Production of Homozygous Transgenic Rainbow Trout with Enhanced Disease Resistance

Previous studies conducted in our laboratory showed that transgenic medaka expressing cecropin B transgenes exhibited resistant characteristic to fish bacterial pathogens, Pseudomonas fluorescens and Vibrio anguillarum. To confirm whether antimicrobial peptide gene will also exhibit anti-bacterial and anti-viral characteristics in aquaculture important fish species, we produced transgenic rainbow trout expressing cecropin P1 or a synthetic cecropin B analog, CF-17, transgene by sperm-mediated gene transfer method. About 30 % of fish recovered from electroporation were shown to carry the transgene as determined by polymerase chain reaction (PCR) amplification assay. Positive P(1) transgenic fish were crossed to non-transgenic fish to establish F(1) transgenic founder families, and subsequently generating F(2), and F(3) progeny. Expression of cecropin P1 and CF-17 transgenes was detected in transgenic fish by reverse transcription (RT)-PCR analysis. The distribution of body sizes among F(1) transgenic fish were not significantly different from those of non-transgenic fish. Results of challenge studies revealed that many families of F(2) and F(3) transgenic fish exhibited resistance to infection by Aeromonas salmonicida and infectious hematopoietic necrosis virus (IHNV). All-male homozygous cecropin P1 transgenic families were produced by androgenesis from sperm of F(3) heterozygous transgenic fish in one generation. The resistant characteristic to A. salmonicida was confirmed in progeny derived from the outcross of all-male fish to non-transgenic females. Results of our current studies confirmed the possibility of producing disease-resistant homozygous rainbow trout strains by transgenesis of cecropin P1 or CF-17 gene and followed by androgenesis.