PRDM1 and viral infectious disease: Our results demonstrate that the expansive evolution of these genes in teleost fish has resulted in a repertoire of six prdm1-like genes, four of them being likely homologs of mammalian prdm1 and two of them homologs of znf683. All six genes were constitutively expressed in a wide range of tissues, and were up-regulated in response to a viral infection, whereas only three of them showed higher mRNA levels in peritoneal B cells with an Ig-secreting profile.