Nested PCR was performed under the same conditions for 45 amplification cycles with 5 µl of the first round PCR product and two
different primer pairs, Gag - I - F (5 ′ - TCTCGAGATCATGGGACAGA - 3 ′) and Gag - I - R (5 ′ - AGAGGGTAAGGGCAGGGTAA - 3 ′) or NP116 (5 ′ - CATGGGACAGACCGTAACTACC - 3 ′) and NP117 (5 ′ - GCAGATCGGGACGGAGGTTG - 3 ′), respectively, both of which have been shown to detect both XMRV and MLV gag sequences [13].