• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
J Infect Dis. Author manuscript; available in PMC May 15, 2011.
Published in final edited form as:
PMCID: PMC2882881
NIHMSID: NIHMS180675

Male circumcision decreases acquisition and increases clearance of high risk human papillomavirus in HIV-negative men: a randomized trial in Rakai, Uganda

Abstract

Uncircumcised HIV-negative men aged 15-49 years were randomized to immediate circumcision (n=441) or delayed circumcision (n=399). HPV was detected by Roche HPV Linear Array at enrollment, 6, 12 and 24 months. Incident HR-HPV was estimated in men who acquired a new HR-HPV genotype. HR-HPV clearance was determined in men with prior genotype-specific HR-HPV infections. Rate ratios (RR) and 95% confidence intervals (95%CI) of HR-HPV acquisition were estimated by Poisson multiple regression

Enrollment characteristics were comparable between groups. HR-HPV incidence was 19.7/100 py in the intervention (70/355.8 py) and 29.4/100 py (125/424.8 py) in the control arm (RR=0.67, 95%CI 0.51-0.89, p = 0.006.) The incidence of multiple HR-HPV infections was 6.7/100 py in the intervention and 14.8/100 py in control arm (RR = 0.45, 95%CI 0.28-0.73), but there was no significant effect on single infections (RR=0.89, 95%CI 0.60-1.30). HR-HPV incidence was lower in the intervention arm for all genotypes and demographic/behavioral subgroups. The clearance of pre-existing HR-HPV infections was 215.8/100py (205/95 py) in intervention and 159.1/100py (255/160.25 py) in control arm men (adjRR=1.39, 95%CI 1.17-1.64).

Male circumcision reduces the incidence of multiple HR-HPV infections and increases clearance of HR-HPV infections in HIV-uninfected men.

The trial was registered with ClinicalTrials.gov numbers NCT00425984

Introduction

Two trials have shown that male circumcision reduces the prevalence of high risk penile human papillomavirus (HR-HPV) infection by approximately 35% in HIV-negative men [1, 2], and several cross-sectional studies have found a lower rate of prevalent penile HPV infection in circumcised HIV-uninfected men [3-7]. However, it is unclear whether circumcision reduces the incidence of HPV acquisition or increases the clearance of preexisting HPV infection. One longitudinal observational study of 285 U.S. men, 25 of whom were circumcised, found no statistically significant difference in the hazards ratio (HR) of acquisition of either high risk HPV (HR-HPV) infections (adj HR = 1.7, 95% 0.6-4.9) or any HPV infection (adj HR = 0.8, 95%CI 0.4-1.9) in circumcised versus uncircumcised men [7]. However, the authors reported a significantly faster rate of HR-HPV clearance (adj HR = 6.5, 95%CI 2.1-19.7). [7]

We used data from a randomized trial of male circumcision conducted in Uganda to assess whether circumcision affected the acquisition of new HR-HPV infections and clearance of pre-existing infections.

Methods

We conducted a trial of male circumcision for prevention of HIV acquisition in initially HIV-uninfected men in Rakai District, Uganda between 2003-06 [2, 8]. The effect of circumcision on HPV was a secondary trial endpoint. The trial design has been previously described.[2, 8] In brief, we enrolled uncircumcised HIV-negative men aged 15-49 years who were randomized to receive immediate circumcision (intervention arm) or circumcision delayed for 24 months (control arm). At enrollment, and at 6, 12 and 24 months follow-up, trial participants provided information on sociodemographic characteristics, sexual risk behaviors and symptoms suggestive of sexually transmitted infections (STIs).

At each study visit penile swabs were collected for HPV detection. Moistened Dacron swabs were taken from the from the coronal sulcus/glans of circumcised men using a standard protocol, placed in Digene specimen transport medium, and stored at −80° C. HPV genotyping was performed using the Roche HPV Linear Array (Roche Diagnostics, Indianapolis, IN) as previously described [9-11]. HPV genotypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68 were considered the primary high risk HPV (HR-HPV), or carcinogenic, viral genotypes. Genotypes 6, 11, 26, 40, 42, 43,53, 54, 55, 61, 67, 70, 71 72, 73, 81 82, 83, 84, and 108 were considered low risk HPV (LR HPV) genotypes. Penile swabs without amplifiable cellular or viral DNA were considered to be insufficient for HR-HPV detection. [12, 13] Informative samples with amplifiable DNA were defined as swabs with detectable beta-globin indicating the presence of cellular DNA, or detectable HPV indicating sufficient viral DNA was present even in the absence of detectable beta-globin.

The study was approved by four Institutional Review Boards (IRBs): the Science and Ethics Committee of the Uganda Virus Research Institute, the Uganda National Council for Science and Technology, the Committee for Human Research at Johns Hopkins University, Bloomberg School of Public Health, and the Western Institutional Review Board. The trial was registered with ClinicalTrials.gov numbers NCT00425984

The trial profile is given in Figure 1. The population assessed in this analysis of HR-HPV incidence/clearance was restricted to HIV-negative married men because we planned to assess HPV infections in their female partners, and given assay costs and limited resources, this was the most efficient sampling design to address effects in men and women. We also excluded men with HIV-infected wives because of high rates of HPV infection in HIV-positive women.[14, 15] In addition, we excluded men whose wives were not concurrently enrolled with their husbands, because we would not be able to rigorously study the efficacy of circumcision for prevention of HPV infection in women, unless these female partners’ enrollment status was known. We then randomly selected married men with concurrently enrolled HIV-negative wives who provided samples obtained at enrollment and at 24 months follow-up to determine the effects of circumcision on prevalent HPV infection as previously reported. [2] There were 835 HIV-negative intervention arm men with HIV-uninfected concurrently enrolled wives, and due to assay cost and resource limitation, we randomly selected 441 (52.8%) of these male participants who provided a penile swab at enrollment. Of these men, seven failed to accept circumcision by the time of the six month visit and, per protocol, were classified as crossovers at that time. In the control arm, there were 803 HIV-negative men with concurrently enrolled HIV-negative wives, of whom we randomly selected 399 (49.7%) who provided a penile swab at enrollment. Three controls became circumcised between the 1 and 2 year visits and were classified as crossovers at that interval. We conducted HPV assays on randomly selected penile samples at the 6 and 12 month follow up visits to further reduce assay costs. There were 330 randomly selected penile samples assayed in intervention arm men at 6 and 12 months. In controls, we assayed 321 randomly selected samples at 6 months and 314 samples at 12 months. Because our original objective was to determine HPV prevalence at 24 months[2] we assayed all available samples at that time point; 440 in the intervention arm and 399 in the control arm.

Figure 1
Trial Profile

Statistical analyses

We assessed participant characteristics at enrollment by study arm. We then determined the proportion of penile swabs with amplifiable cellular or viral DNA by study visit to assess whether detection varied over time between study arms. An intention-to-treat analysis was then used to assess the efficacy of male circumcision for prevention of new HR-HPV infections among participants with amplifiable cellular or viral DNA detected at sequential study visits. An as treated analysis classified the 7 intervention arm crossovers as uncircumcised if they failed to receive surgery by the six month visit, and three control subjects who received circumcision from non-project sources between the 12 and 24 month visits were classified as circumcised for the last follow up interval. Acquisition of HR-HPV was defined as a new infection identified in men who were initially negative for any HR-HPV and who acquired one or two or more new HR-HPV infection(s) during the next follow up, or men who were initially positive for a specific HR-HPV genotype but acquired one or more new HR-HPV genotype(s) during the next follow up. HR-HPV incidence rates per 100 person years (py) were estimated assuming that the new HR-HPV infection was acquired at the mid-point of the sequential follow up interval at which the new infection was detected. Similar analyses were conducted for the low risk HPV (LR-HPV) genotypes. The unit of observation was an individual participant, and each man with an incident HR-HPV infection was counted only once per follow up interval irrespective of whether he acquired a single HR-HPV genotype or multiple HR-HPV genotypes. We separately assessed the incidence of single and multiple (two or more) new HR-HPV genotype-specific infections, again using the individual participant as the unit of observation. We also assessed the incidence of each HR-HPV genotype; for each genotype, the population at-risk was men without that genotype at a prior study visit, irrespective of the co-infection with other HR-HPV genotypes. Acquisition of HR-HPV infection was examined by study arm, stratified by sociodemographic and behavioral covariates at enrollment. We estimated the incidence rate ratio (IRR) and 95% confidence intervals (95%CI) of HR-HPV acquisition in intervention versus control arm cumulatively over 12 and 24 months using a Poisson log linear regression model with offset. Multivariate Poisson models were used to adjust for covariates found to be associated with incident HR-HPV at p<0.20 in univariate analyses.

Clearance of HR-HPV was estimated among men with pre-existing HR-HPV infections who had sequential samples with amplifiable viral or cellular DNA. Clearance was expressed as the proportion of men with pre-existing HR-HPV who were negative for that genotype at a subsequent sequential study visit, and as the rate of clearance per 100 py observation subsequent to detection of a HR-HPV infection. Clearance was assessed for each HR-HPV genotype, irrespective of the number of HR-HPV infections per individual, and genotype-specific clearance rates were summed to provide global estimates. The rate ratio of clearance was estimated using a log-linear model based on an underdispersed Poisson distribution to account for multiple clearance events within individuals. Potential confounders were examined in univariate analyses, and covariates found to be associated at α <0.20, or suspected confounders based on biological reasoning or prior studies were included in multivariate analyses of men with consecutive follow-up samples.

Analyses were performed using Stata™ Version 8.0 (College Station, Texas) and SAS 9.2 (Carry NC).

Results

The intervention and control arm men were comparable with respect to sociodemographic and behavioral characteristics at enrollment (Table 1). The prevalence of HR-HPV at enrollment was 39.1% in the intervention arm and 38.6% in the control arm (p = 0.17).

Table 1
Participant characteristics at enrollment

At enrollment, and prior to circumcision, the proportions of samples with amplifiable cellular DNA were 78.0%% (344/441) in the intervention and 76.7% (306/399) in the control arm. Among the intervention arm men, the proportion of samples with amplifiable cellular DNA declined over time to 63.0% (208/330) at twelve months and 60.8% (240/395) at 24 months (p <0.001). However, there was no decline in the proportion of samples with amplifiable cellular DNA among uncircumcised controls at 12 months (76.8%, 241/314) or 24 months (75.3%, 272/361), and this difference between study arms at 24 months was statistically significant (p<0.001).

The incidence of new HR-HPV infections or genotypes was determined for samples with amplifiable cellular or viral DNA at sequential study visits (Table 2). In an intention to treat analysis over the 24 months follow up, 70 intervention arm men acquired one or more new HR-HPV infections (incidence 19.7/100 py), whereas among controls 125 men acquired one or more HR-HPV infections with an incidence rate of 29.4/100 py (IRR = 0.67, 95%CI 0.50-0.90). During the first year of follow up, the incidence rate was significantly lower in the intervention group (IRR= 0.61, %95CI 0.44-0.85), while during the second year of follow up, the effect was of borderline statistical significance (IRR=0.64, 95%CI 0.38-1.07). HR-HPV incidence declined over time in both study arms, partly because participants with higher risk sexual behaviors acquired infections in the first follow up year, and thus could not contribute to incident infections with the same genotype during the second follow up year. There were no significant differences in HR-HPV incidence between study arms among men who only acquired a single HR-HPV infection (IRR=0.89, 95%CI 0.60-1.30). However, the acquisition of multiple HR-HPV infections over 24 months was markedly lower among men in the intervention arm (6.7/100 py) than in the control arm (14.8/100 py) with an IRR = 0.45 (95%CI 0.28-0.73). In an as treated analysis, the incidence of any HR-HPV infection was 20.6/100 py (72/350) in the intervention arm and 28.6/100 py (123/430.5 py) in the control with an IRR of 0.72 (95%CI 0.54-0.96). The as treated incidence of multiple (two or more) HR_HPV infections was 7.1/100 py (25/350 py) in the circumcised men and 14.4/100 py (62/430.5 py) in the controls with an IRR = 0.50, 95%CI 0.31-0.79).

Table 2
HR-HPV Incidence by study arm and follow up interval for participants with amplifiable cellular or viral DNA at sequential study visits.

The incidence of type-specific HR-HPV over 24 months was lower in intervention than control arm men for all high risk genotypes examined (Table 3), and these differences were statistically significant for HR-HPV genotypes 18 (IRR = 0.30, 95%CI 0.10-0.75) and 33 (IRR = 0.17, 95%CI 0.19-0.0.74).

Table 3
Type-specific HR-HPV Incidence over 24 Months, by Study Arm

The rates of HR-HPV acquisition were lower in the intervention than the control arm in all sociodemographic and behavioral subgroups (Table 4). Among controls, HR-HPV incidence was higher in younger men and declined with age, but no age-related trend was observed among intervention arm men. The effect of circumcision on HR-HPV acquisition was statistically significant among men reporting high risk sexual behaviors such as non-use of condoms (IRR=0.67, 95%CI 0.46-0.98), and multiple sex partners (IRR=0.56, 95% 0.36-0.87). After adjustment for covariates associated with HR-HPV at enrollment (age, education, condom use, alcohol consumption with sex, and number of sex partners), the adjusted incidence rate ratio of HR-HPV acquisition in circumcised relative uncircumcised men was 0.67 (95%CI 0.50-0.91, p = 0.008.)

Table 4
The incidence of High Risk HPV (HR-HPV) over 24 months stratified by sociodemographic and behavioral covariates

We also assessed acquisition of low risk HPV genotypes (LR-HPV). The 24 month incidence of any LR-HPV genotype was 29.9/100 py (102/341.5 py) in the intervention arm and 35.0/100 py (144/411 py) in the control arm (IRR 0.84, 95%CI 0.66-1.10). For single LR-HPV infections, the incidence was 19.3/100py (36/41.5py) in the intervention arm and 17.8/100 py (73/411 py) in the controls (IRR = 1.09, 95%CI 0.78-1.52). However, the incidence of multiple LR-HPV infections was 10.5/100 py (36/341.5py) in the intervention and 17.3/100 py (71/411 py) in the controls (IRR = 0.61, 95%CI 0.41-0.91).

Clearance of HR-HPV infections is shown in Table 5. Clearance rates per 100 py observation were higher in the intervention (215.8/100 py) than the control arm (159.1/100 py), with a RR=1.36 (95%CI 1.13-1.63). The rates of clearance per 100 py were increased for most genotypes and this was statistically significant for types 39, 51 and 58 (Table 7). After adjustment for age, education, number of sex partners and condom use, the ratio of clearance rates in the intervention relative to the control arm was 1.39 (95%CI 1.17-1.64). Among men in the intervention arm, 77.7% (205/264) of pre-existing HR-HPV infections were cleared over the 24 months observation period, whereas clearance was 66.9% (255/381) among the controls (RR = 1.16, 95%CI 1.05-1.28). In multivariate analyses, the adjusted RR of percent clearance was 1.17 (95%CI 1.05-1.31).

Table 5
Clearance of genotype-specific pre-existing HR-HPV infection as a rate per 100 person years, by study arm

Discussion

Circumcision was associated with a significant reduction in the acquisition of HR-HPV infection with an estimated efficacy of approximately 33% over two years. Moreover, the efficacy was 55% for prevention of multiple HR-HPV infections (Table 2). The protective effect of circumcision was observed for all HR-HPV genotypes (Table 4) and was consistently observed in all sociodemographic and behavioral subgroups (Table 4). These findings are consistent with the observed reduction in the prevalence of HR-HPV in two randomized trials [1, 2] and in several observational studies [3-7]. Therefore, it would appear that circumcision protects men from acquiring new HR-HPV infections. Similar reductions were observed in the acquisition of LR-HPV genotypes in circumcised men.

The rate of clearance of HR-HPV per 100 py was greater among circumcised than uncircumcised men (Table 5) which is consistent with one observational study, but the magnitude of the effect of circumcision in this trial was less than that reported in the observational study (adj HR = 6.5, 95%CI 2.1-19.7). [7]

The implications of these findings for male-to-female transmission of HR-HPV are unknown but observational studies suggest lower HR-HPV carriage in female partners of circumcised men. [3, 16] Recent studies have also shown a high degree of type-specific concordance between sexual partners within couples,[15] so it is likely that reduced male HR-HPV carriage following circumcision, resulting from lower acquisition and faster clearance, will reduce female HR-HPV infections. We are currently evaluating the efficacy of circumcision for reducing female infections among sexual partners of men enrolled in this trial.

It is plausible that circumcision might reduce HR-HPV acquisition. In uncircumcised men, the foreskin is retracted over the shaft during intercourse and the inner preputial mucosa is exposed to vaginal and cervical fluids. In addition, the intact foreskin is vulnerable to microtears during intercourse which could facilitate viral entry, and the moist subpreputial cavity may provide a favorable environment for HR-HPV survival [17]. Thus, by removing the foreskin, circumcision may both reduce exposure to female genital HR-HPV and reduce access of HPV to epidermal basal cells. Additionally, keratinization of the circumcision scar may reduce the risk of HR-HPV infection. We observed a significant reduction in detection of beta-globin in penile samples from circumcised men, but there was no change in detection of cellular DNA among uncircumcised controls. This suggests that progressive keratinization of surgical scar may reduce the number of basal cells vulnerable to HPV infections over time.

This study has limitations. The analysis was confined to a random sample of married men so we cannot assess efficacy among single men. The six month intervals between visits in the first follow up year and the 12 month interval between visits in the second year were long and we likely missed incident infections which cleared prior to the subsequent follow up visit. In addition, the long follow up intervals did not allow precise estimation of time to clearance of pre-existing infections. We were conservative in our estimates of incidence and clearance which were restricted to sequential samples with amplifiable cellular or viral DNA to ensure the adequacy of sample collection. Since swabs with amplifiable DNA decreased in the intervention relative to control arm, this led to omission of more follow up intervals for circumcised men (11.0%) than for controls (8.0%), which differentially reduced person time for the intervention arm and thus possibly inflated rates of acquisition and clearance for this group.

We collected swabs from the coronal sulcus/glans and the shaft, but only had resources to assay the corona sulcus/glans samples. Therefore, we do not know whether HR-HPV carriage at other penile sites is affected by circumcision. However, the South African trial sampled the urethral meatus and found that circumcision reduced HR-HPV prevalence, suggesting that the effect may not be site specific [1]. Some studies to determine the optimal site for penile HPV detection report a lower prevalence of HPV from swabs of the coronal sulcus/glans compared to the shaft,[12, 13] whereas others found no difference in detection between these two sites.[18] Collection of samples from one site may be a limitation to this study, but since swab procedures were identical in both study arms, this should not bias the estimates of efficacy.

In summary, circumcision significantly reduced the incidence of multiple penile HR-HPV infections, and increased clearance of pre-existing HR-HPV in married HIV-negative men. Thus, male circumcision may potentially reduce exposure of female partners to HR-HPV infection.

Acknowledgements

The study was primarily supported by a grant (UO1 AI11171-01-02) from the National Institutes of Allergy and Infectious Disease (NIAD), Division of AIDS, National Institutes of Health (NIH), and in part by the Division of Intramural Research, NIAID, NIH. This publication was supported, in part, by a fellowship/grant from the Fogarty International Center/USNIH: Grant # 2 D 43 TW000010-19-AITRP. We also are grateful for the advice provided by the Rakai Community Advisory Board. Finally, we wish to express our gratitude to study participants whose commitment and cooperation made the study possible.

Footnotes

All authors declare that there is no conflict of interest

The authors have no commercial or other associations that might pose a conflict of interest

References

1. Auvert B, Sobngwi-Tambekou J, Cutler E, et al. Effect of male circumcision on the prevalence of high-risk human papillomavirus in young men: results of a randomized controlled trial conducted in orange farm, South Africa. J Infect Dis. 2009;199:14–9. [PMC free article] [PubMed]
2. Tobian AAR, Serwadda D, Quinn TC, et al. Male circumcision for the prevention of HSV-2 and HPV infections and syphilis. N Engl J Med. 2009;360:1298–309. [PMC free article] [PubMed]
3. Castellsague X, Bosch FX, Munoz N, et al. Male circumcision, penile human papillomavirus infection, and cervical cancer in female partners. N Engl J Med. 2002;346:1105–12. [PubMed]
4. Baldwin SB, Wallace DR, Papenfuss MR, et al. Human papillomavirus infection in men attending a sexually transmitted disease clinic. J Infect Dis. 2003;187:1064–70. [PubMed]
5. Bosch FX, Manos MM, Munoz N, et al. Prevalence of human papillomavirus in cervical cancer: a worldwide perspective. International biological study on cervical cancer (IBSCC) Study Group. J Natl Cancer Inst. 1995;87:796–802. [PubMed]
6. Hernandez BY, Wilkens LR, Zhu X, et al. Circumcision and human papillomavirus infection in men: a site-specific comparison. J Infect Dis. 2008;197:787–94. [PMC free article] [PubMed]
7. Lu B, Wu Y, Nielson CM, et al. Factors associated with acquisition and clearance of human papillomavirus infection in a cohort of US men: a prospective study. J Infect Dis. 2009;199:362–71. [PubMed]
8. Gray RH, Kigozi G, Serwadda D, et al. Male circumcision for HIV prevention in men in Rakai, Uganda: a randomised trial. Lancet. 2007;369:657–66. [PubMed]
9. Gravitt PE, Lacey JV, Jr., Brinton LA, et al. Evaluation of self-collected cervicovaginal cell samples for human papillomavirus testing by polymerase chain reaction. Cancer Epidemiol Biomarkers Prev. 2001;10:95–100. [PubMed]
10. Gravitt PE, Peyton CL, Alessi TQ, et al. Improved amplification of genital human papillomaviruses. J Clin Microbiol. 2000;38:357–61. [PMC free article] [PubMed]
11. Gravitt PE, Peyton CL, Apple RJ, Wheeler CM. Genotyping of 27 human papillomavirus types by using L1 consensus PCR products by a single-hybridization, reverse line blot detection method. J Clin Microbiol. 1998;36:3020–7. [PMC free article] [PubMed]
12. Giuliano AR, Nielson CM, Flores R, et al. The optimal anatomic sites for sampling heterosexual men for human papillomavirus (HPV) detection: the HPV detection in men study. J Infect Dis. 2007;196:1146–52. [PMC free article] [PubMed]
13. Weaver BA, Feng Q, Holmes KK, et al. Evaluation of genital sites and sampling techniques for detection of human papillomavirus DNA in men. J Infect Dis. 2004;189:677–85. [PubMed]
14. Safaeian M, Kiddugavu M, Gravitt PE, et al. Determinants of incidence and clearance of high-risk human papillomavirus infections in rural Rakai, Uganda. Cancer Epidemiol Biomarkers Prev. 2008;17:1300–7. [PMC free article] [PubMed]
15. Mbulawa ZZ, Coetzee D, Marais DJ, et al. Genital human papillomavirus prevalence and human papillomavirus concordance in heterosexual couples are positively associated with human immunodeficiency virus coinfection. J Infect Dis. 2009;199:1514–24. [PubMed]
16. Gray RH, Wawer M, Thoma M, et al. Male circumcision and the risks of female HIV and sexually transmitted infections acquisition in Rakai, Uganda. Thirteenth Conference on Retroviruses and Opportunistic Infections; 2006. Abstract 128.
17. Szabo R, Short RV. How does male circumcision protect against HIV infection? Bmj. 2000;320:1592–4. [PMC free article] [PubMed]
18. Smith JS, Moses S, Hudgens MG, et al. Human papillomavirus detection by penile site in young men from Kenya. Sex Transm Dis. 2007;34:928–34. [PMC free article] [PubMed]
PubReader format: click here to try

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...