Antibodies against linear and conformational epitopes of the human papillomavirus (HPV) type 16 E6 and E7 oncoproteins in sera of cervical cancer patients

Abstract

Sera obtained from 137 cervical cancer patients were analysed for the presence of antibodies to the human papillomavirus (HPV) type 16 proteins E6 and E7 by the aid of different assays, i.e. ELISA using as antigen either synthetic peptides or the complete E7 protein and radio-immunoprecipitation (RIPA) which uses the viral protein made by in vitro transcription/translation. In agreement with previous reports, reactivity to the E7 protein was found more frequently than to the E6 protein (31.4% vs. 16.8%) when the sera were assayed by peptide-based ELISA. In contrast, when RIPA was employed, reactivity to either protein was obtained at similar frequency (38.7% vs 46.7%). When the protein was denatured prior to immuno-precipitation the reactivity was lost in all sera tested for E6-specific antibodies but only in a few samples in the E7-RIPA. Therefore it was concluded that the increased sensitivity of the E6-RIPA as compared to the E6 peptide-ELISA is due to the detection of antibodies to conformational epitopes which are presented by the in vitro product but not by the synthetic peptides. Eighty-two sera from healthy donors were tested by HPV 16E6- and E7-RIPA and also by ELISA using the HPV 16E7 protein which was produced in the fission yeast Schizosaccharomyces pombe. One sample reacted each in the E6- and E7-RIPA indicating a high specificity of these assays. The E7 protein-ELISA proved to be less sensitive for the detection of antibodies in cervical cancer patients' sera (22.6% positive) as compared to peptide-based ELISA or RIPA.

Antibodies against oncoproteins E6 and E7 of human papillomavirus types 16 and 18 in cervical-carcinoma patients from Russia

“…We found statistically significantly elevated odds ratios (OR) ranging from 4.9 to 64.4 for all HPV16-antibody patterns except for E7 antibodies alone, and an OR of 26.2 for a combination of any of the 4 antibody types analyzed (Table II). An association of HPV16 E6 or E7 antibodies with cervical carcinoma has been seen with other antibodydetection techniques such as Western-blot analysis (JochmusKudielka et al, 1989), peptide ELISA (Dillner et al, 1995) and RIPA (Viscidi et al, 1993;Nindl et al, 1994).…”

“…They interact with different cellular proteins known to be involved in the control of the cell cycle and of DNA repair, most notably the tumor-suppressor proteins p53 and pRb (Dyson et al, 1989;Werness et al, 1990; reviewed in Barbosa, 1996). Antibodies against the E6 and E7 proteins of HPV types 16 and 18 have been found to be strongly associated with cervical cancer (Viscidi et al, 1993;Nindl et al, 1994;Dillner et al, 1995;Onda et al, 1993;Meschede et al, 1998). We have developed 4 second-generation enzyme-linked immunosorbent assays (ELISA) (Meschede et al, 1998) for the detection of human antibodies against the oncoproteins E6 and E7 of HPV types 16 and 18.…”

Antibodies to human papillomavirus type 11 virus-like particles in sera of patients with genital warts and in control groups

“…HPV-16 E7-specific RIPA was used previously and proved to detect antibodies in HPV-16-positive cervical cancer patients with higher sensitivity than the HPV-16 E7 protein ELISA (Nindl et al, 1994). For the HPV-11 Ll-specific RIPA the protein was produced by in vitro transcription and translation.…”

Direct Human Papillomavirus E6 Whole-Cell Enzyme-Linked Immunosorbent Assay for Objective Measurement of E6 Oncoproteins in Cytology Samples

“…Until recently, most of the antibodies developed against the HPV E6 or E7 protein used either peptides or denatured proteins, as it has been difficult to purify recombinant nondenatured E6 and E7 proteins suitable for antibody production (31). Antibodies produced using these denatured proteins do not have sufficient sensitivity for clinical use (16). We have recently overcome the technical hurdles and have purified recombinant HPV E6 and E7 proteins in their native form to generate monoclonal antibodies that recognize HPV E6 and E7 from many high-risk HPV types.…”