a, Binding site of β-HPV RNA ISH and DNA ISH probes, shown on the HPV9 genome. The RNA ISH and DNA ISH probe against each type of β-HPV comprised a pool of 20 double-Z probes that target a region of 1,000 bases (Advanced Cell Diagnostics). b, H&E and RNA ISH staining of a wart from a 63-year-old immunosuppressed female. Note the abundance of positive signals (red dots) throughout the wart. c, Top, β-HPV RNA ISH of a skin cancer from an 87-year-old immunosuppressed female, including the stains for the positive- and negative-control probes. The detection of β-HPV by RNA ISH correlates with qPCR positivity for transcripts of HPV5 and HPV9 E6 proteins in the same skin cancer. Bottom, β-HPV RNA ISH of a sample of normal skin from an 18-year-old immunocompetent African American female. The lack of RNA ISH signal (red) in this sample correlates with undetectable transcripts of HPV5, HPV9 or HPV15 E6 proteins in qPCR of the same sample. qPCR products were visualized using gel electrophoresis. PCR band sizes: HPV5 E6, 100 bp; HPV9 E6, 66 bp, HPV15 E6, 78 bp; keratin 14, 109 bp. Scale bars, 100 μm (b, c).