Variants of the long control region of human papillomavirus type 16

Expression of the human papillomavirus (HPV) E6 and E7 oncogenes is regulated on the transcriptional level by specific protein-binding sites contained in the viral long control region (LCR). Sequence changes within the LCR region may have an impact on the transcription of viral oncogenes, possibly resulting in differences in the oncogenic potential of the virus. The present study was designed to determine the sequence variability of the LCR of HPV 16 and to assess whether certain LCR variants do correlate with the clinical outcome of the disease of the uterine cervix. The entire LCR segment of HPV 16 was analysed from 37 cervical biopsy specimens derived from 28 women included in the Kuopio long-term prospective follow-up study. The LCR sequence was identical with the reference sequence in six HPV 16 isolates. Overall, 14 different HPV 16 LCR variants were identified. One of the variants showed sequence variation typical of the Asian-American variant lineage of HPV 16, and all the other variants appeared to belong to the European variant group. The European variants exhibited low genetic diversity, and only five of these LCR variants contained nucleotide changes involving known or proposed binding sites for transcription factors. The variants with changes at nucleotide positions 7193 and 7521 was the most prevalent, accounting for almost 37% of infections. This variant (7193; 7521) has been previously demonstrated to have similar transcriptional activity compared with the reference isolate by Veress and colleagues J Gen Virol 1999, 80, 1035-1043. The reference isolate, variant (7193; 7521) and variants with changes within transcription factor binding sites accounted for most of the infections, and no significant differences were found in the comparison of the distribution of these different LCR isolates in cases where the disease showed progression to severe cervical intraepithelial neoplasia (CIN) or carcinoma in situ (CIS). Notably, both the reference isolate and variant (7193; 7521) were also closely associated with infections showing more aggressive behaviour. According to the present findings, in European HPV 16 isolates, intratype genetic variation of the LCR region does not seem to be commonly responsible for differences in the pathogenicity of the virus and thereby for a risk of progressive infections.