KHV is oddball of family

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A team of Israeli scientists have found that Koi Herpes Virus is something of a genetic outsider in the herpes virus family, raising interesting questions on its origins.

Ilouze, Dishon, Kahan and Kotler of the Department of Pathology at the Hebrew University, Hadassah Medical School in Jerusalem, studied the KHV virus and found that, although morphologically similar to other herpes viruses, KHV is considerably larger than any other known member of the Herpesviridae family.

Their paper explaining the finding is due to be published in FEBS Letters, the journal of the Federation of European Biochemical Societies, later this month.

It claims that the genome of KHV, or Cyprinid Herpes Virus-3 (CyHV-3) as it is now officially known, is some 295 kilo base pairs larger than any other member of the herpes virus family, and that it also contains three genes - thymidylate monophosphate kinase, ribonucleotide reductase and thymidine kinase - which resemble those of pox viruses, rather than the stereotypical herpes viruses.

One of the genes, thymidylate monophosphate kinase or TmpK, has not previously been seen in herpes viruses before. Another gene, similar to B22R, is something which was previously exclusive to pox viruses.

The findings suggest that the virus is one of the closer relatives to the pox virus family than the other members of the group.

In May 2005, Practical Fishkeeping announced that KHV was to be renamed Cyprinid Herpes Virus-3, following a study published in the Journal of General Virology, which claimed that the virus was a close relative of Carp Pox (CyHV-1) and the goldfish disease haematopoietic necrosis herpesvirus (CyHV-2).

For more details on the new research see the paper: Ilouze M, Dishon A, Kahan T, Kotler M (2006) - Cyprinid herpes virus-3 (CyHV-3) bears genes of genetically distant large DNA viruses. FEBS Lett. 2006 Aug 7;580(18):4473-8.