Cervical lesions are associated with human papillomavirus type 16 intratypic variants that have high transcriptional activity and increased usage of common mammalian codons

Abstract

Human papillomavirus type 16 (HPV-16) is a major cause of cervical neoplasia, but only a minority of HPV-16 infections result in cancer. Whether particular HPV-16 variants are associated with cervical disease has not yet been clearly established. An investigation of whether cervical neoplasia is associated with infection with HPV-16 intratypic variants was undertaken by using RFLP analyses in a study of 100 HPV-16 DNA-positive women with or without neoplasia. RFLP variant 2 was positively associated [odds ratio (OR) l 2n57] and variant 5 was negatively associated with disease (OR l 0n2). Variant 1, which resembles the reference isolate of HPV-16, was found at a similar prevalence among those with and without neoplasia. Variants 1 and 2 were also more likely to be associated with detectable viral mRNA than variant 5 (respectively P l 0n03 and P l 0n00). When HPV-16 E5 ORFs in 50 clones from 36 clinical samples were sequenced, 19 variant HPV-16 E5 DNA sequences were identified. Twelve of these DNA sequences encoded variant E5 amino acid sequences, 10 of which were novel. Whilst the associations between HPV-16 E5 RFLP variants and neoplasia could not be attributed to differences in amino acid sequences, correlation was observed in codon usage. DNA sequences of RFLP variant 2 (associated with greatest OR for neoplasia) had a significantly greater usage of common mammalian codons compared with RFLP pattern 1 variants.

The cellular transcription factor Brn-3a and the smoking-related substance nicotine interact to regulate the activity of the HPV URR in the cervix

“…Thus, using logistic analysis, the odds ratio for Brn-3a-expressing women infected with V2 getting cervical cancer is 3.34 times greater as a smoker than as a non-smoker (Table 4). In addition, the odds ratio associated with CIN progression for women infected with V5, increased from 0.2, as reported by Bible et al (2000), to 3.2 as observed in this study for those who smoke and present Brn-3a (Table 4). This indicates that women who express Brn-3a in their cervix and are exposed to smoking are 16 times more susceptible to a progressive CIN upon V5 infection (Table 4).…”

“…In addition, our previous studies have shown that the cellular transcription factor Brn-3a, differentially regulates different HPV-16 variants that have previously been shown to be associated with different risks of progression to cervical carcinoma (Bible et al, 2000;Ndisang et al, 2006b). In those studies, we showed that the URRs of the HPV high-risk V2 variant and the intermediate-risk V1 variant were activated by Brn-3a, whereas the URR of the low-risk V5 variant was not (Bible et al, 2000;Ndisang et al, 2006b).…”

“…To identify the specific HPV-16 variant that the patients who smoked or did not smoke were infected with, we used a RFLP (Restriction Fragment Length Polymorphism) assay, which was adapted from the study by Bible et al (2000), and have used previously to type the DNA of different HPV variants in clinical samples (Sindos et al, 2003a;Ndisang et al, 2006a). Thus, we were able to identify the type of HPV-16 variant each of the women were infected with (Table 1).…”

“…Importantly, the RFLP-based typing data, indicate that, even though the cervical material used for this assay were obtained from women who attended clinics in England and Brazil, there were five predominant and common variants among them, that is, variant 1, variant 2, variant 5, variant 7 and variant 8 (Bible et al, 2000;Ndisang et al, 2006b). Of these, the most important variants were as follows: variant 5 that was previously shown to be negatively associated with viral transcription and cervical neoplasia (odds ratio 0.2); variant 2 that is positively associated with disease (odds ratio 2.57); and variant 1 that shows an intermediate risk of disease (Bible et al, 2000;Ndisang et al, 2006b). Hence, it was now possible to characterize each patient as a smoker, non-smoker or ex-smoker, in terms of the HPV variant they were infected with and in terms of E6 and Brn-3a mRNA levels.…”

“…In those studies, we showed that the URRs of the HPV high-risk V2 variant and the intermediate-risk V1 variant were activated by Brn-3a, whereas the URR of the low-risk V5 variant was not (Bible et al, 2000;Ndisang et al, 2006b).…”