Conceived and designed the experiments: PA MAP HG AK. Performed the experiments: ER ANB UB. Analyzed the data: SW AA ER HG. Wrote the paper: ER SW AA ANB UB PA MAP HG AK.
The authors have declared that no competing interests exist.
To determine the incidence of and risk factors for HIV acquisition in a cohort of HIV-uninfected partners from HIV discordant couples in Masaka, Uganda, and to establish its suitability for HIV vaccine trials.
HIV-uninfected adults living in HIV discordant couple relationships were enrolled and followed for 2 years. Interviews, medical investigations, HIV counseling and testing, syphilis and urine pregnancy (women) tests were performed at quarterly visits. Sexual risk behaviour data were collected every 6 months.
495 participants were enrolled, of whom 34 seroconverted during 786.6 person-years of observation (PYO). The overall HIV incidence rate [95% confidence interval (CI)] was 4.3 [3.1–6]; and 4.3 [2.8–6.4] and 4.4 [2.5–8] per 100 PYO in men and women respectively. Independent baseline predictors for HIV acquisition were young age [18–24 (aRR = 4.1, 95% CI 1.6–10.8) and 25–34 (aRR = 2.7, 95% CI 1.2–5.8) years]; alcohol use (aRR = 2.6, 95% CI 1.1–6); and reported genital discharge (aRR = 3.4, 95% CI 1.6–7.2) in the past year. Condom use frequency in the year preceding enrolment was predictive of a reduced risk of HIV acquisition [sometimes (aRR = 0.4, 95% CI 0.2–0.8); always (aRR = 0.1, 95% CI 0.02–0.9)]. In the follow-up risk analysis, young age [18–24 (aRR = 6.2, 95% CI 2.2–17.3) and 25-34 (aRR = 2.3, 95% CI 1.1–5.0) years], reported genital discharge (aRR = 2.5, 95% CI 1.1–5.5), serological syphilis (aRR 3.2, 95% CI 1.3–7.7) and the partner being ART naïve (aRR = 4.8, 95% CI 1.4–16.0) were independently associated with HIV acquisition. There were no seroconversions among participants who reported consistent condom use during the study.
The study has identified important risk factors for HIV acquisition among HIV discordant couples. HIV-uninfected partners in discordant couples may be a suitable population for HIV vaccine efficacy trials. However, recent confirmation that ART reduces heterosexual HIV transmission may make it unfeasible to conduct HIV prevention trials in this population.
HIV/AIDS continues to be a significant global health problem. Sub-Saharan Africa remains the most affected region with heterosexual intercourse being the main mode of HIV transmission
The high prevalence of HIV discordance and the high rates of HIV transmission within discordant couples make them a potentially suitable population for clinical trials evaluating preventive vaccines, microbicides, pre-exposure prophylaxis and other HIV prevention interventions in Africa
We report the incidence of and risk factors for HIV acquisition in a cohort of HIV-uninfected partners from HIV discordant couples enrolled in an HIV vaccine trial feasibility study. The study was part of a set of HIV vaccine preparedness studies (VPS) conducted by the Medical Research Council (MRC)/Uganda Virus Research Institute (UVRI) Uganda Research Unit on AIDS in collaboration with the International AIDS Vaccine Initiative (IAVI) in Masaka district, Uganda.
The VPS study protocol was reviewed and approved by the Science and Ethics Committee of the Uganda Virus Research Institute and by the Uganda National Council for Science and Technology. Couples were given the informed consent document to read or, if illiterate, it was read to them by a study nurse in the presence of an independent witness. The study nurse answered any questions raised by the couple before obtaining written informed consent from the HIV-uninfected partner. Later in the study, written informed consent was also obtained from HIV-infected partners to enable collection of data on receipt of antiretroviral therapy (ART). Informed consent discussions were repeated during follow up visits with both partners to ensure continued understanding of the study. Free condoms were offered throughout the duration of the study. Counseling on male medical circumcision was initiated later on in the study after evidence that this intervention was effective became available. Participants who wished to be circumcised were referred to hospitals with surgical facilities in Masaka district. Couples were also provided with free outpatient medical care including diagnosis and treatment of RTIs. HIV-infected partners were given daily trimethoprim-sulphamethoxazole for prophylaxis against opportunistic infections and had CD4/CD8 T-cell counts measured at study entry and every 6 months throughout the study. Consistent with the 2003 national ART guidelines
Study participants were HIV-uninfected individuals living in discordant couple relationships (one spouse being HIV-uninfected and the other HIV-infected). Couples suspected or already confirmed to be HIV discordant were referred for screening from three sources: (i) the MRC/UVRI home-based HIV voluntary counseling and testing (VCT) service, (ii) the MRC/UVRI clinic-based HIV VCT service, and (iii) major HIV care and VCT providers in Masaka district.
Enrollment was offered to healthy HIV-uninfected individuals aged 18–60 years, who were married to or cohabiting with an HIV-infected sexual partner, willing to give informed consent and provide locator information, be followed for 2 years, complete interviewer administered questionnaires on HIV risk factors, undergo repeated HIV counseling and testing, accept to receive and share their HIV results with their partner, and for females to be tested for pregnancy every 3 months.
Screening procedures consisted of: provision of study information to the couples, obtaining informed consent from the HIV-uninfected partners, couples' HIV voluntary counseling and testing (CVCT), and study eligibility assessment. Upon enrolment, demographic and sexual risk data including data on reported symptoms of reproductive tract infections (RTIs), extramarital sex, condom use frequency and alcohol consumption were collected using a structured questionnaire. A medical history was collected and a complete physical examination performed. Venous blood was drawn for HIV and syphilis serology. Genital examinations were only conducted on participants who reported symptoms of RTIs. Data collection on receipt of antiretroviral therapy (ART) by the HIV-infected partners was initiated later in the study. Detailed locator information including telephone numbers for those who owned or had access to a phone was collected. Participants were issued with study identification cards on which scheduled study visit dates were recorded. Costs for time and travel were reimbursed.
Couples were followed at 3-month intervals for 2 years. At each follow up visit, CVCT was performed. On this occasion, study participants were asked about their recent medical history, and a symptom directed physical examination was performed. Specimens were collected and laboratory tests conducted as during the enrolment visit. Sexual risk behavior data were collected every 6 months. Interim visits were conducted for: (i) administrative reasons; (ii) HIV VCT for presumed exposure to HIV; (iii) obtaining laboratory test results from previous visits; (iv) assessment and treatment of illnesses; (v) and other reasons as requested by the participant and in response to tracing efforts. Locator information was updated as necessary.
Participants who missed study visits were reminded to come for follow up within 2 days of the missed visit by a community mobiliser. At least 2 reminder visits were conducted for each missed visit. Participants who failed to attend follow up visits without clear reason despite the reminders, and those that could not be traced were considered lost to follow up. Participants who reported separation from or death of the HIV-infected partner were withdrawn from study as soon as this information became available.
Determine (Abbot Laboratories, Japan) rapid test was used to screen for HIV antibodies. All positive test results were confirmed by two parallel ELISAs (Vironostika Uni-Form II Ag/Ab, BioMerieux, Netherlands and Murex HIV.2.O, Murex Biotech Ltd., UK). Western blot (Genetic Systems, Biorad Laboratories) was used to resolve discrepant ELISA results. HIV testing was repeated after 2–4 weeks on a fresh specimen if the Western blot test was indeterminate. Sero-syphilis testing was done using the rapid plasma reagin (RPR) test (Biotec). RPR reactive specimens were confirmed with the Treponema pallidum Haemaglutination (TPHA) assay (Biotec). Participants were considered to have serological syphilis infection if they tested positive for TPHA and RPR with RPR titres of 1∶4 or greater
Data were recorded in MS Access and analysed in Stata 10 (StataCorp, College Station, Texas, USA). All participants who completed at least one follow-up visit were eligible for statistical analysis. Person-years of observation (PYO) were calculated as the sum of the time from enrolment (baseline) to the date of the last HIV-uninfected result, or to the estimated date of HIV infection for each participant. Date of HIV infection was imputed as the mid-point of the interval between the last HIV-uninfected and the first HIV-infected result dates. Rate ratios and 95% confidence intervals were obtained for potential risk factors using a Poisson regression model. The purposeful selection algorithm
Screening and enrolment were conducted from March 2006 to May 2007; quarterly follow up visits were completed in March 2009.
The study profile is shown in
Thirty-four participants seroconverted over 786.6 PYO. The overall HIV incidence rate [95% confidence interval] was 4.3 [3.1–6]; and 4.3 [2.8–6.4] and 4.4 [2.5–8] per 100 PYO in men and women respectively. Crude and adjusted associations between risk factors present at baseline and HIV incidence are presented in
N (%) | Seroconverters | PYO | Rate/ 100 PYO | RR (95% CI) | LRT p-value | aRR (95% CI) | |
|
482 (100.0) | 34 | 786.6 | 4.3 | |||
|
|||||||
Circumcised | 93 (19.3) | 3 | 152.5 | 2.0 | 1.0 | 0.21 | 1.0 |
Uncircumcised | 237 (49.2) | 20 | 386.4 | 5.2 | 2.6 (0.8-8.9) | 1.6 (0.4-5.7) | |
Female | 152 (31.5) | 11 | 247.7 | 4.4 | 2.3 (0.6-8.1) | 1.3 (0.3-4.9) | |
|
|||||||
≥35 | 260 (53.9) | 11 | 447.9 | 2.5 | 1.0 | 0.01 | 1.0 |
25-34 | 175 (36.3) | 16 | 269.1 | 5.9 | 2.4 (1.1-5.2) | 2.7 (1.2-5.8) | |
18-24 | 47 (9.8) | 7 | 69.6 | 10.1 | 4.1 (1.6-10.7) | 4.1 (1.6-10.8) | |
|
|||||||
Married | 396 (82.2) | 25 | 646.5 | 3.9 | 1.0 | 0.21 | |
Steady partner | 86 (17.8) | 9 | 140.1 | 6.4 | 1.7 (0.8-3.6) | ||
|
|||||||
Non Muslim | 383 (79.5) | 30 | 622.6 | 4.8 | 1.0 | 0.16 | |
Muslim | 99 (20.5) | 4 | 164.0 | 2.4 | 0.5 (0.2-1.4) | ||
|
|||||||
≥Secondary | 94 (19.5) | 6 | 151.4 | 4.0 | 1.0 | 0.93 | |
Primary | 338 (70.1) | 25 | 555.2 | 4.5 | 1.1 (0.5-2.8) | ||
None | 50 (10.4) | 3 | 80.1 | 3.7 | 0.9 (0.2-3.8) | ||
|
|||||||
No | 213 (44.2) | 8 | 350.3 | 2.3 | 1.0 | 0.01 | 1.0 |
Yes | 269 (55.8) | 26 | 436.3 | 6.0 | 2.6 (1.2-5.8) | 2.6 (1.1-6.0) | |
|
|||||||
No | 310 (64.3) | 21 | 511.3 | 4.1 | 1.0 | 0.69 | |
Yes | 172 (35.7) | 13 | 275.4 | 4.7 | 1.1 (0.6-2.3) | ||
|
|||||||
Did not use | 193 (40.0) | 23 | 308.2 | 7.5 | 1.0 | 0.001 | 1.0 |
Sometimes | 210 (43.6) | 10 | 344.3 | 2.9 | 0.4 (0.2-0.8) | 0.4 (0.2-0.8) | |
Always | 79 (16.4) | 1 | 134.2 | 0.7 | 0.1 (0.01-0.7) | 0.1 (0.02-0.9) | |
|
|||||||
No | 354 (73.4) | 22 | 585.6 | 3.8 | 1.0 | 0.21 | |
Yes | 128 (26.6) | 12 | 201.0 | 6.0 | 1.6 (0.8-3.2) | ||
|
|||||||
No | 378 (78.4) | 19 | 626.4 | 3.0 | 1.0 | 0.002 | 1.0 |
Yes | 104 (21.6) | 15 | 160.2 | 9.4 | 3.1 (1.6-6.1) | 3.4 (1.6-7.2) | |
|
|||||||
Negative | 457 (94.8) | 31 | 745.9 | 4.2 | 1.0 | 0.37 | |
Positive | 25 (5.2) | 3 | 40.7 | 7.4 | 1.8 (0.5-5.9) | ||
|
|||||||
Yes | 80 (16.6) | 3 | 138.6 | 2.2 | 1.0 | 0.33 | |
No | 359 (74.5) | 29 | 612.9 | 4.7 | 2.2 (0.7-7.2) | ||
Data not collected | 43 (8.9) | 2 | 35.1 | 5.7 | 2.6 (0.4-15.8) |
PYO, person-years of observation; RR, unadjusted rate ratio; aRR, adjusted rate ratio (All factors were adjusted for gender, age group at study entry, male circumcision, alcohol use, condom use frequency, and genital discharge in the past year); CI, confidence interval; LRT, likelihood ratio test.
Baseline factors that remained significantly associated with increased risk of HIV acquisition at multivariate analysis were young age [18–24 (aRR = 4.1, 95% CI, 1.6–10.8) and 25–34 (aRR = 2.7, 95% CI 1.2–5.8) years], alcohol use (aRR = 2.6, 95% CI 1.1–6), and reported genital discharge (aRR = 3.4, 95% CI: 1.6–7.2) in the past year. Condom use frequency in the year preceding enrolment was associated with a reduced risk of HIV acquisition [sometimes (aRR = 0.4, 95% CI 0.2–0.8); always (aRR = 0.1, 95% CI 0.02–0.9)]. Similar predictors of HIV acquisition were identified with Turnbull's exact interval censored maximum likelihood analysis method.
Crude and adjusted associations between risk factors present during study follow up and HIV incidence are presented in
N (%) | Seroconverters | PYO | Rate/100 PYO | RR (95% CI) | LRT p-value | aRR (95% CI) | |
|
482 (100.0) | 34 | 786.6 | 4.3 | |||
|
|||||||
Circumcised | 94 (19.5) | 3 | 154.3 | 1.9 | 1.0 | 0.20 | 1.0 |
Uncircumcised | 236 (49.0) | 20 | 384.6 | 5.2 | 2.7 (0.8-9.0) | 2.7 (0.8-9.2) | |
Female | 152 (31.5) | 11 | 247.7 | 4.4 | 2.3 (0.6-8.2) | 2.0 (0.5-7.7) | |
|
|||||||
≥35 | 293 (60.8) | 11 | 504.0 | 2.2 | 1.0 | 0.001 | 1.0 |
25-34 | 166 (34.4) | 17 | 255.0 | 6.7 | 3.1 (1.4-6.5) | 2.3 (1.1-5.0) | |
18-24 | 23 (4.8) | 6 | 27.6 | 21.7 | 10.0 (3.7-26.9) | 6.2 (2.2-17.3) | |
|
|||||||
≥Secondary | 94 (19.5) | 6 | 151.4 | 4.0 | 1.0 | 0.93 | |
Primary | 338 (70.1) | 25 | 555.2 | 4.5 | 1.1 (0.5-2.8) | ||
None | 50 (10.4) | 3 | 80.1 | 3.7 | 0.9 (0.2-3.8) | ||
|
|||||||
Non Muslim | 383 (79.5) | 30 | 622.6 | 4.8 | 1.0 | 0.16 | |
Muslim | 99 (20.5) | 4 | 164.0 | 2.4 | 0.5 (0.2-1.4) | ||
|
|||||||
Married | 396 (82.2) | 25 | 646.5 | 3.9 | 1.0 | 0.21 | |
Steady partner | 86 (17.8) | 9 | 140.1 | 6.4 | 1.7 (0.8-3.6) | ||
|
|||||||
No | 162 (33.6) | 5 | 265.6 | 1.9 | 1.0 | 0.01 | |
Yes | 320 (66.4) | 29 | 521.1 | 5.6 | 3.0 (1.1-7.6) | ||
|
|||||||
No | 270 (56.0) | 19 | 445.2 | 4.3 | 1.0 | ||
Yes | 212 (44.0) | 15 | 341.5 | 4.4 | 1.03 (0.5-2.0) | 0.93 | |
|
|||||||
Sometimes | 454 (94.2) | 34 | 735.8 | 4.6 | - | - | |
Always | 28 (5.8) | 0 | 50.9 | 0.0 | - | - | |
|
|||||||
No | 305 (63.3) | 17 | 502.4 | 3.4 | 1.0 | 0.10 | |
Yes | 177 (36.7) | 17 | 284.2 | 6.0 | 1.8 (0.9-3.5) | ||
|
|||||||
No | 323 (67.0) | 16 | 531.9 | 3.0 | 1.0 | 0.01 | 1.0 |
Yes | 159 (33.0) | 18 | 254.7 | 7.1 | 2.3 (1.2-4.6) | 2.5 (1.1-5.5) | |
|
|||||||
Negative | 438 (90.9) | 27 | 717.0 | 3.8 | 1.0 | 0.04 | 1.0 |
Positive | 44 (9.1) | 7 | 69.6 | 10.1 | 2.7 (1.2-6.1) | 3.2 (1.3-7.7) | |
|
|||||||
Yes | 152 (31.5) | 3 | 270.6 | 1.1 | 1.0 | 0.002 | 1.0 |
No | 287 (59.5) | 29 | 480.9 | 6.0 | 5.4 (1.7-17.9) | 4.8 (1.4-16.0) | |
Data not collected | 43 (8.9) | 2 | 35.1 | 5.7 | 5.1 (0.9-30.7) | 3.9 (0.6-23.8) |
PYO, person-years of observation; RR, unadjusted rate ratio; aRR, adjusted rate ratio (All factors were adjusted gender, age group at study exit, male circumcision, reported genital discharge, serological syphilis and ART use in the HIV-infected partner); CI, confidence interval; LRT, likelihood ratio test.
Factors that remained significantly associated with increased risk of HIV acquisition at multivariate analysis were young age [18–24 (aRR = 6.2; 95% CI: 2.2–17.3) and 25–34 (aRR = 2.3; 95% CI: 1.1–5.0) years], reported genital discharge (aRR = 2.5; 95% CI: 1.1–5.5), serological syphilis (aRR = 3.2; 95% CI: 1.3–7.7) and the HIV-infected partner being ART naïve (aRR = 4.8; 95% CI: 1.4–16.0). Similar predictors of HIV acquisition were identified with Turnbull's exact interval censored maximum likelihood analysis method.
The overall HIV incidence of 4.3 per 100 PYO in this cohort was high but lower than the rates reported in previous HIV discordant couple studies in Uganda
Also, participants who dropped out of the study were younger than those who completed it. This may have resulted in underestimation of HIV incidence since the risk of HIV acquisition was higher among younger participants. A higher HIV incidence among younger people has also been documented in previous studies
We found no significant difference in HIV incidence between men and women, the rate being about 4 per 100 PYO for each gender. Data on gender-specific HIV transmission risk from available literature is inconclusive. A study in the neighbouring district of Rakai found similar HIV transmission risks among men and women
Alcohol use before sexual intercourse has been associated with increased risk of HIV acquisition in discordant couple
As expected, we found that regular condom use was strongly protective against HIV acquisition. Therefore, consistent condom use for prevention of HIV transmission among discordant couples in stable unions should be strongly promoted
Treatable RTIs are common and important correlates of HIV transmission within discordant heterosexual couples
Though only borderline significant, the risk of HIV acquisition was higher among uncircumcised compared to circumcised men. Recent randomized clinical trials
We found that ART initiated according to the national HIV treatment guidelines
With the exception of ART, we did not collect data on other risk factors among HIV-infected partners that could facilitate HIV transmission. This was because the VPS protocol primarily targeted HIV-uninfected individuals at high risk of HIV acquisition. Early and late stage HIV infection, higher HIV load, genital ulcer disease, and younger age of the HIV-infected partner have all been associated with higher rates of HIV transmission
Enrolment of participants in the current study overlapped that of the Microbicides Development Programme (MDP) 301 trial. MDP301 was a multicentre phase III trial of the PRO 2000/5 vaginal gel. At our centre, the trial recruited HIV-uninfected women who were in HIV discordant partnerships
Our study has shown that in addition to being in an HIV discordant relationship, there are other important risk factors for HIV transmission among HIV discordant couples that need to be urgently targeted. The high HIV incidence and moderate participant retention observed in this study suggest that HIV-uninfected partners in discordant couples may be a suitable population for phase IIb/III preventive HIV vaccine trials in our setting. However, recent findings confirming that ART significantly reduces HIV transmission from an infected partner to an uninfected spouse may make it unfeasible to conduct future HIV prevention trials in this population.
We thank the study participants, and the clinical, laboratory, field, data management and administrative staff. We are also grateful to The AIDS Support Organisation (TASO), Uganda Cares, Kitovu Mobile AIDS Organisation and Villa Maria Hospital for their kind collaboration and support.