Antibodies against human papillomavirus (HPV) type 16 and 18 E2, E6 and E7 proteins in sera: correlation with presence of papillomavirus DNA

Abstract

Human papillomavirus (HPV) infection is associated with cervical cancer. The E2 and E1 papillomavirus proteins are expressed at the early stage of infection and regulate DNA replication. The E2 protein activates and represses transcription from different HPVs promoters. At some stage when viral DNA gets integrated into the cellular genome, the E2 gene is disrupted or inactivated. This event leads to a derepression of the E6 and E7 viral oncogenes. These viral proteins are required normally for the maintenance of the malignant phenotype. Therefore, the E2, E6, and E7 proteins are present in all patients infected by papillomavirus. In this study, the association of antibody levels against E2, E6, and E7 proteins of HPV types 16, 18, and 6 was determined in relation to the presence of HPV DNA at the initial stages of HPV infection. Serum samples from 172 women with HPV infection, determined by Papanicolau (Pap) smears and colposcopy, were tested. Elevated antibody titers against E2 protein from the HPV 6 and HPV 16 were detected in 46.42 and 66.96% of the patients, respectively. Antibodies against the E7 and E6 proteins of HPV 16 were found in 51.78 and 36.60% of the patients, respectively. Antibodies against the E6 and E7 proteins of HPV 18 were 35 and 45%, respectively. A statistical difference was found for antibody titers against the E2, E6, and E7 proteins between patients with papillomavirus DNA and controls cases who had no cytological abnormalities and no HPV DNA. Sera titers were 1/500 for patients HPV positive and 1/50 for control individuals. Antibodies titers against E6 and E7 proteins were also examined in patients at 6 and 24 months after cryosurgery. In these patients, a slight decrease in the antibody level against the E2, E6, and E7 proteins was found. No correlation was found between age and number of sexual partners, with serum positivity to the E2, E6, and E7 papillomavirus proteins. These data suggest that antibodies against the E2, E6, and E7 proteins are good candidates for use as markers for monitoring cervical HPV infections.