COMPARISON OF PEPTIDE ENZYME-LINKED-IMMUNOSORBENT-ASSAY AND RADIOIMMUNOPRECIPITATION ASSAY WITH IN VITRO-TRANSLATED PROTEINS FOR DETECTION OF SERUM ANTIBODIES TO HUMAN PAPILLOMAVIRUS TYPE-16 E6 AND E7 PROTEINS

Antibodies to human papilloma virus (HPV) type 16 (HPV-16) E6 and E7 p roteins in serum are markers for HPV-associated invasive cervical carc inoma. We compared two assays, a radioimmunoprecipitation assay with i n vitro-translated HPV-16 E6 and E7 proteins and an enzyme-linked immu nosorbent assay (ELISA) with E6 and E7 synthetic peptides, for their a bilities to discriminate serologically between patients with invasive cervical cancer and controls. Among the patients, antibody prevalences were higher by the E6 radioimmunoprecipitation assay (55.7%) than by the E6 peptide ELISA (15.5%), but among the controls, they were lower by the radioimmunoprecipitation assay (1.7%) than by the E6 peptide EL ISA (5%). For E7, antibody prevalences among the patients were compara ble by the radioimmunoprecipitation assay (43%) and the peptide ELISA (41%), but among the controls they were higher by the E7 peptide ELISA (17.4%) than by the radioimmunoprecipitation assay (4.1%). There was good agreement between the E7 radioimmunoprecipitation assay and the E 7 peptide ELISA among patients but not among controls. In tests with r epresentative sera, heat denaturation of the translated proteins resul ted in a complete loss of reactivity to the E6 protein and a marked de crease in reactivity to the E7 protein. Our study showed that the radi oimmunoprecipitation assay discriminates better than the peptide ELISA between patients with invasive cervical cancer and controls and that this is related to the ability of the radioimmunoprecipitation assay t o detect conformational epitopes.