lactoferrin and Aspergillosis

Invasive fungal infections are recognized as an important cause of morbidity and mortality in the immunocompromised host. Rapid initiation of adequate antifungal treatment is often hampered by the limitations of current diagnostic methods. This review encompasses the promises and limitations of newer tracers (believed to target the infectious agents), i.e., radiolabeled antimicrobial peptides, antifungals and chitin-specific agents, for fungal infection imaging by scintigraphy. In mice (99m)Tc-labeled peptides derived from human ubiquicidin (UBI29-41) and lactoferrin (hLF1-11) distinguished local Candida albicans and Aspergillus fumigatus infections from sterile inflammatory processes, but not from bacterial infections. Clinical trials showed that (99m)Tc-UBI29-41 can distinguish infections from inflammatory lesions with 80% specificity and 100% sensitivity. (99m)Tc-hLF1-11 was able to monitor the antifungal effects of fluconazole on C. albicans infections. Moreover, (99m)Tc-fluconazole proved to be an excellent tracer for C. albicans infections as it did not accumulate in bacterial infections and inflammatory processes. However this tracer poorly detected A. fumigatus infections. Furthermore, (123)I-chitinase and (99m)Tc-HYNIC-CBP21 accumulated in both C. albicans and A. fumigatus infections in mice at later time points. In conclusion, despite the recent advances in radiolabeled imaging techniques for invasive fungal infections, the search for better tracers for fungal infection imaging should be continued.

Topics: Animals; Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Candida albicans; Candidiasis; Chitin; Diagnosis, Differential; Fluconazole; Humans; Lactoferrin; Mice; Peptide Fragments; Radioactive Tracers; Radionuclide Imaging; Radiopharmaceuticals; Sensitivity and Specificity; Technetium

Chronic Granulomatous Disease (CGD) is a rare disorder caused by mutations in the NADPH oxidase. The CGD phenotype includes granuloma formation and susceptibility to infection with microorganisms including Aspergillus. The immune adjuvant interferon-gamma and the antifungal agent itraconazole have reduced the incidence of infections in CGD. Studies using CGD phagocytes have shown that reactive oxygen species (ROS), products of the NAPDH oxidase, are critical for killing Aspergillus hyphae. But despite lack of ROS production, CGD patients generally only get infected with Aspergillus after heavy exposure. To study why CGD patients are not infected with Aspergillus more frequently we studied host defense against this ubiquitous mold further. We found that neutrophil lactoferrin is fungistatic for Aspergillus fumigatus spores by chelation of iron, an essential growth factor. Thus, the neutrophil employs both nonoxidative (lactoferrin) and oxidative (hydrogen peroxide) defense mechanisms against A. fumigatus spores and hyphae, respectively.

Topics: Antifungal Agents; Aspergillosis; Aspergillus; Granulomatous Disease, Chronic; Humans; Iron Chelating Agents; Lactoferrin; Phagocytes; Reactive Oxygen Species

Recent advances in the research on host defense mechanisms against infections with Candida and Aspergillus were reviewed. Modes of the defense mechanisms were divided into three phases by thedifferent physiological circumstances surrounding the fungi: 1, the exocrine fluid in which fungi exist on the mucosal membranes; 2, the tissues invaded by fungi with the circulating blood; and 3, the limited lesions where fungi continue to be alive with a restricted blood flow. In each defense mechanism, theroles of the endogenous antifungal substances such as lactoferrin, defensins and calprotectin and leukocytes were discussed.

Topics: Aspergillosis; Candidiasis; Defensins; Humans; Lactoferrin; Leukocyte L1 Antigen Complex; Leukocytes; Membrane Glycoproteins; Neural Cell Adhesion Molecules; Proteins

To establish a novel strategy for the control of fungal infection, we examined the antifungal and neutrophil-activating activities of antimicrobial peptides. The duration of survival of 50% of mice injected with a lethal dose of Candida albicans (5 x 10(8) cells) or Aspergillus fumigatus (1 x 10(8) cells) was prolonged 3 to 5 days by the injection of 10 microg of peptide 2 (a lactoferrin peptide) and 10 microg of alpha-defensin 1 for five consecutive days and was prolonged 5 to 13 days by the injection of 0.1 microg of granulocyte-monocyte colony-stimulating factor (GM-CSF) and 0.5 microg of amphotericin B. When mice received a combined injection of peptide 2 (10 microg/day) with amphotericin B (0.5 microg/day) for 5 days after the lethal fungal inoculation, their survival was greatly prolonged and some mice continued to live for more than 5 weeks, although the effective doses of peptide 2 for 50 and 100% suppression of Candida or Aspergillus colony formation were about one-third and one-half those of amphotericin B, respectively. In vitro, peptide 2 as well as GM-CSF increased the Candida and Aspergillus killing activities of neutrophils, but peptides such as alpha-defensin 1, beta-defensin 2, and histatin 5 did not upregulate the killing activity. GM-CSF together with peptide 2 but not other peptides enhanced the production of superoxide (O2-) by neutrophils. The upregulation by peptide 2 was confirmed by the activation of the O2- -generating pathway, i.e., activation of large-molecule guanine binding protein, phosphatidyl-inositol 3-kinase, protein kinase C, and p47phox as well as p67phox. In conclusion, different from natural antimicrobial peptides, peptide 2 has a potent neutrophil-activating effect which could be advantageous for its clinical use in combination with antifungal drugs.

Topics: alpha-Defensins; Amphotericin B; Animals; Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Candida albicans; Candidiasis; Cells, Cultured; Female; Lactoferrin; Mice; Neutrophil Activation; Peptides; Signal Transduction

The aim of this study was to investigate whether technetium-99m labelled fluconazole can distinguish fungal from bacterial infections. Fluconazole was labelled with (99m)Tc and radiochemical analysis showed less than 5% impurities. The labelling solution was injected into animals with experimental infections. For comparison, we used two peptides for infection detection, i.e. UBI 29-41 and hLF 1-11, and human IgG, all labelled with (99m)Tc. Mice were infected with Candida albicans or injected with heat-killed C. albicans or lipopolysaccharides to induce sterile inflammation. Also, mice were infected with Staphylococcus aureus or Klebsiella pneumoniae. Next, accumulation of (99m)Tc-fluconazole and (99m)Tc-labelled peptides/IgG at affected sites was determined scintigraphically. (99m)Tc-fluconazole detected C. albicans infections (T/NT ratio=3.6+/-0.47) without visualising bacterial infections (T/NT ratio=1.3+/-0.04) or sterile inflammatory processes (heat-killed C. albicans: T/NT ratio=1.3+/-0.2; lipopolysaccharide: T/NT ratio=1.4+/-0.1). C. albicans infections were already seen within the first hour after injection of (99m)Tc-fluconazole (T/NT ratio=3.1+/-0.2). A good correlation (R(2)=0.864; P<0.05) between T/NT ratios for this tracer and the number of viable C. albicans was found. Although (99m)Tc-UBI 29-41 and (99m)Tc-hLF 1-11 were able to distinguish C. albicans infections from sterile inflammatory processes in mice, these (99m)Tc-labelled peptides did not distinguish these fungal infections from bacterial infections. It is concluded that (99m)Tc-fluconazole distinguishes infections with C. albicans from bacterial infections and sterile inflammations.

Topics: Animals; Aspergillosis; Aspergillus fumigatus; Candidiasis; Diagnosis, Differential; Fluconazole; Humans; Immunoglobulin G; Inflammation; Lactoferrin; Leukopenia; Lipopolysaccharides; Male; Mice; Myositis; Peptide Fragments; Radionuclide Imaging; Reproducibility of Results; Ribosomal Proteins; Sensitivity and Specificity; Technetium; Thigh; Tissue Distribution

Evidence suggests that neutrophils are important in host defenses against invasive aspergillosis and mucormycosis, although hyphae in these lesions are too large to be phagocytized. Interactions of neutrophils with hyphae of Aspergillus fumigatus and Rhizopus oryzae were studed in vitro. Light and electron microscopic observations indicated that neutrophils attached to and spread over the surfaces of hyphae, even in the absence of serum. This was followed by dramatic morphologic changes which suggested severe damage and probably death of hyphae. An assay of neutrophil-induced reduction of uptake of radioisotopes was used to quantitate damage to the fungi by neutrophils from normal subjects. Damage to hyphae was inhibited by a variety of compounds which are known to affect neutrophil surface functions, motility, and metabolism. Use of inhibitors of oxidative microbicidal mechanisms of neutrophils indicated the central importance of these mechanisms in damage to hyphae. Inhibitors of neutrophil cationic proteins altered damage only to Rhizopus. Damage to hyphae by lysozyme suggested that it may play a secondary role in the neutrophil, primarily against Aspergillus. This new nonphagocytic mechanism may play an important role in host defenses against these and other hyphal forms of fungi.

Topics: Aspergillosis; Aspergillus fumigatus; Humans; Lactoferrin; Mucormycosis; Muramidase; Neutrophils; Rhizopus