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Parasiticidal activity of a novel synthetic peptide from the core α-helical region of NK-lysin

Sung Hyen Lee, Hyun S. Lillehoj, Wenbin Tuo, Charles A. Murphy, Yeong H. Hong, Erik P. Lillehoj
Veterinary parasitology 2013 v.197 no.1-2 pp. 113-121
Apoidea, Eimeria, Neospora caninum, chickens, coccidiosis, immunity, pathogens, plasma membrane, poultry production, sporozoites, transmission electron microscopy, venoms, weight gain
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 1.5μM of cNK-2 peptide against E. acervulina following 6h incubation was equal to that of 2.5μM 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 0.3μM of cNK-2 peptide was equivalent to 2.5μM 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 1.5μM 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.