Anal Human Papillomavirus Infection among HIV-Infected Men in Korea

Background Little is known about the epidemiology on human papillomavirus (HPV) infection among HIV-infected men in Korea. The objective of this study was to determine the prevalence, genotype distribution and risk factors associated with anal HPV infection among HIV-infected men in Korea. Methods A single-center cross-sectional study was conducted with HIV-infected men in Korea. Participants completed a detailed sexual behavior risk factor questionnaire. Anal samples were collected for cytology and HPV genotyping. Factors associated with anal HPV infection were assessed using multivariable logistic regression, stratifying by sexual behaviour. Results A total of 201 HIV-infected men were included in the study: 133 were from men who have sex with men (MSM) and 68 from men who have sex with women (MSW). Any anal HPV infection was detected in 82.7% of HIV-infected MSM and in 51.5% of HIV- infected MSW (P < 0.001). High-risk HPV (HR-HPV) prevalence was higher among MSM (47.4%) than MSW (25.0%; P = 0.002). The HR-HPV types identified most frequently were HPV 16 (11%), HPV 18 (9.9%), and HPV 58 (5%) in MSM, and HPV 58(11%) and HPV 16 (8.9%) in MSW. Prevalence of any HPV types in 9-valent vaccine types was higher among MSM than MSW (47.4% vs 22.1%. P = 0.001). Abnormal anal cytology was more commonly detected in MSM than MSW (42.9% vs.19.1%, P < 0.001). In HIV-infected MSM, higher number of lifetime male sex partners was significantly associated with any anal HPV infection, but age was a significant risk factor associated with anal HR-HPV infection. Conclusion Anal HPV infection was highly prevalent in HIV-infected MSM in Korea, and also commonly found in HIV-infected MSW. In HIV-infected MSM, the significant risk factor for being infected with any HPV infection was lifetime number of male sexual partners, and with anal oncogenic HPV infection was age.


Introduction
Human papillomavirus (HPV), the major cause of cervical cancer, also causes a substantial disease burden in men, including genital warts, penile cancer, anal cancer and certain oropharyngeal cancers. Anal cancer is relatively rare in general population, whereas anal cancer incidence is substantially higher in HIV-infected patients, particularly among men who have sex with men (MSM) [1]. Despite the widespread use of potent antiretroviral therapy (ART), the incidence of anal cancer has not declined, but rather with increased survival, it appears to have increased in HIV-infected patient [2][3][4][5].
In Korea, anal cancer is a rare malignancy with an estimated incidence in the general population of 0.5 cases per 100,000 person-years [6,7], and was also rarely reported among HIVinfected patients [8,9]. In two separate studies encompassing a total of 1,533 HIV-infected patients of Korea, only one case of anal cancer (0.07%) was reported [8,9]. Since HIV reporting began in Korea in 1985, a cumulative total of 9,982 Korean people were diagnosed with HIV infection by the end of 2014 [7]. The man-to-woman ratio was increased about two times from 7.1:1 in 1997-2001 to 14.3:1 in 2010-2014. Steep increases in the proportion of MSM among the newly diagnosed HIV-infected men were also seen, which doubled in the same period [7].
The prevalence of HPV infection and the burden of HPV-related cancers varied in different geographic areas. With the introduction of HPV vaccine, knowledge regarding high risk-HPV genotype distribution can inform decisions on vaccination strategies for HIV-infected men. To date, there are no data on the prevalence of anal HPV infection in HIV-infected men as well as in general population in Korea The objectives of this cross sectional study were to assess prevalence and type distribution of anal HPV infection among HIV-infected men in Korea. Risk factors associated with anal HPV infection among MSM were also determined.

Study population
This cross sectional study was conducted at the Pusan National University Hospital. The hospital is 1,220 bed, university-affiliated teaching hospital and provides HIV care for HIV-infected patients in southeastern region of Korea. We enrolled HIV-infected men who attended the HIV outpatient clinic of the study hospital between July 2014 and January 2015, who were aged 18 years, and who had not received a diagnosis of anal cancer prior to enrollment. The protocol was reviewed and approved by the institutional review board (IRB) of Pusan National University Hospital (IRB No. E-2014013). We obtained the written informed consent from all participants before inclusion in the study. The patients who accepted to participate were interviewed using a self-administered questionnaire that included questions on socio-demographic factors, substance use, sexual behavior, and status of circumcision. We also reviewed the medical records to collect the clinical data, and also to compare the reported sexual behavior in questionnaire with those in the medical records. Non-HIV related comorbidity was assessed with Charlson Comorbidity Index (CCI) [10]. We excluded AIDS as a co-morbidity.
Sample collection, anal cytology and human papillomavirus genotyping Specimen collection was performed by a health care provider. Anal samples were obtained by introducing a cytobrush blindly into 3 cm into the anal canal and gently rotating it for 30 to 45 seconds in a spiral pattern until the device exits the anal verge [11]. The cytobrush was rinsed in the PreservCyt 1 solution (Hologic Inc., Boxborough, MA) by rotating the device in the solution 10 times while pushing against the vial wall, and was swirled vigorously to further release material. All samples were sent to the Green Cross Laboratories in Seoul. Cytologic smear results were categorized according to the 2001 Bethesda classification system terminology [12]. HPV genotype was determined using an PCR based DNA microarray system, the HPV DNA chip (HPV Genotypeing Chip™ Kit, AGBIO Diagnostics, Seoul, Korea). This contains 32 type specific probes detecting 13 types of high risk HPV (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68) and 19 types of low risk HPV (6, 11, 26, 32, 34, 40,

Statistical analysis
The statistical analyses were conducted using PASW Statistics 18 (SPSS Inc., Chicago, IL, USA). Categorical variables were compared using Pearson's chi-square test or Fisher's exact test, whereas non-categorical variables were tested with Student t test or the Mann-Whitney Utest. Potential demographic, sexual, behavioral, and other predictors for the HPV infection were analyzed by multivariate logistic regression. All variables with P < 0.25 in univariate analysis were assessed in multivariate models using stepwise backward selection. All tests were considered statistically significant at P < 0.05.

Patients' characteristics
A total of 133 HIV-infected MSM and 68 HIV-infected MSW were included in this study. Their demographic characteristics are described in Table 1. Median age (interquartile range, IQR) was 46 years old (37-56) for HIV-infected MSM and 50 years old (43-58) for HIVinfected MSW. Among 133 HIV-infected MSM, 81 (60.9%) reported having had sexual intercourses with both men and women. More than 60% of HIV-infected MSM was single compared with 41.2% of HIV-infected MSW (P = 0.041). Approximately 34% of HIV-infected MSM had never smoked prior to enrollment compared with 17.6% of HIV-infected MSW (P = 0.02). More than half of both HIV-infected MSM and MSW were circumcised (60.9% vs 54.4%). The median baseline CD4 cell count (IQR) among HIV-infected MSM and MSW was 605(486-851) and 594(419-776) cells/mL, respectively. More than 85% of patients of both groups were receiving ART more than 1 year and have undetectable HIV viral load. More than 60% of HIV-infected MSM reported > 5 male sex partners during life, about 50% reported having 1 male sex partners within 3 months of enrollment. Approximately 47% of HIVinfected MSW reported > 5 lifetime female sex partners, 23.5% reported having 1 female sex partners during the 3 months before study entry. More than 45% of both groups infrequently used condom.

Discussion
To our knowledge, this is the first report of anal HPV prevalence among HIV-infected men in Korea. In this study, the prevalence of anal HPV infection with the 32 virus types tested and HR-HPV infection among HIV-infected MSM was 82.7% and 47.4%, respectively. Although there can be some differences in the prevalence of anal HPV infection across different studies according to the sampling methods and diagnostic methods [13], this is consistent with the results from the earlier studies conducted in HIV-infected MSM [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].
Similar to previous studies [19-21, 25, 28], the most commonly detected HR-HPV types in HIV-infected MSM in our study were HPV 16 and 18, which are the types most commonly associated with anal cancer. In contrast to HIV-infected MSM, the most prevalent HR-HPV in HIV-infected MSW was HPV 58, which has been found to be prevalent among patients with cervical cancer in East Asia [36]. The type-specific prevalence of anal HPV infection has ranged widely in studies among HIV-infected men in East Asia [19,20,23,28,31,37]. In HIV-infected MSM, HPV-16 was the most frequently detected HR-HPV types both in China (14.3-34%) [19,20,23,37] and in Taiwan (10%) [28], while HPV-58 was most commonly found in Japan (30.2%) [31]. In HIV-infected MSW, although there are limited data in East Asia due to small number of subjects, HPV-16 was the most prevalent HR-HPV types both in Taiwan (15.6%) [28] and in Japan (14.7%) [31]. On the other hand, HPV-58, the most common HR-HPV type of HIV-infected MSW in our study, was infrequently detected both in Taiwan (1.6%) [28] and in Japan (2.9%) [31]. Consistent with our results, HPV-6 and HPV-11 were consistently among the most common LR-HPV types detected in both MSM and MSW across studies regardless of the geographic locales [19,20,23,28,31,37]. In the present study, significantly more HIVinfected MSM (24.8%) than HIV-infected MSW (11.8%) had multiple HPV infections, findings were broadly in line with those in previous studies. In Taiwan, multiple HPV infection was observed in 6.2% of HIV-infected MSM and in 4.7% of HIV-infected MSW [28]. In Japan, compared to HIV-infected MSW (14.7), multiple HR-HPV infection was more commonly found in HIV-infected MSM (30.2) [31]. In this study, overall prevalence of vaccine-preventable HPV types in anal specimens of HIV-infected men was 17.4%, 27.9%, and 38.8% for the 2vHPV, 4vHPV and 9vHPV types, respectively. The prevalence was much higher in HIV-infected MSM (respectively 22.6%, 36.8% and 47.4%) than in HIV-infected MSW (respectively 7.4%, 10.3%, and 22.1%). None had all 4vHPV or 9vHPV types detected. These vaccine-preventable type prevalence may be underestimated because a cross-sectional design with HPV DNA testing detect current infection but gives no information on previous resolved HPV infections [38]. This indicate significant proportion of HIV-infected MSM as well as HIV-infected MSW have already acquired HPV vaccine types, which may reduce the benefit of vaccination.
In HIV-infected MSM, several risk factors, including number of sex partners [21,28,39], receptive anal intercourse [21,39], and unprotected oral sex [20] have been suggested as a predictors of anal HPV infection. Consistent with previous studies, lifetime numbers of male sex partner was a main predictor for anal HPV infection in HIV-infected MSM in our study [21,28,39]. The patients having more than 10 male sexual partners in their lifetime were about 4.8 times more likely to have HPV infection in anus than those having less than 5 partners. In the previous studies investigating risk factors for anal HR-HPV infection in HIV-infected MSM, reported risk factors for anal HR-HPV infection varied across different studies. They included lower education [20], smoking [17,40], younger age [15,18,31], lower CD4 cell counts [18,31,40,41], higher nadir CD4 cell counts [15], number of sex partners, receptive anal intercourse [15,28], having sexual transmitted infections (STIs) [31,40]. In our study, age was a significant risk factor for anal HR-HPV in HIV-infected MSM. These findings are consistent with other studies that have shown that younger age was a significant risk factors for anal HR-HPV [15,18,31]. This finding may results from age-specific sexual behavior. In our study, the proportion of having any male sex partners in last 3 months was higher in MSM 40 years of age (53.5%) compared with HIV-infected MSM aged > 50 years (37.5%).
In the present study, we also found high prevalence of abnormal anal cytology in both HIVinfected MSM (42.9%) and HIV-infected MSW (19.1%). Our results are similar to those of previous studies in that HIV-infected MSW also have substantial prevalence of abnormal anal cytology [29][30][31][32][33][34], suggesting that anal cancer screening needs to be considered in HIV-infected MSW.
This study has some limitations. First, this study was a cross-sectional study. The longitudinal follow-up data were not available. Second, our study was conducted in a single center, therefore our findings may not be generalized to other region of the country. Third, we did not test all genotypes of HPV, and the proportion of persons with untypeable HPV was relatively high. Forth, our study was designed to assess the cytology, so we did not include the histologic findings. Fifth, data on socio-demographic and risk behaviors collected by self-administered questionnaire may have potential information bias caused by inaccurate response. We also did not include some risky sexual behaviors as variables, such as anal sex history. Sixth, we were not able to assess the risk factors for anal HPV infection in HIV-infected MSW, because of insufficient number of enrolled subjects. Even with these limitations, our study could reflect the overall situation of HPV infection among HIV-infected men in Korea.
In conclusion, although anal cancer was rarely reported in HIV-infected men in Korea, high prevalence of HPV infection was observed in HIV-infected MSM, and also commonly found in HIV-infected MSW. Lifetime number of male sex partner and younger age were main predictors for anal any HPV infection and anal HR-HPV infection in HIV-infected MSM, respectively. Although public health programs for prevention of cervical cancer, such as national cervical cancer screening program (since 1999) and national HPV vaccination program for 12-year-old girls (since June, 20016), has been conducted, there is no effective program currently available for anal cancer prevention in Korea. Public health program to promote knowledge about HPV infection and anal cancer, particularly in risk groups including MSM, are needed in Korea. Further studies are also needed to determine the predictors for anal HPV infection in HIV-infected MSW.