With increasing needs for the global animal industry to address the regulatory restrictions on the use of antibiotic growth promoters (AGPs) in animal production, there is much interest to find alternatives to AGPs. To develop alternatives to antibiotics against major poultry parasitic diseases, we have identified a chicken gene which encodes an antimicrobial peptide, NK lysin, from an EST cDNA library that we prepared from Eimeria-infected chicken intestine. The contig 171 (NK-lysin like sequence), composed of 87 ESTs, occurred with the highest prevalence in an Eimeria-induced intestinal cDNA library. Chicken NK lysin showed less than 20% identity to granulysin and other mammalian NK-lysins. Although NK-lysin in humans showed antimicrobial activity against numerous targets including Gram-positive and Gram-negative bacteria, as well as protozoan parasites, chicken NK-lysin shows exclusive activity against apicomplexan parasites. This presentation will report the expression of chicken NK-lysin in various expression vectors, its efficacy in ameliorating clinical signs of avian coccidiosis, and identification of lytic peptide (cNK-2) sequence derived from NK lysin which has a direct killing activity against multiple Eimeria species as well as against other Apicomplexa parasites including Neospora and Cryptosporidia. The results demonstrate that chicken NK-lysin can be an antibiotic alternative to mitigate the intestinal damages due to protozoan parasites in poultry.
Abstract presented at the 3rd International Symposium on Alternatives to Antibiotics 2019.