A New Sandwich ELISA Test Simultaneously Detecting E7 Proteins of HPV-16,
18 and 45 in Cervical Smears

Persistent infections by high-risk papilloma viruses (HPV) are the main etiological factor for cervical cancer, and E7 oncoproteins were suggested as new markers for tumor progression. The objective of this study was to generate a new Enzyme-Linked Immunosorbent Assay (ELISA)-based detection system to monitor expression of the E7 proteins of the high-risk HPV (hrHPV) types HPV-16, HPV-18, and HPV-45 in cervical smears. Using a combination of rabbit monoclonal antibodies raised against E7 proteins of HPV-16 and HPV-18/HPV-45, respectively, a trivalent E7-ELISA was developed and validated, using recombinant E7 proteins of various HPV types and lysates from E7- positive cervical carcinoma cells. The amount of 0.5 picogram of E7 protein per well was determined as detection limit. The E7-ELISA was used to determine E7 protein levels in cervical smears obtained from a total of 67 women. E7 protein concentration was below the detection limit in all HPV-negative smears, and E7 protein concentrations above background were found in some HPV-positive cervical samples. Together the work described herein provides a new tool for the simultaneous detection of E7 proteins of the three most prevalent in cervical neoplasia hrHPV types.