ELISA of PCa patient's sera using recombinant XMRV proteins. Mean ODs with two replicates of each patient sera diluted 1:200 (dark bars) and of serially diluted sera from immunized mice (light bars). Cut-off was calculated as the mean of four (gp70) and five (pr65) sera from healthy controls plus two times standard deviation. (A) ELISA of randomly chosen PCa patient sera using the gp70 (Env) fragment (aa 1-245). (B) ELISA using a mixture of both pr65 (Gag) fragments. In general there was a higher background against the pr65 proteins, seen also with the sera of healthy humans and the preimmune mouse sera.