Human papillomavirus infection in Danish female sex workers. Decreasing prevalence with age despite continuously high sexual activity

[Up to date in sexually transmitted infections: epidemiology, diagnostic approaches and treatments]

In the last years, there have been important advances in sexually transmitted infections such as genome sequencing of Treponema pallidum, Chlamydia trachomatis or Mycoplasma genitalium; the new taxonomic position of Calymmatobacterium granulomatis; commercial diagnostic systems based on nucleic acid amplification; the emergence of quinolone resistance in Neisseria gonorrhoeae; new therapeutic approaches in vulvovaginal candidiasis that include boric acid; the demonstration that valacyclovir reduces the risk of transmission of genital herpes or the availability of immune-response modifier in the treatment of genital warts, and that are questions in the goal of this review. Viral hepatitis and HIV were no reviewed by space reasons.

Genital warts

Genital warts are an epidermal manifestation attributed to the epidermotropic human papillomavirus (HPV). Over 100 types of double-stranded HPV have been isolated and completely sequenced thus far. HPV are grouped into low-risk (non-oncogenic) types such as type 6 and type 11, which cause benign anogenital warts (condyloma accuminata), and high-risk (oncogenic) types, such as types 16, 18, 31, and 45, which occasionally lead to cancer.

Concordance of prevalence of human papillomavirus DNA in anogenital and oral infections in a high-risk population

The concordance of the prevalence of human papillomavirus (HPV) DNA in 188 sex workers in five different locations was investigated. HPV was found in 43.6% of the women, and its prevalence at genital sites was similar. Prevalence was highest among women aged 20 years or younger but declined thereafter in specimens from all anogenital sites.

Genital human papillomavirus genotyping by HPV oligonucleotide microarray in Korean commercial sex workers

Because of the diversity in human papillomavirus (HPV) distribution, according to the population and region, detailed investigations of HPV genotypes are important in designing more effective HPV vaccines for any given country. HPV DNA oligonucleotide microarray was used to investigate the distribution of HPV genotypes among commercial sex workers. The prevalence of HPV in Korean commercial sex workers was 47%, with HPV-16 and HPV-51 as the dominant genotypes. HPV subtypes in 148 commercial sex workers comprised 70 with one genotype, 42 with two genotypes, 17 with three genotypes, and 19 with four or more genotypes. HPV-40, the most dominant low-risk genotype, was not detected in single-infection commercial sex workers. All women with multiple infections of low-risk genotypes had the HPV-40 genotype. This molecular epidemiological study of genital HPV will be useful for the development of a favorable strategy to prevent the spread of this potentially serious infection.

Chapter 2: Natural history of anogenital human papillomavirus infection and neoplasia

This chapter suggests promising areas of future epidemiologic research on human papillomavirus (HPV) and anogenital cancer, organized around our understanding of cervical carcinogenesis. The major steps in cervical carcinogenesis include HPV infection, HPV persistence over a certain period of time, progression to precancer, and invasion. Backward steps include clearance of HPV infection and regression of precancer. Additional studies of incident HPV infections among virgins initiating sexual activity could clarify the earliest aspects of transmission and immune response. Research on older women and their male partners should focus on understanding the determinants of varying age-specific HPV prevalence curves and underlying dynamics of viral persistence, clearance, and latency. It will be particularly important for epidemiologists to define HPV persistence rigorously in order to guide clinical management and vaccine trials. Intensive longitudinal studies that collect visual, microscopic (cytologic and histologic), and molecular data will be needed to understand the fate of individual HPV infections and to clarify whether multiple, concurrent infections act independently on the cervix. Case-control designs will be useful mainly in searching for new biomarkers of risk of progression among HPV-infected women that could then be validated prospectively. Prospective confirmation is also needed for the etiologic cofactors established by case-control studies of invasive cervical cancer. Much of the knowledge about cervical cancer might apply to anal neoplasia. Epidemiologic studies of other genital tumors such as penile neoplasia are still needed, but multicentric groups must place great emphasis on measurement technology, given the difficulty in obtaining reliable comprehensive measurements.

Human papillomavirus: epidemiology and public health

Approximately 15 types of human papillomavirus (HPV) infection cause virtually all cases of cervical cancer. Human papillomavirus 16 is the major type, accounting for approximately 50% of cases. The major steps of cervical carcinogenesis include HPV infection, viral persistence and progression to precancer (as opposed to viral clearance), and invasion. Human papillomavirus is the most common sexually transmitted infection. However, most HPV infections become undetectable by even sensitive HPV DNA testing within 1 to 2 years. The prevalence of infection peaks at young ages and declines thereafter, perhaps as the result of HPV type-specific acquired immunity. Most HPV infections are neither microscopically evident nor visible, making HPV DNA detection the diagnostic reference standard. Poorly defined immunologic factors are the major determinants of viral outcome. Smoking, multiparity, and long-term oral contraceptive use increase the risk of persistence and progression. Other sexually transmitted infections (eg, Chlamydia trachomatis), chronic inflammation, and nutritional factors might also play a role. Overt, long-term viral persistence in the absence of precancer is uncommon. New prevention strategies can be derived from the evolving knowledge of HPV carcinogenesis. Human papillomavirus vaccination is the ultimate prevention strategy, and large-scale trials are already underway. In the meantime, HPV DNA diagnostics are more sensitive although less specific than cytology, permitting a consideration of lengthened screening intervals. In terms of public health education, clinicians and patients will need to shift discussions of the mildly abnormal Papanicolaou test to consideration of HPV infection as a common sexually transmitted infection that rarely causes cervical cancer.

Repetitive and consistent cervicovaginal exposure to certain viral pathogens appears to protect against their sexual acquisition in some women: potential mechanisms

Several groups have proposed that human female promiscuity or polyandry, with repetitive and consistent cervicovaginal exposure to human immunodeficiency virus type 1 (HIV-1), can lead to protection against sexual acquisition of HIV-1 in some of these women. The mechanism of this phenomenon, the highly exposed persistently HIV-seronegative (HEPS) state, is unknown. Thus far, it has been correlated with viral epitope-specific immune responses in only about half of the women evaluated. But when present, these responses decline rapidly following interruption of pathogen exposure, and correlate with prompt acquisition of HIV. I have extended the concept of HEPS to another sexually transmitted viral pathogen, human papillomavirus (HPV). Supporting clinical and immunological information were identified from a literature search using PubMed as well as several sets of epidemiological data, including longitudinal surveys of HIV-1 incidence among female commercial sex workers (CSWs) in Africa and Thailand, and follow-up of a Danish cohort of CSWs and a large group of Brazilian women, both at high risk for HPV infection. These studies suggest that male-to-female penile-vaginal transmission of at least two viruses, HIV-1 and HPV, is blocked by local mucosal responses, immunologic or otherwise, which require repetitive, uninterrupted exposure to pathogen. Exploration of the mechanisms underlying such ostensibly protective responses may facilitate development of STD vaccines.

Do condoms prevent genital HPV infection, external genital warts, or cervical neoplasia? A meta-analysis

BACKGROUND

Although condoms most likely prevent HIV infection, evidence of their effectiveness against other sexually transmitted diseases is mixed.

GOAL

The goal of the study was to determine whether condom use prevents genital human papillomavirus (HPV) infection and HPV-related conditions.

STUDY DESIGN

We conducted a literature review and meta-analysis of the effect of condom use on the prevention of genital warts, subclinical HPV infection, cervical intraepithelial neoplasia (CIN), and invasive cervical cancer (ICC).

RESULTS

Among 27 estimates from 20 studies, there was no consistent evidence that condom use reduces the risk of becoming HPV DNA-positive. However, risk for genital warts, CIN of grade II or III (CIN II or III), and ICC was somewhat reduced.

CONCLUSIONS

Available data are too inconsistent to provide precise estimates. However, they suggest that while condoms may not prevent HPV infection, they may protect against genital warts, CIN II or III, and ICC.

Genotype spectrum of cervical human papillomavirus infection among sexually transmitted disease clinic patients in Hong Kong

Previous studies have suggested that a few uncommon human papillomavirus (HPV) genotypes are prevalent in Chinese cervical cancer patients. To elucidate the genotype spectrum of HPVs circulating among Hong Kong Chinese, a cross-sectional study was conducted on 553 women who attended a public sexually transmitted disease clinic. HPV DNA was detected from cervical samples using the polymerase chain reaction, followed by genotype identification based on restriction fragment length polymorphism and direct sequencing. The prevalence of HPV was 30.6% for all types combined, 14.8% for high-risk types, 10.8% for low-risk types, and 7.1% for unknown-risk types. Among the HPV-positive women, 89.9% had single type infections; whereas the other 10.1% harboured more than one HPV type. HPV11 was the most prevalent genotype, detected in 5.1% of subjects; followed by HPV16 (4.9%), HPV58 (4.3%), HPV6 (3.3%), and HPV53 and CP8304 (2.2% each). Other less common genotypes found were HPV18, 33, 39, 61, LVX160, MM4, MM7 (range: 0.7-1.6%); HPV26, 45, 54, 56, 59, and LVX100 (range: 0.4-0.5%); HPV35, 40, 52, 55, 68, MM8, and MM9 (0.2% each). This study shows that HPV58 is the second most common high-risk HPV genotype circulating among Chinese female sexually transmitted disease clinic patients in Hong Kong. This together with previous reports of the high prevalence of HPV58 among Chinese cervical cancer patients accentuate the importance of developing vaccines targeting at this otherwise uncommon genotype.

Risk factors for genital HPV DNA in men resemble those found in women: a study of male attendees at a Danish STD clinic

OBJECTIVES

Genital infection with certain types of human papillomavirus (HPV) is the most important risk factor for cervical cancer. The male sexual partner is supposed to be the vector of the infection. However, the knowledge of risk factors for genital HPV DNA in men is limited. The objective of this paper is to study the risk factors for HPV infection in men and to compare them with those found in women, including the study of whether there are different risk profiles for oncogenic and non-oncogenic HPV types.

METHODS

From a sexually transmitted diseases (STD) clinic in Denmark, 216 men were consecutively included. A personal interview was done and material for genital HPV DNA detection was obtained with swabs. HPV DNA was detected by polymerase chain reaction (PCR). Odds ratios (OR) for HPV as well as for oncogenic and non-oncogenic types separately were computed with a 95% confidence interval (CI) by means of unconditional multiple logistic regresssion.

RESULTS

The most important predictors of any HPV were lifetime number of sex partners (OR = 4.3; 95% CI 1.4 to 13.1 for 25-39 v 1-9 partners), young age, and being uncircumcised. The most important risk factor for oncogenic HPV types was lifetime number of partners, whereas number of partners in the past year and ever having genital warts were risk factors for the non-oncogenic HPV types. Young age predicted risk of both oncogenic and non-oncogenic HPV types.

CONCLUSIONS

Most risk factors for HPV DNA detection in men resemble those found in women. As in women, the risk factor profile for the oncogenic HPV types was different from that of the non-oncogenic HPV types.