Cloning and sequencing of interleukin-18 gene in an inbred pig

Interleukin18(IL-18)is a novel potent inducer of IFN-γ production.One pair of primers were designed according to porcine IL-18 gene sequence published in GenBank.IL-18 gene was amplified by RT-PCR from total RNA extracts of porcine splenocytes and then cloned and sequenced.The result indicated that the full length of porcine IL-18 gene was 579 bp,and encoded 192 amino acids.The nucleotide sequence of homology to the porcine IL-18 gene(Accession number:ABO10003)was 99.8%,and at the site of 550 bp the nucleotide changed from A to G.The deduced amino acid sequence of homologies to those of the porcine IL-18 genes(Accession number:ABO10003,AF176949,AY262109,NM1997)were 99%,98.5%,99.8% and 99%.Analysis of phylogenetic trees demonstrated that genetic relationship between the porcine IL-18 gene(ABO10003 and AY262109)were the closest.Comparison of the nucleotides sequence of porcine IL-18 gene with those from human,cat,cattle,chicken,duck,fugu,goat,horse,house mouse,rat and sheep showed that the nucleotides homologies were 83.1%,88.3%,90.7%,26.8%,31.4%,26.3%,90.0%,91.5%,67.7%,65.1% and 90.8%,individually.