Title: Parasiticidal activity of a novel synthetic peptide from the core a-helical region of NK-lysin Authors
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2013
Publication Date: August 1, 2013
Citation: Citation: Lee, SH, Lillehoj, HS, Tuo, W., Murphy, CA, Hong, YH, Lillehoj, EP. 2013. Parasiticidal activity of a novel synthetic peptide from the core a-helical region of NK-lysin. Veterinary Parasitology 197:113-121. Interpretive Summary: Avian coccidiosis is an economically important enteric disease of commercial poultry caused by several species of Eimeria protozoa. Avian coccidiosis is estimated to cost the international poultry industry approximately $3 billion annually due to the combined expenses associated with vaccination, in-feed coccidiostatic drugs, and impaired growth performance. This high economic expenditure is expected to increase given the prohibitively high costs of new drug development and there is now large interest towards drug-free poultry production in response to growing consumer concerns of chemical food residues. Therefore, ARS scientists collaborated with scientists at a Korean University to develop a synthetic peptide with an anticoccidial activity based on the previous study that discovered chicken NK-lysin, an anti-microbial peptide that plays an important role during innate immunity against coccidiosis with its selective membrane disruptive property. In this paper, the authors showed that a synthetic peptide is directly cytotoxic against Eimeria apicomplexan protozoa and modulates host resistance to experimental avian coccidiosis in vivo. These results demonstrate that this synthetic peptide may be useful as therapeutic agent against avian coccidiosis during commercial poultry production. This new information will lead to the design of novel drug-free strategy against avian coccidiosis.
Technical Abstract: NK-lysin is an anti-microbial peptide that plays a critical role during 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 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 alpha-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 micromole of cNK-2 peptide against E. acervulina following 6 hr incubation was equal to that of 2.5 micromole 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 micromole of cNK-2 peptide was equivalent to 2.5 micromole 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 micromole 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 may be useful for protection against avian coccidiosis during commercial poultry production.