Recent studies suggest an increased risk of HIV acquisition among men and women infected with human papillomavirus (HPV) [1–4]. Effect measures for HIV acquisition associated with high-risk HPV in women ranged from 2 to 2.4 after adjustment for behavioral and biological covariates [3,4]. Clearance of HPV infection was associated with a higher risk of HIV acquisition than persistent infection, suggesting that the immune response to HPV may increase the number of target cells for HIV . HPV infection is very common, with highest prevalence rates in sub-Saharan Africa, which also experiences high HIV incidence rates . We assessed the association between prior high-risk HPV infection and HIV acquisition in a prospective cohort study among high-risk women in Kigali, Rwanda.
From 2006 to 2007, 397 HIV-negative high-risk women were enrolled in a prospective cohort study in Kigali, Rwanda. The main objective was to assess HIV incidence for the design of future HIV prevention intervention trials. Follow-up was quarterly for 1 year, with one additional visit in year 2. Written informed consent was obtained prior to study procedures. Ethical approvals were obtained from ethics committees in Rwanda, Columbia University in New York and the University of Antwerp.
HIV testing was performed at each visit according to the national testing guidelines, indicating two positive rapid tests for a positive diagnosis (First Response, Premier Medical Corporation, Daman, India; Uni-gold, Trinity Biotech Plc, Ireland), and a third test as tiebreaker if needed (Capillus, Trinidity Biotech Plc, Ireland). Positive results were, per study protocol, confirmed with Murex HIV Ag/Ab Combination ELISA test (Abbott Laboratories, Germany). Herpes simplex virus (HSV)-2 antibody testing was done by HerpeSelect-2 ELISA (Focus Technologies, Chanhassen, Minnesota, USA) at enrolment, month 12 and year 2. Bacterial vaginosis was diagnosed by Gram stain Nugent scoring at enrolment, month 6, month 12 and year 2. Cervical samples for HPV genotyping were collected at month 6 and year 2. Samples were stored in PreservCyt medium at −80°CC until testing. HPV genotying was performed using linear array PCR (Roche Molecular Systems, Indianapolis, Indiana, USA) according to manufacturer's instructions. This PCR system identifies 37 high and low-risk HPV types. An in-house real-time PCR was developed to further classify the mixed probe in the linear array PCR (types 33/35/52/58).
HPV classification was as follows: types considered high risk were HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, 82 and iso39 [6–8]. All other types were considered low risk. Women were classified according to their high-risk HPV status, irrespective of low-risk HPV detection. Sensitivity analyses were performed excluding low risk HPV infections. For the purpose of this analysis, HIV seroconverters were defined as women testing HIV-negative at month 6 and HIV-positive at any of the later visits. The control group consisted of women who were HIV-negative at month 6 and remained negative until the year 2 visit. Women who seroconverted in the period from enrolment to month 6 were excluded because no HPV data were available for this time period.
Data were analyzed using STATA 9.2 (StataCorp, College Station, Texas, USA). Fisher's exact test was used to compare prevalence rates. Wilcoxon rank sum test was used to compare medians. Multivariable analysis was not possible owing to limited statistical power.
HPV results at month 6 were available of 366 HIV-negative women. Three hundred twenty-four of them attended the year 2 visit. The average time interval between these visits was 16.6 months (SD 1.8). During this interval, 10 women seroconverted for HIV [3%; 95% confidence interval (CI) = 1–5]. The median age of women attending the month 6 visit was 25 years [interquartile range (IQR)=22–29]. Ninety-six percent of these women were self-reported female sex workers. Their median number of vaginal sex acts in the past month was 24 (IQR=15–42), median number of clients in the past week was six (IQR=4–12), and 44% reported consistent condom use during vaginal intercourse in the past month. These characteristics were not different between HIV seroconverters and women who remained HIV-negative. Incident HSV-2 infection at month 6 was associated with HIV seroconversion [odds ratio (OR) = 15; P = 0.006]. Other genital infections diagnosed at month 6 were not associated with HIV acquisition between month 6 and year 2 (Table 1).
The high-risk HPV prevalence at month 6 was 32% (95% CI = 27–37) in women who remained HIV seronegative compared with 70% (95% CI = 35–100) among women who subsequently seroconverted for HIV. This corresponds to an OR of 4.9 (95% CI = 1.2–19.7). Among HIV seroconverters, HPV type 52 was by far the most prevalent (40%). Other high-risk HPV types detected among HIV seroconverters were HPV 16, 31, 33, 56 and 68, each with a 10% prevalence rate. Among women who remained HIV-negative, high-risk HPV types 16 (5%) and 45 (5%) were the most prevalent types, followed by high-risk HPV types 18, 31, 35, 58, 59 and 68 each with a 4% prevalence rate. Other types had prevalence rates less than 4%.
Sensitivity analysis excluding women with low-risk HPV only, or excluding everyone with low-risk HPV regardless of high-risk HPV, did not change the association between high-risk HPV and HIV seroconversion. None of the women who seroconverted had low-risk HPV only and it was, therefore, not possible to assess the association between low-risk HPV only and HIV acquisition.
In conclusion, we found an increased risk of HIV acquisition in high-risk HIV-negative women with prior high-risk HPV infection. HPV 52 was most prevalent among women who subsequently seroconverted for HIV. In the study by Smith-McCune et al., high-risk HPV types 31, 58 and 70 were most strongly associated with increased risk of HIV acquisition. The two currently available HPV vaccines include high-risk HPV types 16 and 18, which are the most important HPV types in cervical carcinogenesis. HPV vaccines that include more high-risk HPV types than HPV 16 and 18 alone may provide better protection against HIV acquisition than the currently available vaccines.
The authors wish to acknowledge the study participants, the Projet Ubuzima study team and laboratory staff at the Institute of Tropical Medicine, Antwerp, Belgium, Academic Medical Center of the University of Amsterdam and the Amsterdam Municipal Health Service.
The work described in this paper was funded by the European and Developing Countries Clinical Trials Partnership (EDCTP) through a project entitled: ‘Preparing for Phase III vaginal microbicide trials in Rwanda and Kenya: Preparedness studies, capacity building, and strengthening of medical referral systems’. EDCTP cannot accept any responsibility for information or views expressed herein. The main HIV incidence study, of which the reported work was a substudy, was also supported by the International Partnership for Microbicides, Inc. There are no conflicts of interest.
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