Amplified products with gag primers were unspecific. Representative nested PCR amplification of 17 gDNA samples from 9 patient samples (lanes 1–9) and 8 healthy controls (lanes 10–17) visualized on 2% agarose real-safe stained gels. Lane 18 corresponds to the VP62 XMRV positive control and lane 19 is a negative control with no DNA template. M is the 100 bp ladder marker (Promega). Panel A shows the products amplified with the GAG-I-F and GAG-I-R primers (410 bp) [7, 44] while Panel B shows the products of the NP116 and NP117 primers (380 bp) . All amplifications were performed under the permissive conditions described in materials and methods.