Human papillomavirus prevalence and associated factors in women and men in south China: a population-based study:
Feixue Wei1,*, Kai Yin2,*, Xin Wu2, Jian Lan2, Shoujie Huang1, Wei Sheng1, Jun Zhao1, Yingying Su1, Ying Wang3, Yanping Li4, Rongcheng Li4, Jun Zhang1, Mingqiang Li2, Ting Wu1 and Ningshao Xia1
1State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, National Institute of Diagnostics and Vaccine Development in Infectious Diseases, Strait Collaborative Innovation Center of Biomedicine and Pharmaceutics, School of Public Health, Xiamen University, Xiamen 361102, Fujian, China
2Liuzhou Center for Disease Control and Prevention, Liuzhou 545027, Guangxi, China
3Policy Coordination Division, China National Center for Biotechnology Development, Beijing 100039, China
4Centre for Vaccine Clinical Research, Guangxi Center for Disease Control and Prevention, Nanning 530028, Guangxi, China
Correspondence: T Wu; MQ Li, E-mail: wuting@xmu.edu.cn; lzscdclmq@126.com
*These authors contributed equally to this work.
Received 21 July 2016; Revised 9 September 2016; Accepted 12 September 2016
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ABSTRACT
Oncogenic human papillomavirus (HPV) infection is a cause of many anogenital cancers in women and men; however, there is little research on HPV prevalence and risk factors that includes both women and men from the same population. A total of 4687 participants, including 2378 women and 2309 men aged 18–55 years old from the same community, were enrolled in the study in Liuzhou, China. Exfoliated cells were collected from the participants from different anatomic sites and were tested for 13 oncogenic and 3 non-oncogenic HPV types. The prevalence of any oncogenic HPV type was higher in women than in men (18.7% vs 9.4%,P<0.001), whereas the prevalence of HPV 6 and 11 infection was similar (1.4% vs 1.2%, P=0.6832). HPV 52, 58, 16, 39 and 18 were the five most prevalent types in both sexes. Sexual and hygienic behaviors were associated with HPV infection in both women and men. We found that oncogenic HPV DNA detection is more prevalent in women than in men in China, whereas the prevalence of HPV 6 and 11 is similar in both sexes. The data indicate that the interaction of host and virus might be different among high- and low-risk HPV types.
Keywords:
human papillomavirus; men; prevalence; risk factors; women
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INTRODUCTION
Oncogenic human papillomavirus (HPV) infection is a cause of many cancers in the anogenital and oropharyngeal areas in women and men. HPV is assumed to be responsible for 100% of cervical cancers, 90% of cancers of the anus, 50% of cancers of the penis, 40% of cancers of the vulva (VU), 70% of cancers of the vagina (VA) and 20%–60% of cancers of the oropharynx.1 Non-oncogenic HPV, especially HPV 6 and 11, is responsible for up to 90% of genital warts in both sexes.2
The first generation of preventive HPV vaccines are bivalent (HPV 16 and 18) or quadrivalent (HPV 6, 11, 16 and 18) and can prevent ~70% of cervical cancer cases. The second-generation HPV vaccine is nine-valent, adding five more HPV types (HPV 31, 33, 45, 52 and 58) to the quadrivalent HPV vaccine and is expected to prevent 20% more cervical cancer cases.1 Licensed HPV vaccines are used mainly in girls aged ≥nine years and in young women. HPV is mainly transmitted through sexual activity, and case–control studies have shown that the sexual behavior of male partners affects a woman’s risk of cervical neoplasia.3, 4 Recently, a cohort study conducted in heterosexual couples illustrated that the male-to-female and female-to-male HPV transmission rates were 7.11 and 5.56 per 1000 person months, respectively.5 Therefore, the epidemiological characterization of HPV infection in both sexes from the same population is important to understand the whole picture of HPV transmission and natural history in humans.
Much has been learned about HPV prevalence in women and men, but few studies have included both sexes.6, 7, 8, 9, 10 A direct comparison of the prevalence data between sexes in different studies has been hampered by the differences in the population sampling strategy, the sensitivity of the HPV genotyping assay and the number of genotypes detected. Thus, less is known about the sex-dependent differences of anogenital HPV infection characteristics. Only one study reported that HPV prevalence was lower in the cervical samples of women than in the penile samples of men (36.7% vs 50.8%, respectively) in an HIV-negative population in South Africa, but the sample size was relatively small.11
The aim of this study was to define the prevalence and type distribution of HPV in the general population of women and men in southern China using the same protocol for HPV genotyping. The whole picture of HPV distribution and the risk factors in both sexes would be helpful for developing more effective preventive policies for HPV infection.
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MATERIALS AND METHODS
Study population
A population-based study among women and men was conducted in a rural site and an urban site of Liuzhou city, Guangxi, China, from March to July 2014. Participants were eligible if they were 18–55 years old, had ever been involved in sexual activity at enrollment, and were willing to refrain from sexual activity (including vaginal penetration, anal penetration, or any genital contact) and to avoid washing the genitals for 48 h before sample collection. Exclusion criteria consisted of having received an HPV vaccine, having reported serious illnesses or current pregnancy for women. Most of the volunteers were recruited from the general population through media advertising, including local newspapers and TV news, and educational presentations in communities. In addition, to increase the enrollment of younger people, students from Guangxi University of Science and Technology were recruited through flyers and posters.
Before study initiation, the Ethics Committee of Liuzhou Centers for Disease Controls approved all of the study procedures. At the enrollment visit, all of the participants gave written informed consent and underwent a clinical examination. Each participant was interviewed individually by a trained interviewer to complete a questionnaire. Then, genital exfoliated cell samples were obtained from each participant.
Specimen collection
For women, three iCleanhcy flocked swabs (Huachenyang Corporation, Shenzhen, China) were used to collect specimens from the VU, VA and perianal/anal (PA) canal. Physicians used a swab to swipe the region from the clitoris to the labia minora and the labia majora in a zigzag pattern to ensure acquisition of the exfoliated cells. A second swab was used to collect a sample from the lower 1/3 of the VA by separating the labia of the VU. Then, a single-use speculum was inserted into the VA, and exfoliated cells from the upper 1/3 of the VA were obtained. A third swab was used to sweep 360° around the perianal area and was then inserted into the anal canal to obtain exfoliated cells.
For men, two pre-wetted saline iCleanhcy flocked swabs (Huachenyang Corporation, Shenzhen, China) were used to collect specimens from the penis/glans penis/coronary sulcus (PGC) and PA canal. Physicians used a swab to rub up and down the entire skin surface of each of the quadrants of the penis shaft. Then, the same swab was swept 360° around the glans penis and coronary sulcus. For uncircumcised men, exfoliated cells of the foreskin were collected using the same swab. The cells of the perianal and anal canal were obtained using the second swab in the same way as for women.
The swab samples were placed into separate vials containing 1 ml of PreservCyt solution (Hologic Corporation, Marlborough, MA, USA), and the tubes containing the specimens were stored at room temperature until they were transported to the laboratory of Zeesan Biotech Corporation, Xiamen, China, within two weeks for detection and typing of HPV DNA.
HPV DNA testing
HPV testing of the swab specimens was conducted using a multicolor real-time PCR and melting curve analysis. GP5+/6+ was used as the general primer rather than the MY09/MY11 or SPF10 primers, which amplified longer or shorter target L1 fragments, respectively.12, 13, 14 DNA extraction was performed using the Lad-Aid 824 system (Zeesan Biotech Corporation, Xiamen, China) according to the instructions of the manufacturer. In brief, 200 μL aliquots of the clinical material were digested with 3 M guanidine hydrochloride solution for 300 s. The DNA was eluted in 150 μL of 10 mmol/L Tris-HCl buffer (pH 7.5) at room temperature. The DNA was stored at −80 °C until use.
The specimens were tested for the presence of HPV by amplifying 5 μL of the DNA extracts with the GP5+/6+ L1 consensus primer system and Taq HS polymerase (Takara Biotechnology Corporation, Dalian, China). Each 25 μL amplification reaction contained 75 mmol/L Tris-HCl (pH 8.0), 20 mmol/L (NH4)2SO4, 4 mmol/L MgCl2, 0.01% (vol/vol) Tween 20, 1 unit of Taq HS DNA polymerase, 200 μmol/L of each deoxynucleoside triphosphate, 100 nmol/L primer GP5+, 1 μmol/L primer GP6+, 100 nmol/L primer IPC-F, 1 μmol/L primer IPC-R, and 250 nmol/L of each of the 16 HPV and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) probes, which were used to determine the adequacy of specimens. For every PCR plate, a negative control (H2O) and a positive control (containing HPV 16-, HPV 45- and HPV 58-positive plasmids) were run to control for possible contamination and accuracy. The samples were amplified using an SLAN-96p real-time PCR instrument. The following amplification profile was used: 50 °C 5 min→95 °C 3 min→(95 °C 15 s→50 °C 20 s (−1 °C per cycle)→78 °C 20 s) for 10 cycles→(95 °C 15 s→56 °C 16 s→78 °C 20 s) for 50 cycles. HPV genotyping was conducted based on the specific melting temperature of the product produced by hybridization of the PCR products and fluorescent probes. The procedure was set up as follows: 95 °C 1 min→35 °C 3 min→40 °C ~85 °C (at a heating rate of 0.04 °C /s).
Definition of outcomes
Thirteen HPV types are labeled oncogenic types, including 12 types (HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59) that are carcinogenic to humans and HPV 68, which is probably carcinogenic to humans. In addition, HPV types 6, 11 and 66 were also detected in our study. HPV 66 is possibly carcinogenic to humans, and HPV 6 and 11 are not carcinogenic to humans.15 A specimen was deemed adequate if the GAPDH or HPV genotyping was positive. The subject having at least one adequate specimen was included in the analysis. The presence of any HPV DNA in the VA, VU or PA for women or in the PGC or PA for men was defined as a positive result. The absence of any HPV DNA from the VA, VU and PA for women or in the PGC and PA for men was defined as a negative result. Subjects without adequate samples were excluded from the analysis. The classification of any HPV or oncogenic HPV was defined as a positive test result for at least one of the 16 tested HPV types or at least one of 13 oncogenic HPV types.
Statistical analyses
The data were analyzed using SAS version 9.4 (SAS Institute, Cary, NC, USA), and P<0.05 was considered statistically significant. The HPV prevalence in women and men was estimated for any, oncogenic and specific HPV type. The HPV prevalence was compared using Pearson’s χ2-test, correction for the χ2-test, or the Fisher exact test. The 95% confidence intervals (CIs) for prevalence were calculated by the binomial exact test.
Bivariate analysis and multivariate logistic regression were conducted to assess the odds ratios (ORs) and 95% CIs, respectively, for oncogenic HPV and HPV 6/11 infection factors. Variables with a P-value<0.20 in the bivariate logistic analysis were included in the multivariate logistics model using stepwise selection, with a 0.05 significance level for entry into the model and 0.05 for removal.
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RESULTS
A total of 4687 participants, including 2378 women and 2309 men, aged 18–55 years were enrolled. After removing the participants without adequate samples, 2344 (98.6%) women and 1937 (83.9%) men were included in the analysis. Table 1shows the distribution of the sociodemographic and sexual behavioral characteristics of the volunteers in the analysis by sex. The median ages of both women and men were 38 years. Most of the participants had a low education level and low income and were married or cohabitating. The majority had stayed in a hotel, and a larger percentage of men than women had used a towel supplied by the hotel (62.2% vs 37.5%, respectively, P<0.0001). Overall, the majority of the participants reported their age at first sexual intercourse was 18–25 years. At enrollment, most (56.2%) of the participants had one lifetime sex partner (LSP), 30.4% had two to three LSPs and 13.3% had four or more LSPs. Women were more conservative than men, having fewer LSPs and sexual partners in the year before the study (P<0.0001). The percent of women reporting a history of sexually transmitted diseases (STDs) was more than that of men (16.7% vs 7.2%, respectively, P<0.0001).
Table 1 - Sociodemographic and sexual behavioral characteristics of the study participants by sex.
Full table
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