Stable expression of a foreign gene, delivered by gene gun, in the muscle of rainbow trout Oncorhynchus mykiss

We report the efficient delivery of a foreign gene into muscle of rainbow t rout Oncorhynchus mykiss with a gene gun. The foreign gene was a reporter g ene, chloramphenicol acetyltransferase (CAT). Two CAT-containing plasmids w ere used: pCMV-CAT, which contains cytomegalovirus immediate early promoter , and pSV2-CAT, which contains the simian virus 40 early promoter. All plas mids were introduced by particle bombardment using a gene gun. During the 9 0-day sampling period following bombardment, CAT was strongly and stably ex pressed in the muscle of all the fish bombarded with pCMV-CAT and pSV2-CAT. No CAT expression was detected in the blood samples until 90 days after in troduction, when it was found in only one fish from the pCMV-CAT group and one from the pSV2-CAT group. The stable and long-term expression of plasmid DNA in muscle makes muscle an attractive target tissue for the introductio n of viral DNA for the purpose of DNA vaccination.