An accessory open reading frame (orf-x) of jaagsiekte sheep retrovirus is conserved between different virus isolates

Jaagsiekte sheep retrovirus (JSRV) is the etiological agent of a contagious lung tumour of sheep known as sheep pulmonary adenomatosis (syn: ovine pul monary carcinoma, jaagsiekte). JSRV exhibits a simple genetic organization, characteristic of the type D and type B retroviruses. with the canonical r etroviral sequences gag, pro, pol and env encoding the structural proteins of the virion. An additional open reading frame (orf-x), of approximately 5 00 bp overlapping pol, is present in the only two complete sequences of JSR V published to date. Since very little information is available on the biol ogy of JSRV it is important to establish if orf-x is conserved between diff erent virus isolates. In this study we analysed the orf-x region of JSRV is olates collected from the United Kingdom, Italy, Spain and South Africa. In addition we also analysed the presence of orf-x in JSRV-related endogenous sequences (enJSRVs) present in the sheep genome. Orf-x was highly conserve d in all the exogenous isolates (n = 10) and in most of the endogenous sequ ences (n = 8). Thus orf-x may be an accessory gene of JSRV and haves a biol ogical function which might be advantageous to JSRV. Phenetic analysis cond ucted on the complete orf-x nucleotide sequences seems to highlight the pre sence of three distinct groups statistically well supported by bootstrappin g: i) exogenous JSRV sequence from the UK; ii) exogenous JSRV sequences fro m Southern Europe and iii) the exogenous South African strain plus all the endogenous sequences analyzed and collected from Australia, Italy, UK and S outh Africa. (C) 2000 Elsevier Science B.V. All rights reserved.