Sequence variation in the E7 gene of human papillomavirus type 18 in tumor and non-tumor patients and antibody response to a conserved seroreactive epitope.

We have determined nucleotide sequences of the E7 open reading frame (ORF) of human papillomavirus type 18 (HPV-18) isolates obtained from 18 cervical carcinomas from Tanzanian and German patients and 8 cervical scrapings from Tanzanian non-tumor patients. The HPV-18 prototype sequence was detected in only 3 out of 26 isolates. Silent mutations were found at nt positions 640 and 751, whereas the mutations observed at nt positions 770, 806, 864 and 865 all change the respectively encoded amino acid. The HPV-18 isolates of 3 German carcinomas showed the same mutations (at position 751) as those of 2 established cervical carcinoma cell lines (HeLa and C4-1), whereas different mutations were found in 16/23 African isolates (at positions 640 and 864), to which the isolate of cell line SW756 was similar (changes at positions 640 and 865). Seven out of 15 HPV-18-positive Tanzanian tumor patients (46.7%) reacted in a peptide ELISA against a recently described seroreactive epitope of the HPV-18 E7 ORF (nt positions 704-769). Mutational changes of the E7 ORF were excluded as a possible explanation for the lack of antibody response, because there was no correlation with the serological results. The seroreactive region appears to be well conserved despite geographically varying mutations within the E7 ORF of HPV-18.

Geographical dependence of sequence variation in the E7 gene of human papillomavirus type 16.

We have determined nucleotide sequences of the E7 open reading frame (ORF) of human papillomavirus type 16 (HPV-16) isolates obtained from 32 genital tumours and two HPV-16-transformed human keratinocyte cell lines. In comparison to the prototype HPV-16 isolated from a German cervical cancer biopsy, no sequence variations were noticed in either the two cell lines or the 10 biopsies that were obtained from German patients. In contrast only three of 22 (13.6%) of Tanzanian isolates showed the prototype sequence. In 18 of these biopsies two alterations (T to C and T to G) not affecting the amino acid sequence were found within the HPV-16 E7 ORF (nucleotide positions 789 and 795) but eight of these isolates contained an additional change (nucleotide position 647) coding for serine instead of asparagine (amino acid position 29). One tumour harbours HPV-16 DNA with a mutation (C to T) at nucleotide 790 changing the E7 amino acid sequence (arginine to cysteine) at position 76. Our findings suggest that clustering of E7 sequence variants may occur in different geographical regions of the world.

Human papillomavirus (HPV) infection, HIV infection and cervical cancer in Tanzania, east Africa.

The presence of HPV-DNA was determined in tumor biopsies of cervical-cancer patients and in cervical swabs of non-cancer patients from Tanzania, East Africa, by Southern blot hybridization and/or PCR. HPV types 16 and 18 were detected in 38% and 32%, respectively, of 50 cervical-carcinoma biopsies. A consensus primer PCR capable of detecting a broad spectrum of HPV types revealed the presence of HPV-DNA in 59% of 359 cervical swabs of non-cancer patients. Type-specific PCR showed that types 16 and 18 accounted for 13.2% and 17.5%, respectively, of all HPV infections. Therefore we concluded that HPV 18 is more prevalent in Tanzania than in any other geographical location so far reported. The strongest risk factors for the presence of any HPV-DNA in the 359 female non-cancer patients were young age and HIV infection. The epidemiology of HPV types 16 and 18 was found to differ from that of other HPV types, being associated in univariate analysis with trichomonas vaginalis infection, martial status (single/divorced), age at first intercourse, and young age at menarche. However, young age at menarche accounted for most of the effects of all other, variables in multivariate analysis. Of the non-cancer patients, 12.8% had antibodies against HIV I (no patient being severely symptomatic), and HIV infection was highly correlated with the presence of HPV-DNA, especially types 16 and 18. While HPV-DNA of any type was detectable 1.4-fold more often in HIV-positive patients than in HIV-negative patients, evidence of an infection with HPV types 16 or 18 was found 2.2-fold more often in the HIV-positive patients. The HIV-positive women did not show an increased rate of cervical cytological abnormalities as assessed by PAP staining of a single cervical smear, the overall rate of abnormalities being 2.8%. Furthermore, the age-adjusted prevalence of HIV antibodies was found to be considerably lower in 270 cervical-carcinoma patients (3% HIV-positive) in comparison with non-cancer patients. Thus there was no association observable between the prevalence of HIV infections and the frequency of cervical cytological abnormalities or cervical cancer in the setting of this cross-sectional study.

PIP: Southern blot hybridization and/or PCR was used to examine tumor biopsies of 53 women with cervical or vaginal cancer at Ocean Road Hospital in Dar es Salaam, Tanzania, and the cervical swabs of 359 women with no cancer at the gynecologic clinic at Muhimbili University College of Health Sciences in Dar es Salaam. Tanzanian and German scientists wanted to determine whether an association existed between human papillomavirus (HPV) infections and HIV, and whether the high prevalence of HIV infection was matched by a high prevalence of HPV infections, cervical dysplasias, and cervical cancer in HIV-positive cases. 59% of the noncancerous women had HPV-DNA. Young age and HIV infection were the greatest risk factors for HPV-DNA in these women (p .0001 for age and HPV-16/18; p = .08 for other HPVs; and p = .03 for HIV). 13.2% and 17.5% of all HPV infections were HPV types 16 and 18, respectively. Tanzania had the highest prevalence of HPV 18 ever reported. HPV-16/18 risk factors included: Trichomonas vaginalis infection (odds ratio [OR] = 2.23; p = .04), single status (OR = 2.55; p = .01), 16 years old or less at first intercourse (OR = 2.1; p = .03), and young age at menarche (OR = 6 for or=12 years old; p = .02 and OR = 3.25 for or=13 years old and or=16 years old; p = .05). Yet, the multivariate analysis revealed young age at menarche had the greatest effect (OR = 6.2 for or= 12 years old, p = .03; OR = 3.73 for or=16 years old, p = .08). 12.8% of noncancerous women tested positive for HIV-1, but none of them were obviously symptomatic. These HIV-positive women had a higher OR if they had HPV-16/18 than if they had other HPV types (4.25 vs. 2.02). Further, they did not have more cervical cytological abnormalities than did the HIV-negative women (overall cervical cytological abnormality rate - 2.8%). The HIV-positive rate for cancerous patients was only 3%. In conclusion, no association existed between HIV infection and cervical cytological abnormalities or cervical cancer.