Papillomaviruses are an ideal model system for the study of DNA virus evolution. On several levels, phylogenetic trees of papillomaviruses reflect the relationship of their hosts. Papillomaviruses isolated from remotely related vertebrates form major branches. One branch of human papillomaviruses (HPVs) includes an ape and two monkey papillomaviruses, possibly because the diversification of the viruses predated the separation of the infected-primate taxa. This hypothesis predicts that the root of the evolution of some if not all HPV types should point to Africa, since humans evolved from nonhuman primates in this continent. We tested this hypothesis and compared the genomic sequences of HPV type 18 (HPV-18) isolates from four continents. Diversity within HPV-18 correlates with patterns of the evolution and spread of Homo sapiens: HPV-18 variants, just like HPV-16 variants, are specific for the major human races, with maximal diversity in Africa. Outgroup rooting of the HPV-18 tree against HPV-45, which is closely related to HPV-18, identifies African HPV-18 variants at the root of the tree. The identification of an African HPV-45 isolate further reduces the evolutionary distance between HPV-18 and HPV-45. HPV-18 variants from Amazonian Indians are the closest relatives to those from Japanese and Chinese patients and suggest that a single point mutation in the phylogenetically evaluated genomic segment represents at least 12,000 years of evolution. We estimate that diversity within HPV-18 and probably within other HPV types evolved over a period of more than 200,000 years and that diversity between HPV types evolved over several million years.

Radiation proctitis is a common complication of radiotherapy for pelvic malignancy. In the more severe form, it leads to intractable or massive hemorrhage, which may require repeated hospital admissions and blood transfusions. Medical therapy in patients with radiation proctitis is usually ineffective, whereas surgery is associated with a high morbidity and mortality. Eight patients (seven females and one male) with hemorrhagic radiation proctitis were treated over a six-month period with endoluminal formalin. The technique used ensured minimal contact with formalin. The median age of the patients was 68 years (range, 42-73 years). Seven patients had had cancer of the uterine cervix, and one patient had had cancer of the prostate treated with radiotherapy at a median time of 30 months (range, 9-46 months) previously. The median duration of time of symptomatic rectal hemorrhage before formalin therapy was eight months (range, 1-12 months). The median number of units of blood transfused previously per patient was four (range, 2-32). The time taken for formalin therapy was 20 minutes (range, 10-70 minutes). One patient required repeat formalin application at two weeks. Bleeding ceased immediately in seven patients after formalin treatment. No further bleeding was noted, nor was any blood transfusion needed, at follow-up at four months (range, 1-6 months). Formalin therapy is a simple, inexpensive, and effective treatment for hemorrhagic radiation proctitis.

Genomic variability between different viral isolates provides a powerful epidemiological tool for verifying ultrasensitive diagnostic procedures, understanding infectious pathways in individuals and human populations, and studying viral evolution. The potential of this approach has not yet been exploited for the diagnosis of human papillomaviruses (HPVs) like HPV type 16 (HPV-16), which are involved in genital cancer. Toward this end, we amplified by polymerase chain reaction, cloned, and sequenced a 364-bp noncoding segment of the HPV-16 genome from cell lines, cervical biopsy specimens, and cervical smears. The HPV-16 genomes in the cell lines SiHa and CaSki showed an identical point mutation, and in the SiHa cell line it had an additional 38-bp deletion. Only 4 of 22 cervical lesions biopsied from patients at several hospitals in Singapore contained HPV-16 DNA with the prototype sequence, while the DNAs of the other 18 cervical lesions differed by 1 to 10 mutations. This excludes contaminations with cloned HPV-16 DNA as the source of this DNA. To test whether this diversity was a geographic idiosyncrasy, we analyzed 25 cervical biopsy specimens from Brazil. Eight of these contained the prototype sequence, while 17 were mutated. Altogether, 11 genomic variants were found in the Singaporean samples and 12 genomic variants were found in the Brazilian samples, and only 5 of these occurred identically in both cohorts. All variants could be connected to form a phylogenetic tree, with some branches being specific for each cohort. This suggests that the variants did not originate over a short period in the individual patient but, rather, evolved consecutively while spreading throughout humankind. Repeated amplification with the low-error Vent polymerase suggested that at least five patients each had two variants in the same biopsy specimen, while another patient exhibited different variants in two separate biopsy specimens. This documents the possibility of multiple infections with variants of the same papillomavirus type. We do not believe that the observed variants have greater carcinogenicity, since similar variants were found in cervical smears from asymptomatic women. In chloramphenicol acetyltransferase assays, enhancer segments of some selected samples that were analyzed did not show altered transcriptional activity. This was expected since most of the mutations did not coincide with known cis-responsive elements. The observed sequence variability can be used as a natural tag of the viral genome to unambiguously assess a variety of epidemiological questions.

BackgroundHuman papillomavirus (HPV) vaccines are widely available and there have been studies exploring their potential clinical impact and cost-effectiveness. However, few studies have compared the cost-effectiveness among the 2 main vaccines available - a bivalent vaccine against HPV 16/18, and a quadrivalent vaccine against 6/11/16/18. We explore the cost-effectiveness of these two HPV vaccines in tropical Singapore.MethodsWe developed a Markov state-transition model to represent the natural history of cervical cancer to predict HPV infection, cancer incidence, mortality, and costs. Cytologic screening and treatment of different outcomes of HPV infection were incorporated. Vaccination was provided to a cohort of 12-year old females in Singapore, followed up until death. Based on available vaccines on the market, the bivalent vaccine had increased effectiveness against a wider range of HPV types, while the quadrivalent vaccine had effectiveness against genital warts. Incremental cost-effectiveness ratios (ICER) compared vaccination to no-vaccination, and between the two vaccines. Sensitivity analyses explored differences in vaccine effectiveness and uptake, and other key input parameters.ResultsFor the no vaccination scenario, 229 cervical cancer cases occurred over the cohort's lifetime. The total discounted cost per individual due to HPV infection was SGD$275 with 28.54 discounted life-years. With 100% vaccine coverage, the quadrivalent vaccine reduced cancers by 176, and had an ICER of SGD$12,866 per life-year saved. For the bivalent vaccine, 197 cancers were prevented with an ICER of $12,827 per life-year saved. Comparing the bivalent to the quadrivalent vaccine, the ICER was $12,488 per life-year saved. However, the cost per QALY saved for the quadrivalent vaccine compared to no vaccine was $9,071, while it was $10,392 for the bivalent vaccine, with the quadrivalent vaccine dominating the bivalent vaccine due to the additional QALY effect from reduction in genital warts. The overall outcomes were most sensitive to vaccine cost and coverage.ConclusionHPV vaccination is a cost-effective strategy, and should be considered a possible strategy to reduce the impact of HPV infection.