Amplification of Epstein-Barr virus (EBV) from DNA isolated from breast cancer and blood specimens. Real time PCR using minor groove binding (MGB)-TaqMan technology was used to quantify the viral load contained in the samples. Internal repeat region (IR)1 target sequences showed that this probe amplified its respective target over a broad range and detected low levels (2.3 EBV genomes per reaction; unpublished observation). (a) A characteristic amplification plot showing the change in fluorescence (ΔRn) as a function of amplification cycle. The horizontal red line indicates the fluorescence at 10× the standard deviation of the control. The upper left arrow indicates the fluorescence detected from Daudi, an EBV-associated endemic Burkitt lymphoma. The lower arrow indicates the fluorescence of a negative control (water). The amplification, in triplicate, of the DNA from each of the patient tumor samples is indicated. (b) The standard was constructed to contain from 2 to 200,000 copies of EBV genome. The graph shows the linear regression of the Cts (the PCR cycle number when the amplification fluorescence value reaches and exceeds the predetermined background threshold value) using each of the standards. This characteristic standard line had an r2 = 0.995 with a slope of -3.2.