However, expression for the cluster of differentiation-8 receptor (cd8a) and granzyme-A (gzma) – two transcripts exclusively associated with adaptive immune cytotoxic T-cells and involved in intracellular antigen recognition and cell mediated killing, respectively – were significantly increased (mean of 4–20 fold) in heart tissues of PRV infected fish during the persistent phase of infection. The gene discussed is CD8A; the disease is infection.