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

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)=2.57] and variant 5 was negatively associated with disease (OR=0.2). 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=0.03 and P=0.00). 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.

High prevalence of human papillomavirus type 16 infection among children

Infection with high-risk human papillomaviruses (HPV), is the most significant risk factor for cervical cancer and it may be possible to prevent this malignancy by immunisation. Before immunisation programmes can be designed, however, it is necessary to know the age of acquisition and all routes of infection for these viruses. Sexual transmission is well documented and vertical transmission has also been demonstrated, although the frequency of transmission remains controversial. We previously showed that vertical transmission frequently results in persistent infection, and now present data on the prevalence of HPV-16 DNA (the most prevalent high-risk HPV type) in healthy children. Buccal samples from 267 healthy children aged 3-11 years were tested for HPV DNA by generic PCR (MY09/MY11), and a HPV-16 specific nested PCR. Reverse transcriptase (RT)-PCR was used to determine the prevalence of transcriptionally active HPV-16 infection in a subset of children. HPV-16 DNA was detected by nested PCR in 138 of 267 (51.7%) samples, whereas HPV DNA was detected in only 45 (16.8%) specimens by generic PCR, that has a lower analytical sensitivity. There were no significant differences in prevalence according to age or sex. Early region mRNA was detected by RT-PCR in six (11.3%) of 53 HPV-16 E5 DNA positive samples. HPV-16 E5 DNA sequences from 10 children confirmed the identity of the sequences detected and identified 13 HPV-16 variants.

Proliferative T-cell responses to human papillomavirus type 16 E5 are decreased amongst women with high-grade neoplasia

Proliferative responses to human papillomavirus type 16 (HPV-16) E5 peptides were determined for short-term cell lines derived from peripheral blood mononuclear cells of 75 women. Cell lines from 16 of the 75 women proliferated in response to stimulation with pooled E5 peptides; this was most common for patients with low-grade squamous cervical intraepithelial lesions (LSIL; 6 of 15 patients, 40%) and less frequent for asymptomatic women with no cervical lesions (4 of 20, 20%), those with high-grade squamous intraepithelial lesions(HSIL; 5 of 33, 15%) and others with cervical cancer (1 of 7, 14%, P = 0.027). Amongst these patients, proliferative responses were exclusive to those that were positive for HPV-16 DNA (12 of 41, 29%; c.f. none of 13 HPV-16 DNA-negative subjects exhibited a proliferative response; P= 0023) and were again most prevalent amongst HPV-16 DNA-positive LSIL (6 of 14, 43%), as compared with HPV-16 DNA-positive HSIL (5 of 23, 22%) or HPV-16 DNA-positive cervical cancer patients (1 of 4, 25%, P > 0.05). In contrast, for asymptomatic women, responsiveness was statistically independent of HPV-16 DNA status, i.e. responsiveness in HPV-16 DNA-positive and DNA-negative subjects was observed in 3 of 15 (20%) and 1 of 5 (20%) cases, respectively (P > 0.05). There were no associations between detection of HPV-16 mRNA and proliferative responses (P> 0.05). These data suggest that HPV-16 E5-specific T-helper activity is depressed amongst women with HSIL lesions.

Polymerase chain reaction protocols for the detection of DNA from mucosal human papillomavirus types -6, -11, -16, -18, -31 and -33

Individual types of human papillomaviruses (HPV) which infect mucosal surfaces have been implicated as the causative agents for carcinomas of the cervix, anus, penis, larynx and the buccal cavity, occasional periungal carcinomas, as well as benign anogenital warts. The identification of particular HPV types is thus important for: identifying patients with premalignant lesions who are at risk of progression to malignancy; epidemiological studies; studies of the natural history of these viruses; and even medico-legal cases of suspected sexual abuse of children. In this protocol we describe PCR assays for: the identification of DNA from the mucosal HPVs types -6, -11, -16, -18, -31 and -33; a consensus HPV PCR for detecting DNA from 20 characterised mucosal HPVs, as well as more than 25 novel HPVs; and, for a control PCR for beta-globin.

Detection of human papillomavirus type 16 early-gene transcription by reverse transcription-PCR is associated with abnormal cervical cytology

Human papillomavirus type 16 (HPV-16) is associated with abnormal Papanicolou smears, indicative of cervical intraepithelial neoplasia. HPV-16 is the most common genital HPV and is found in up to 40% of young women with normal cervical cytology. In order to investigate whether transcriptionally active HPV-16 infection is associated with abnormal cervical smears, a reverse transcription-nested PCR assay with primers from the E5 open reading frame was developed to detect all HPV-16 early-region mRNA (E-mRNA) transcripts. It was used to study HPV-16-infected women with normal and abnormal cervical cytologies to obtain evidence of active infection. Among HPV-16 DNA-positive women, HPV-16 E-mRNA was detected in 15 of 37 (40.5%) women with abnormal cervical cytology but in only 4 of 35 (11.4%) women with normal cytology (P = 0.007). Thus, HPV-16 E-mRNA transcription is associated with abnormal cervical smears and may have value as a prognostic marker of progressive disease.

Analytic sensitivities of hybrid-capture, consensus and type-specific polymerase chain reactions for the detection of human papillomavirus type 16 DNA

Human papillomavirus type 16 (HPV-16) DNA is detected commonly in cervical carcinomas; in this study, we have determined the analytical sensitivities of Hybrid Capture, HPV-consensus PCR, and three HPV-16-specific polymerase chain reactions (PCRs) for the detection of HPV-16 DNA. Samples investigated included a cervical cancer cell line, cervical scrapes from 20 patients attending colposcopy clinics, and buccal swabs from eight immunosuppressed children. HPV-16 E7 and E5-nested PCRs [Cavuslu et al. (1996): Journal of Virological Methods, in press] produced positive signals from samples containing fewer than ten HPV-16 genomes per reaction. HPV-consensus PCR [Manos et al. (1989): Cancer Cells 7:209-214] and HPV-16 PCR using primers of van den Brule et al. [(1990): Journal of Clinical Microbiology 25:2739-2743] were of intermediate sensitivity (i.e., produced positive signals from samples containing 250 and 2,500 HPV-16 genoms/reaction, respectively) and Hybrid Capture could detect just 50,000 HPV-16 genomes/reaction. Highest rates of positivity for cervical samples were detected with HPV-16 E7 or E5-nested PCRs [50% (10 of 20 samples) and 60% (12 of 20 samples) positive, respectively], intermediate rates with HPV-consensus PCR and PCRs using the primers of van den Brule et al. [both 35% (7 of 20 samples)], and lowest rates of positivity [25% (5 of 20 samples)] with Hybrid Capture. None of eight buccal swab samples from immunosuppressed children were positive by Hybrid Capture, yet three (37.5%) were positive by HPV-16 E5-nested PCR. These data indicate that HPV-16 type-specific PCRs should be used for the investigation of specimens that may contain low amounts of HPV-16 DNA.

Human papillomavirus type 16 in infants: use of DNA sequence analyses to determine the source of infection

Perinatal transmission of human papillomavirus type 16 (HPV-16) and persistence of virus DNA in infants until 6 months of age has been described. To confirm the origin of infant infections as maternal, we determined the nucleotide sequence of the upstream regulatory region (URR; bp 7540 to 157) of HPV-16 in samples from 13 HPV-16 DNA-positive mothers and their infants at 6 weeks and 2 years of age. Identical HPV-16 variant URR sequences were found in two mother/infant samples and similar variants were found in three sets. Four mothers with samples which contained prototypic HPV-16 sequences delivered infants who also had the prototypic sequence. Four mothers with variant URRs delivered infants who harboured either prototypic or different URR variants. Thus, concordant variants or prototypic sequences were detected in nine of 13 mother/infant samples, indicating that up to 69.2% of HPV-16-positive infants acquire virus from their mothers.

Detection of human papillomavirus type 16 in microtitre plate based immuno-enzymatic assays: use to determine E5 gene expression in cervical carcinomas

BACKGROUND

E5-based nested polymerase chain reaction (PCR) assays and a PCR-enzyme immunoassay (EIA) to detect human papillomavirus type 16 (HPV-16) DNA have been developed. These assays were designed to detect small amounts of HPV-16 DNA for epidemiological studies of subclinical infection.

OBJECTIVES

The E5 gene of HPV-16 may be lost in some cell lines derived from cervical carcinomas. The aim of this study was to determine if, and how frequently, E5 gene loss occurs in biopsy samples from patients with cervical lesions.

STUDY DESIGN

Sixteen HPV-16 (E7) DNA positive and five HPV-16 DNA negative cervical lesions (nineteen cervical carcinomas, two cervical intraepithelial neoplasias) were investigated by E5 nested PCR and EIA.

RESULTS

Overall, 15 of the 16 (93.75%) HPV-16 E7 positive samples were positive for HPV-16 E5 DNA: 14 of 16 (87.5%) were positive by E5 PCR and 15 of 16 (93.75%) were positive by E5 PCR, nested PCR and by PCR-EIA. One of 14 HPV-16 (E7) DNA positive cervical carcinomas was negative for E5 DNA in all three assays.

CONCLUSION

Loss of the HPV-16 E5 open reading frame (ORF) is a rare event in HPV-16 positive cervical carcinomas and was detected in just one of 14 (7.1%) cases.

Detection of human papillomavirus type-16 DNA utilising microtitre-plate based amplification reactions and a solid-phase enzyme-immunoassay detection system

The development of a nested polymerase chain reaction (PCR) assay to detect low concentrations of human papillomavirus type-16 (HPV-16) DNA for epidemiological studies is described. The PCR utilises primers located in the E5 open reading frame, has an analytical sensitivity of 4 HPV-16 genomes and does not produce amplicons from other common genital HPVs (types-6, -11, -18, -31 and 33). This assay was carried out in 96-well plates utilising internal primers labelled with dinitrophenol (DNP) and biotin so that amplicons can be captured onto streptavidincoated plates and detected using an alkaline phosphatase-labelled monoclonal antibody to DNP. The assay was effective for detecting HPV-16 DNA in plasmids, cell-lines and, both freshly collected or archival (formalin-fixed/paraffin embedded) clinical specimens. This system is therefore suitable for epidemiological studies to identify individuals infected with HPV-16 DNA in episomal form who may be at increased risk of developing anogenital carcinomas.

Perinatal infection and persistence of human papillomavirus types 16 and 18 in infants

Perinatal transmission of genital human papillomaviruses (HPVs), including HPV-16 and -18 which are associated with anogenital carcinomas have been described previously [Pakarian et al. (1994): British Journal of Obstetrics and Gynaecology 101:514-517; Kaye et al. (1994) Journal of Medical Virology 44:415-421]. A study was undertaken to investigate whether HPV-16 and -18 DNA in infants contaminated at delivery persists until they are 6 months of age. Of 61 pregnant women recruited, 42 (68.8%) were HPV-16 and 13 (21.3%) were HPV-18 DNA positive. At 24 hr there were transmission rates from HPV DNA positive mothers to their infants of about 73% (HPV-16: 69%; HPV-18: 76.9%). Ten mothers who were both HPV-16 and -18 DNA positive produced six (60%) infants who were also doubly positive at 24 hr. HPV DNA persisted to 6 weeks in 79.5% (HPV-16: 84%; HPV-18: 75%) of those infants who were positive at birth. At 6 months of age, persistent HPV-16 DNA was detected in 83.3% of cases, but HPV-18 DNA persistence at this time was 20%. To extend these observations over a greater age range of children HPV-16 L1 and L2 proteins were expressed in insect cells via recombinant baculoviruses and sera from 229 children were examined to determine at what age IgM antibodies to HPV were acquired. There was a bimodal distribution of IgM seropositivity which peaked between 2 and 5 and 13 and 16 years of age, suggesting that two distinct modes of transmission may occur. The observation that infection with high cancer risk genital HPVs may occur in early life and persist is of considerable importance for HPV vaccine strategies.

Viral load as a determinant for transmission of human papillomavirus type 16 from mother to child

Whilst genital papillomaviruses are commonly believed to be sexually transmitted, transmission of human papillomavirus type 16 (HPV-16) from mother to child at delivery has been described previously [Pakarian et al. (in press) British Journal of Obstetrics and Gynaecology]. In order to determine whether viral load in cervical/vaginal cells was an important determinant of transmission 15 pregnant women with HPV-16 infections were studied. Eight of these women had infants who were positive for HPV-16 DNA at genital and/or buccal sites. Viral load was estimated by laser densitometry of polymerase chain reaction (PCR) products. The eight mothers--four with a previous history of abnormal smears and two with previous genital warts--who transmitted infection to their infants had significantly higher viral loads (P < 0.05) than those who did not. It is concluded that viral load is an important, but not the sole, determinant for the transmission of HPV-16 from mother to infant.

Detection of E5 oncoprotein in human papillomavirus type 16-positive cervical scrapes using antibodies raised to synthetic peptides

Polyclonal antibodies were raised to partial and full-length synthetic peptides of human papillomavirus type 16 (HPV-16) E5. Antisera specificity for HPV-16 E5 was demonstrated by their ability to recognize not only their peptide immunogens but also full-length peptide and a glutathione S-transferase-E5 fusion protein. The most reactive antiserum, PE-6, raised to a full-length peptide, was used in Western blot analysis to identify HPV-16 E5 protein from exfoliated cervical cells. A strong, single band at approximately 20K was detected in two of six HPV-16-positive samples from women with a history of low-grade cervical intraepithelial neoplasia. The apparent M(r) by SDS-PAGE suggests that HPV-16 E5 forms homodimers in vivo, but not through cysteine linkage.

Cancer associated human papillomaviruses: perinatal transmission and persistence

OBJECTIVE

To demonstrate the perinatal transmission and persistence of the cancer associated human papillomavirus types 16, 18, 31 and 33.

DESIGN

Cervical swabs were taken from pregnant women between 20 and 38 weeks of gestation. Buccal and genital swabs were taken from infants at 24 h and at six weeks after delivery and examined for HPV-16, -18, -31 and -33 DNA by the polymerase chain reaction.

SETTING

Maternity Unit at St Thomas's Hospital, London.

SUBJECTS

Thirty-one pregnant women, 16 with a previous history of cervical intraepithelial neoplasia or genital warts, or both, and their 32 infants (one set of twins).

RESULTS

Twenty of the 31 (65%) women were positive for HPV-DNA prior to delivery. Twelve of 32 (38%) and eight of 31 (26%) infants were HPV-DNA positive at 24 h and six weeks respectively. Swabs taken at 24 h demonstrated HPV type 16 in five mother-infant pairs and HPV type 18 in two mother-infant pairs. Dual infections with HPV types 16 and 18 were demonstrated in swabs from three mother-infant pairs. At six weeks, HPV-16 was demonstrated in swabs from six infants and HPV-18 in swabs from two infants.

CONCLUSIONS

Perinatal transmission of human papillomavirus types 16 and 18 occurred in 55% cases. Persistent human papillomavirus infection was demonstrated at six weeks of age. Whether acquisition of human papillomavirus during the perinatal period predisposes to an increased risk of cervical intraepithelial neoplasia among female infants in later life remains to be established. Information on the persistence of perinatally acquired human papillomavirus is required before rational vaccination programmes can be considered.

Regions of human papillomavirus type 16 E7 oncoprotein required for immortalization of human keratinocytes

Binding of the retinoblastoma gene product (pRB) by viral oncoproteins, including the E7 of human papillomavirus type 16 (HPV 16), is thought to be important in transformation of cells. One of the steps in transformation is the immortalization process. Here we show that mutations in E7 within the full-length genome which inhibit binding of pRB do not abrogate the ability of the HPV 16 DNA to immortalize primary human epithelial (keratinocyte) cells. A mutation in one of the cysteines of a Cys-X-X-Cys motif which is contained in the carboxy half of the E7 and is part of a zinc finger arrangement completely eliminates the ability of HPV 16 DNA to immortalize cells. The results indicate the importance of E7 in the immortalization of primary keratinocytes but suggest that the binding of pRB is not essential.

Sequence dependent effects in methylphosphonate deoxyribonucleotide double and triple helical complexes

Deoxyribooligonucleotides containing 19 repeating bases of A, T or U were prepared with normal phosphodiester (dA19, dT19, dU19) or methylphosphonate (dA*19, dT*19, dU*19) linkages. Complexes of these strands have been investigated at 1:1 and 1:2 molar ratios (purine:pyrimidine) by thermal melting and gel electrophoresis. There are dramatic sequence dependent differences in stabilities of complexes containing methylphosphonate strands. Duplexes of dA*19 with dT19 or dU19 have sharp melting curves, increased Tm values, and slopes of Tm versus log (sodium ion activity) plots reduced by about one half relative to their unmodified 'parent' duplexes. Duplexes of dA19 with either dT*19 or dU*19, however, have broader melting curves, reduced Tm values at most salt concentrations and slopes of less than one tenth the values for the unmodified duplexes. Duplex stabilization due to reduced phosphate charge repulsion is offset in the pyrimidine methylphosphonate complexes by steric and other substituent effects. Triple helical complexes with dA19 + 2dT19 and dA19 + 2dU19, which can be detected by biphasic melting curves and gel electrophoresis, are stable at increased Na+ or Mg+2 concentrations. Surprisingly, however, no triple helix forms, even at very high salt concentrations, when any normal strand(s) is replaced by a methylphosphonate strand. Since triple helical complexes with methylphosphonates have been reported for shorter oligomers, inhibition with larger oligomers may vary due to their length and extent of substitution.

Synthesis and characterization of oligodeoxyribonucleotides containing terminal phosphates. NMR, UV spectroscopic and thermodynamic analysis of duplex formation of [d(pGGAATTCC)]2, [d(GGAATTCCp)]2 and [d(pGGAATTCCp)]2

Derivatives of the oligomer [d(GGAATTCC)]2 with 5' (5'-P), 3' (3'-P) and both 5' and 3' (5',3'-P2) terminal phosphate groups have been synthesized and studied by temperature dependent UV and NMR spectroscopic methods. Thermodynamic studies of the helix to strand transition indicate that addition of 3' phosphate groups has very little effect on the delta G degree for helix formation at 37 degrees C while addition of 5' phosphate groups adds approximately -0.5 kcal/mole to the delta G degree for duplex formation. The helix stabilization by 5' phosphate groups occurs at salt concentrations of 0.1 M and above, and is primarily enthalpic in origin. Tm studies as a function of ionic strength also indicate that the oligomers fall into two groups with the parent and 3'-P derivatives being similar but less stable than the 5'-P and 5',3'-P2 derivatives. Imino proton and 31P NMR studies also divide the oligomers into these same two groups based on spectral comparisons and temperature induced chemical shift and linewidth changes. 31P NMR analysis suggests that addition of 5' phosphate groups results in a small change in phosphodiester torsional angles in the g,t to g,g direction, indicating improved base stacking at the 5' end of the modified oligomer. No such changes are seen at the 3' end of the oligomer on adding 3' phosphate groups.