Enhanced alloimmunization to HOD transfusion by PyV.OVA-II requires linkage of (OVA)_323-339 to HEL on the antigen. C57BL/6 mice were infected with PyV.WT or PyV.OVA-II and transfused with mHEL or HOD RBCs (uninfected and/or untransfused control groups were also included). One week after transfusion, sera were analyzed for anti-HEL IgG. Similar results were observed at 14 days (data not shown). A representative experiment with 5 mice/group is shown (mean ± SD depicted, with sera at 1:50 dilution); this experiment has been repeated twice (using C57BL/6 as well as C57BL/6 × B10.BR recipients) with similar results.