The Section has achieved significant advances in the areas of augmentation of host defense, molecular detection and pharmacology of these life-threatening infections. Augmentation of Host Defenses. Immunopharmacological interactions between innate host defenses and antimicrobial agents are a key component of developing new strategies for augmenting host response against emerging or resistant pathogens. We have extensively characterized the immunopharmacological interactions between phagocytic effector cells (pulmonary alveolar macrophages, monocytes, and neutrophils) of the innate host defense and antifungal agents (polyenes, echinocandins, and triazoles) with and without immunomodulators (IFN-g, GCSF, GMCSF) against several of the key pathogens infecting oncology patients: Aspergillus fumigatus, Fusarium solani, Scedosporium spp., and Zygomycetes. We have further extended our work in Th1/Th2 dysimmunoregulation of invasive candidiasis to the filamentous fungi (Aspergillus spp., Fusarium spp., Scedosporium spp., and Zygomycetes) with particular focus on IL-15, IL-4, and TGF-beta. Reversal of the Th2 immunophenotypic expression augments host response against these organisms. We have completed the first known kinetic studies of the functional genomic response of innate host defenses of human monocytes to Candida albicans, Aspergillus fumigatus, Rhizopus oryzae, and Fusarium solani. These studies will provide fundamental guidance to investigators worldwide in understanding the coordinated transcriptional responses of their selected genes of interest for further exploration. In order to further understand the host factors contributing to infections in pediatric and adult oncology and HSCT patients, we have completed a series of complementary targeted population-based studies in collaboration with the Centers for Disease Control, Roswell Park Cancer Center, and Childrens Hospital al of Philadelphia. Molecular Detection. Following an extensive series of correlative laboratory animal studies with iterative platforms for detection of galactomannan an (GM) antigenemia, as well as subsequent clinical evaluation, as EIA was recently approved in the US for detection of invasive aspergillosis. The laboratory animal findings correlated with and were predictive of the results of expression of GM antigenemia in oncology and HSCT patients with invasive aspergillosis. As little is known about the pathogenesis of invasive pulmonary aspergillosis, and its relationship between the kinetics of diagnostic markers and the outcome of antifungal therapy, we developed an in vitro model of the human alveolus, consisting of a bilayer of human alveolar epithelial and endothelial cells. An A. fumigatus strain expressing green fluorescent protein was used to study the invasion of the cell bilayer was studied using confocal and electron microscopy. The kinetics of culture, PCR and galactomannan were determined by a series of differential equations. Galactomannan was used to measure the antifungal effect of macrophages and amphotericin B. A mathematical model was developed and results bridged to humans. Galactomannan levels were found to be inextricably tied to Aspergillus invasion, and were a robust measure of the antifungal effect of macrophages and amphotericin B. Neither amphotericin nor macrophages alone was able to suppress growth of A. fumigatus; rather, the combination was required. This new model provides a strategy by which relationships between pathogenesis, immunological effectors and antifungal drug therapy for invasive pulmonary aspergillosis may be further understood. In order to improve the design and implementation of qPCR for the detection of deeply invasive candidiasis, we sought to develop a more comprehensive understanding of the kinetics of DNA from C. albicans in vitro and in vivo. These studies of the kinetics of DNA-release by C. albicans collectively demonstrated that cell-free fungal DNA is released into the bloodstream of hosts with disseminated candidiasis, that phagocytic cells may play an active role in increasing this release over time, and that plasma is a suitable fraction for detection of C. albicans DNA. Using the rRNA regions, we also have developed a qPCR system for the detection of the key organisms causing life-threatening pulmonary zygomycosis, an emerging infection in patients with cancer and HSCT. We are currently preparing a prospective study to bring the benefits of these molecular diagnostic assays to the detection of the causes of pneumonia in our patients with cancer and HSCT. Pharmacology. In exploring new molecules, our sustained collaboration with the USDA has yielded a series of novel water-soluble agriculturally derived plant molecules with potent antimicrobial activity. In studying CAY-1, we recently demonstrated synergism between CAY-1 and amphotericin B or itraconazole against Aspergillus species and Candida albicans. As part of our ongoing effort to understand the properties of newer antimicrobial agents for pediatric patients, we are characterizing the plasma pharmacokinetics, safety and efficacy of novel combinations of triazoles, polyenes, and echinocandins in predictive rabbit models of experimental pulmonary aspergillosis, subacute disseminated candidiasis, and hematogenous candida meningoencephalitis, as well as pulmonary zygomycosis, scedosporiosis, and fusariosis. These laboratory studies have provided a rational translational foundation for design and interpretation of interventional clinical trials in profoundly immunocompromised patients. We also have demonstrated through a series of in vitro and in vivo studies with mathematical modeling (e.g., Bliss surface modeling, and Loewe additivity models) that certain combinations of compounds may be highly antagonistic against experimental invasive pulmonary aspergillosis and probably should not be used in immunocompromised patients. In applying mathematical modeling of these data, we are able to detect significant interactions documenting synergy or antagonism as a guide to clinical trial development. As a continuity of our efforts to advance the understanding of the infectious diseases supportive care in pediatric oncology patients, we have systematically continued our studies of the safety and plasma pharmacokinetics of key systemic antifungal agents. These studies provide a rational basis for selection of correct dosages that provide plasma levels comparable to those of adults. These studies have demonstrated that approximately one-half of all agents studied required new dosage adjustments in order to optimize plasma-concentration time curves in our pediatric oncology patients. Optimal dosing becomes particularly critical in profoundly immunocompromised pediatric patients where host response is abrogated and clearance of infection dependent upon the principally upon compound. Resource to the Oncology/HSCT Community. The Section serves as an international resource (available on a 24/7 basis) in assisting in the care of pediatric and adult oncology patients with life-threatening infections. Publications: From 2006-7, the Section published 74 original papers, reviews, monographs, and chapters and 57 abstracts. These studies provide new approaches for more effective and safer management of severe infections in immunocompromised children
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