Efficacy of prophylactic aerosol amphotericin B lipid complex in a rat model of pulmonary aspergillosis

Inhaled Antifungal Agents for Treatment and Prophylaxis of Bronchopulmonary Invasive Mold Infections

Pulmonary mold infections are life-threatening diseases with high morbi-mortalities. Treatment is based on systemic antifungal agents belonging to the families of polyenes (amphotericin B) and triazoles. Despite this treatment, mortality remains high and the doses of systemic antifungals cannot be increased as they often lead to toxicity. The pulmonary aerosolization of antifungal agents can theoretically increase their concentration at the infectious site, which could improve their efficacy while limiting their systemic exposure and toxicity. However, clinical experience is poor and thus inhaled agent utilization remains unclear in term of indications, drugs, and devices. This comprehensive literature review aims to describe the pharmacokinetic behavior and the efficacy of inhaled antifungal drugs as prophylaxes and curative treatments both in animal models and humans.

Biodistribution and histopathology studies of amphotericin B sodium deoxycholate sulfate formulation following intratracheal instillation in rat models

Aerosol inhalation of amphotericin B (AmB) can be a clinically compliant way to administer the drug directly to the pulmonary route for treatment as well as prophylaxis of invasive pulmonary aspergillosis (IPA). We report aerosol formulation of AmB using sodium deoxycholate sulfate (SDCS), a lipid carrier synthesized in-house using natural precursor deoxycholic acid. In vitro toxicity was determined by MTT assay. Biodistribution and histopathology in rats were evaluated in targeted organs including the lungs, kidneys, spleen, and liver. No toxicity was observed when lung and kidney cells treated with AmB-SDCS formulations up to 8 μg/mL and minimal toxicity at higher concentration 16 μg/mL, while the Fungizone®-like formulation induced toxicity to lung and kidney cells with viability decreasing from 86 to 41% and 100 to 49%, respectively, when compared with an equivalent concentration of AmB-SDCS. Renal and hepatic markers were raised for Fungizone®-like formulation-treated rats but not for AmB-SDCS formulations following 7 days of regular dosing by intratracheal instillation. AmB concentrations were highest in the lungs (5.4-8.3 μg/g) which were well above minimum inhibitory concentration (MIC) of all Aspergillus species. Plasma concentration was also above MIC (> 2 μg/mL) for all AmB-SDCS formulations in comparison with Fungizone®-like formulation. No evidence of abnormal histopathology was observed in the lungs, liver, spleen, and kidneys for all AmB-SDCS formulations but was observed for the group treated with Fungizone®-like formulation. It is concluded that AmB-SDCS formulations can be efficiently administered via intratracheal instillation with no evidence of toxicity and may find great value in the treatment as well as prophylaxis of IPA through inhalation route.

Therapies and Vaccines Based on Nanoparticles for the Treatment of Systemic Fungal Infections

Treatment modalities for systemic mycoses are still limited. Currently, the main antifungal therapeutics include polyenes, azoles, and echinocandins. However, even in the setting of appropriate administration of antifungals, mortality rates remain unacceptably high. Moreover, antifungal therapy is expensive, treatment periods can range from weeks to years, and toxicity is also a serious concern. In recent years, the increased number of immunocompromised individuals has contributed to the high global incidence of systemic fungal infections. Given the high morbidity and mortality rates, the complexity of treatment strategies, drug toxicity, and the worldwide burden of disease, there is a need for new and efficient therapeutic means to combat invasive mycoses. One promising avenue that is actively being pursued is nanotechnology, to develop new antifungal therapies and efficient vaccines, since it allows for a targeted delivery of drugs and antigens, which can reduce toxicity and treatment costs. The goal of this review is to discuss studies using nanoparticles to develop new therapeutic options, including vaccination methods, to combat systemic mycoses caused by Candida sp., Cryptococcus sp., Paracoccidioides sp., Histoplasma sp., Coccidioides sp., and Aspergillus sp., in addition to providing important information on the use of different types of nanoparticles, nanocarriers and their corresponding mechanisms of action.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection: let the virus be its own demise

There has been a collaborative global effort to construct novel therapeutic and prophylactic approaches to SARS-CoV-2 management. Although vaccine development is crucial, acute management of newly infected patients, especially those with severe acute respiratory distress syndrome, is a priority. Herein we describe the rationale and potential of repurposing a dual plasmid, Vigil (pbi-shRNA^furin-GM-CSF), now in Phase III cancer trials, for the treatment of and, in certain circumstances, enhancement of the immune response to SARS-CoV-2.

Clinical Pharmacokinetics, Pharmacodynamics, Safety and Efficacy of Liposomal Amphotericin B

Since its introduction in the 1990s, liposomal amphotericin B (LAmB) continues to be an important agent for the treatment of invasive fungal diseases caused by a wide variety of yeasts and molds. This liposomal formulation was developed to improve the tolerability of intravenous amphotericin B, while optimizing its clinical efficacy. Since then, numerous clinical studies have been conducted, collecting a comprehensive body of evidence on its efficacy, safety, and tolerability in the preclinical and clinical setting. Nevertheless, insights into the pharmacokinetics and pharmacodynamics of LAmB continue to evolve and can be utilized to develop strategies that optimize efficacy while maintaining the compound's safety. In this article, we review the clinical pharmacokinetics, pharmacodynamics, safety, and efficacy of LAmB in a wide variety of patient populations and in different indications, and provide an assessment of areas with a need for further clinical research.

Animal Models of Aspergillosis

Aspergillosis is an airborne fungal disease caused by Aspergillus spp., a group of ubiquitous molds. This disease causes high morbidity and mortality in both humans and animals. The growing importance of this infection over recent decades has created a need for practical and reproducible models of aspergillosis. The use of laboratory animals provides a platform to understand fungal virulence and pathophysiology, assess diagnostic tools, and evaluate new antifungal drugs. In this review, we describe the fungus, various Aspergillus-related diseases in humans and animals and various experimental animal models. Overall, we highlight the advantages and limitations of the animal models, the experimental variables that can affect the course of the disease and the reproducibility of infection, and the critical need for standardization of the species, immunosuppressive drugs, route of infection, and diagnostic criteria to use.

Rodent Models of Invasive Aspergillosis due to Aspergillus fumigatus: Still a Long Path toward Standardization

Invasive aspergillosis has been studied in laboratory by the means of plethora of distinct animal models. They were developed to address pathophysiology, therapy, diagnosis, or miscellaneous other concerns associated. However, there are great discrepancies regarding all the experimental variables of animal models, and a thorough focus on them is needed. This systematic review completed a comprehensive bibliographic analysis specifically-based on the technical features of rodent models infected with Aspergillus fumigatus. Out the 800 articles reviewed, it was shown that mice remained the preferred model (85.8% of the referenced reports), above rats (10.8%), and guinea pigs (3.8%). Three quarters of the models involved immunocompromised status, mainly by steroids (44.4%) and/or alkylating drugs (42.9%), but only 27.7% were reported to receive antibiotic prophylaxis to prevent from bacterial infection. Injection of spores (30.0%) and inhalation/deposition into respiratory airways (66.9%) were the most used routes for experimental inoculation. Overall, more than 230 distinct A. fumigatus strains were used in models. Of all the published studies, 18.4% did not mention usage of any diagnostic tool, like histopathology or mycological culture, to control correct implementation of the disease and to measure outcome. In light of these findings, a consensus discussion should be engaged to establish a minimum standardization, although this may not be consistently suitable for addressing all the specific aspects of invasive aspergillosis.

Aerosolized amphotericin B as prophylaxis for invasive pulmonary aspergillosis: a meta-analysis

OBJECTIVES

Invasive pulmonary aspergillosis (IPA) is associated with high mortality in high-risk (immunosuppressed) patients. Many studies have investigated whether prophylactic inhalation of amphotericin B (AMB) reduces the incidence of IPA, but no definitive conclusions have been reached. The present meta-analysis was performed to evaluate the efficacy of prophylactic inhalation of AMB for the prevention of IPA.

METHODS

MEDLINE and other databases were searched for relevant articles published until December 2013. Randomized controlled trials that compared aerosolized AMB with placebo were included. Two reviewers independently assessed and extracted the data of all trials.

RESULTS

Six animal studies and two clinical trials involving 768 high-risk patients were eligible. The animal studies showed lower overall mortality rate among animals that underwent aerosolized AMB prophylaxis (odds ratio (OR) 0.13, 95% confidence interval (CI) 0.08-0.21). Similarly, the clinical trials showed a lower incidence of IPA among patients who underwent aerosolized AMB prophylaxis (OR 0.42, 95% CI 0.22-0.79).

CONCLUSIONS

This analysis provides evidence supporting the notion that the prophylactic use of aerosolized AMB effectively reduces the incidence of IPA among high-risk patients.

Development of a novel inhalational model of invasive pulmonary aspergillosis in rats and comparative evaluation of three biomarkers for its diagnosis

Aspergillus fumigatus, a thermotolerant fungus, is the main causative agent of invasive pulmonary aspergillosis (IPA) in immunocompromised patients that is associated with high mortality rates. Early diagnosis of IPA is crucial for mortality reduction and improved prognosis. An experimental inhalational model of IPA was developed in rats and the efficacy of three biomarkers, namely β-D-glucan (BDG), a panfungal marker, galactomannan (GM), a genus-specific marker, and A. fumigatus DNA, a species-specific marker was evaluated in serum and bronchoalveolar lavage (BAL) specimens at different time points postinfection for early diagnosis of IPA. BDG and GM were detected by using commercial Fungitell and Platelia Aspergillus EIA kits, respectively. A. fumigatus DNA was detected by developing a sensitive, single-step PCR assay. IPA was successfully developed in immunosuppressed rats and all animals until 5 days post-infection were positive for A. fumigatus by culture and KOH-calcofluor microscopy also showed A. fumigatus in 19 of 24 (79%) lung tissue samples. Fourteen of 30 (47%) and 27 of 30 (90%) serum and BAL specimens, respectively, were positive for all three biomarkers with 100% specificity (none of sera or BAL specimens of 12 control rats was positive for biomarkers). Our data show that BAL is a superior specimen than serum and combined detection of BDG, GM and A. fumigatus DNA provide a sensitive diagnosis of IPA in an experimental animal model. Moreover, combined detection of GM and DNA in BAL and detection of either GM or DNA in serum was also positive in 27 of 30 (90%) animals. For economic reasons and considering that the positive predictive value of BDG is low, the detection of GM and/or DNA in serum and BAL samples has the potential to serve as an integral component of the diagnostic-driven strategy in high-risk patients suspected for IPA.

Aerosolized amphotericin B lipid complex as adjunctive treatment for fungal lung infection in patients with cancer-related immunosuppression and recipients of hematopoietic stem cell transplantation

STUDY OBJECTIVE

Aerosolized amphotericin B lipid complex (aeABLC) has been successfully used to prevent fungal disease. Experience with aeABLC as treatment of fungal lung disease is limited.

DESIGN

We evaluated the safety and efficacy of aeABLC adjunct therapy for fungal lung disease in a retrospective study of 32 immunosuppressed adults. All values are given as ± standard deviation.

SETTING

National Cancer Institute-designated Comprehensive Cancer Center.

PATIENTS

Acute leukemia (69%) and severe neutropenia (63%) were common. Fifty-six percent of patients had undergone allogeneic hematopoietic stem cell transplantation 185 ± 424 days prior to aeABLC was commenced.

MEASUREMENT AND MAIN RESULTS

High-dose corticosteroids were administered during aeABLC in 28% of patients. Fungal lung disease was proven or probable in 41% of patients. Most patients (78%) received concurrent systemic antifungal therapy for a median of 14 ± 18 days before aeABLC. The median cumulative aeABLC dose was 1050 ± 2368 mg, and the median duration of aeABLC therapy was 28 ± 130 days. Most patients (78%) received 50 mg aeABLC twice daily. Partial or complete resolution of fungal lung disease was noted in 50% of patients. In three patients (9%) modest cough, mild bronchospasm, and transient chest pain with accompanying nausea and vomiting resolved completely after discontinuation of aeABLC. No patient required hospitalization for drug toxicity or had a serious (grade III or IV) drug-related adverse event.

CONCLUSION

Treatment with aeABLC was tolerated without serious toxicity and may be considered in the setting of severe immunosuppression, cancer, and/or hematopoietic stem cell transplantation in patients with difficult-to-treat fungal lung disease.

Amphotericin B lipid nanoemulsion aerosols for targeting peripheral respiratory airways via nebulization

Amphotericin B (AmB) lipid nanoemulsions were prepared and characterized and their suitability for pulmonary delivery via nebulization was evaluated. AmB nanoemulsions were prepared by sonicating and vortexing the drug with two commercially available lipid nanoemulsions: the Intralipid(®) or Clinoleic(®). Loading the nanoemulsions with the drug slightly increased the size of the lipid droplets and did not affect the zeta potential of the nanoemulsions. The loading efficiency of AmB was found to be 87.46±2.21% in the Intralipid(®) nanoemulsions and 80.7±0.70% in the Clinoleic(®) formulation. This respectively corresponded to 21.86 mg and 20.19 mg of AmB being successfully loaded in the nanoemulsions. On aerosolization using a Pari Sprint jet nebulizer, both nanoemulsions produced very high drug output which was approximately 90% for both formulations. Using the two-stage impinger, the Clinoleic(®) emulsion had higher fine particle fraction (FPF) than the Intralipid(®), since the Clinoleic(®) displayed higher deposition of AmB in the lower impinger stage (exceeding 80%), compared to 57% for the Intralipid(®). Overall, the ease of preparation of the AmB lipid nanoemulsions, along with their in vitro nebulization performance suggest that lipid nanoemulsions could be successful nanocarriers for delivery of AmB to the peripheral respiratory airways.

Antibacterial efficacy of inhaled squalamine in a rat model of chronic Pseudomonas aeruginosa pneumonia

OBJECTIVES

Squalamine is a steroid extracted from sharks with proven in vitro antibacterial activity. We assessed its efficacy in reducing the lung bacterial load and histological lesions when given via inhalation in a rat model of chronic Pseudomonas aeruginosa pneumonia.

METHODS

Sprague-Dawley rats were inoculated by tracheal intubation with 150 μL of a solution containing 10(8) cfu/mL of agar bead-embedded P. aeruginosa strain PAO1. MICs of squalamine and colistin for this strain were 2-8 and 0.5-1 mg/L, respectively. Starting the day after infection, the animals were treated twice daily with aerosolized squalamine (3 mg), colistin (160 mg) or 0.9% saline for 6 days. The bacterial load and lung histological lesions were evaluated on the seventh day.

RESULTS

Aerosols of squalamine and colistin resulted in a significant reduction in median (IQR) pulmonary bacterial count compared with saline [10(3) (6 × 10(2)-2 × 10(3)), 10(3) (9 × 10(2)-6 × 10(3)) and 10(5) (9 × 10(4)-2 × 10(5)) cfu/lung, respectively; P < 0.001 for both treated groups versus saline]. The lung weight and the lung histological severity score were significantly lower in both treated groups.

CONCLUSIONS

In a model of chronic P. aeruginosa pneumonia, treatment twice daily with a squalamine aerosol for 6 days leads to a significant reduction in the pulmonary bacterial count and pneumonia lesions with an efficacy comparable to that of colistin.

Use of nebulized amphotericin B in the treatment of allergic bronchopulmonary aspergillosis in cystic fibrosis

Background. Systemic steroids and adjunctive antifungal therapy are the cornerstone in treating allergic bronchopulmonary aspergillosis (ABPA) in the context of CF. Aim. Evaluate the use of inhaled amphotericin B (iAMB) as antifungal agent in this context. Methods. Report of 7 CF patients with recurrent or difficult to treat ABPA and failure to taper systemic corticosteroids treated with AMB deoxycholate (AMB-d) (Fungizone 25 mg 3× a week) or AMB lipid complex (ABLC) (Abelcet 50 mg twice weekly). Successful therapy was defined as steroid withdrawal without ABPA relapse within 12 months. Results. Therapy was successful in 6 of 7 patients treated with iAMB. In 5/6, lung function improved. The patient with treatment failure has concomitant MAC lung infection. Conclusion. Inhaled AMB may be an alternative to commonly used adjunctive antifungal therapy in the treatment of ABPA. More data are needed on safety and efficacy.

Efficacy of PTX3 in a rat model of invasive aspergillosis

Pentraxin 3 (PTX3) is an acute-phase glycoprotein with a nonredundant function in the host resistance to Aspergillus fumigatus. PTX3 activity was evaluated against pulmonary aspergillosis in rats immunosuppressed with cortisone acetate. PTX3 enhanced the survival rate and reduced the lung fungal burden of infected rats in both therapeutic and prophylactic modalities. Thus, we extended the protective activity of PTX3 in pulmonary aspergillosis to corticosteroid-induced immunodeficiency, which is a relevant clinical condition in graft-versus-host disease and in solid organ transplant.

Prophylactic Antifungal Agents Used After Lung Transplantation

Objective:

To review the data supporting available antifungal agents and compare regimens utilized to prevent fungal infection in lung transplant recipients.

Data Sources:

Literature retrieval was accessed through MEDLINE (1950 through October 2009) and United Network for Organ Sharing online database (available data through October 2009), using the terms lung transplantation, prophylaxis, and fungal infection. In addition, reference citations from publications identified were reviewed.

Study Selection And Data Extraction:

All articles or related abstracts in English identified from the data sources above were evaluated. Literature including adult lung transplant recipients who received systemic antifungal prophylaxis to prevent invasive fungal infections (IFIs) was included in the review.

Data Synthesis:

IFIs after lung transplantation remain a common postoperative problem and are associated with high mortality. The lung is the most vulnerable solid organ to be transplanted, as it is the main organ responsible for gas exchange and therefore the high risk for pulmonary-related IFIs. It is most susceptible to developing an IFI, as it serves as a medium for organisms traveling from air to human tissue, potentially causing life-threatening infections. Such infections typically involve Candida and Aspergillus spp. and tend to occur within the first 12 months after transplant. Although there has been an increase in lung transplants performed over the past decade, no standard antifungal prophylactic regimen exists. Literature describing antifungals used to prevent IFI after transplant is scarce, which may be due to a lack of consistency in regimens used between transplant centers. Several regimens have been described utilizing different antifungal agents as both monotherapy and combination therapy. The majority of the literature reviewed here describes aerosolized amphotericin B formulations and azole antifungals demonstrating an overall decreased risk of fungal infection after lung transplantation. It has become the standard of practice to initiate some form of antifungal prophylaxis in these patients.

Conclusions:

The risk of fungal infection after lung transplant is multifactorial and optimal prophylactic regimens should include agents with adequate activity against the most pathogenic fungi.

Nebulization of four commercially available amphotericin B formulations in persistently granulocytopenic rats with invasive pulmonary aspergillosis: evidence for long-term biological activity

The nebulization of amphotericin B desoxycholate (AMB-DOC), liposomal amphotericin B (L-AMB), amphotericin B lipid complex (ABLC) and amphotericin B colloidal dispersion (ABCD) has been investigated. Particle sizes of generated aerosol droplets were measured. Pulmonary amphotericin B deposition and amphotericin B concentration in blood directly after nebulization and at six weeks after nebulization was measured in healthy rats. The efficacy of nebulized amphotericin B formulations was evaluated in persistently granulocytopenic rats with invasive pulmonary aspergillosis. Treatment was given either after or before fungal inoculation. The endpoint was survival of animals. Aerosol particle sizes, expressed as the values for the mass median diameter were 1.38, 2.43, 0.90 and 2.29 μm for AMB-DOC, L-AMB, ABLC and ABCD, respectively. Amphotericin B concentrations in the lungs directly after nebulization exceeded the minimum inhibitory concentration of Aspergillus fumigatus and amphotericin B was still detected in lungs of rats at six weeks after nebulization. Treatment, started at 16 h after fungal inoculation, resulted in a significantly prolonged survival as compared with sham-treated rats for all four formulations. Prophylactic treatment at one week before fungal inoculation resulted in a significantly prolonged survival for all four formulations. Aerosol treatment given at two weeks before inoculation was effective only for AMB-DOC and L-AMB, whereas treatment given at six weeks resulted in a significantly prolonged survival for L-AMB only. All commercially available amphotericin B preparations could be nebulized efficiently and may be of value in the prophylactic treatment of invasive pulmonary aspergillosis.

A review on the clinical use of inhaled amphotericin B

BACKGROUND

Despite the systemic toxicity of amphotericin B (AMB), it still has a place in treatment or prophylactic regimes of fungal infections.

METHODS

A strategy for minimizing the potential of systemic side effects is to bring it in direct contact with the body site most likely to be infected, such as the administration of AMB as an aerosol. Nebulized amphotericin has been used in humans since 1959. However, due to a lack of sufficient data regarding efficacy, its use is still not established. Little is known about the optimal dose, frequency, duration of administration, and the pharmacokinetics of inhaled AMB in humans.

RESULTS AND CONCLUSIONS

In this review, published data regarding inhaled AMB are summarized, including available descriptions regarding preparation, dose, efficacy, and toxicity, and its place in therapy is discussed. The results from the studies that were reviewed in this article indicate that inhaled AMB may have a place in the prophylactic regimens of patients with prolonged neutropenia and in lung transplant recipients. Furthermore, nebulized (liposomal) AMB may have a place in the treatment of allergic bronchopulmonary aspergillosis (ABPA) in patients with corticosteroid-dependent ABPA.

Inhaled therapeutics for prevention and treatment of pneumonia

The lungs are the most common site of serious infection owing to their large surface area exposed to the external environment and minimum barrier defense. However, this architecture makes the lungs readily available for topical therapy. Therapeutic aerosols include those directed towards improving mucociliary clearance of pathogens, stimulation of innate resistance to microbial infection, cytokine stimulation of immune function and delivery of antibiotics. In our opinion inhaled antimicrobials are underused, especially in patients with difficult-to-treat lung infections. The use of inhaled antimicrobial therapy has become an important part of the treatment of airway infection with Pseudomonas aeruginosa in cystic fibrosis and the prevention of invasive fungal infection in patients undergoing heart and lung transplantation. Cytokine inhaled therapy has also been explored in the treatment of neoplastic and infectious disease. The choice of pulmonary drug delivery systems remains critical as air-jet and ultrasonic nebulizer may deliver sub-optimum drug concentration if not used properly. In future development of this field, we recommend an emphasis on the study of the use of aerosolized hypertonic saline solution to reduce pathogen burden in the airways of subjects infected with microbes of low virulence, stimulation of innate resistance to prevent pneumonia in immunocompromised subjects using cytokines or synthetic pathogen-associated molecular pattern analogues and more opportunities for the use of inhaled antimicrobials. These therapeutics are still in their infancy but show great promise.

Efficiency and safety of inhaled amphotericin B lipid complex (Abelcet) in the prophylaxis of invasive fungal infections following lung transplantation

BACKGROUND

Invasive fungal infections (IFIs) in patients undergoing lung transplantation (LT) are associated with significant mortality. Previous studies have shown the efficacy of aerosolized amphotericin B deoxycholate and oral fluconazole for antifungal prophylaxis. Evolving data show a potential advantage of prophylaxis with lipid-based formulations of amphotericin B in the prevention of IFIs. We reviewed the incidence of IFIs among patients receiving aerosolized amphotericin B lipid complex (ABLC) in LT.

METHODS

We undertook a retrospective review of the results of our antifungal protocol in a cohort of 60 LT patients. We analyzed the efficiency, safety, and tolerability of 50 mg of aerosolized ABLC administered postoperatively for IFI prophylaxis once every 2 days for 2 weeks and then once per week for at least 13 weeks. In addition, these transplanted patients received fluconazole (200 mg/d) during the first 21 days posttransplant. The prophylaxis-related efficiency and safety were quantified for IFIs and adverse events (AEs) for 6 months after study drug initiation.

RESULTS

Prophylaxis was efficient in 59 (98.3%) patients. Only one patient developed a possible IFI, due to Aspergillus fumigatus. Four patients presented nausea and vomiting as an AE, although aerosolized amphotericin B was ongoing.

CONCLUSIONS

Nebulized ABLC was effective, safe, and well tolerated for the prophylaxis of aspergillosis in lung transplant patients during the early posttransplant period.

Amphotericin B lipid preparations: what are the differences?

To reduce the in-vivo toxicity of the broad-spectrum antifungal drug amphotericin B, various lipid formulations of amphotericin B, ranging from lipid complexes to small unilamellar liposomes, have been developed and subsequently commercialized. These structurally diverse formulations differ in their serum pharmacokinetics as well as their tissue localisation, tissue retention and toxicity. These differences can affect the choice of formulation for a given infection, the time of initiation of treatment, and the dosing regimen. Although preclinical studies have shown similarities in the in-vitro and in-vivo antifungal activity of the formulations with comparable dosing, their acute and chronic toxicity profiles are not the same, and this has a significant impact on their therapeutic indices, especially in high-risk, immunosuppressed patients. With the recent introduction of new antifungal drugs to treat the increasing numbers of infected patients, the amphotericin B lipid formulations are now being studied to evaluate their potential in combination drug regimens. With proven efficacy demonstrated during the past decade, it is expected that amphotericin B lipid formulations will remain an important part of antifungal drug therapy.

Disease guided optimization of the respiratory delivery of microparticulate formulations

BACKGROUND

Inhalation of microparticulate dosage forms can be effectively used in the treatment of respiratory and systemic diseases.

OBJECTIVE

Disease states investigated for treatment by inhalation of microparticles were reviewed along with the drugs' pharmacological, pharmacokinetic and physical chemical properties to identify the advantages of microparticulate inhalation formulations and to identify areas for further improvement.

METHODS

Microbial infections of the lung, asthma, diabetes, lung transplantation and lung cancer were examined, with a focus on those systems intended to provide a sustained release.

CONCLUSION

In developing microparticulate formulations for inhalation in the lung, there is a need to understand the pharmacology of the drug as the key to revealing the optimal concentration time profile, the disease state, and the pharmacokinetic properties of the pure drug as determined by IV administration and inhalation. Finally, in vitro release studies will allow better identification of the best dosing strategy to be used in efficacy and safety studies.

Meta-analysis of nebulized amphotericin B to prevent or treat pulmonary aspergillosis in immunosuppressed animals

OBJECTIVES

Pulmonary aspergillosis in immunosuppressed patients is associated with significant mortality and morbidity. We assessed the prophylactic and therapeutic effect of nebulized amphotericin B (AmB) on mortality of immunosuppressed animals with pulmonary aspergillosis in this meta-analysis.

METHODS

Literature search was based on MEDLINE (1966 to January 15, 2007), EMBASE, and Cochrane-Controlled Trials Register (2006 issue 4) databases. Only randomized-controlled studies comparing nebulized AmB with placebo on immunosuppressed animals were included. Two reviewers reviewed and extracted the data independently.

RESULTS

Eight studies including 839 immunosuppressed animals were considered. The overall mortality of the immunosuppressed animals with pulmonary aspergillosis treated with nebulized AmB was reduced (69.4% versus 87.7%, odds ratio [OR] 0.12, 95% confidence interval [CI]: 0.08-0.19; P < 0.0001). The effect of nebulized AmB on mortality was more significant when the drug was administered as prophylaxis before the inoculation of Aspergillus fumigatus (OR 0.07, 95% CI: 0.03-0.12, P = 0.0001; I(2) = 0) than as a therapeutic agent (OR 0.20, 95% CI: 0.11-0.36, P < 0.0001; I(2) = 0) (ratio of the 2 ORs = 2.86, 95% CI: 1.03-6.11; P = 0.04). The effectiveness of AmB desoxycholate (OR 0.16, 0.06-0.38, P < 0.0001; I(2) = 0) and lipid-associated (liposomal, or lipid complex or colloidal dispersion) amphotericin (OR 0.11, 95% CI: 0.06-0.20, P < 0.0001; I(2) = 0) was not significantly different (ratio of the 2 ORs = 1.46, 95% CI: 0.49-4.39; P = 0.50). Three studies evaluated the potential side effects of nebulized amphotericin and showed that there was no significant renal toxicity but the amphotericin desoxycholate had some detrimental effects on pulmonary surfactant function.

CONCLUSIONS

The use of nebulized amphotericin, either as a prophylactic or therapeutic agent, is effective in reducing mortality of immunosuppressed animals with pulmonary aspergillosis. A large randomized controlled trial is needed to confirm whether combining nebulized amphotericin with systemic antifungal agents will reduce mortality in immunosuppressed patients with suspected or proven pulmonary aspergillosis.

Safety of aerosolized amphotericin B

Aerosolized delivery of a number of antimicrobial agents has been studied. Despite a theoretical soundness behind this strategy, full consideration of the potential toxicities associated with this mode of administration is imperative. Aerosolized amphotericin B, as both deoxycholate and lipid formulations, has been studied in a variety of high-risk patient populations for prophylaxis and treatment against fungal infections. Although available data remain inconclusive regarding the clinical efficacy of this therapy, variability among results may be due to lack of standardization of administration methods and doses. Akin to the lack of clinical consensus, data regarding the tolerability of this means of amphotericin B delivery are conflicting. This variability may again be accounted for by the lack of standardized means for aerosolized administration. Owing to uncertain clinical benefit and concern for pulmonary toxicities, the use of aerosolized amphotericin B should be limited to clinical investigations at this time.

Infections in solid organ transplant recipients

A disturbing trend in evolution for sometime has culminated in the fact that resistant Gram-positive bacteria including enterococci and staphylococci have emerged as the leading pathogens at many transplant centers. Recently published reports have highlighted the formidable challenge such antimicrobial-resistant microorganisms now pose in transplant recipients. Studies published within the past year have documented the clinical relevance of human herpesvirus-6 after transplantation, as well as the transmission of human herpesvirus-8 by transplanted allograft and the subsequent development of Kaposi's sarcoma in these patients. A novel hepatitis virus has been discovered; studies to elucidate its significance in the transplant setting are underway.

Advanced Techniques in the Diagnosis and Management of Infectious Pulmonary Diseases in Horses

Techniques for novel approaches to the diagnosis and management of equine pulmonary disease continue to be developed and used in clinical practice. Diagnostic techniques involving immunoassays and nucleic acid-based tests not only decrease the time in which results become available but increase the sensitivity and specificity of test results. These assays do not substitute for careful clinical evaluation but can shorten the time to a confirmed accurate diagnosis, and thus allow for early initiation of therapeutic strategies and prevention protocols. With further understanding of the molecular biology and immunology of equine pulmonary disease, diagnostic and management techniques should become further refined.

Design of aerosolized amphotericin b formulations for prophylaxis trials among lung transplant recipients

BACKGROUND

Emphasis has been placed on the need for antifungal prophylaxis when transplanted organs are directly exposed to the environment. In lung transplantation, one strategy for prevention has been aerosolization of polyenes into the lung. Despite widespread use of amphotericin B aerosols, there are still few studies on how to validate their effectiveness or optimize pharmacokinetics.

METHODS

We compared results of several of our own studies of lung transplant recipients receiving formulations of amphotericin B with results of other studies.

RESULTS

Recent aerosol studies suggest that aerosols of a lipid formulation of amphotericin B are safe and better tolerated than is amphotericin B deoxycholate. Their use in prophylaxis is associated with very few pulmonary fungal infections.

CONCLUSION

This safe drug delivery at a local body site to directly protect the transplanted organ without systemic antifungal drug exposure is attractive from a cost and toxicity standpoint. However, careful multicenter, comparative studies are still needed to ensure that this strategy is consistently successful.

The use of topical nonabsorbable gastrointestinal antifungal prophylaxis to prevent fungal infections in critically ill immunocompetent patients: A meta-analysis

OBJECTIVE

To investigate the preventive effect of topical nonabsorbable gastrointestinal antifungal prophylaxis on the incidence of fungal infection in critically ill immunocompetent patients.

DATA SOURCE

Randomized controlled studies involving critically ill pediatric and adult patients in different languages from the Cochrane Controlled Trial Register (2004, issue 1), EMBASE, and MEDLINE databases (1966 to 30 April 2004) were included. Studies evaluating absorbable antifungal prophylaxis were excluded. Two reviewers assessed the quality of the studies and performed data extraction independently.

DATA

Amphotericin B and nystatin were used as the nonabsorbable antifungal prophylaxis in the 15 studies included in this meta-analysis. Ten studies used a concomitant systemic antibiotic and four more studies used concomitant topical nonabsorbable antibiotics in the treatment group. Only one study compared topical nonabsorbable antifungal prophylaxis alone with placebo. The total incidence of fungal infections (relative risk [RR], 0.30; 95% confidence interval [CI], 0.18-0.48; p < .00001; extent of inconsistency [I(2)] = 0%) and proportion of patients with fungal infection (RR, 0.50; 95% CI, 0.28-0.87; p = .02; I(2) = 0%) were significantly reduced with topical nonabsorbable antifungal prophylaxis. The incidence of fungal urinary tract infection was significantly reduced (RR, 0.27; 95% CI, 0.10-0.74; p = .01; I(2)= 0%) but not fungal pneumonia (RR, 0.57; 95% CI, 0.28-1.16; p = .12; I(2)= 0%). Fungemia and catheter-related fungal sepsis were rare and not significantly reduced with nonabsorbable antifungal prophylaxis. The results remained unchanged in the sensitivity analyses after exclusion of studies with unclear study quality or exclusion of the contribution of fungal urinary tract infections to the total incidence of fungal infections.

CONCLUSIONS

In critically ill immunocompetent patients who are at high risk of fungal infection, topical nonabsorbable gastrointestinal antifungal prophylaxis was associated with a reduced incidence of urinary fungal infections and a trend toward reduction in respiratory fungal infections and fungemia. Limitations in study data are such that many of these infections may have represented superficial infections of uncertain clinical importance; a large, randomized, controlled trial is needed to assess the cost-effectiveness and safety of topical nonabsorbable antifungal prophylaxis in critically ill patients.

Efficacy of nebulized liposomal amphotericin B in treatment of experimental pulmonary aspergillosis

The efficacy of therapeutic aerosolized amphotericin B (AMB) was studied in a steroid-immunosuppressed murine model of invasive pulmonary aspergillosis. Nebulized liposomal AMB can be a valid approach to the treatment of this infection, with subjects showing significantly improved survival relative to that of subjects given intravenous deoxycholate AMB, as well as lower lung weights and pulmonary glucosamine levels.

Efficacy of Abelcet and caspofungin, alone or in combination, against CNS aspergillosis in a murine model

OBJECTIVES

Currently, few options exist to treat central nervous system (CNS) aspergillosis, which is usually fatal. We tested the efficacy of Abelcet and caspofungin, alone and in combination for treatment of this disease.

METHODS

Male CD-1 mice were immunosuppressed with 200 mg/kg cyclophosphamide 2 days prior to infection and every 5 days thereafter. In the first study, mice were infected intracerebrally with 2.1 x 10(6) conidia/mouse of Aspergillus fumigatus; 10 days of once daily therapy began one day later. Groups of 10 received 0.8, 4, or 8 mg/kg of Abelcet, intravenously (iv), or caspofungin, intraperitoneally, 0.8 mg/kg of conventional amphotericin B (AmB) iv, or no treatment. In a second study, mice were challenged with 6.4 x 10(6) conidia and given no treatment, 8 mg/kg of Abelcet or caspofungin, alone or in combination. On day 14, cfu were determined in survivors by plating of organ homogenates.

RESULTS

In the first study, mice given any regimen of Abelcet or caspofungin had a survival rate > or =80% whereas untreated had 90% mortality. All drug regimens prolonged survival (P < or = 0.0008) and reduced cfu (P < or = 0.0001-0.003) recovered from the brains and kidneys compared with untreated. Abelcet showed an apparent dose-related reduction of cfu in the brains. Abelcet at 4 or 8 mg/kg were equivalent to AmB in reducing cfu from both organs (P > 0.05); AmB was superior to 0.8 mg/kg of Abelcet in the brain only (P < 0.02). Abelcet at 8 mg/kg or AmB at 0.8 mg/kg were superior to all regimens of caspofungin in reducing cfu (P < or = 0.05-0.001). In the second study, Abelcet alone significantly prolonged survival and reduced cfu in the organs versus the controls. Caspofungin did not significantly prolong survival or reduce cfu in comparison with the controls. In combination, Abelcet and caspofungin were equivalent to Abelcet alone.

CONCLUSIONS

Abelcet proved to be efficacious, but not curative, in the treatment of CNS aspergillosis and was equivalent overall to conventional AmB. Caspofungin was not as effective against the larger inoculum, but did not enhance or interfere with the efficacy of Abelcet. Since Abelcet displayed dose-responsive efficacy, it is possible higher doses could produce superior results, yet not show toxicity.

Aspergillus infections in transplant recipients

Aspergillus infections are occurring with an increasing frequency in transplant recipients. Notable changes in the epidemiologic characteristics of this infection have occurred; these include a change in risk factors and later onset of infection. Management of invasive aspergillosis continues to be challenging, and the mortality rate, despite the use of newer antifungal agents, remains unacceptably high. Performing molecular studies to discern new targets for antifungal activity, identifying signaling pathways that may be amenable to immunologic interventions, assessing combination regimens of antifungal agents or combining antifungal agents with modulation of the host defense mechanisms, and devising diagnostic assays that can rapidly and reliably diagnose infections represent areas for future investigations that may lead to further improvement in outcomes.

New and emerging antifungal agents: impact on respiratory infections

Fungal pathogens are increasingly important causes of respiratory disease, yet the number of antifungal agents available for clinical use is limited. Use of amphotericin B deoxycholate is hampered by severe toxicity. Triazole agents currently available have significant drug interactions; fluconazole has a limited spectrum of activity and itraconazole was, until recently, available only in oral formulations with limited bioavailability. The development of resistance to all three agents is increasingly being recognized and some filamentous fungi are resistant to the action of all of these agents. In the past few years, new antifungal agents and new formulations of existing agents have become available.The use of liposomal amphotericin B preparations is associated with reduced, but still substantial, rates of nephrotoxicity and infusion-related reactions. An intravenous formulation of itraconazole has been introduced, and several new triazole agents have been developed, with the view of identifying agents that have enhanced potency, broader spectra of action and improved pharmacodynamic properties. One of these, voriconazole, has completed large-scale clinical trials. In addition, caspofungin, the first of a new class of agents, the echinocandins, which inhibit cell wall glucan synthesis, was approved for use in the US in 2001 as salvage therapy for invasive aspergillosis. It is hoped that the availability of these agents will have a significant impact on the morbidity and mortality of fungal respiratory infections. However, at the present time, our ability to assess their impact is limited by the problematic nature of conducting trials for antifungal therapy.

Comparative safety of amphotericin B lipid complex and amphotericin B deoxycholate as aerosolized antifungal prophylaxis in lung-transplant recipients

BACKGROUND

Aerosolized administrations of amphotericin B deoxycholate (AmBd) and amphotericin B lipid complex (ABLC) in lung transplant recipients were compared for safety and tolerability. The incidence of invasive fungal infections in patients receiving aerosolized amphotericin B formulations as sole prophylaxis was determined.

METHODS

A prospective, randomized (1:1), double-blinded trial was conducted with 100 subjects. AmBd and ABLC were administered postoperatively by nebulizer at doses of 25 mg and 50 mg, respectively, which were doubled in mechanically ventilated patients. The planned treatment was once every day for 4 days, then once per week for 7 weeks. Treatment-related adverse events and invasive fungal infections were quantitated for 2 months after study drug initiation.

RESULTS

Intent-to-treat analysis revealed study drug was discontinued for intolerance in 6 of 49 (12.2%) and 3 of 51 (5.9%) patients in the AmBd- and ABLC-treated groups, respectively (p=0.313). Subjects receiving AmBd were more likely to have experienced an adverse event (odds ratio 2.16, 95% confidence interval 1.10, 4.24, p=0.02). Primary prophylaxis failure within 2 months of study drug initiation was observed in 7 of 49 (14.3%) AmBd-treated patients and 6 of 51 (11.8%) ABLC-treated patients. No fungal pneumonias were observed. Only two (2%) patients experienced documented primary prophylaxis failure with Aspergillus infections within the follow-up period.

CONCLUSIONS

Both aerosol AmBd and ABLC appear to be associated with a low rate of invasive pulmonary fungal infection in the early posttransplant period. Patients receiving ABLC were less likely to experience a treatment-related adverse event.

Pathophysiology of pulmonary aspergillosis

A description of the pathophysiology of aspergillosis is followed by a review of investigational considerations of animal models. Because a large body of invasive Aspergillus infection occurs as opportunistic infection, there is a large spectrum of the histopathological feature of lesions demonstrated at the site of infection. Histopathology of the lesions can be understood as a phenotypical representation of interaction between lowered defense mechanisms in the host and the virulence of invading fungi. Detailed observations with a consideration of previous pathological knowledge of infection and inflammation provide much important information useful in predicting the pathophysiology of the patient. Moreover, experimental studies can also provide much insight to elucidate pathogenesis of the infection that emerges from the clinical and pathological investigations. The importance of pathophysiology should be emphasized to understand the implications of radiographic images, clinical symptoms, and laboratory dates. By reviewing these, especially computed tomography (CT) images, we can see that they accurately mirror the histological features of the lesion that can be recognized as a phenotypical representation of pathophysiology of Aspergillus infection. This is also confirmed by the reports emphasizing the importance of CT scans to identify hallmark clinical signs and symptoms of the disease.

Nebulized amphotericin B prophylaxis for Aspergillus infection in lung transplantation: study of risk factors

BACKGROUND

Aspergillus infection remains a major cause of morbidity and mortality after lung transplantation. Therefore, some strategies have been attempted, one of which is nebulized amphotericin B (nAB); however, the efficacy of this prophylaxis has not been shown clearly. The aim is to study whether nAB can protect against Aspergillus infection in lung transplant recipients.

PATIENTS AND METHODS

A study of risk factors was conducted in 55 consecutive lung allograft recipients. Twenty-three potential risk factors were analyzed. In 44 (80%) patients, nAB was indicated as prophylaxis. Multivariate analysis using logistic regression was performed.

RESULTS

Eighteen of the 55 patients (33%) developed infection due to Aspergillus spp. Multivariate analysis showed nAB to be a preventive factor (odds ratio: 0.13; 95% confidence interval [CI] 0.02-0.69; p < 0.05) and cytomegalovirus (CMV) disease was an independent risk factor for developing Aspergillus infection (odds ratio: 5.1; 95% CI 1.35-19.17; p < 0.05). Only 1 patient required withdrawal of the prophylaxis owing to bronchospasm. nAB was well-tolerated in the remaining patients with only a few, mild, easily controlled side effects.

CONCLUSIONS

The present results show that nAB prophylaxis may be efficient and safe in preventing Aspergillus infection in lung-transplanted patients, and CMV disease increases the probability of Aspergillus infection.

Safety of aerosolized amphotericin B lipid complex in lung transplant recipients

BACKGROUND

Fungal infections remain an important cause of morbidity and mortality in lung transplant recipients. Aerosolized amphotericin B lipid complex (ABLC) may be more efficacious than conventional amphotericin B in the prevention of fungal infections in animal models, but experience with aerosolized ABLC in humans is lacking.

METHODS

We conducted a prospective, noncomparative study designed to evaluate safety of aerosolized ABLC in lung or heart-lung transplant recipients.

RESULTS

A total of 381 treatments were administered to 51 patients. Complete spirometry records were available for 335 treatments (69 in intubated patients, 266 in extubated patients). ABLC was subjectively well tolerated in 98% of patients. Pulmonary mechanics worsened by 20% or more posttreatment in less than 5% of all treatments. There were no significant adverse events related to study medication in any patient, and 1-year survival for all enrolled patients was 78%.

CONCLUSION

Administration of nebulized ABLC is safe in the short-term and well-tolerated in lung transplant recipients. Additional prospective, randomized studies are needed to determine the efficacy of aerosolized ABLC alone or in conjunction with systemic therapies in the prevention of fungal infections in lung transplant recipients.

Efficacy of liposomal amphotericin B with prolonged circulation in blood in treatment of severe pulmonary aspergillosis in leukopenic rats

The therapeutic efficacy of long-circulating polyethylene glycol-coated liposomal amphotericin B (AMB) (PEG-AMB-LIP) was compared with that of AMB desoxycholate (Fungizone) in a model of severe invasive pulmonary aspergillosis in persistently leukopenic rats as well as in temporarily leukopenic rats. PEG-AMB-LIP treatment (intravenous administration) consisted of a single, or double (every 72 h), or triple (every 72 h) dose of 10 mg of AMB/kg of body weight, a double dose (every 72 h) of 14 mg of AMB/kg, or a 5-day treatment (every 24 h) with 6 mg/kg/dose. AMB desoxycholate was administered for 10 consecutive days at 1 mg of AMB/kg/dose. Treatment was started 30 h after fungal inoculation, at which time mycelial growth was firmly established. Both persistently and temporarily leukopenic rats died between 4 and 9 days after Aspergillus fumigatus inoculation when they were left untreated or after treatment with a placebo. In persistently leukopenic rats, a single dose of PEG-AMB-LIP (10 mg/kg) was as effective as the 10-day treatment with AMB desoxycholate (at 1 mg/kg/dose) in significantly prolonging the survival of rats infected with A. fumigatus and in reducing the dissemination of A. fumigatus to the liver. Prolongation of PEG-AMB-LIP treatment (double or triple dose or 5-day treatment) did not further improve efficacy. For temporarily leukopenic rats no major advances in efficacy were achieved compared to those for persistently leukopenic rats, probably because the leukocyte numbers in blood were restored too late in the course of infection.

Antifungal prophylaxis in neutropenia

Despite the widespread prophylactic use of antifungal agents in neutropenic patients, invasive fungal infections continue to emerge as major causes of morbidity and mortality. With the exception of fluconazole prophylaxis in allogeneic marrow transplant recipients, no firm conclusions can be drawn due to the lack of reliable, randomized trials. At the present time, it seems that antifungal chemoprophylaxis is more a matter of faith rather than science. Earlier diagnosis based on noninvasive diagnostic techniques and pre-emptive strategies may offer more promise than a liberal prophylactic approach.

Emerging Issues in Nosocomial Fungal Infections

Nosocomial fungal infections remain a serious cause of morbidity and mortality. As immunodeficient populations increase, the incidence of nosocomial fungal infections continues to rise. Although a wide variety of new and emerging fungi can cause nosocomial infections, Candida species remain the major etiologic agent. Candida species vary in their epidemiology and therapy. New diagnostic, epidemiologic, and therapeutic tools have been developed and are discussed in this review. They include the use of polymerase chain reaction-based diagnostic methods, recent advances in antifungal susceptibility testing, and comparative therapeutic and prophylactic trials. As advances in prevention, diagnosis, and therapy continue, nosocomial fungal infections and the morbidity and mortality associated with them can be reduced.

Efficacy of NND-502, a novel imidazole antimycotic agent, in experimental models of Candida albicans and Aspergillus fumigatus infections

In vitro and in vivo anti-Candida albicans and anti-Aspergillus fumigatus activities of NND-502, a new imidazole-antimycotic, were compared with those of fluconazole (FCZ), itraconazole (ITZ) and/or amphotericin B (AmB). NND-502 exhibited strong in vitro antifungal activity against both fungal species; its MIC against C. albicans was 1-4 times lower than that of FCZ, and its MIC against A. fumigatus was at least 60-2000 times lower than that of ITZ and AmB. In vivo antifungal treatments with each drug were initiated 1 h after inoculation in the experimental models, so that antifungal potential reflected prophylactic activity rather than therapeutic activity. The oral regimen of NND-502 in a murine model of systemic C. albicans infection was much less effective than that of FCZ. In vivo anti-A. fumigatus activity of oral NND-502 in a murine model of systemic infection was apparently superior to that of FCZ and ITZ in terms of prolonging survival. In addition to the murine model of systemic aspergillosis, intravenous NND-502 was shown to be highly effective in a rat model of pulmonary aspergillosis compared with intravenous AmB; 90% of animals survived at a dose of 2.5 mg/kg per day of NND-502 while only 30% of animals escaped death when 5 mg/kg per day of AmB was used. This potent efficacy of NND-502 was also confirmed in a sublethal challenge study in which the administration of the agent at a dose as low as 1.25 mg/kg per day resulted in the significant reduction of organisms in the lung; no comparable effect of AmB was found.