Fig. (3) Strong E2 staining coincides with HPV DNA replication. A) Serial adjacent sections of paraffin embedded biopsies of CIN2, CIN3 and SCC were stained by IHC with the E2 and p16 antibodies as previously described [10] and as indicated. Viral DNA was revealed by in situ hybridization (ISH) with no amplification for CIN2 while the signal was amplified for the CIN3 and SCC samples in order to detect low copy number of HPV DNA (40X magnification). B) Higher magnification (63X) of cells exhibiting uniform strong dark blue nuclei in replicating cells of CIN2 while the punctate signal is homogeneous in SCC and more heterogeneous in CIN3.