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

Certain human papillomaviruses (HPV), mainly types 16 and 18, have been widely recognized as an essential etiologic factor for the development of carcinoma of the uterine cervix. The early HPV proteins E6 and E7 are consistently expressed in the tumor cells, and cervical-carcinoma patients can develop antibodies against these oncoproteins. For cervical-carcinoma patients from Eastern Europe and Russia, detailed information on HPV DNA prevalence and HPV-specific immune responses is limited. The presence of HPV DNA in 128 Russian cervical-carcinoma tissues was determined: HPV16 DNA was found in 78% of the cases, HPV18 DNA in 14%, and no HPV-DNA in 10%. Using 4 recently developed sensitive and highly specific second-generation enzyme-linked immunosorbent assays, we also analyzed the prevalence of antibodies against HPV16 and -18 E6 and E7 proteins in sera from 95 cervical-carcinoma patients, from 61 female patients with non-HPV-associated tumors and from 83 female healthy controls. The strong association of E6 and/or E7 antibodies with cervical carcinoma was confirmed, with 36% seropositives in this group against only 2% in the control groups. The detected antibodies are highly HPV-type-specific since all 26 HPV16-E6- or -E7-antibody-positive patients had HPV16 DNA in their tumor and 6 out of the 8 HPV18-antibody-positive patients had HPV18 DNA. Antibody responses to HPV16 E6 and E7 appear to be dependent on clinical stage of the disease, with 21% seropositives found in FIGO stage I, 42% in stage II and 53% in stage III. Antibody response to HPV16 E6 is more frequent than to E7, especially in early stages.