Quantitative real-time PCR enumeration of viral genome copy number. DNA was extracted from splenic tissue taken 7 to 10 weeks after infection from recipient mice infected with wild-type polyoma virus (PyV.WT) or polyoma virus expressing (OVA)_323-339 (PyV.OVA-II) and then transfused with HOD RBCs. Quantitative RT-PCR was used to determine the polyoma virus genome copy number. No statistically significant difference in genome copy number between the 2 groups was seen. A compilation of data from 3 individual experiments (3-5 mice/group per experiment) is shown; uninfected mice had an undetectable viral genome copy number (data not shown).