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

Niche adaptation and viral transmission of human papillomaviruses from archaic hominins to modern humans

Recent discoveries on the origins of modern humans from multiple archaic hominin populations and the diversity of human papillomaviruses (HPVs) suggest a complex scenario of virus-host evolution. To evaluate the origin of HPV pathogenesis, we estimated the phylogeny, timing, and dispersal of HPV16 variants using a Bayesian Markov Chain Monte Carlo framework. To increase precision, we identified and characterized non-human primate papillomaviruses from New and Old World monkeys to set molecular clock models. We demonstrate specific host niche adaptation of primate papillomaviruses with subsequent coevolution with their primate hosts for at least 40 million years. Analyses of 212 HPV16 complete genomes and 3582 partial sequences estimated ancient divergence of HPV16 variants (between A and BCD lineages) from their most recent common ancestors around half a million years ago, roughly coinciding with the timing of the split between archaic Neanderthals and modern Homo sapiens, and nearly three times longer than divergence times of modern Homo sapiens. HPV16 A lineage variants were significantly underrepresented in present African populations, whereas the A sublineages were highly prevalent in European (A1-3) and Asian (A4) populations, indicative of viral sexual transmission from Neanderthals to modern non-African humans through multiple interbreeding events in the past 80 thousand years. Remarkably, the human leukocyte antigen B*07:02 and C*07:02 alleles associated with increased risk in cervix cancer represent introgressed regions from Neanderthals in present-day Eurasians. The archaic hominin-host-switch model was also supported by other HPV variants. Niche adaptation and virus-host codivergence appear to influence the pathogenesis of papillomaviruses.

Synonymous codon changes in the oncogenes of the cottontail rabbit papillomavirus lead to increased oncogenicity and immunogenicity of the virus

Papillomaviruses use rare codons with respect to the host. The reasons for this are incompletely understood but among the hypotheses is the concept that rare codons result in low protein production and this allows the virus to escape immune surveillance. We changed rare codons in the oncogenes E6 and E7 of the cottontail rabbit papillomavirus to make them more mammalian-like and tested the mutant genomes in our in vivo animal model. While the amino acid sequences of the proteins remained unchanged, the oncogenic potential of some of the altered genomes increased dramatically. In addition, increased immunogenicity, as measured by spontaneous regression, was observed as the numbers of codon changes increased. This work suggests that codon usage may modify protein production in ways that influence disease outcome and that evaluation of synonymous codons should be included in the analysis of genetic variants of infectious agents and their association with disease.

Papillomavirus E5: the smallest oncoprotein with many functions

Papillomaviruses (PVs) are established agents of human and animal cancers. They infect cutaneous and mucous epithelia. High Risk (HR) Human PVs (HPVs) are consistently associated with cancer of the uterine cervix, but are also involved in the etiopathogenesis of other cancer types. The early oncoproteins of PVs: E5, E6 and E7 are known to contribute to tumour progression. While the oncogenic activities of E6 and E7 are well characterised, the role of E5 is still rather nebulous. The widespread causal association of PVs with cancer makes their study worthwhile not only in humans but also in animal model systems. The Bovine PV (BPV) system has been the most useful animal model in understanding the oncogenic potential of PVs due to the pivotal role of its E5 oncoprotein in cell transformation. This review will highlight the differences between HPV-16 E5 (16E5) and E5 from other PVs, primarily from BPV. It will discuss the targeting of E5 as a possible therapeutic agent.

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

The cellular transcription factor Brn-3a differentially regulates different human papilloma virus (HPV)-16 variants that are associated with different risks of progression to cervical carcinoma in infected humans. The upstream regulatory regions (URRs) of high- and intermediate-risk HPV-16 variants are activated by the cellular transcription factor Brn-3a, whereas the URR of a low-risk HPV-16 variant is not. In this study, we show in transfection assays that Brn-3a and the smoking-related substance nicotine produce stronger responsiveness of the URR of the low- and high-risk variants than with either factor alone, but not the intermediate-risk variant. We determined that this synergistic activity of Brn-3a/nicotine is due to two nucleotide differences in the URR, crucial for oncogenic E6/E7 transactivation. Mutant constructs in which the nucleotide residues were substituted alter Brn-3a/nicotine responsiveness. Importantly, women smokers with high levels of Brn-3a infected with low- or high-risk HPV-16 variants have augmented E6 levels, and were more frequently diagnosed with higher grades of cervical intraepithelial neoplasia (CIN) and cancer, as compared with non-smokers who were infected with similar variants and expressed similar levels of Brn-3a. Therefore, this study defines the specific interplay between the cellular transactivator Brn-3a, the environmental smoking-related substance nicotine and specific HPV variants in cervical carcinogenesis, and thus helps to explain why some women are susceptible to rapid CIN progression and cancer and others are not.

All 4 di-leucine motifs in the first hydrophobic domain of the E5 oncoprotein of human papillomavirus type 16 are essential for surface MHC class I downregulation activity and E5 endomembrane localization

The E5 oncoprotein of human papillomavirus type 16 downregulates surface MHC Class I and interacts with the heavy chain of the MHC complex via the first hydrophobic domain, believed to form the first helical transmembrane region (TM1) of E5. TM1 contains 4 equally spaced di-leucine (LL1-LL4) motifs. Di-leucine motifs have been implicated in protein-protein interactions and as localization signals. To see if any of the 4 di-leucine motifs of TM1 are involved in MHC downregulation by E5, we mutated each LL pair into valine pairs (VV1-VV4), as mutation of leucine to valine is not expected to cause major structural alterations in E5. We found that all 4 mutations disrupted the intracellular location of E5 and abrogated its MHC I downregulating activity; however VV2 and VV4 mutants were still able to interact physically with the MHC I heavy chain (HC) in vitro, while VV1 and VV3 mutants had lost this activity. We conclude that LL1 and LL3 are necessary for the interaction with HC, but LL2 and LL4 are not. However all 4 LL motifs are responsible for the proper localization of E5 in the Golgi/ER, and the displacement of E5 from this location contributes to the abrogation of MHC I downregulation. LL1 and LL3 motifs are expected to be on one face of the TM1 helix and LL2 and LL4 on the opposite face. We propose that E5 interacts with HC via LL1 and LL3 and that all 4 di-leucine motifs act as a targeting signal.

Upstream regulatory region alterations found in human papillomavirus type 16 (HPV-16) isolates from cervical carcinomas increase transcription, ori function, and HPV immortalization capacity in culture

Human papillomavirus (HPV) DNAs isolated from cervical and head and neck carcinomas frequently contain nucleotide sequence alterations in the viral upstream regulatory region (URR). Our study has addressed the role such sequence changes may play in the efficiency of establishing HPV persistence and altered keratinocyte growth. Genomic mapping of integrated HPV type 16 (HPV-16) genomes from 32 cervical cancers revealed that the viral E6 and E7 oncogenes, as well as the L1 region/URR, were intact in all of them. The URR sequences from integrated and unintegrated viral DNA were found to harbor distinct sets of nucleotide substitutions. A subset of the altered URRs increased the potential of HPV-16 to establish persistent, cell growth-altering viral-genome replication in the cell. This aggressive phenotype in culture was not solely due to increased viral early gene transcription, but also to augmented initial amplification of the viral genome. As revealed in a novel ori-dependent HPV-16 plasmid amplification assay, the altered motifs that led to increased viral transcription from the intact genome also greatly augmented HPV-16 ori function. The nucleotide sequence changes correlate with those previously described in the distinct geographical North American type 1 and Asian-American variants that are associated with more aggressive disease in epidemiologic studies and encompass, but are not limited to, alterations in previously characterized sites for the negative regulatory protein YY1. Our results thus provide evidence that nucleotide alterations in HPV regulatory sequences could serve as potential prognostic markers of HPV-associated carcinogenesis.

High risk of human papillomavirus type 16 infections and of development of cervical squamous intraepithelial lesions in systemic lupus erythematosus patients

OBJECTIVE

To determine rates of human papillomavirus (HPV) infections, abnormal cervical smears, and squamous intraepithelial lesions (SIL) among women with systemic lupus erythematosus (SLE).

METHODS

We investigated 30 women with SLE, 67 with abnormal smears from colposcopy clinics, and 15 community subjects with normal smears. Polymerase chain reaction results for viral DNA and HPV-16 sequencing data were correlated to cytology and colposcopic findings.

RESULTS

SLE and colposcopy patients were more likely (P < 0.05) to be HPV positive (15 [54%] and 37 [67%] patients, respectively) and HPV-16 DNA positive (16 [57%] and 17 [31%] patients, respectively) than community subjects (0% HPV DNA positive and 1 [6%] HPV-16 DNA positive). SLE patients were also more likely to be HPV-16 DNA positive than colposcopy patients (P < 0.05). SLE patients with a high HPV-16 viral load more frequently had SIL (n = 6) than those with a low HPV-16 viral load (n = 1; P < 0.05). HPV and HPV-16 DNA positivity were not associated with previous or current drug therapy for SLE patients. All HPV-16 DNA sequences from 6 SLE and 5 colposcopy patients were the European-type variant. Eighteen (60%) SLE patients had a previous or current cervical abnormality. At the time of study, 5 (17%) SLE patients had an abnormal cervical smear and 8 (27%) had SIL. For those diagnosed with SLE for >10 years, the rate of SIL was 44% lower than those with SLE for <5 years (odds ratio 0.56, 95% confidence interval 0.1-3.5).

CONCLUSION

UK women with a recent SLE diagnosis had disturbingly elevated levels of HPV infections (particularly with European HPV-16 variants at a high viral load), abnormal cervical cytology, and SIL.

Analyses of variant human papillomavirus type-16 E5 proteins for their ability to induce mitogenesis of murine fibroblasts

BACKGROUND

Human papillomavirus type 16 (HPV-16) E5 protein co-operates with epidermal growth factor to stimulate mitogenesis of murine fibroblasts. Currently, little is known about which viral amino acids are involved in this process. Using sequence variants of HPV-16 E5 we have investigated their effects upon E5 transcription, cell-cycling and cell-growth of murine fibroblasts.

RESULTS

We demonstrate that: (i) introduction of Thr64 into the reference E5 sequence of HPV-16 abrogates mitogenic activity: both were poorly transcribed in NIH-3T3 cells; (ii) substitution of Leu44Val65 or, Thr37Leu44Val65 into the HPV-16 E5 reference backbone resulted in high transcription in NIH-3T3 cells, enhanced cell-cycle progression and high cell-growth; and, (iii) inclusion of Tyr8 into the Leu44Val65 backbone inhibited E5 induced cell-growth and repression of p21 expression, despite high transcription levels.

CONCLUSION

The effects of HPV-16 E5 variants upon mitosis help to explain why Leu44Val65 HPV-16 E5 variants are most prevalent in 'wild' pathogenic viral populations in the UK.

Epidemiological and functional implications of molecular variants of human papillomavirus

Human papillomavirus genomes are classified into molecular variants when they present more than 98% of similarity to the prototype sequence within the L1 gene. Comparative nucleotide sequence analyses of these viruses have elucidated some features of their phylogenetic relationship. In addition, human papillomavirus intratype variability has also been used as an important tool in epidemiological studies of viral transmission, persistence and progression to clinically relevant cervical lesions. Until the present, little has been published concerning the functional significance of molecular variants. It has been shown that nucleotide variability within the long control region leads to differences in the binding affinity of some cellular transcriptional factors and to the enhancement of the expression of E6 and E7 oncogenes. Furthermore, in vivo and in vitro studies revealed differences in E6 and E7 biochemical and biological properties among molecular variants. Nevertheless, further correlation with additional functional information is needed to evaluate the significance of genome intratypic variability. These results are also important for the development of vaccines and to determine the extent to which immunization with L1 virus-like particles of one variant could induce antibodies that cross-neutralize other variants.

Detection of cervical abnormalities in a developing country using measurement of Brn-3a in cervical smears

OBJECTIVE

We have previously shown that Brn-3a is elevated in biopsies from women in the United Kingdom with high grade cervical neoplasia, and that it specifically trans-activates the HPV URR in vitro and in vivo. The aim of this study is to establish the relationship of Brn-3a, HPV E6 and pathological diagnosis in cervical smear from women in a developing country with a high prevalence of cervical disease. This is a follow-up of our previous work in which for the first time Brn-3a and E6 levels in cervical smears from women in United Kingdom were shown to correlate with the histological diagnosis of cervical neoplasia and were even better in predicting underlying pre-malignant disease than conventional procedures.

METHOD

Cervical smears from 295 women with cervical abnormalities attending gynecological clinics in Brazil were used to make RNA. The mRNA levels of Brn-3a and HPV E6 were measured and the data obtained were used to establish the relationship between Brn-3a and the histological diagnosis.

RESULTS

The cellular transcription factor Brn-3a was readily measured in cervical smears from the Brazilian population. Its presence was shown to be frequently associated with the expression of HPV E6. The measured level of Brn-3a parallels the severity of the cervical ailment and predicts the pathological categories.

CONCLUSIONS

The ability of Brn-3a to predict for cervical ailments is independent to the geographical characteristics of the population, and hence it could be used routinely as an adjunct to colposcopy and pathological diagnosis in developing and developed countries.

Differential regulation of different human papilloma virus variants by the POU family transcription factor Brn-3a

The Brn-3a POU family transcription factor is overexpressed in human cervical carcinoma biopsies and is able to activate expression of the human papilloma virus type 16 (HPV-16) upstream regulatory region (URR), which drives the expression of the E6 and E7 oncoproteins. Inhibition of Brn-3a expression in human cervical cancer cells inhibits HPV gene expression and reduces cellular growth and anchorage independence in vitro as well as the ability to form tumours in vivo. Here, we show that Brn-3a differentially regulates different HPV-16 variants that have previously been shown to be associated with different risks of progression to cervical carcinoma. In human cervical material, Brn-3a levels correlate directly with HPV E6 levels in individuals infected with a high risk variant of HPV-16, whereas this is not the case for a low-risk variant. Moreover, the URRs of high- and intermediate-risk variants are activated by Brn-3a in transfection assays, whereas the URR of a low-risk variant is not. The change of one or two bases in a low-risk variant URR to their equivalent in a higher-risk URR can render the URR responsive to Brn-3a and vice versa. These results help explain why the specific interplay between viral and cellular factors necessary for the progression to cervical carcinoma only occurs in a minority of those infected with HPV-16.

Analysis of human papillomavirus type-16 variants in Italian women with cervical intraepithelial neoplasia and cervical cancer

Human papillomavirus type 16 (HPV-16) classes (E, AA, As, Af1, Af2) and their variants have different geographic distribution and different degrees of association with cervical lesions. This study was designed to examine HPV-16 variants among Italian women and their prevalence in case patients (affected by invasive cervical carcinoma or cervical intraepithelial neoplasia grade 2-3 and cervical intraepithelial neoplasia grade 1), versus control subjects with normal cervical epithelium (controls). A total of 90 HPV-16 positive cervical samples from women of Italian Caucasian descent have been tested, including 36 invasive cervical carcinomas, 21 with cervical intraepithelial neoplasias grade 2-3, 17 with cervical intraepithelial neoplasia grade 1 and 16 controls. HPV-16 was detected with an E6/E7 gene-specific polymerase chain reaction, and variant HPV-16 classes and subclasses were identified by direct nucleotide sequencing of the region coding for the E6 and the E7 oncoproteins, the MY09/11-amplified highly conserved L1 region, and the long control region (LCR). Among the 90 HPV-16 samples, nine viral variants have been identified belonging to the European (Ep-T350 and E-G350) and non-European (AA and Af-1) branches. The E-G350 is the prevalent variant in all analyzed different disease stages being present in 55.5% of ICC, 52.4% of cervical intraepithelial neoplasias 2-3, 47.1% of cervical intraepithelial neoplasia grade 1, and 50.0% of control samples. The non-European variants AA and Af1, rarely detected in control samples, represent 33.3% of all HPV-16 infections in invasive cervical carcinoma (with a peak of 19.4% and 13.9%, respectively), showing a statistically significant increase in frequency in more advanced lesions (chi(2) trend = 7.2; P < 0.05). The prevalence of HPV-16 Ep-T350, however, is higher in controls (43.7%) and in of cervical intraepithelial neoplasia grade 1 (41.2%) than in cervical intraepithelial neoplasia grade 2-3 (28.6%) and in invasive cervical carcinoma (11.1%) cases strongly suggesting lack of progression for pre-neoplastic lesions associated with such variant. The increased frequency of non-European variants in invasive lesions suggests that they are more oncogenic than European variants. This could have implications for future diagnostic and therapeutic strategies.

Denaturing high-performance liquid chromatography for detecting and typing genital human papillomavirus

Human papillomaviruses (HPVs) are important in the development of human cancers, including cervical and oral tumors. However, most existing methods for HPV typing cannot routinely distinguish among the more than 100 distinct types of HPV or the natural HPV intratypic variants that have also been documented. To address this problem, we developed a novel method, general primer-denaturing high-performance liquid chromatography (GP-dHPLC), for the detection and typing of genital HPV using an automated 96-well plate format. GP-dHPLC uses general primer PCR (GP-PCR) to amplify the viral DNA and then analyzes the GP-PCR products by denaturing high-performance liquid chromatography (dHPLC). A number of different primer pairs with homology to most known genital HPV types were tested, and the L1C1-L1C2M pair specific for the L1 region of the viral genome was chosen. A set of HPV standard control patterns, consisting of those for HPV types 16, 18, 31, 33, 39, 45, 51, 52, 56, 58, 59, 6, and 11, was established for genital HPV typing. One hundred eighty-six frozen and formalin-fixed cervical cancer tissue samples were analyzed for the presence of HPV and the HPV type by this method, and 95.8% of them were found to contain HPV DNA. GP-dHPLC accurately discriminated among HPV variants that differed by as little as one nucleotide. Several new variants of HPV types 16, 18, 39, 45, 52, and 59 were identified. Moreover, multiple HPV infections were detected in 26.6% of the samples. Our results indicate that HPV typing by GP-dHPLC permits discrimination of common genital HPV types, detection of multiple HPV infections, and identification of HPV variants in clinical samples.

Buccal exposure to human papillomavirus type 16 is a common yet transitory event of childhood

High-risk human papillomaviruses, such as type 16 (HPV-16), are established etiological agents for cervical carcinoma. In most cases, this virus is transmitted sexually, though can also be spread from mother to infant at delivery. We have demonstrated previously a high prevalence ( approximately 52%) of HPV-16 DNA in the mouths of prepubertal children, albeit with low levels of transcription [Rice et al., 2000]. We investigated whether childhood buccal infections with HPV-16 are persistent or transient and whether children became infected through contact with their immediate family members. Two groups of children were selected: one group were all initially HPV-16 E5 DNA-positive in sensitive polymerase chain reaction tests of swabs from their buccal mucosa (n = 20), and the other group consisted of children who were all HPV-16 E5-negative (n = 19). Thirty months later, a second oral swab was collected from each child and tested for HPV DNA. At this second visit, 40% of the HPV-16-positive group had no detectable HPV-16 DNA; conversely, 63% of children who were originally HPV-16-negative had now acquired the virus. Three months later, a third sample was collected from eight children and their immediate families (seven were HPV-16 E5 DNA-positive at the second visit). Amongst the family samples tested, in two families a single previously untested child was HPV-16 DNA-positive. It is concluded that HPV-16 DNA in the oral cavities of children is a transient event and is most probably acquired from their peers.

A synthetic E7 gene of human papillomavirus type 16 that yields enhanced expression of the protein in mammalian cells and is useful for DNA immunization studies

A synthetic E7 gene of human papillomavirus (HPV) type 16 was generated that consists entirely of preferred human codons. Expression analysis of the synthetic E7 gene in human and animal cells showed levels of E7 protein 20- to 100-fold higher than those obtained with wild-type E7. Enhanced expression of E7 protein resulted from highly efficient translation, as well as increased stability of the E7 mRNA due to its codon optimization. Higher levels of E7 protein in cells transfected with synthetic E7 correlated with significant loss of cell viability in various human cell lines. In contrast, lower E7 protein expression driven by the wild-type gene resulted in a slight induction of cell proliferation. Furthermore, mice inoculated with plasmids expressing the synthetic E7 gene produced significantly higher levels of E7 antibodies than littermates injected with wild-type E7, suggesting that synthetic E7 may be useful for DNA immunization studies and the development of genetic vaccines against HPV-16. In view of these results, we hypothesize that HPVs may have retained a pattern of G + C content and codon usage distinct from that of their host cells in response to selective pressure. Thus, the nonhuman codon bias may have been conserved by HPVs to prevent compromising viability of the host cells by excessive viral early protein expression, as well as to evade the immune system.

Red queen dynamics of protein translation

We explore adaptive theories for the diversity of translational binding based on the genetic code viewed as a primitive mechanism of resistance. Modifying the set of codons bound by tRNA anticodon molecules or changing the specificity of binding, reduces the replication rate of translational parasites such as viruses. Increased translational efficiency of the parasite requires a high degree of specificity of host tRNAs for the parasite codons. This suggests that the genetic code might serve as the first line of defense against infection. We construct a red queen theory for translational diversity: a theory in which host-translational strategies- as defined by the degree of redundancy (a single anticodon binding many codons for a single amino acid) or degeneracy (many anticodons binding many codons for a single amino acid)-are constantly shifting through time to evade parasitism but where neither parasite nor host gain a systematic advantage.

Host and viral genetics and risk of cervical cancer: a review

Infection with human papillomaviruses (HPV) is known to play a central role in the development of cervical cancer. Both host and viral genetic factors have been postulated to be important determinants of risk of HPV progression to neoplasia among infected individuals. In this report, we review epidemiological studies that have evaluated the role in cervical cancer pathogenesis of genetic variation in human leukocyte antigen (HLA) genes and in the HPV genome itself. A protective effect of HLA Class II DRB1*13/DBQ1*0603 alleles is the most consistent HLA finding in the published literature. A consistent association between HPV16 non-European variants and risk of disease is also evident from published work. These findings are discussed. Gaps in our understanding and future research needs are also discussed.

Oncogene lineages of human papillomavirus type 16 E6, E7 and E5 in preinvasive and invasive cervical squamous cell carcinoma

Human papillomavirus (HPV)16 accounts for about 60% of the HPV infections in invasive cervical cancer (ICC). There are many sequence variations within HPV16, some of which have been associated with different biological properties, although no definite correlations have yet been established. However, the definition 'variant' has been a source of confusion in research and diagnosis, since it is based on all sequence deviations from a randomly selected prototype. This study has sequenced the HPV16 oncogenes E6, E7 and E5 from 61 Swedish cases with cervical intraepithelial neoplasia grade III (CIN III) or ICC. Clustering the sequence variations at the three common sites of variation (nucleotide 350 in E6, which has previously been associated with the progression from CIN III to ICC, and nucleotides 3979 and 4042 in E5) resulted in the distinction of three major oncogene lineages encompassing more than 95% of the cases, and two minor oncogene lineages. Simple comparison of the distribution of the individual variations or oncogene lineages between CIN III and ICC showed no significant difference, but the number of variations in addition to the three common ones was significantly higher in ICC. This novel classification scheme, based on the variations in the E6, E7 and E5 region, is considered to be a major improvement over the classical 'prototype-variant' classification, and can help to clarify the interpretation of HPV sequence data in relation to the progression of cervical cancer.

Analysis of E6 variants of human papillomavirus type 33, 52 and 58 in Japanese women with cervical intraepithelial neoplasia/cervical cancer in relation to their oncogenic potential

The variation of the E6 region of human papillomavirus type 16 (HPV16) is associated with a high risk for cervical carcinogenesis. To see whether the same is the case with HPV33, 52 and 58, known to have high homology with HPV16, we analyzed the E6 sequence variation of these HPVs in 107 Japanese women with cervical intraepithelial neoplasia (CIN) or invasive cervical cancer (ICC): 20 HPV33-positive, 46 HPV52-positive and 41 HPV58-positive cases. HPV33 variants were more frequently observed in CINs I/II than in CIN III/ICCs (71% (5/7) versus 15% (2/13), P=0.02). In HPV52-positive cases, a single E6 variant was detected in 98% of the cases, whereas the prototype accounted for 98% of HPV58-positive cases. In summary, the distribution of E6 variants is different among HPV types tested, suggesting a link between E6 variation and oncogenic potential being type-specific.

Novel method for detection, typing, and quantification of human papillomaviruses in clinical samples

We report the development of a novel detection and typing methodology for human papillomaviruses (HPV) based on real-time PCR with the self-probing fluorescent primers known as Scorpions. This technique is quick, simple, specific, sensitive, and capable of estimating viral load per cell. We report the results of over 100 typing reactions performed on cell lines, biopsies, and cervical cytobrush samples which, when compared to the current reference HPV detection and typing technique, present a kappa value of 0.89. We further report preliminary data suggesting a relationship between viral load per cell and grade of cervical disease.

Diagnosing human papillomaviruses: recent advances

The biological importance of a group of human papillomaviruses, known as high-risk human papillomaviruses, as the key causal agent for almost all cervical cancer has now been established. Many aspects of the natural history of high-risk human papillomaviruses as sexually transmitted infections and as oncogenic agents have been researched. Although human papillomavirus diagnosis is largely confined to DNA detection techniques in cervical smears, there is accumulating evidence that the best polymerase chain reaction and hybrid capture techniques are more sensitive and probably of similar specificity compared with cervical cytology as a triage test for women with borderline smear abnormalities and for screening older women. This is strong presumptive evidence that high-risk human papillomavirus testing could be useful in cervical screening. Current research is aimed at establishing a place for high-risk human papillomavirus testing in routine screening practice. Randomised clinical trials, long-term natural history studies, mathematical modelling, and economic and psychosocial studies are being used to demonstrate whether this testing can improve both the effectiveness and efficiency of cervical screening in a range of situations.