Endotheliotropic elephant herpesvirus, the first betaherpesvirus with a thymidine kinase gene

1 Molekulare Genetik und Epidemiologie von Herpesviren, Robert Koch-Institut, Nordufer 20, 13353 Berlin, Germany 2 Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, Schlossgarten 4, 91054 Erlangen, Germany 3 Institut für Lebensmittel, Arzneimittel und Tierseuchen, Invalidenstr. 60, 10557 Berlin, Germany Correspondence Bernhard Ehlers ehlersb{at}rki.de Endotheliotropic elephant herpesvirus (elephantid herpesvirus 1; ElHV-1) is apathogenic for African elephants ( Loxodonta africana ), but causes fatal haemorrhagic disease in Asian elephants ( Elephas maximus ). This is thought to occur through transmission from African elephants in places where both species are housed, such as zoological gardens. The virus has caused considerable losses in North American and European zoological gardens and thus severely impedes breeding of the endangered Asian elephant. Previously, the ultrastructural and genetic characterization of ElHV-1 from a male Asian elephant that died from the disease at the Berlin zoological gardens in 1998 have been reported. Here, a partial characterization of the ElHV-1 genome is presented. A 60 kbp locus, spanning 34 open reading frames, was analysed. Most of the detected genes were found to be conserved among the herpesviruses and showed an overall arrangement most similar to that of betaherpesviruses, in particular Human herpesvirus 6 and Human herpesvirus 7 . Most importantly, in addition to a protein kinase gene that is homologous to the human cytomegalovirus UL97 gene, a thymidine kinase (TK) gene was found, which is generally missing in betaherpesvirus genomes. Thus, ElHV-1 is the only known betaherpesvirus to encode a TK gene. This peculiarity might contribute to the fulminant pathogenicity of ElHV-1, but also provide a crucial enzymic activity for developing an efficient antiviral therapy with currently available nucleoside analogues. Published online ahead of print on 23 June 2006 as DOI 10.1099/vir.0.81977-0.