Immunobiology 211 (2006) 315–322 REVIEW Host defence peptides from invertebrates – emerging antimicrobial strategies Robert E.W. Hancock à , Kelly L. Brown, Neeloffer Mookherjee Department of Microbiology and Immunology, University of British Columbia, 2259 Lower Mall, Vancouver, BC, Canada V6 T 1Z4 Received 23 August 2005; accepted 18 October 2005 Abstract Cationic antimicrobial (host defence) peptides are found as potent components of the innate immune system of all invertebrates in which they have been investigated. They vary substantially in their amino acid sequences, secondary structures, inducibility, potency and antimicrobial activity spectra. This enormous diversity is providing templates for the design and development of both antibiotic peptides and peptides that selectively modulate innate immunity to increase protection against infections and sepsis. r 2006 Elsevier GmbH. All rights reserved. Keywords: Antibiotics; Antimicrobial peptides; Cationic peptides; Invertebrate immunity; Innate immunity Contents Properties of cationic antimicrobial (host defence) peptides ............................................... 315 Functions of cationic peptides in invertebrate immunity.................................................. 316 Peptide antibiotics ............................................................................ 318 Immunomodulation ........................................................................... 319 Conclusions ................................................................................. 320 Acknowledgements ............................................................................ 320 References .................................................................................. 320 Properties of cationic antimicrobial (host defence) peptides Cationic amphiphilic peptides are found as a compo- nent of the innate immune system of all species of life, including invertebrates and vertebrates (Hancock and Diamond, 2000; Zasloff, 2002; Bulet et al., 2004; Iwanaga and Lee, 2005). Collectively they have been termed (cationic) antimicrobial peptides due to the observation that many have direct antimicrobial activity under physiological conditions, or cationic host defence peptides, reflecting their broader involvement in mam- malian immunity, including an ability to neutralize bacterial endotoxins such as LPS (a property shared by many invertebrate peptides) and to modulate the activities of the innate and adaptive immune systems. Cationic antimicrobial (host defence) peptides in nature comprise short sequences of amino acids ranging from around 12 to 50 amino acids in length. They have ARTICLE IN PRESS www.elsevier.de/imbio 0171-2985/$ - see front matter r 2006 Elsevier GmbH. All rights reserved. doi:10.1016/j.imbio.2005.10.017 à Corresponding author. Tel.: +1 604 822 2682. E-mail address: bob@cmdr.ubc.ca (R.E.W. Hancock).