IAP and XMRV amplification sensitivity assays. Panel A: the indicated amounts of mouse genomic DNA were spiked into 1 μg of human gDNA and IAP sequences (236–312 bp) were amplified using previously described conditions . Panels B and C show amplification of the env (973 bp) and gag (730 bp) genes using each outer primer set respectively, from the pcDNA3.1-VP62 construct (AIDS Research and Reference Reagent Program Cat# 11881) (number of copies 0–1000 as indicated) spiked into 1 μg of human gDNA with the outer amplification primers and conditions described in Methods. All PCR products were visualized on 2% agarose real-safe stained gels. M: molecular DNA markers correspond to PCR markers (Promega) (panel A) and marker XIII (Roche) (panels B and C).