Figure 1. PCR-amplification of XMRV-gag fragments.

PCR fragments were analysed on a 2% agarose-gel. (A) Using a cloned XMRV-gag fragment, the sensitivity of our nested PCR reaction amplifying a fragment of 450 bp was determined to be around 5 copies input DNA spiked in XMRV- negative seminal plasma (left panel). High input copy numbers resulted in high molecular weight products that are most likely the result of trapping of excess DNA. MS2 RNA was used as an internal control during the extraction and reverse-transcription reaction, and was amplified in all cases (right panel). (B) PCR-results for five representative patient seminal plasma samples where no XMRV-gag fragments were amplified are shown (left panel). The MS2 internal control fragment of 225 bp was always amplified (right panel), suggesting that no degradation of nucleic acid during extraction, or inhibition during amplification, had occurred.