XMRV sequences in in-bred mouse strains analysed by deep sequencing

Xenotropic murine leukaemia viruses are endogenous gammaretroviruses that infect cells from many species, including humans. Xenotropic murine leukaemia virus-related virus (XMRV) is a retrovirus that has been the subject of intense debate since its detection in samples obtained from human patients with prostate cancer and chronic fatigue syndrome. To better understand the provenance of XMRV we performed deep amplicon sequencing of inbred mouse strains, using primers flanking a 24nt deletion in the gag-leader region reported to be XMRV-specific. This deletion was detected in the gag-leader of endogenous proviruses in 4 mouse strains (129X1/SvJ, Balb/cJ, CBA/J and LPT/LeJ) at a low frequency, consistent with it being present in just one (or a few) of many endogenous proviral copies. Sequences of several other endogenous proviruses were present as well, in part with much higher frequencies. These data indicate that primer sets previously described as XMRV-specific can readily amplify common murine endogenous viral sequences and that some targets exist at high copy number in genomes of mice. Laboratory contamination of patient samples or reagents is highly likely to underlie the association between XMRV and human disease. See Retrovirology 2010, 7:111 doi:10.1186/1742-4690-7-111