Use of antibodies against a synthetic peptide of the E6 protein of human papillomavirus (HPV) type 16 for the diagnosis of genital HPV lesions.

The E6 open reading frame of the human papillomavirus (HPV) 16 codes for a protein of 158 amino acids with a theoretical molecular weight of 19.1 kD. A peptide corresponding to 147-158 amino acids (NH2-RSSRTRRETQLC-COOH) was synthesized, coupled to haemocyanin and used for immunization of rabbits. The antibodies obtained were used for the immunohistochemical analysis of a series of 41 paraffin-embedded biopsies including 29 cases of HPV 16-associated cervical lesions, five HPV 6, four HPV 11, and three HPV 18-associated genital warts. Expression of a reacting molecule (both intranuclear and cytoplasmic) could be demonstrated in 28/29 (96.6%) of the HPV 16 lesions, in 2/5 (40%) of the HPV 6, in 2/4 (50%) of the HPV 11, and in 3/3 of HPV 18 lesions. The intensity of the staining was weak in the HPV 6 and HPV 11 lesions, whereas it was classified as intense in 21/29 (72%) of the E6-positive HPV 16 lesions. Negative staining was almost invariably (5/6, 83%) confined to HPV-non-cervical intraepithelial neoplasia (HPV-NCIN) lesions, only 5/18 (27%) of which showed an intense staining. In contrast, intense staining was associated with CIN; 11/1 2 (92%) in HPV-CIN I and 8/11 (73%) in HPV-CIN II lesions. In the HPV 16 group, intense reactivity was more frequent in lesions shown to make clinical progression (8/9, 89%) as compared with those which underwent spontaneous regression (10/15,66.7%). Topography of the immunostaining paralleled the localization of HPV DNA hybridization signals in 20/21 (95%) evaluable HPV 16 cases, in contrast to only 1/3 in HPV 18 cases and in none of the HPV 6 and HPV 11 lesions. These differences between HPV 16 and HPV 6/11 lesions in the staining with the HPV 16 E6 protein antibody might help explain at least some of the differences in their known biological behaviour.