Human Neutrophil-Mediated Nonoxidative Antifungal Activity againstCryptococcus neoformans

Abstract

It has long been appreciated that polymorphonuclear leukocytes (PMN) kill Cryptococcus neoformans, at least in part via generation of fungicidal oxidants. The aim of this study was to examine the contribution of nonoxidative mechanisms to the inhibition and killing of C. neoformans. Treatment of human PMN with inhibitors and scavengers of respiratory burst oxidants only partially reversed anticryptococcal activity, suggesting that both oxidative and nonoxidative mechanisms were operative. To define the mediators of nonoxidative anticryptococcal activity, PMN were fractionated into cytoplasmic, primary (azurophil) granule, and secondary (specific) granule fractions. Incubation of C. neoformans with these fractions for 18 h resulted in percents inhibition of growth of 67.4 ؎ 3.4, 84.6 ؎ 4.4, and 29.2 ؎ 10.5 (mean ؎ standard error, n ‫؍‬ 3), respectively. Anticryptococcal activity of the cytoplasmic fraction was abrogated by zinc and depletion of calprotectin. Antifungal activity of the primary granules was significantly reduced by pronase treatment, boiling, high ionic strength, and magnesium but not calcium. Fractionation of the primary granules by reverse phase high-pressure liquid chromatography on a C 4 column over an acetonitrile gradient revealed multiple peaks with anticryptococcal activity. Of these, peaks 1 and 6 had substantial fungistatic and fungicidal activity. Peak 1 was identified by acid-urea polyacrylamide gel electrophoresis (PAGE) and mass spectroscopy as human neutrophil proteins (defensins) 1 to 3. Analysis of peak 6 by sodium dodecyl sulfate-PAGE revealed multiple bands. Thus, human PMN have nonoxidative anticryptococcal activity residing principally in their cytoplasmic and primary granule fractions. Calprotectin mediates the cytoplasmic activity, whereas multiple proteins, including defensins, are responsible for activity of the primary granules.

Characterization of IL-22 and antimicrobial peptide production in mice protected against pulmonary Cryptococcus neoformans infection

“…S100 proteins are calcium-binding cytosolic proteins that can be expressed by multiple cell types, including alveolar epithelial cells, endothelial cells, monocytes, macrophages, neutrophils and dendritic cells (DCs) (Ehrchen et al, 2009;Foell et al, 2007;Ramirez-Ortiz et al, 2011). Importantly, calprotectin may have direct antifungal and fungistatic activity against fungi, including C. neoformans (Mambula et al, 2000;McCormick et al, 2010;Urban et al, 2009). …”

Blockade of S100A8 and S100A9 Suppresses Neutrophil Migration in Response to Lipopolysaccharide

“…Together, these activities indicate a putative role in regulating leukocyte migration to inflammatory sites. S100A8/A9 is also known to inhibit microbial growth, presumably by chelating zinc (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) and to inhibit bacterial adhesion to mucosal epithelial cells (34). Thus, it is reasonable to propose a role in innate immune responses to bacterial infections for these molecules.…”

A retrospective study of antibiotic sensitivity pattern of uropathogens in the Federal Capital Territory, Nigeria

“…For instance, the protein beta defensin-1 (BD1) and Cathelicidin (LL-37) peptide shows constitutive expression in the urinary tract, as both molecules from previous studies have demonstrated to play key roles in UTI's mitigation (Mambula et al, 2000;Chromek et al, 2006). Also, in a study of uncomplicated UTI subject, elevated level of LL-37 was observed (Nielsen et al, 2014), whilst E. coli isolates from healthy controls exhibited more susceptibility to LL-37 than isolates from UTI patients.…”

“…Also, in a study of uncomplicated UTI subject, elevated level of LL-37 was observed (Nielsen et al, 2014), whilst E. coli isolates from healthy controls exhibited more susceptibility to LL-37 than isolates from UTI patients. Further, BD1 has also exhibited constitutive expression in the urinary tract and hence, BD1 is suggested to play a role in pyelonephritis (Smith et al, 2011;Mambula et al, 2000;Morrison et al, 2002) and act as a defence against Gram-positive uropathogens (Morrison et al, 2002). Moreover, studies on defensins (Mambula et al, 2000), contained in neutrophil granules, indicated antifungal activity.…”

“…Further, BD1 has also exhibited constitutive expression in the urinary tract and hence, BD1 is suggested to play a role in pyelonephritis (Smith et al, 2011;Mambula et al, 2000;Morrison et al, 2002) and act as a defence against Gram-positive uropathogens (Morrison et al, 2002). Moreover, studies on defensins (Mambula et al, 2000), contained in neutrophil granules, indicated antifungal activity. These peptides combined are potential molecules of the immune system that could provide clues for the biochemical processes that can be modified to overcoming the increasing level of superbugs in general and bacterial resistance to antibiotic in UTI management in particular.…”