MOLECULAR CHARACTERIZATION AND DETERMINATION OF THE CODING CAPACITY OF THE GENOME OF EQUINE HERPESVIRUS TYPE-2 BETWEEN THE GENOME COORDINATE-0.235 AND COORDINATED-0.258 (THE ECORI DNA FRAGMENT N-4.2-KBP)

The complete DNA nucleotide sequence of the EcoRI DNA fragment N (0.23 5 to 0.258 viral map units) of equine herpes virus type 2 (EHV-2) stra in T400/3 was determined. This DNA fragment comprises 4237 bp with a b ase composition of 55.23% G + C and 44.77% A + T. Nineteen open readin g frames (ORFs) of 50-287 amino acid (aa) residues were detected. ORF number 10 is located between the nucleotide position 2220 and 2756 cod ing for a protein of 179 amino acid residues. This protein shows signi ficant homology to the cytokine synthesis inhibitory factor (CSIF; int erleukin 10) of human (76.4%) and mouse (68.5%), and to the Epstein-Ba rr virus (EBV) protein BCRF1 (70.6%). The existence of an interleukin 10 (IL-10) analogous gene within the genome of the EHV-2 was confirmed by screening the genome of nine EHV-2 strains using specific oligonuc leotide primers corresponding to the 5' and 3' region of this particul ar gene by polymerase chain reaction. In all experiments an 870 bp DNA product was amplified. The specifity of the amplified DNA fragments o btained from individual EHV-2 strains was confirmed by DNA-DNA hybridi zation experiments. The DNA sequence analysis of the amplified DNA pro ducts of the EHV-2 strain LK was carried out. This analysis revealed t he identity of the corresponding IL-10 gene (540 bp) of this strain to the IL-10 gene of EHV-2 strain T400/3. The presented data indicate th at the EHV-2 genome harbors a viral interleukin 10-like gene. This is further evidence that the IL-10 gene can be present in the genomes of members of the Herpesviridae family.