A large DNA virus, designated koi herpes virus
(KHV), carp interstitial nephritis gill necrosis virus (CNGV)
and Cyprinid herpes virus-3 (CyHV-3), causes massive mortality
of carp. Morphologically, the virus resembles herpes viruses, but
it contains a genome of ca 295 kbp, larger than that of any Herpesviridae
member. Interestingly, three CyHV-3 genes, thymidylate
monophosphate kinase (TmpK), ribonucleotide reductase
and thymidine kinase, which are involved in deoxynucleotide
tri-phosphate synthesis, resemble those of pox viruses. In addition
to the TmpK gene, which is nonexistent in the genome of
herpes viruses, CyHV-3 contains a B22R-like gene, exclusively
expressed by pox viruses. These results raise questions on the
phylogenic origin of CyHV-3.
2006 Federation of European Biochemical Societies. Published
by Elsevier B.V. All rights reserved.