Testing for xenotropic murine leukemia virus–related virus (XMRV) in patients with fibromyalgia. Lanes 1 and 13, molecular weight marker ΦX174RF HaeIII; lanes 2–5, hBG for patients 1–4 (primers: hBG-FI-170/hBG-RI-273 (103 bp); lanes 6–12, positive control (pcDNA3.1-XMRV-Vp62) 1,000 copies (lanes 6 and 10) and 100 copies (lanes 7–9 and 11–12); lane 6, primers gag 419F/1154R (735 bp); lane 7, primers gag MLV-GAG-I-F/MLV-GAG-I-R (413 bp); lane 8, primers gag MLV-NP116/MLV-NP117 (380 bp); lane 9, pr