DNA vaccination by immersion and ultrasound to trout viral haemorrhagic septicaemia virus

This work reports preliminary data on the application of a novel method, ul trasound, for the DNA vaccination of rainbow trout. First, the best formula tions were selected that increased the transfer by immersion of a plasmid c oding for the green fluorescent protein (GFP) gene into trout fry. Quantifi cation of GFP expression by fluorescence in the fin cells was used to study time course, DNA concentration dependence and comparison of different form ulations. The best GFP expression results were obtained with short pulses o f ultrasound. DOTAP liposomes and recombinant bacteria or bactofection. Oth er liposomes or microencapsulation formulations resulted in a GFP fluoresce nce similar to background values. Second, DNA immersion-vaccination of immu nocompetent fingerling trout with the selected formulations was performed b y using a plasmid coding for the glycoprotein G gene of the viral haemorrha gic septicaemia virus (VHSV). The immunization of fingerling trout was esti mated by measuring humoral antibody, lymphoproliferation and VHSV challenge responses. Short pulses or low intensity ultrasound were the only method b y which both humoral antibody responses and survival after VHSV challenge w ere obtained. Immersion DNA-vaccination using short pulses of ultrasound co uld eventually lead to a practical way to vaccinate small fish. (C) 2001 El sevier Science Ltd. All rights reserved.