title: Parasiticidal activity of a novel synthetic peptide from the core α-helical region of NK-lysin.
abstract: NK-lysin is an anti-microbial peptide that plays a critical role in innate immunity against infectious pathogens through its selective membrane disruptive property. We previously expressed and purified a full-length chicken NK-lysin (cNKL) recombinant protein, and demonstrated its in vitro anti-parasitic activity against the apicomplexan protozoan, Eimeria, the etiologic agent of avian coccidiosis. This study evaluated the in vitro and in vivo anti-parasitic properties of a synthetic peptide (cNK-2) incorporating a predicted membrane-permeating, amphipathic α-helix of the full-length cNKL protein. The cNK-2 peptide exhibited dose- and time-dependent in vitro cytotoxic activity against E. acervulina and E. tenella sporozoites. The cytotoxic activity of 1.5 μM of cNK-2 peptide against E. acervulina following 6h incubation was equal to that of 2.5 μM of melittin, the principal active component of apitoxin (bee venom) that also exhibits anti-microbial activity. Even greater activity was detected against E. tenella, where 0.3 μM of cNK-2 peptide was equivalent to 2.5 μM of melittin. Against Neospora caninum tacyzoites, however, the cytotoxic activity of cNK-2 peptide was inferior to that of melittin. Transmission electron microscopy of peptide-treated E. tenella sporozoites revealed disruption of the outer plasma membrane and loss of intracellular contents. In vivo administration of 1.5 μM of cNK-2 peptide increased protection against experimental E. acervulina infection, as measured by greater body weight gain and reduced fecal oocyst shedding, compared with saline controls. These results suggest that the cNK-2 synthetic peptide is a novel anti-infective peptide that can be used for protection against avian coccidiosis during commercial poultry production.
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705, USA.
authors.forename: Sung Hyen
authors.initials: SH
authors.lastname: Lee
authors.forename: Hyun S
authors.initials: HS
authors.lastname: Lillehoj
authors.forename: Wenbin
authors.initials: W
authors.lastname: Tuo
authors.forename: Charles A
authors.initials: CA
authors.lastname: Murphy
authors.forename: Yeong H
authors.initials: YH
authors.lastname: Hong
authors.forename: Erik P
authors.initials: EP
authors.lastname: Lillehoj
mesh_terms: D000818:Animals; D002645:Chickens; D003048:Coccidiosis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary; D003049:Coccidiostats / Q000737:chemistry* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D016786:Eimeria tenella / Q000187:drug effects*; D008555:Melitten / Q000494:pharmacology; D010455:Peptides / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology*; D011201:Poultry Diseases / Q000188:drug therapy / Q000469:parasitology; D011510:Proteolipids / Q000737:chemistry*
chemical_list: D003049:Coccidiostats; C093238:NK-lysin; D010455:Peptides; D011510:Proteolipids; D008555:Melitten
keywords: Alternative to antibiotics; Avian; Coccidiosis; Eimeria; NK-lysin; Neospora