict the likelihood of clinical success, strain variability, and variations in pharmacodynamic/pharmacokinetic properties of antifungals used in combination. The issue of antagonism between polyenes and azoles is beginning to be addressed, but data regarding other drug combinations are not adequate for us to draw definite conclusions. However, recent data have identified potentially useful combinations. Standardization of assay methods and adoption of common interpretive criteria are essential to avoid discrepancies between different in vitro studies. Larger clinical trials are needed to assess whether combination therapy improves survival and treatment outcome in the most seriously debilitated patients afflicted with life-threatening fungal infections.

Modulation of proinflammatory responses to Pneumocystis carinii f. sp. muris in neonatal mice by granulocyte-macrophage colony-stimulating factor and IL-4: role of APCs

Clearance of Pneumocystis carinii f. sp. muris (PC) organisms from the lungs of neonatal mice is delayed due to failure of initiation of inflammation over the first 3 wk after infection. The ability of neonatal lung CD11c(+) dendritic cells (DCs) to induce Ag-specific T cell proliferative responses was significantly reduced compared with adult lung DCs. However, neonatal bone marrow-derived DCs were as competent at presenting PC Ag as were adult bone marrow-derived DCs. Because GM-CSF mRNA expression and activity were significantly reduced in neonatal lungs compared with adults, we treated neonates with exogenous GM-CSF and IL-4 and found enhanced clearance of PC compared with untreated neonates. This was associated with increased lung TNF-alpha, IL-12p35, and IL-18 mRNA expression, indicating enhanced innate immune responses. Cytokine-treated mice had marked expansion of CD11c(+) DCs with up-regulated MHC-II in the lungs. Moreover, increased numbers of activated CD4(+)CD44(high)CD62L(low) cells in the lungs and draining lymph nodes suggested improved Ag presentation by the APCs. Together these data indicate that neonatal lungs lack maturation factors for efficient cellular functioning, including APC maturation.

Antifungal activities of posaconazole and granulocyte-macrophage colony-stimulating factor ex vivo and in mice with disseminated infection due to Scedosporium prolificans

Invasive infection due to Scedosporium prolificans is characterized by drug resistance and a high rate of mortality. The effects of posaconazole (POS), an investigational antifungal triazole, murine granulocyte-macrophage colony-stimulating factor (GM-CSF), and their combination against S. prolificans were evaluated ex vivo and in a newly developed murine model of disseminated infection due to this organism. When POS was combined with polymorphonuclear leukocytes from untreated or GM-CSF-treated mice (P < 0.01) ex vivo, it had increased activity in terms of the percentage of hyphal damage. Immunocompetent BALB/c mice were infected with 4 x 10(4) conidia of S. prolificans via the lateral tail vein. At 24 h postinfection the mice were treated with GM-CSF (5 microg/kg of body weight/day subcutaneously), POS (50 mg/kg/day by gavage), both agents, or saline only. Half of the brain, lung, liver, and kidney from each animal were cultured; and the other half of each organ was processed for histopathology. The mean survival times were 7.0 +/- 0.3 days for the controls, 7.4 +/- 0.4 days for POS-treated mice, 8.0 +/- 0.3 days for GM-CSF-treated mice (P = 0.08 compared with the results for the controls), and 7.3 +/- 0.3 days for POS-GM-CSF-treated mice. Fungal burdens (determined as the numbers of CFU per gram of tissue) were found in descending orders of magnitude in the kidneys, brains, livers, and lungs. The burdens were significantly reduced in the brains of GM-CSF-treated mice (P < 0.05) and the livers of POS-treated mice (P < 0.05). The numbers of lesions in the organs closely corresponded to the fungal burdens. GM-CSF tended to prolong survival (P = 0.08 compared with the results for the controls). While the combination of POS and GM-CSF showed enhanced activity ex vivo, it did not increase the activities of the two agents against this highly refractory filamentous fungus in mice.

Combined action of micafungin, a new echinocandin, and human phagocytes for antifungal activity against Aspergillus fumigatus

Micafungin, a new echinocandin, inhibits fungal cell wall beta-glucan synthesis. We postulated micafungin and host phagocytic cells could act together in damaging fungi. Using the metabolic XTT assay, micafungin alone (0.01 and 0.10 microg/ml) inhibited Aspergillus fumigatus germlings by 48% and 61%, respectively. Polymorphonuclear neutrophils (PMNs) inhibited germlings by 53%. Micafungin at 0.01 or 0.10 microg/ml and PMNs resulted in additive inhibition, 82% and 99%, respectively. Monocyte-derived macrophage (MDM) monolayers inhibited germling growth by 66%; micafungin (0.01 or 0.10 microg/ml) alone inhibited by 32% and 42%, respectively. MDMs and micafungin (0.01 or 0.10 microg/ml) caused an additive inhibition of growth, 85% and 95%, respectively. Hyphae were generated by incubation of conidia for 24 h with or without micafungin. PMNs alone, added to hyphae, inhibited growth by 19% in the subsequent 20 h. Hyphae generated in the presence of micafungin (0.10 microg/ml) and subsequently cultured with micafungin for 24 h inhibited growth by 64%. PMNs plus micafungin resulted in 82% inhibition. Monocytes alone inhibited hyphal growth by only 5%. Hyphae produced in the presence of micafungin (0.01 microg/ml) and incubated again with micafungin for 24 h inhibited growth by 47%; combination with monocytes resulted in 62% inhibition. These data indicate that micafungin inhibits growth of tissue forms of A. fumigatus, and phagocytes and micafungin together have an additive effect. These findings support the thesis that the greater efficacy of micafungin in vivo compared with in vitro could be due to combined effect of phagocytic cells and micafungin.

Polyene and cytokine treatment of experimental aspergillosis

The aim of the present study was to assess the efficacy of amphotericin B (AMB), AMB-intralipid admixture (AMB-IL) or nystatin-IL formulation (Ny-IL) in combination with granulocyte colony stimulating factor (G-CSF) in treatment of experimental murine aspergillosis. ICR mice were immunosuppressed by cyclophosphamide and 3 days later inoculated intravenously (i.v.) with Aspergillus fumigatus. Treatment was initiated 2 h later and administered for 5 consecutive days (polyenes, i.v.; G-CSF, intraperitoneally). Combination therapy, particularly G-CSF with AMB or AMB-IL, significantly increased the survival rate (up to 87.3%) and prolonged the mean survival time (MST) (up to 28.8 days) in comparison to untreated controls (0% survival, MST 6.7 days) and to treatment with polyenes alone (up to 51.5% survival, MST 18.4 days). These data indicate that combination therapy could be beneficial for management of disseminated aspergillosis in humans.

Cytokines in immunodeficient patients with invasive fungal infections: an emerging therapy

Immune response is the major contributor to host defense against opportunistic fungal infections such as candidiasis, aspergillosis and other rare infections. A number of cytokines have been developed and studied in vitro for activity against fungal pathogens. The most studied among them in relation to fungal infections are granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) and interferon-gamma (IFN-gamma). The fields where these cytokines have been predominantly studied or where they may need more study are primary immunodeficiencies of the phagocytic cells, neonatal age, human immunodeficiency virus infection and cancer-related conditions such as neutropenia and hemopoietic cell transplantation. In this review, the in vitro, experimental animal and clinical data of cytokines are summarized in relation to invasive candidiasis, aspergillosis and emerging fungal infections. Cytokine administration to patients together with antifungal agents, as well as transfusion of cytokine-upgraded phagocytes, are promising immunotherapeutic modalities for further research.

Protection of peritoneal macrophages by granulocyte/macrophage colony-stimulating factor (GM-CSF) against dexamethasone suppression of killing of Aspergillus, and the effect of human GM-CSF

Murine peritoneal macrophages in vitro could kill Aspergillus fumigatus conidia, and this activity could be suppressed with dexamethasone. Treatment with granulocyte/macrophage colony-stimulating factor (GM-CSF) alone did not boost killing, but GM-CSF treatment concurrently with dexamethasone reversed the dexamethasone suppression. Both recombinant human and recombinant murine GM-CSF were equivalent in this activity, even though the human reagent reportedly does not stimulate differentiation of murine stem cells. Recombinant human GM-CSF could also reverse dexamethasone suppression of bronchoalveolar macrophage conidiacidal activity. Sequential studies with peritoneal macrophages indicated that recombinant human GM-CSF pretreatment also blocked dexamethasone suppression, but the GM-CSF treatment given after dexamethasone did not block the suppressive effect. Recombinant human GM-CSF did not boost spleen cell proliferation to a mitogenic stimulus, and did not reverse dexamethasone suppression of proliferation. These studies suggest GM-CSF treatment prior to and concurrent with steroid immunosuppression may ameliorate the steroid effect on tissue macrophage antifungal activity, but does not affect steroid suppression of T-cell immunity.

Effect of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor on polymorphonuclear neutrophils, monocytes or monocyte-derived macrophages combined with voriconazole against Cryptococcus neoformans

The antifungal activity of voriconazole (VCZ) was tested against Cryptococcus neoformans (Cn) with and without the addition of polymorphonuclear neutrophils (PMN), monocytes or monocyte-derived macrophages (MDM) in vitro. Human effector cells with and without the addition of VCZ were incubated with Cn for 24 h. PMN, mono and MDM alone resulted in 61%, 34% and 23% inhibition of Cn, respectively (n = 3, P<0.01). VCZ at 0.01 and 0.05 microg ml(-1) alone resulted in 48% inhibition and 19% killing (n = 6). The addition of VCZ at 0.01 and 0.05 microg ml(-1) to human effector cells enhanced killing of Cn by 51% and 71% for the PMN, 41% and 58% for the mono, and 14% and 34% for the MDM, respectively. The addition of either granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony stimulating factor (GM-CSF) significantly enhanced the ability of human effector cells to kill Cn. G-CSF and GM-CSF plus PMN resulted in 47% and 46% killing, respectively; GM-CSF plus monocytes or MDM resulted in 31% or 22% killing, respectively. G-CSF and GM-CSF further enhanced the collaborative killing effect of human effector cells and VCZ. At 0.01 and 0.05 microg ml(-1) of VCZ, G-CSF or GM-CSF enhanced PMN killing to 92% and 93% or 87% and 94%, respectively. GM-CSF enhanced both mono and MDM with VCZ at 0.01 and 0.05 microg ml(-1) in killing Cn to 62% and 86%, and 61% and 84%, respectively. These results suggest that VCZ would have good efficacy in the treatment of Cn infection in humans. Furthermore, VCZ would have enhanced efficacy in clinical settings where either G-CSF or GM-CSF was being used.

Granulocyte colony-stimulating factor and other cytokines in antifungal therapy

Invasive fungal infections (IFIs) have emerged as a serious threat in immunocompromised patients during the last two decades. Host defenses including appropriate cytokine responses and intact phagocytic function are necessary to combat IFIs. Several cytokines have been investigated and developed for preventive and therapeutic use. Among them, granulocyte colony-stimulating factor (G-CSF) has been mostly studied and used for various purposes, the most important being the faster recovery from neutropenia. Other cytokines with potential clinical significance in relation to IFI are granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma) and macrophage colony-stimulating factor. Supported by a large number of preclinical studies but limited clinical results their potential utility against IFI has been suggested. In this review, certain questions related to this issue are discussed based on data already available and an attempt to consider future research is made.

Protection of bronchoalveolar macrophages by granulocyte-macrophage colony-stimulating factor against dexamethasone suppression of fungicidal activity for Aspergillus fumigatus conidia

The objectives of this study were to: (i) see if granulocyte macrophage colony-stimulating factor (GM-CSF) could protect bronchoalveolar macrophages (BAM) against suppression by dexamethasone (DEX) and (ii) test the combined effect of GM-CSF and DEX on lymphocyte responses. Murine BAM killed Aspergillus fumigatus conidia by 33 +/- 4% (mean +/- SD) in a 2.5-h assay, unaffected by GM-CSF treatment. Killing by BAM treated with DEX (10(-7) M) for 48 h in vitro was reduced to 13 +/- 6%; however, if GM-CSF (500 U ml(-1)) was present during DEX treatment of BAM, killing of conidia (33 +/- 2%) by BAM was preserved. By contrast, DEX suppression of lymphocyte responses to concanavalin A was maintained during co-culture with GM-CSF. In sequence treatment experiments, initial treatment of BAM with GM-CSF protected against subsequent treatment with DEX. When macrophages were pretreated with DEX, GM-CSF could reverse suppression even when added subsequently, provided DEX treatment was discontinued. These data suggest that it may be possible to suppress lymphocyte responses with DEX, yet at the same time maintain BAM defenses with GM-CSF against pulmonary infections by conidia of A. fumigatus.

Immunotherapy in patients with systemic mycoses: a promising adjunct

Evidence from several in vitro and animal model studies suggests a modulatory role of haemopoietic, T(H)1 and T(H)2 cytokines in host defence against fungi, and highlights their potential utility as adjunctive therapy for management of systemic mycoses (SM). However, there are limited clinical data to support the use of cytokines in prevention and treatment of SM. Thus, at present no adjunctive treatment is justified for routine use in all patients. Potential application of these immunomodulatory agents include the use of granulocyte-macrophage colony-stimulating factor or macrophage colony-stimulating factor in the management of mycoses in neutropenic patients with myelogenous leukaemia or bone marrow transplantation. Interferon-gamma may have a useful role against aspergillosis in patients with chronic granulomatous disease. Granulocyte colony-stimulating factor-elicited white blood cell transfusions may be life saving to patients with refractory SM. Better understanding of synergy between cytokines and specific antifungals may provide powerful tools for managing these serious infections.

Isolation and in vitro susceptibility to amphotericin B, itraconazole and posaconazole of voriconazole-resistant laboratory isolates of Aspergillus fumigatus

OBJECTIVES

To select voriconazole-resistant mutants of Aspergillus fumigatus in the laboratory from drug-susceptible clinical isolates and examine their in vitro susceptibility to amphotericin B and investigational azoles, and to compare the intramycelial accumulation of voriconazole in the resistant isolates with that in the susceptible parent.

METHODS

Voriconazole-resistant Aspergillus fumigatus isolates were selected in the laboratory from three highly susceptible (MIC < or = 0.5 mg/L) clinical isolates by stepwise selection on peptone yeast extract glucose (PYG) agar containing 0.5 mg and 4 mg voriconazole/L. Twenty-three colonies that grew in the presence of 4 mg voriconazole/L on PYG agar (frequency 1.9 x 10(-8)) were tested for their in vitro susceptibility to amphotericin B, itraconazole, voriconazole and posaconazole by a broth macrodilution technique. The accumulation of voriconazole in the mycelia of two representative resistant isolates (VCZ-W42 and VCZ-W45) was determined by a previously described bioassay.

RESULTS

The geometric mean MICs (mg/L) of amphotericin B, itraconazole, voriconazole and posaconazole for these isolates were 0.45 +/- 0.19, 0.69 +/- 0.45, 5.24 +/- 3.74 and 0.27 +/- 0.18, respectively. A comparison of the geometric mean MICs of the antifungals obtained for the resistant isolates to those of the susceptible parents showed 1.15-, 2.76-, 16.90- and 1.42-fold increases, respectively, for amphotericin B, itraconazole, voriconazole and posaconazole, suggesting that low-level cross-resistance exists between the azole antifungals. The susceptible parent and the resistant isolates accumulated similar amounts of voriconazole.

CONCLUSIONS

These results suggest that spontaneous mutants of Aspergillus fumigatus resistant to voriconazole could emerge among clinical isolates under selection pressure and that the observed reduced in vitro susceptibility to voriconazole may not be due to reduced accumulation of the drug in the mycelia.

Antifungal pharmacodynamics: review of the literature and clinical applications

Invasive fungal infections are seen with growing frequency, likely due to increases in numbers of patients at risk of infection. Optimal selection and dosing of antifungal agents are important, as these infections are often refractory to available therapy. In contrast to antibacterials, studies examining the pharmacodynamic properties of antifungals and their application in treating invasive disease often are lacking. Agents administered for invasive infections are amphotericin B, flucytosine, and azole antifungals. Several drugs are under investigation, such as posiconazole, voriconazole, and the echinocandins, and preliminary pharmacodynamic data likely will help shape dosing regimens. Clinical trials that investigated dosage and administration, as well as the potential benefits of combination and sequential therapy, are addressed. In addition, antifungal susceptibility and animal models of infection are discussed.

Voriconazole: a new triazole antifungal

OBJECTIVE

To review the currently available information on the pharmacology, pharmacokinetics, efficacy, adverse effects, drug interactions, and dosage guidelines of voriconazole. Comparative data for voriconazole and other azole antifungal agents are described where available.

DATA SOURCES

A MEDLINE search restricted to English-language articles (1966 to September 1999) was conducted, and an extensive review of journals and meeting abstracts was performed. MeSH headings included itraconazole, fluconazole, voriconazole, UK-109,496, and amphotericin B.

DATA EXTRACTION

The data on pharmacokinetics, adverse effects, and drug interactions were obtained from open-label and controlled studies and case reports. Controlled studies and case reports were evaluated to demonstrate the efficacy of voriconazole in treatment of various fungal infections.

DATA SYNTHESIS

Voriconazole is a derivative of fluconazole that demonstrates enhanced in vitro activity against existent and emerging fungal pathogens. Limited data have revealed a favorable pharmacokinetic and safety profile for the agent. Moreover, select clinical trials and case studies of voriconazole suggest good in vivo efficacy against several fungal pathogens including Candida, Aspergillus, and Scedosporium.

CONCLUSIONS

Voriconazole has shown promise in the treatment of superficial and systemic mycoses. While several unresolved issues remain, voriconazole may be a viable therapeutic alternative for fluconazole-resistant mucocutaneous candidiasis and in cases of mild to moderate systemic mycoses requiring chronic treatment or that are refractory to currently available agents.

New drugs and novel targets for treatment of invasive fungal infections in patients with cancer

Invasive fungal infections have emerged as important causes of morbidity and mortality in profoundly immunocompromised patients with cancer. Current treatment strategies for these infections are limited by antifungal resistance, toxicity, drug interactions, and expense. In order to overcome these limitations, new antifungal compounds are being developed, which may improve our therapeutic armamentarium for prevention and treatment of invasive mycoses in high-risk patients with neoplastic diseases.

A new azole derivative of 1,4-benzothiazine increases the antifungal mechanisms of natural effector cells

The most widely used drug for treatment of candidiasis is fluconazole (FCZ). Recently, a new derivative of 1,4-benzothiazine, compound FS5, was developed. FS5 had an appreciable protective effect against murine candidiasis. The present study was designed to dissect the antifungal mechanisms triggered by FS5 and to establish whether this compound could enhance the antimicrobial abilities of natural effector cells. The results show that intraperitoneal injection of FS5 in mice (i) induced an increase in circulating neutrophil levels comparable to that observed in FCZ-treated mice; (ii) enhanced phagocytosis and the killing activities of macrophages (Mphis) isolated from the spleen or peritoneal cavity, with the latter effect correlating with induction of nitric oxide synthesis and production by Mphis; and (iii) increased the levels of expression and synthesis of tumor necrosis factor alpha. These results suggest that the compound-induced synthesis of antimicrobial and proinflammatory molecules by heterogeneous Mphi populations is part of the beneficial effect of FS5 exerted against murine candidiasis.

Novel strategies for treating candidiasis

In this review the recent achievements in the field of chemotherapy and immunotherapy of candidiasis are outlined. The current limitations of chemotherapeutic approaches and the lack of well defined preventive tools and strategies make it imperative to exploit the potential of novel immunotherapeutic venues. In this prospect the rather extensive work performed on cytokine patterns in experimental models and the upsurge of antibodies as one mechanism of anti-Candida protection raises great promise for the clinical use of immunotherapy possibly in conjunction with chemotherapy to improve the fight against this increasingly prevalent human opportunistic infection.