Treatment of Infections in Immunocompromised Children

Division Of Clinical Sciences - Nci

Investigators

Linked publications & trials

Abstract

We achieved significant advances in augmentation of innate host defense, molecular detection, and pharmacology of life-threatening infections. Immunopharmacological interactions between innate host defenses and antimicrobial agents are key components in developing new strategies for increasing host response against emerging or resistant pathogens. We characterized the interactions between phagocytic effector cells of the innate host defense and antifungal agents (polyenes, echinocandins, and triazoles) with and without immunomodulators (IFN-gamma, granulocyte colony-stimulating factor (CSF), and granulocyte macrophage-CSF) against several pathogens infecting oncology patients: Aspergillus fumigatus, Fusarium solani, Scedosporium spp., and key species of the Zygomycetes. Our studies demonstrate new immunopharmacological mechanisms for augmenting host response. For example, a combination of voriconazole and hyphae of Aspergillus fumigatus increases mRNA and protein expression of TLR2, TNF-alpha, and NF-kappaB. We extended our work in Th1/Th2 dysimmunoregulation of invasive candidiasis to the filamentous fungi (Aspergillus spp., Fusarium spp., Scedosporium spp., and Zygomycetes), focusing specifically on IL-15, IL-4, and TGF-beta. We also identified a new immunomodulatory mechanism of amphotericin B and its lipid formulations, which enhance host response by reversing Th2 immunophenotypic expression. Gene expression profiles of these compounds against Aspergillus hyphae demonstrate increased expression of the genes encoding TNF-alpha and IL-1-beta and a reciprocal down regulation of the gene encoding IL-10. Thus, the antifungal activity of polyenes is immunologically augmented by both a pro-inflammatory response and a reversal of Th2-mediated immunosuppression. Our understanding of host response helped us develop new approaches for assessing the expression profiles of genes encoding innate host defense molecules. We completed the first kinetic studies of the functional genomic response of innate host defenses of human monocytes to Candida albicans, Aspergillus fumigatus, Rhizopus oryzae, and Fusarium solani. To further understand the host factors contributing to infections in oncology and hematopoietic stem cell transplant (HSCT) patients, we completed several targeted population-based studies in collaboration with the CDC, Roswell Park Cancer Center, and Childrens Hospital of Philadelphia. A multicenter clinical trial will characterize the proteomic, genomic, and cytokine profile in patients with focal pneumonias to develop a better predictive model of this disease. Ongoing efforts to understand new antimicrobial agents include characterizing the pharmacokinetics, safety, and efficacy of novel combinations of triazoles, polyenes, echinocandins, and other agents in predictive models of pulmonary aspergillosis, subacute disseminated candidiasis, hematogenous candida meningoencephalitis, zygomycosis, scedosporiosis, and fusariosis. Our collaboration with the USDA has yielded new water-soluble molecules with potent antimicrobial activity. Through several studies, we demonstrated that certain combinations of compounds may be highly antagonistic against invasive pulmonary aspergillosis and probably should not be used in immunocompromised patients. We also detected significant interactions documenting synergy or antagonism and will use this data to guide clinical trial development. We continue our efforts to advance infectious disease supportive care in pediatric patients and improve the safety and pharmacokinetics of key systemic antifungal agents. Our studies provide a rational basis for selecting correct dosages that provide plasma levels comparable to those of adults and demonstrate that approximately 50% of all agents studied require dosage adjustments to optimize plasma concentration in our pediatric patients. Our studies are the basis for new adaptive pharmacotherapy strategies to improve outcome, particularly in profoundly immunocompromised pediatric patients where host response is abrogated and clearance of infection is primarily dependent upon the compound. We completed the first prospective adaptive pharmacotherapy protocol for voriconazole in complicated oncology and HSCT patients with invasive aspergillosis and other mycoses. This study will help us develop an adaptive model that incorporates age, gender, weight, CYP2C19 genotype, and concomitant medications, resulting in a tool that will have practical implications for accurate dosing in children and adults with cancer. We developed the first in vitro model of human alveolar aspergillosis. Galactomannan was used to measure the antifungal effect of macrophages and amphotericin B. We found that galactomannan levels are inextricably linked to Aspergillus invasion, and are a robust measure of the antifungal effect of macrophages and amphotericin B. This model provides a strategy for studying the relationships between pathogenesis, immunological effectors, and antifungal therapy for pulmonary aspergillosis. We have extended these studies to 4 species of Aspergillus: A. fumigatus, A. flavus, A. terreus, and A. niger. The results demonstrate significant species-dependent differences in response to macrophage immune reconstitution that also parallel their epidemiological distribution. Hematogenous Candida meningoencephalitis (HCME) is a devastating infectious complication of candidemia that is disproportionally represented in children with cancer and in infants and diagnosis and monitoring of HCME in patients is difficult. We developed the first diagnostic marker for HCME in children. This biomarker, 1,3-beta-D-glucan (beta glucan) is found in CSF and plasma in non-neutropenic animal models of HCME. We found that a CSF beta-glucan assay was more sensitive than CSF or blood cultures in diagnosing and detecting therapeutic response. We have translated these findings to patients and have found that CSF beta glucan is a useful biomarker for detecting and monitoring therapeutic response. To improve the design and implementation of qPCR for detecting invasive candidiasis, we examined the DNA kinetics of C. albicans, both in vitro and in vivo. These studies demonstrated that cell-free fungal DNA is released into the bloodstream of the host 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 developed the first qPCR system to detect the key organisms that cause pulmonary zygomycosis, an emerging infection in patients with cancer and HSCT. This led to the first circulating biomarker of mucormycosis in our models, which included Rhizopus, Mucor, and Cunninghamella spp. A multicenter clinical study will incorporate these new diagnostic assays, which rapidly detect invasive pulmonary aspergillosis and zygomycosis. We also developed the first in vitro blood-brain barrier model for studying antifungal agents in the central nervous system (CNS). This system accurately predicted the in vivo disposition of amphotericin B and flucaonzole into the CNS in both the intact and disrupted blood-brain barrier state and has the potential for wide use in understanding antimicrobials and immunomodulators. Finally, in 177 patients with severe aplastic anemia, we demonstrated that the infectious disease supportive care protocols developed by our Section over the past 2 decades has resulted in a significant improvement in survival [summary truncated at 7800 characters]