Human papillomavirus (HPV) DNA copy number is dependent on grade of cervical disease and HPV type

The association between human papillomavirus (HPV) DNA copy number and cerv ical disease was investigated. Viral DNA copy number for the most common hi gh-risk HPV types in cervical cancer (types 16, 18, 31, and 45) was determi ned in cervical cytobrush specimens from 149 women with high-grade cervical intraepithelial neoplasias (CIN II-CIN III), 176 with low-grade CIN (CIN I ), and 270 with normal cytology. Quantitative, PCR-based fluorescent assays for each of the HPV genotypes and for the beta-globin gene were used. The amount of cellular DNA increased significantly with increasing disease; thu s, HPV was expressed as copies per microgram of cellular DNA. The assay had a dynamic range of >10(7), allowing documentation for the first time of th e wide range of HPV copy numbers seen in clinical specimens, Median HPV DNA copy number varied by more than 10(4) among the viral types. HPV16 was pre sent in the highest copy number; over 55% of HPV16-positive samples contain ed more than 10(8) copies/mu g. Median copy number for HPV16 sheared dramat ic increases with increasing epithelial abnormality, an effect not seen wit h the of her HPV types. HPV16 increased from a median of 2.2 x 10(7) in pat ients with normal cytology, to 4.1 x 10(7) in CIN 1 patients, to 1.3 x 10(9 ) copies/mu g in CIN II-III patients. Even when stratified by cervical dise ase and viral type, the range of viral DNA copies per microgram of cellular DNA was quite large, precluding setting a clinically significant cutoff va lue for "high" copy numbers predictive of disease. This study suggests that the clinical usefulness of HPV quantitation requires reassessment and is a ssay dependent.