A nucleic acid sequence, the rainbow trout interferon regulatory factor-1 (IRF1A) promoter, is disclosed. This promoter is capable of expressing a nucleic acid sequence operably linked to it in fish cells. IRF1A can be operably linked to antigenic sequences for fish or shellfish pathogens, thus inducing an immune response in a fish transformed with such a nucleic acid. Some of the vectors described utilize a nucleic acid containing an inducible promoter operably linked to a nucleic acid sequence encoding a polypeptide capable of inducing programmed cell death (PCD).