ORIGINAL ARTICLE EXPERIMENTAL ALLERGY AND IMMUNOLOGY Eotaxin-3 (CCL26) exerts innate host defense activities that are modulated by mast cell proteases A. Gela 1 , G. Kasetty 1 , S. Jovic 1 , M. Ekoff 2 , G. Nilsson 2 , M. M€ orgelin 3 , S. Kjellstr € om 4 , J. E. Pease 5 , A. Schmidtchen 6,7 & A. Egesten 1 1 Respiratory Medicine & Allergology, Lund University, Lund; 2 Clinical Immunology and Allergy Unit, Department of Medicine, Karolinska Institutet, Stockholm; 3 Infection Medicine, Lund University; 4 Department of Clinical Sciences Lund, Molecular and Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, Lund, Sweden; 5 Leukocyte Biology Section, Faculty of Medicine, Imperial College of Science, Technology, and Medicine, NHLI, London, UK; 6 Dermatology & Venerology, Lund University, Lund, Sweden; 7 Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore To cite this article: Gela A, Kasetty G, Jovic S, Ekoff M, Nilsson G, M€ orgelin M, Kjellstr€ om S, Pease JE, Schmidtchen A, Egesten A. Eotaxin-3 (CCL26) exerts innate host defense activities that are modulated by mast cell proteases. Allergy 2015; 70: 161–170. Keywords allergy; bacterial infection; eotaxins; host defense. Correspondence Anele Gela, Respiratory Medicine & Allergology, Lund University, BMC B14, Tornav€ agen 10, SE-221 84 Lund, Sweden. Tel.: +46-46-222-7118 Fax: +46-46-157-756 E-mail: Anele.Gela@med.lu.se Accepted for publication 30 October 2014 DOI:10.1111/all.12542 Edited by: Hans-Uwe Simon Abstract Background: During bacterial infections of the airways, a Th1-profiled inflamma- tion promotes the production of several host defense proteins and peptides with antibacterial activities including b-defensins, ELR-negative CXC chemokines, and the cathelicidin LL-37. These are downregulated by Th2 cytokines of the allergic response. Instead, the eosinophil-recruiting chemokines eotaxin-1/CCL11, eotaxin-2/CCL24, and eotaxin-3/CCL26 are expressed. This study set out to investigate whether these chemokines could serve as innate host defense molecules during allergic inflammation. Methods: Antibacterial activities of the eotaxins were investigated using viable count assays, electron microscopy, and methods assessing bacterial permeabiliza- tion. Fragments generated by mast cell proteases were characterized, and their potential antibacterial, receptor-activating, and lipopolysaccharide-neutralizing activities were investigated. Results: CCL11, CCL24, and CCL26 all showed potent bactericidal activity, med- iated through membrane disruption, against the airway pathogens Streptococcus pneumoniae, Staphylococcus aureus, Nontypeable Haemophilus influenzae, and Pseudomonas aeruginosa. CCL26 retained bactericidal activity in the presence of salt at physiologic concentrations, and the region holding the highest bactericidal activity was the cationic and amphipathic COOH-terminus. Proteolysis of CCL26 by chymase and tryptase, respectively, released distinct fragments of the COOH- and NH 2 -terminal regions. The COOH-terminal fragment retained antibacterial activity while the NH 2 -terminal had potent LPS-neutralizing properties in the order of CCL26 full-length protein. An identical fragment to NH 2 -terminal frag- ment generated by tryptase was obtained after incubation with supernatants from activated mast cells. None of the fragments activated the CCR3-receptor. Conclusions: Taken together, the findings show that the eotaxins can contribute to host defense against common airway pathogens and that their activities are modulated by mast cell proteases. During normal conditions, several arms of host defense protect our airways from infection. Effector molecules include constitutively produced host defense proteins and peptides (HDPs) with antibacterial activity. These are pres- ent in the thin periciliary liquid layer of the airways and include lactoferrin, lysozyme, and SLPI (1). Upon bacterial infection, a Th1 inflammatory response induces the expression of additional HDPs, for example, the b-defensins hBD-2 and hBD-3 and the cathelicidin-derived peptide LL- 37 (2–5). In addition, several chemokines, constitutively expressed or induced during Th1-profiled inflammation, have defensin-like antibacterial properties, for example, CCL20, CCL28, MIG/CXCL9, CXCL17, and GCP-2/ CXCL6 (6–10). Allergy 70 (2015) 161–170 © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 161 Allergy