Molecular cloning, characterization, and quantification of squirrel monkey (Saimiri sciureus) Th1 and Th2 cytokines

Primates have long been used as models to study the basic mechanisms of human disease. The squirrel monkey, Saimiri sciureus, is a New World monkey that can be satisfactorily bred in captivity and infected with various human pathogens. The basic immunological parameters of squirrel monkeys, including immunoglobulin subclasses and markers for lymphocyte subsets, have already been characterized. However, immunological reagents and assays specific for the detection and quantification of squirrel monkey cytokines are required to elucidate the immunological and physiopathological changes that occur during experimental infection of these animals with pathogens. We therefore cloned, sequenced, and characterized the cDNAs encoding various squirrel monkey Th1 and Th2 cytokines, including interleukin (IL)-1beta, IL-2, IL-5, IL-6, IL-10, tumor necrosis factor alpha, and gamma interferon. We found 91.4%-98.1% homology between the nucleotide sequence of the squirrel monkey cytokine genes and published sequences of equivalent human and non-human primate genes. The aligned sequences of cytokines for Saimiri and several New and Old World primates and human are shown, and a phylogenetic analysis of published sequences of selected cytokines in other species and those of non-human primates is given. In addition, we adapted a previously described quantitative, reverse transcriptase, competitive polymerase chain reaction technique to measure the mRNA expression of those cytokines in squirrel monkeys. The primer and competitor plasmids that allowed quantification are described. We showed that the assay is sensitive and reproducible.