Complement activation is needed to restore tissue injury; however, inappropriate activation of complement, as seen in chronic wounds can cause cell death and enhance inflammation, thus contributing... Show moreComplement activation is needed to restore tissue injury; however, inappropriate activation of complement, as seen in chronic wounds can cause cell death and enhance inflammation, thus contributing to further injury and impaired wound healing. Therefore, attenuation of complement activation by specific inhibitors is considered as an innovative wound care strategy. Currently, the effects of several complement inhibitors, for example, the C3 inhibitor compstatin and several C1 and C5 inhibitors, are under investigation in patients with complement-mediated diseases. Although (pre)clinical research into the effects of these complement inhibitors on wound healing is limited, available data indicate that reduction of complement activation can improve wound healing. Moreover, medicine may take advantage of safe and effective agents that are produced by various microorganisms, symbionts, for example, medicinal maggots, and plants to attenuate complement activation. To conclude, for the development of new wound care strategies, (pre)clinical studies into the roles of complement and the effects of application of complement inhibitors in wound healing are required. Show less
The hLF1-11 peptide comprising the first 11 N-terminal residues of human lactoferrin exerts antimicrobial activity in vivo, enhances the inflammatory response of monocytes and directs monocyte... Show moreThe hLF1-11 peptide comprising the first 11 N-terminal residues of human lactoferrin exerts antimicrobial activity in vivo, enhances the inflammatory response of monocytes and directs monocyte-macrophage differentiation toward cells with enhanced antimicrobial properties. In this study, we investigated the effects of hLF1-11 on human monocyte-dendritic cell (DC) differentiation and subsequent T cell activation. Results revealed that - compared to control (peptide-incubated) DCs - hLF1-11-differentiated DCs displayed enhanced expression of HLA class II antigens and dectin-1, and increased phagocytosis of Candida albicans. In addition, hLF1-11-differentiated DCs produced enhanced amounts of reactive oxygen species, IL-6 and IL-10, but not IL-12p40 and TNF-α, upon stimulation with C. albicans. Moreover, 6-day-cultured hLF1-11-differentiated DCs and control (peptide-incubated) DCs that had been stimulated with a Th17-inducing mix of antigens (including C. albicans) for 24 h were cocultured with autologous CD4+ T cells for 72 h and then the levels of IL-10, IL-17 and IFN-γ production and the percentage of cytokine-producing T cells were assessed. The results revealed that the hLF1-11-differentiated DCs induced an enhanced IL-17, but reduced IFN-γ, production by T cells as compared to control (peptide-incubated) DCs. Collectively, the hLF1-11 peptide drives monocyte-DC differentiation toward DCs that promote antifungal responses and enhance Th17 polarization. Show less
In this paper, we describe the crystal structure of previously reported ring-extended gramicidin S (GS) derivative 2 (GS14K4), containing a D-amino acid residue in one of the beta-strand regions.... Show moreIn this paper, we describe the crystal structure of previously reported ring-extended gramicidin S (GS) derivative 2 (GS14K4), containing a D-amino acid residue in one of the beta-strand regions. This structure is in agreement with a previously reported modeling study of the same molecule. The polar side chain of the additional D-amino acid residue is positioned at the same face of the molecule as the hydrophobic side chains, and we believe that because of this compound 2 is considerably less hydrophobic than extended GS derivatives in which the strand regions are exclusively composed of L-amino acids. Using this backbone structure as our benchmark we prepared a small series of ring-extended GS analogues featuring sugar amino acid dipeptide isosteres of varied hydrophobicity at the turn region. We show that via this approach hydrophobicity of extended GS analogues can be tuned without affecting the secondary structure (as observed from NMR and CD spectra). Biological evaluation reveals that hydrophobicity correlates to cell toxicity, but still bacteriolysis is induced with GS analogues that are too hydrophilic to efficiently lyse human red blood cells. (C) 2011 Elsevier Ltd. All rights reserved. Show less
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... Show moreInvasive 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-specifi c agents, for fungal infection imaging by scintigraphy. In mice Tc-99m-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 Tc-99m-UBI29-41 can distinguish infections from inflammatory lesions with 80% specificity and 100% sensitivity. Tc-99m-hLF1-11 was able to monitor the antifungal effects of fluconazole on C. albicans infections. Moreover, Tc-99m-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 Tc-99m-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. Show less
Kapoerchan, V.V.; Knijnenburg, A.D.; Niamat, M.; Spalburg, E.; Neeling, A.J. de; Nibbering, P.H.; ... ; Overhand, M. 2010
The cyclic cationic antimicrobial peptide gramicidin S (GS) is an effective topical antibacterial agent that is toxic for human red blood cells (hemolysis). Herein, we present a series of... Show moreThe cyclic cationic antimicrobial peptide gramicidin S (GS) is an effective topical antibacterial agent that is toxic for human red blood cells (hemolysis). Herein, we present a series of amphiphilic derivatives of GS with either two or four positive charges and characteristics ranging between very polar and very hydrophobic. Screening of this series of peptide derivatives identified a compound that combines effective antibacterial activity with virtually no toxicity within the same concentration range. This peptide acts against both Gram-negative and Gram-positive bacteria, including several MRSA strains, and represents an interesting lead for the development of a broadly applicable antibiotic. Show less
The human cathelicidin LL-37 has broad-spectrum antimicrobial activity. It also participates at the interface of innate and adaptive immunity by chemoattracting immune effector cells, modulating... Show moreThe human cathelicidin LL-37 has broad-spectrum antimicrobial activity. It also participates at the interface of innate and adaptive immunity by chemoattracting immune effector cells, modulating the production of a variety of inflammatory mediators by different cell types, and regulating the differentiation of monocytes into dendritic cells. In this study, we investigated the effects of LL-37 on the differentiation of human monocytes into anti-inflammatory macrophages (M Phi-2; driven by M-CSF) versus proinflammatory macrophages (M Phi-1; driven by GM-CSF) as well as on fully differentiated M Phi-1 and M Phi-2. Results revealed that monocytes cultured with M-CSF in the presence of LL-37 resulted in macrophages displaying a proinflammatory signature, namely, low expression of CD163 and little IL-10 and profound IL-12p40 production on LPS stimulation. The effects of LL-37 on M-CSF-driven macrophage differentiation were dose-and time-dependent with maximal effects observed at 10 mu g/ml when the peptide was present from the start of the cultures. The peptide enhanced the GM-CSF-driven macrophage differentiation. Exposure of fully differentiated M Phi-2 to LL-37 for 6 d resulted in macrophages that produced less IL-10 and more IL-12p40 on LPS stimulation than control M Phi-2. In contrast, LL-37 had no effect on fully differentiated M Phi-1. Peptide mapping using a set of 16 overlapping 22-mer peptides covering the complete LL-37 sequence revealed that the C-terminal portion of LL-37 is responsible for directing macrophage differentiation. Our results furthermore indicate that the effects of LL-37 on macrophage differentiation required internalization of the peptide. Together, we conclude that LL-37 directs macrophage differentiation toward macrophages with a proinflammatory signature. The Journal of Immunology, 2010, 185: 1442-1449. Show less
P>Rapid identification and antimicrobial susceptibility testing (AST) of the causative agent(s) of bloodstream infections are essential for the selection of appropriate antimicrobial therapy. To... Show moreP>Rapid identification and antimicrobial susceptibility testing (AST) of the causative agent(s) of bloodstream infections are essential for the selection of appropriate antimicrobial therapy. To speed up the identification and AST of the causative agent, the fluid from blood culture bottles of a Bactec 9240 instrument (Becton Dickinson) containing Gram-positive cocci was mixed with saponin. After a 15-min incubation, the bacteria were harvested and transferred to the appropriate panel of a BD Phoenix automated microbiology system (Becton Dickinson) for identification and AST. With this approach (referred to as the direct method), we concordantly/correctly identified 56 (82%) of 68 monomicrobial cultures using the results obtained with the method currently used in our laboratory (current method) as comparator. Two (3%) isolates could not be identified and ten (15%) were misidentified. Complete agreement, concerning clinical susceptibility categories and MIC values, between the AST results determined with the direct method and the current method was found for 32 (55%) of 58 isolates. The E-test indicated that the direct method yielded a correct susceptibility profile for 13 of the remaining 26 blood culture isolates. Therefore, a concordant/correct susceptibility profile (with all antimicrobial agents tested) was obtained for 45 (77%) of 58 cultures. The overall error rate amounted to 1.9%, with the majority (1.3%) of errors being minor. Importantly, the results obtained with the direct method were available 12-24 h earlier than those obtained with the current method. Show less
