That is notsurprising in itself, butitmeans that the virusmust havebecomeendogenous fairlyrecently, otherwiseit would not look so similar toitsfree-living counterpart.
Indeed, the clone reported by the authors which contained a 24 base pair deletion in glycogag would be a classic example of a viral variant caused by the recombination of XMRV and an endogenous MLV virus.
That is not surprising in itself, but it means that the virus must have become endogenous fairly recently, otherwise it would not look so similar to its free-living counterpart.