FIG.5.

Detection of viral DNA amplification and E4 and L1 expression in CT and NZW rabbit papillomas. (a) CT rabbit papillomas. E4 expression (left panel; green), DNA amplification (middle panel; red), and L1 expression (right panel; green) were detected in the differentiated layers of the CRwt DNA-induced CT papilloma tissues but not in any CRst9/0 DNA-induced CT papilloma tissues. It should be noted that the weak green staining in the CRst9/0/E4 panel is nonspecific staining of cornified (dead) cells that folded onto the tissue section during coverslip mounting. (b) NZW rabbit papillomas. DNA amplification (middle panel; red) was detected in the CRwt DNA-induced papillomas but was not detectable in any CRst9/0 DNA-induced papillomas (right panel). In CRwt tissue sections, numerous areas that contained cells supporting viral DNA amplification were found. E4 expression was restricted to areas that were shown to support viral DNA amplification (left panel; green). (c) NZW rabbit papillomas. Low levels of viral DNA amplification (red) were apparent in the papillomas induced by E4 mutants CRst41, CRst74, and CRst82. Blue indicates the nuclear counterstain. Dotted lines indicate the epithelial basal layers. Arrowheads indicate the tops of the lesions. The staining patterns shown are representative of the results obtained in repeated experiments.