| Background Approximately85%of anal cancers worldwide were attributed to the oncogenic HPV. Although anal cancers from HPV infection can afflict both men and women and were rare in the general population (1.5cases/100,000population), men who have sex with men (MSM) were at greatest risk with an incidence of35cases/100,000population, similar to incidence of cervical cancer before implementation of routine cervical screening. The estimated incidence of anal cancer in HIV positive MSM was even greater (60-70cases/100,000population). The special sexual behaviors (anal sex) and the similar histological characteristic of anal canal to the cervix may refer to this phenomenon. Similar to the cervix, a squamo-columnar junction was just between the upper colorectal type mucosa and the lower squamous epithelium in the anal canal. On October25,2011, the Advisory Committee on Immunization Practices (ACIP) had recommended routine use of quadrivalent human papillomavirus (HPV) vaccine (HPV6/11/16/18)in males aged11or12years. Since MSM were at higher risk for infection with HPV types6,11,16, and18and associated conditions, including genital warts and anal cancer, ACIP recommended routine vaccination with HPV4(the quadrivalent HPV vaccine against HPV6,11,16, and18) for all MSM including HIV sero-positive MSM. The high prevalence of oncogenic HPV infection and its association with anal cancer among MSM called for molecular epidemiological studies on anal HPV infection among MSM before the implementation of HPV vaccines in China. In China, rarely studies focused on anal HPV infection in MSM, and the few studies on prevalence of anal HPV infection among MSM were all in northern part of China, while the data on molecular epidemiological studies of anal HPV infection in southern China is limited. The current study firstly described HPV prevalence and genotype distribution in anal canal of MSM in Southern China.Objectives The current study was aimed to describe the prevalence and genotype distribution of HPV in anal canal and estimate the possible risk factors for anal canal HPV infection and commercial sex encounters in MSM in Shenzhen, China.Methods A cross-sectional study was conducted among MSM between July and September of2009in a sexual health clinic providing medical care for MSM in Shenzhen, China. Socio-demographic and sexual behavior data were collected through a face-to-face interview by the trained clinical staff in a separate room using a standardized questionnaire. Blood was collected for HIV serological testing and syphilis serological screening, anal swabs were collected for HPV genotyping, and urine was collected for nucleic acid detection of Chlamydia trachomas (CT) and Neisseria gonorrhoeae (NG). HPV DNA was extracted by QIAamp DNA Mini Kit (Qiagen, Gaithersburg, MD) according to the manufacturer’s instructions. Then HPV DNA was amplified and viral types were determined using the HPV Geno Array test kit (Hybribio, Chaozhou, China) according to the manufacturer’s instructions. Difference of HPV prevalence between HIV, syphilis, chlamydia and gonococcus positive and negative MSM were assessed by chi-square test. Outcome variables included prevalence rates of any type HPV, oncogenic HPV, non-oncogenic HPV, multiple HPV and single HPV infections, et al. Univariate and multivariate Logistic analysis were used to determine association between socio-demographic, behavioral and biomedical characteristics and the infections. The possible risk factors of commercial sex encounters were assessed by chi-square test and unconditional Logistic regression.Results A total of408MSM were consented to provide the blood, anal swabs and urine samples and finished the questionnaires (although not everyone finished all the questions).404of the anal swabs gave valid genotyping results (4/408swabs,0.98%, did not show β-globin amplification). The prevalence of anal HPV, HIV, syphilis, Chlamydia and gonococcus in urine were36.4%,36.4%、6.9%、24.5%、16.2%and7.4%, respectively. The HPV genotypes detected most frequently were HPV06(8.2%), HPV16(7.2%), HPV11(6.4%), HPV18(4.7%), HPV58(4.7%), and HPV52(4.2%). Prevalences of total HPV, oncogenic HPV and multiple HPV infection were significantly higher in HIV or syphilis seropositive MSM than the negatives. Prevalences of total HPV, non-oncogenic HPV and multiple HPV infection were significantly higher in MSM with the infection of Chlamydia than not. Ever had STD (sexually transmitted diseases) associated symptoms (including abnormal secretions, bleeding, breakage, and neoplasia in skin or mucous) was independently associated with detection of any type HPV (AOR:4.15,95%CI:1.50-11.83, P=0.006) and oncogenic HPV (AOR:2.88,95%CI:1.16-7.14, P=0.023) compared to those never had STD associated symptoms. Age between30-39years was independently associated with decreased prevalence of non-oncogenic HPV (AOR:0.32,95%CI:0.11-0.91, P=0.033comparing to40years or plus). Living with families not the spouse was associated with lower prevalence of single HPV in anal canal (AOR:0.26,95%CI:0.09-0.77, P=0.015) compared to those living alone. The frequency of condom using in anal sex with men during the previous6months was not associated with anal HPV infections among MSM in Shenzhen, China. Of143MSM who gave clear answers to whether or not ever had commercial sex encounters,24.5%(35/143) reported ever had commercial sex encounters. Commercial sex encounters were more common in MSM always using condoms in anal sexual behaviors with men in the previous6months (AOR:3.78,95%CI:1.59-8.98, P=0.003comparing to MSM never used condoms in anal sexual behaviors) and MSM ever having sexual maltreat (AOR:13.79,95%CI:1.84-160.60, P=0.036).Conclusions Our study confirms a high burden of anal HPV infection among MSM population in Shenzhen, China. The most popular genotypes were HPV6,16.11,18,58and52. The prevalence and genotype distribution of HPV were different in anal canal of MSM with different HIV, syphilis and Chlamydia infection status. The risk factors for anal canal HPV infection may be different from those for HIV, syphilis and Chlamydia infection. Commercial sex encounters may be more common in MSM ever had sexual maltreat or using condoms in every anal sexual behavior with males in the previous6months. |
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