Serologic response to human papillomavirus 16 among Australian women with high-grade cervical intraepithelial neoplasia

Use of the normalized absorbance ratio as an internal standardization approach to minimize measurement error in enzyme-linked immunosorbent assays for diagnosis of human papillomavirus infection

The serological detection of antibodies against human papillomavirus (HPV) antigens is a useful tool to determine exposure to genital HPV infection and in predicting the risk of infection persistence and associated lesions. Enzyme-linked immunosorbent assays (ELISAs) are commonly used for seroepidemiological studies of HPV infection but are not standardized. Intra- and interassay performance variation is difficult to control, especially in cohort studies that require the testing of specimens over extended periods. We propose the use of normalized absorbance ratios (NARs) as a standardization procedure to control for such variations and minimize measurement error. We compared NAR and ELISA optical density (OD) values for the strength of the correlation between serological results for paired visits 4 months apart and HPV-16 DNA positivity in cervical specimens from a cohort investigation of 2,048 women tested with an ELISA using HPV-16 virus-like particles. NARs were calculated by dividing the mean blank-subtracted (net) ODs by the equivalent values of a control serum pool included in the same plate in triplicate, using different dilutions. Stronger correlations were observed with NAR values than with net ODs at every dilution, with an overall reduction in nonexplained regression variability of 39%. Using logistic regression, the ranges of odds ratios of HPV-16 DNA positivity contrasting upper and lower quintiles at different dilutions and their averages were 4.73 to 5.47 for NARs and 2.78 to 3.28 for net ODs, with corresponding significant improvements in seroreactivity-risk trends across quintiles when NARs were used. The NAR standardization is a simple procedure to reduce measurement error in seroepidemiological studies of HPV infection.

Human papillomavirus 16 and 18 L1 serology in Korean women with high-grade cervical intraepithelial neoplasia and cervical cancer

We aimed to determine the prevalence of HPV-16/18 antibodies in Korean women with high-grade cervical intraepithelial neoplasia (CIN) and cervical cancer. We conducted the hospital-based case-control study at the university hospital between 2003 and 2006. Cases were 130 high-grade CIN and 43 cervical cancer patients and the control group was 106 women showing normal cervical cytology. Enzyme-linked immunosorbent assays were performed for HPV-16/18 L1 virus-like particles (VLPs) as an antigen. Seropositivity for HPV-16 VLP and HPV-18 VLP was found in 67.4% and 30.2% of cancer patients and 59.2% and 20.0% of high-grade CIN patients, respectively. Seropositivity for HPV-16 with high-grade CIN (OR 6.91; 95% CI 3.74-12.76) and cervical cancer (OR 8.99; 95% CI 3.88-20.84) presented significant associations, as did seropositivity for HPV-18 (high-grade CIN: OR 3.64; 95% CI 1.67-7.95, cervical cancer: OR 6.82; 95% CI 2.52-18.45). Patients with both HPV-16 and 18 seropositivity were 9.38 times (95% CI 2.98-29.51) more likely to have high-grade CIN and 17.05 times (95% CI 4.55-63.87) more likely to have cancer. Both HPV 16 and 18 L1 VLP serology is the clear disease predictors of presence of high-grade CIN and cervical cancer.

Expression and purification of human papillomavirus 18 L1 virus-like particle from saccharomyces cerevisiae

Cervical cancer caused by human papillomavirus (HPV) might be successfully prevented by HPV vaccination and screening. HPV vaccination and HPV serology assays have been investigated using HPV virus-like particles (VLPs). In this study we produced HPV18 L1 VLPs in Saccharomyces cerevisiae and purified them. The HPV18 L1 gene was cloned into the yeast expression vector YEGalpha-HIR525, and transformed into Saccharomyces cerevisiae. Expression of HPV18 L1 protein was demonstrated by Western blotting. The HPV18 L1 protein was purified by ultracentrifugation, size-exclusion chromatography and cation-exchange chromatography, and was up to 95% pure. We showed by transmission electron microscopy that the purified protein self-assembled into VLPs. These findings should be useful for establishing vaccine efficacy as well as characterizing vaccine candidates, and may provide an international reference standard for HPV serology assays.