Sensitive detection of nucleic acids and protein of human papillomavirus type 6 in respiratory and genital tract papillomata

We have developed a sensitive method to detect and localize HPV-6 viral DNA, mRNA and protein in biopsy specimens of genital and respiratory tract lesions by using in situ hybridization and immunoperoxidase assays on sections of plastic-embedded tissue. This modified in situ hybridization technique, using ultrathin sections and strand-specific ³H-labelled riboprobes, offers the advantages of superior morphological preservation and detection of viral genomes at low copy number with good resolution. This modified immunocytochemistry provides better sensitivity when compared to previous methods using paraffin-embedded materials. In respiratory tract lesions, immunoperoxidase assay detected only a few capsid antigen positive cells, while in the genital tract lesions, there were more capsid antigen positive cells. Southern transfer analyses and in situ hybridizations demonstrated the presence of more viral nucleic acids in genital tract papillomata than respiratory tract papillomata. Epithelial cells throughout the papillomata were infected by HPV-6 as evidenced by positive hybridization, with more viral DNA present in superficial cells. Our results suggest that genital tract epithelium is more permissive for HPV-6 replication than respiratory tract epithelium. Using stand-specific probes synthesized from subgenomic fragments of the HPV-6 genome in conjunction with nuclease digestions, we were able to demonstrate that HPV-6 transcripts specific to open reading frames (ORFs) E6, E7, E1, L1, and L2 occur in maturing superficial cells. In contrast, transcripts specific to ORFs E1, E2, E4, E5a, and E5b could be detected throughout the whole of the epithelium with more signals noted at the basal cell areas. In addition, the distribution of HPV-6 nucleic acids and protein in a carcinoma in situ of the larynx was analyzed. In comparison to benign respiratory tract papillomata, more viral DNA was found in the malignant lesion, but the pattern and distribution of transcription and capsid antigen was similar.