Characterizing HIV-Preventive, Plasma Tenofovir Concentrations-A Pooled Participant-level Data Analysis From Human Immunodeficiency Virus Preexposure Prophylaxis Clinical Trials

BACKGROUND

Daily dosing of tenofovir disoproxil fumarate, with or without emtricitabine, has high efficacy in preventing human immunodeficiency virus (HIV) infection when individuals are adherent. The target protective plasma concentration of tenofovir (TFV), however, is not fully understood. The aim of this study is to estimate the protective TFV plasma concentration.

METHODS

Participant data from TFV-based daily oral and topical active arms of phase 3 trials (iPrEx, VOICE, and Partners PrEP) were pooled (n = 2950). Individual specific risk scores (low and high risk) of acquiring HIV, based on an earlier placebo analysis, were created. Longitudinal TFV pharmacokinetics (PK), HIV outcome, individual risk scores and the effect of sex at birth data were integrated and analyzed using non-linear mixed effects models.

RESULTS

Around 50% of the individuals were estimated to be adherent, which differed from self-reported adherence (∼90%) and large variation between longitudinal adherence patterns were identified. Following oral administration, the estimated protective TFV trough concentration was substantially higher in high-risk females (45.8 ng/mL) compared with high-risk males (16.1 ng/mL) and to low-risk individuals (∼7.5 ng/mL). Dosing simulations indicated that high-risk women require full adherence to maintain protective levels.

CONCLUSIONS

Using the largest PK-HIV outcome database to date, we developed a population adherence-PK-risk-outcome model. Our results indicate that high-risk females need higher levels of plasma TFV to achieve HIV protection compared with males. HIV protection exceeds 90% in all populations if daily adherence is achieved.

Modeling the Probability of HIV Infection over Time in High-Risk Seronegative Participants Receiving Placebo in Five Randomized Double-Blind Placebo-Controlled HIV Pre-Exposure Prophylaxis Trials: A Patient-Level Pooled Analysis

The World Health Organization recommends pre-exposure prophylaxis (PrEP) for individuals at substantial risk of HIV infection. The aim of this analysis is to quantify the individual risk of HIV infection over time, using a large database of high-risk individuals (n = 5583). We used data from placebo recipients in five phase III PrEP trials: iPrEx, conducted in men who have sex with men and transgender women; VOICE, conducted in young women at high sexual risk; Partners PrEP, conducted in HIV serodiscordant heterosexual couples; TDF2, conducted in high-risk heterosexual men and women; and BTS, conducted in persons who inject drugs. The probability of HIV infection over time was estimated using NONMEM7.4. We identified predictors of HIV risk and found a substantial difference in the risk of infection among and within trial populations, with each study including a mix of low, moderate, and high-risk individuals (p < 0.05). Persons who were female at birth were at a higher risk of HIV infection than people who were male at birth. Final models were integrated in a tool that can assess person-specific risk and simulate cumulative HIV risk over time. These models can be used to optimize future PrEP clinical trials by identifying potential participants at highest risk.

Altered Antibody Responses in Persons Infected with HIV-1 While Using Preexposure Prophylaxis

Preexposure prophylaxis (PrEP) is an effective HIV prevention tool, although effectiveness is dependent upon adherence. It is important to characterize the impact of PrEP on HIV antibody responses in people who experience breakthrough infections to understand the potential impact on timely diagnosis and treatment. Longitudinal HIV-1-specific antibody responses were evaluated in 42 people who inject drugs (PWID) from the Bangkok Tenofovir Study (BTS) (placebo = 28; PrEP = 14) who acquired HIV while receiving PrEP. HIV-1 antibody levels and avidity to three envelope proteins (gp41, gp160, and gp120) were measured in the plasma using a customized Bio-Plex (Bio-Rad Laboratories, Hercules, CA) assay. A time-to-event analysis was performed for each biomarker to compare the distribution of times at which study subjects exceeded the recent/long-term assay threshold, comparing PrEP and placebo treatment groups. We fit mixed-effects models to identify longitudinal differences in antibody levels and avidity between groups. Overall, longitudinal antibody levels and avidity were notably lower in the PrEP breakthrough group compared to the placebo group. Time-to-event analyses demonstrated a difference in time to antibody reactivity between treatment groups for all Bio-Plex biomarkers. Longitudinal gp120 antibody levels within the PrEP breakthrough group were decreased compared to the placebo group. When accounting for PrEP adherence, both gp120 and gp160 antibody levels were lower in the PrEP breakthrough group compared to the placebo group. We demonstrate hindered envelope antibody maturation in PWID who became infected while receiving PrEP in the BTS, which has significant implications for HIV diagnosis. Delayed maturation of the antibody response to HIV may increase the time to detection for antibody-based tests. Clinical Trial Registration Number, NCT00119106.

HIV-1 genetic diversity to estimate time of infection and infer adherence to preexposure prophylaxis

OBJECTIVE

To estimate time of HIV infection in participants from the Bangkok Tenofovir Study (BTS) with daily oral tenofovir disoproxil fumarate (TDF) for preexposure prophylaxis (PrEP) and relate infection with adherence patterns.

DESIGN

We used the diversity structure of the virus population at the first HIV RNA-positive sample to estimate the date of infection, and mapped these estimates to medication diaries obtained under daily directly observed therapy (DOT).

METHODS

HIV genetic diversity was investigated in all 17 PrEP breakthrough infections and in 16 placebo recipients. We generated 10-25 HIV env sequences from each participant by single genome amplification, and calculated time since infection (and 95% confidence interval) using Poisson models of early virus evolution. Study medication diaries obtained under daily DOT were then used to compute the number of missed TDF doses at the approximate date of infection.

RESULTS

Fifteen of the 17 PrEP breakthrough infections were successfully amplified. Of these, 13 were initiated by a single genetic variant and generated reliable estimates of time since infection (median = 47 [IQR = 35] days). Eleven of these 13 were under daily DOT at the estimated time of infection. Analysis of medication diaries in these 11 participants showed 100% adherence in five, 90-95% adherence in two, 55% adherence in one, and nonadherence in three.

CONCLUSION

We estimated time of infection in participants from BTS and found several infections when high levels of adherence to TDF were reported. Our results suggest that the biological efficacy of daily TDF against parenteral HIV exposure is not 100%.

Hepatitis C virus infection among people who inject drugs in Bangkok, Thailand, 2005-2010

BACKGROUND

Approximately 1% of adults in Thailand are infected with hepatitis C virus (HCV). New direct-acting antiviral agents achieve sustained virologic responses in >95% of HCV-infected patients and are becoming available in countries around the world. To prepare for new HCV treatment options in Thailand, this study characterized HCV infections among people who inject drugs (PWID) in Bangkok.

METHODS

The Bangkok Tenofovir Study (BTS) was a pre-exposure prophylaxis trial conducted among PWID, 2005-2013. Blood specimens were randomly selected from PWID screened for the BTS, to test for anti-HCV antibody and HCV RNA. The HVR1 region was amplified by polymerase chain reaction, using multiplex primer sets with unique identifier sequences; amplification products were pooled in sets of 25; and consensus sequencing was performed to characterize individual HCV genotypes.

RESULTS

The median age of 3679 participants tested for anti-HCV antibody was 31 years, 3016 (82.0%) were male and 447 (12.2%) were HIV infected. The prevalence of anti-HCV antibody was 44.3%. The adjusted odds of testing positive for anti-HCV antibody were higher in men (adjusted odds ratio [aOR] 3.2, 95% confidence interval [CI] 2.4-4.3), those aged 40 years or older (aOR 2.7, 95% CI 2.1-3.5), those who had more than a primary school education (aOR 1.7, 95% CI 1.4-2.1), and those who tested HIV positive (aOR 5.2, 95% CI 3.7-7.4). HCV RNA was detected in 644 (81.3%) of the 792 anti-HCV antibody-positive specimens, yielding an HCV RNA-positive prevalence of 36.0% (95% CI 33.8-38.2). Among a random sample of 249 of the 644 specimens, 218 could be characterized, and the most common HCV subtypes were 1a (30.3%), 1b (12.8%), 3a (35.8%), 3b (6.9%) and 6n (8.7%).

CONCLUSION

The prevalence of anti-HCV antibody among PWID was 44.3% and more than one third (36.0%) were HCV RNA positive. Genotypes 1, 3 and 6 accounted for all typable infections. As the government of Thailand considers introduction of direct-acting antiviral medications for people with hepatitis C, it will be important to ensure that the medications target these subtypes.

HIV Incidence and Risk Behaviours of People Who Inject Drugs in Bangkok, 1995-2012

BACKGROUND

Three consecutive prospective studies were conducted among people who inject drugs (PWID) from May 1995 through June 2012 in Bangkok, Thailand. We examined data from these studies to evaluate HIV incidence and explore trends in risk behaviours.

METHODS

We used data from a 1995-1998 cohort study, a 1999-2004 HIV vaccine trial, and a 2005-2012 HIV pre-exposure prophylaxis (PrEP) study to examine per-quarter trends in HIV incidence, using a restricted cubic spline function for time in a Poisson regression. We also examined temporal trends in HIV-associated risk behaviours.

FINDINGS

HIV incidence declined from 5.7 per 100 person-years during the cohort study, to 2.7 per 100 person-years in the vaccine trial, to 0.7 per 100 person-years among PrEP study placebo recipients. Incidence peaked at 12.1 per 100 person-years in 1996 and declined to < 1 per 100 person-years during 2005-2012. Reports of injecting drugs and sharing needles also declined from the cohort study to the PrEP study (p < 0.0001). Heroin was the most common drug injected during the cohort study and the vaccine trial, but stimulants (e.g., methamphetamine) and sedatives (e.g., midazolam) were injected more often during the PrEP study.

INTERPRETATION

HIV incidence among PWID declined during 2005-2012. Several factors likely contributed to the decline, including decreases in the frequency of injecting and sharing, improved access to HIV testing and antiretroviral therapy, and the use of PrEP. Expanding access to effective HIV prevention tools can hasten control of the HIV epidemic among PWID.

FUNDING

The Bangkok Metropolitan Administration and U.S. Centers for Disease Control and Prevention, Division of HIV/AIDS Prevention.

Factors associated with the uptake of and adherence to HIV pre-exposure prophylaxis in people who have injected drugs: an observational, open-label extension of the Bangkok Tenofovir Study

BACKGROUND

Results of the randomised, double-blind, placebo-controlled Bangkok Tenofovir Study (BTS) showed that taking tenofovir daily as pre-exposure prophylaxis (PrEP) can reduce the risk of HIV infection by 49% in people who inject drugs. In an extension to the trial, participants were offered 1 year of open-label tenofovir. We aimed to examine the demographic characteristics, drug use, and risk behaviours associated with participants' uptake of and adherence to PrEP.

METHODS

In this observational, open-label extension of the BTS (NCT00119106), non-pregnant, non-breastfeeding, HIV-negative BTS participants, all of whom were current or previous injecting drug users at the time of enrolment in the BTS, were offered daily oral tenofovir (300 mg) for 1 year at 17 Bangkok Metropolitan Administration drug-treatment clinics. Participant demographics, drug use, and risk behaviours were assessed at baseline and every 3 months using an audio computer-assisted self-interview. HIV testing was done monthly and serum creatinine was assessed every 3 months. We used logistic regression to examine factors associated with the decision to take daily tenofovir as PrEP, the decision to return for at least one PrEP follow-up visit, and greater than 90% adherence to PrEP.

FINDINGS

Between Aug 1, 2013, and Aug 31, 2014, 1348 (58%) of the 2306 surviving BTS participants returned to the clinics, 33 of whom were excluded because they had HIV (n=27) or grade 2-4 creatinine results (n=6). 798 (61%) of the 1315 eligible participants chose to start open-label PrEP and were followed up for a median of 335 days (IQR 0-364). 339 (42%) participants completed 12 months of follow-up; 220 (28%) did not return for any follow-up visits. Participants who were 30 years or older (odds ratio [OR] 1·8, 95% CI 1·4-2·2; p<0·0001), injected heroin (OR 1·5, 1·1-2·1; p=0·007), or had been in prison (OR 1·7, 1·3-2·1; p<0·0001) during the randomised trial were more likely to choose PrEP than were those without these characteristics. Participants who reported injecting heroin or being in prison during the 3 months before open-label enrolment were more likely to return for at least one open-label follow-up visit than those who did not report injecting heroin (OR 3·0, 95 % CI 1·3-7·3; p=0·01) or being in prison (OR 2·3, 1·4-3·7; p=0·0007). Participants who injected midazolam or were in prison during open-label follow-up were more likely to be greater than 90% adherent than were those who did not inject midazolam (OR 2·2, 95% CI 1·2-4·3; p=0·02) or were not in prison (OR 4·7, 3·1-7·2; p<0·0001). One participant tested positive for HIV, yielding an HIV incidence of 2·1 (95% CI 0·05-11·7) per 1000 person-years. No serious adverse events related to tenofovir use were reported.

INTERPRETATION

More than 60% of returning, eligible BTS participants started PrEP, which indicates that a substantial proportion of PWID who are knowledgeable about PrEP might be interested in taking it. Participants who had injected heroin or been in prison were more likely to choose to take PrEP, suggesting that participants based their decision to take PrEP, at least in part, on their perceived risk of incident HIV infection.

FUNDING

US Centers for Disease Control and Prevention and the Bangkok Metropolitan Administration.

Assessment of Oral Fluid HIV Test Performance in an HIV Pre-Exposure Prophylaxis Trial in Bangkok, Thailand

Background

Rapid easy-to-use HIV tests offer opportunities to increase HIV testing among populations at risk of infection. We used the OraQuick Rapid HIV-1/2 antibody test (OraQuick) in the Bangkok Tenofovir Study, an HIV pre-exposure prophylaxis trial among people who inject drugs.

Methods

The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial. We tested participants’ oral fluid for HIV using OraQuick monthly and blood using a nucleic-acid amplification test (NAAT) every 3 months. We used Kaplan-Meier methods to estimate the duration from a positive HIV NAAT until the mid-point between the last non-reactive and first reactive oral fluid test and proportional hazards to examine factors associated with the time until the test was reactive.

Results

We screened 3678 people for HIV using OraQuick. Among 447 with reactive results, 436 (97.5%) were confirmed HIV-infected, 10 (2.2%) HIV-uninfected, and one (0.2%) had indeterminate results. Two participants with non-reactive OraQuick results were, in fact, HIV-infected at screening yielding 99.5% sensitivity, 99.7% specificity, a 97.8% positive predictive value, and a 99.9% negative predictive value. Participants receiving tenofovir took longer to develop a reactive OraQuick (191.8 days) than participants receiving placebo (16.8 days) (p = 0.02) and participants infected with HIV CRF01_AE developed a reactive OraQuick earlier than participants infected with other subtypes (p = 0.04).

Discussion

The oral fluid HIV test performed well at screening, suggesting it can be used when rapid results and non-invasive tools are preferred. However, participants receiving tenofovir took longer to develop a reactive oral fluid test result than those receiving placebo. Thus, among people using pre-exposure prophylaxis, a blood-based HIV test may be an appropriate choice.

Trial Registration

ClinicalTrials.gov NCT00119106.

HIV pre-exposure prophylaxis and health and community systems in the Global South: Thailand case study

INTRODUCTION

Pre-exposure prophylaxis (PrEP) is recommended by the World Health Organization as an effective method of HIV prevention for individuals at risk for infection. In this paper, we describe the unique role that Thailand has played in the global effort to combat the HIV epidemic, including its role in proving the efficacy of PrEP, and discuss the opportunities and challenges of implementing PrEP in a middle-income country.

DISCUSSION

Thailand was one of the first countries in the world to successfully reverse a generalized HIV epidemic. Despite this early success, HIV prevalence has remained high among people who inject drugs and has surged among men who have sex with men (MSM) and transgender women (TGW). Two pivotal trials that showed that the use of oral antiretroviral medication as PrEP can reduce HIV transmission were conducted partially or entirely at Thai sites. Demonstration projects of PrEP, as well as clinical trials of alternative PrEP regimens, began or will begin in 2014-2015 in Thailand and will provide additional data and experience on how to best implement PrEP for high-risk individuals in the community. Financing of drug costs, the need for routine laboratory monitoring and lack of awareness about PrEP among at-risk groups all present challenges to the wider implementation of PrEP for HIV prevention in Thailand.

CONCLUSIONS

Although significant challenges to wider use remain, PrEP holds promise as a safe and highly effective method to be used as part of a combined HIV prevention strategy for MSM and TGW in Thailand.

Biomedical HIV Prevention Including Pre-exposure Prophylaxis and Opiate Agonist Therapy for Women Who Inject Drugs: State of Research and Future Directions

Women who inject drugs (WWID) are at higher risk of HIV compared with their male counterparts as a result of multiple factors, including biological, behavioral, and sociostructural factors, yet comparatively little effort has been invested in testing and delivering prevention methods that directly target this group. In this article, we discuss the need for expanded prevention interventions for WWID, focusing on 2 safe, effective, and approved, yet underutilized biomedical prevention methods: opiate agonist therapy (OAT) and oral pre-exposure prophylaxis (PrEP). Although both interventions are well researched, they have not been well examined in the context of gender. We discuss the drivers of women injectors' higher HIV risk, review the effectiveness of OAT and PrEP interventions among women, and explain why these new HIV prevention tools should be prioritized for WWID. There is substantial potential for impact of OAT and PrEP programs for WWID in the context of broader gender-responsive HIV prevention initiatives. Although awaiting efficacy data on other biomedical approaches in the HIV prevention research "pipeline," we propose that the scale-up and implementation of these proven, safe, and effective interventions are needed now.

High Mortality Among Non-HIV-Infected People Who Inject Drugs in Bangkok, Thailand, 2005-2012

OBJECTIVES

We examined the causes of hospitalization and death of people who inject drugs participating in the Bangkok Tenofovir Study, an HIV preexposure prophylaxis trial.

METHODS

The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial conducted during 2005 to 2012 among 2413 people who inject drugs. We reviewed medical records to define the causes of hospitalization and death, examined participant characteristics and risk behaviors to determine predictors of death, and compared the participant mortality rate with the rate of the general population of Bangkok, Thailand.

RESULTS

Participants were followed an average of 4 years; 107 died: 22 (20.6%) from overdose, 13 (12.2%) from traffic accidents, and 12 (11.2%) from sepsis. In multivariable analysis, older age (40-59 years; P = .001), injecting drugs (P = .03), and injecting midazolam (P < .001) were associated with death. The standardized mortality ratio was 2.9.

CONCLUSIONS

People who injected drugs were nearly 3 times as likely to die as were those in the general population of Bangkok and injecting midazolam was independently associated with death. Drug overdose and traffic accidents were the most common causes of death, and their prevention should be public health priorities.

Recalibration of the limiting antigen avidity EIA to determine mean duration of recent infection in divergent HIV-1 subtypes

Background

Mean duration of recent infection (MDRI) and misclassification of long-term HIV-1 infections, as proportion false recent (PFR), are critical parameters for laboratory-based assays for estimating HIV-1 incidence. Recent review of the data by us and others indicated that MDRI of LAg-Avidity EIA estimated previously required recalibration. We present here results of recalibration efforts using >250 seroconversion panels and multiple statistical methods to ensure accuracy and consensus.

Methods

A total of 2737 longitudinal specimens collected from 259 seroconverting individuals infected with diverse HIV-1 subtypes were tested with the LAg-Avidity EIA as previously described. Data were analyzed for determination of MDRI at ODn cutoffs of 1.0 to 2.0 using 7 statistical approaches and sub-analyzed by HIV-1 subtypes. In addition, 3740 specimens from individuals with infection >1 year, including 488 from patients with AIDS, were tested for PFR at varying cutoffs.

Results

Using different statistical methods, MDRI values ranged from 88–94 days at cutoff ODn = 1.0 to 177–183 days at ODn = 2.0. The MDRI values were similar by different methods suggesting coherence of different approaches. Testing for misclassification among long-term infections indicated that overall PFRs were 0.6% to 2.5% at increasing cutoffs of 1.0 to 2.0, respectively. Balancing the need for a longer MDRI and smaller PFR (<2.0%) suggests that a cutoff ODn = 1.5, corresponding to an MDRI of 130 days should be used for cross-sectional application. The MDRI varied among subtypes from 109 days (subtype A&D) to 152 days (subtype C).

Conclusions

Based on the new data and revised analysis, we recommend an ODn cutoff = 1.5 to classify recent and long-term infections, corresponding to an MDRI of 130 days (118–142). Determination of revised parameters for estimation of HIV-1 incidence should facilitate application of the LAg-Avidity EIA for worldwide use.

Risk behaviors and risk factors for HIV infection among participants in the Bangkok tenofovir study, an HIV pre-exposure prophylaxis trial among people who inject drugs

INTRODUCTION

HIV spread rapidly among people who inject drugs in Bangkok in the late 1980s. In recent years, changes in drug use and HIV-associated risk behaviors have been reported. We examined data from the Bangkok Tenofovir Study, an HIV pre-exposure prophylaxis trial conducted among people who inject drugs, to assess participant risk behavior and drug use, and to identify risk factors for HIV infection.

METHODS

The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial. HIV status was assessed monthly and risk behavior every 3 months. We used generalized estimating equations logistic regression to model trends of injecting, needle sharing, drugs injected, incarceration, and sexual activity reported at follow-up visits; and proportional hazards models to evaluate demographic characteristics, sexual activities, incarceration, drug injection practices, and drugs injected during follow-up as predictors of HIV infection.

RESULTS

The proportion of participants injecting drugs, sharing needles, and reporting sex with more than one partner declined during follow-up (p<0.001). Among participants who reported injecting at enrollment, 801 (53.2%) injected methamphetamine, 559 (37.1%) midazolam, and 527 (35.0%) heroin. In multivariable analysis, young age (i.e., 20-29 years) (p = 0.02), sharing needles (p<0.001), and incarceration in prison (p = 0.002) were associated with incident HIV infection. Participants reporting sex with an opposite sex partner, live-in partner, casual partner, or men reporting sex with male partners were not at a significantly higher risk of HIV infection compared to those who did not report these behaviors.

CONCLUSION

Reports of HIV-associated risk behavior declined significantly during the trial. Young age, needle sharing, and incarceration were independently associated with HIV infection. Sexual activity was not associated with HIV infection, suggesting that the reduction in HIV incidence among participants taking daily oral tenofovir compared to those taking placebo was due to a decrease in parenteral HIV transmission.

Antiretroviral prophylaxis for HIV infection in injecting drug users in Bangkok, Thailand (the Bangkok Tenofovir Study): a randomised, double-blind, placebo-controlled phase 3 trial

BACKGROUND

Antiretroviral pre-exposure prophylaxis reduces sexual transmission of HIV. We assessed whether daily oral use of tenofovir disoproxil fumarate (tenofovir), an antiretroviral, can reduce HIV transmission in injecting drug users.

METHODS

In this randomised, double-blind, placebo-controlled trial, we enrolled volunteers from 17 drug-treatment clinics in Bangkok, Thailand. Participants were eligible if they were aged 20-60 years, were HIV-negative, and reported injecting drugs during the previous year. We randomly assigned participants (1:1; blocks of four) to either tenofovir or placebo using a computer-generated randomisation sequence. Participants chose either daily directly observed treatment or monthly visits and could switch at monthly visits. Participants received monthly HIV testing and individualised risk-reduction and adherence counselling, blood safety assessments every 3 months, and were offered condoms and methadone treatment. The primary efficacy endpoint was HIV infection, analysed by modified intention-to-treat analysis. This trial is registered with ClinicalTrials.gov, number NCT00119106.

FINDINGS

Between June 9, 2005, and July 22, 2010, we enrolled 2413 participants, assigning 1204 to tenofovir and 1209 to placebo. Two participants had HIV at enrolment and 50 became infected during follow-up: 17 in the tenofovir group (an incidence of 0·35 per 100 person-years) and 33 in the placebo group (0·68 per 100 person-years), indicating a 48·9% reduction in HIV incidence (95% CI 9·6-72·2; p=0·01). The occurrence of serious adverse events was much the same between the two groups (p=0·35). Nausea was more common in participants in the tenofovir group than in the placebo group (p=0·002).

INTERPRETATION

In this study, daily oral tenofovir reduced the risk of HIV infection in people who inject drugs. Pre-exposure prophylaxis with tenofovir can now be considered for use as part of an HIV prevention package for people who inject drugs.

FUNDING

US Centers for Disease Control and Prevention and the Bangkok Metropolitan Administration.

Enrollment characteristics and risk behaviors of injection drug users participating in the Bangkok Tenofovir Study, Thailand

Background

The Bangkok Tenofovir Study was launched in 2005 to determine if pre-exposure prophylaxis with tenofovir will reduce the risk of HIV infection among injecting drug users (IDUs). We describe recruitment, screening, enrollment, and baseline characteristics of study participants and contrast risk behavior of Tenofovir Study participants with participants in the 1999–2003 AIDSVAX B/E Vaccine Trial.

Methods

The Bangkok Tenofovir Study is an ongoing, phase-3, randomized, double-blind, placebo-controlled, HIV pre-exposure prophylaxis trial of daily oral tenofovir. The Tenofovir Study and the Vaccine Trial were conducted among IDUs at 17 drug-treatment clinics in Bangkok. Tenofovir Study sample size was based on HIV incidence in the Vaccine Trial. Standardized questionnaires were used to collect demographic, risk behavior, and incarceration data. The Tenofovir Study is registered with ClinicalTrials.gov, number-NCT00119106.

Results

From June 2005 through July 2010, 4094 IDUs were screened and 2413 enrolled in the Bangkok Tenofovir Study. The median age of enrolled participants was 31 years (range, 20–59), 80% were male, and 63% reported they injected drugs during the 3 months before enrollment. Among those who injected, 53% injected methamphetamine, 37% midazolam, and 35% heroin. Tenofovir Study participants were less likely to inject drugs, inject daily, or share needles (all, p<0.001) than Vaccine Trial participants.

Discussion

The Bangkok Tenofovir Study has been successfully launched and is fully enrolled. Study participants are significantly less likely to report injecting drugs and sharing needles than participants in the 1999–2003 AIDSVAX B/E Vaccine Trial suggesting HIV incidence will be lower than expected. In response, the Bangkok Tenofovir Study enrollment was increased from 1600 to 2400 and the study design was changed from a defined 1-year follow-up period to an endpoint-driven design. Trial results demonstrating whether or not daily oral tenofovir reduces the risk of HIV infection among IDUs are expected in 2012.

Factors associated with incarceration and incident human immunodeficiency virus (HIV) infection among injection drug users participating in an HIV vaccine trial in Bangkok, Thailand, 1999-2003

AIMS

To determine if incarceration was associated with human immunodeficiency virus (HIV) infection and identify risk factors for incarceration among injection drug users (IDUs) participating in an HIV vaccine trial in Bangkok.

DESIGN

The AIDSVAX B/E HIV vaccine trial was a randomized, double-blind, placebo-controlled study. A proportional hazards model was used to evaluate demographic characteristics, risk behavior and incarceration as predictors of HIV infection and generalized estimation equation logistic regression analysis to investigate demographic characteristics and risk behaviors for predictors of incarceration.

SETTING

The trial was conducted in Bangkok Metropolitan Administration drug-treatment clinics, 1999-2003.

PARTICIPANTS

A total of 2546 HIV-uninfected IDUs enrolled in the trial.

MEASUREMENTS

HIV testing was performed and an interviewer-administered questionnaire was used to assess risk behavior and incarceration at baseline and every 6 months for a total of 36 months.

FINDINGS

HIV incidence was 3.4 per 100 person-years [95% confidence interval (CI), 3.0-3.9] and did not differ among vaccine and placebo recipients. In multivariable analysis, being in jail (P < 0.04), injecting (P < 0.0001), injecting daily (P < 0.0001) and sharing needles (P = 0.02) were associated with HIV infection and methadone maintenance was protective (P = 0.0006). Predictors of incarceration in multivariable analysis included: male sex (P = 0.04), younger age (P < 0.0001), less education (P = 0.001) and being in jail (P < 0.0001) or prison (P < 0.0001) before enrollment.

CONCLUSIONS

Among IDUs in the AIDSVAX B/E trial, incarceration in jail was associated with incident HIV infection. IDUs in Thailand remain at high risk of HIV infection and additional prevention tools are needed urgently. HIV prevention services, including methadone, should be made available to IDUs.

Cross-reactive T cell responses in HIV CRF01_AE and B'-infected intravenous drug users: implications for superinfection and vaccines

Abstract We previously observed limited cross-reactive T cell responses in two HIV-1-superinfected injection drug users (IDUs) before superinfection [Ramos A, et al.: J Virol 2002;76(15):7444-7452]. To elucidate the role of such responses in superinfection we examined cross-reactive T cell responses in IDUs infected with a single HIV-1 subtype. In this study, IFN-gamma ELISPOT assays were performed using recombinant vaccinia constructs and peripheral blood mononuclear cells (PBMCs) from 43 IDUs singly infected with CRF01_AE or B' from the same cohort as the superinfected IDUs. PBMCs were from time points corresponding to pre- (early) or post- (late) superinfection in the superinfected IDUs. We observed that most singly infected IDUs had cross-reactivity in samples from early (84% of CRF01_AE and 78% of B'-infected IDUs) and late (96% of CRF_01AE and 77% of B'-infected IDUs) time points. Frequent homologous reactivity at early (67% of CRF-01AE and 100% of B') and late (84% of CRF01_AE-infected and 100% of B'-infected IDUs) time points was also observed. Cross-reactive responses were predominantly to Pol and were broader and higher in CRF01_AE than in B'-infected IDUs (medians of 825 vs. 90 and 585 vs. 60 spot-forming units/10(6) PBMCs at early and late time points, respectively). Our results show that cross-reactive responses were more prevalent with greater height and breadth in singly infected IDUs than previously observed in corresponding collection time points of superinfected IDU. Thus, low or absent cross-reactivity may have contributed to the previously observed superinfections. These data are relevant for understanding superinfection and improving vaccine design.

The Thai HIV/AIDS epidemic at 15 years: sustained needle sharing among southern Thai drug injectors

To explore perceptions and attitudes towards needle sharing among clinic-based injecting drug abusers (IDUs) at a drug-treatment clinic in Hat Yai City, Songkla Province, Southern Thailand. Qualitative methods were used to gather data, including: in-depth interviews with 17 active IDUs and with three nurses, participant observation, review of the IDUs' files, and validation after interview completion to ensure data triangulation. A form of comparative content analysis, including thematic analysis, was used for data analysis. After 15 years of the Thai HIV/AIDS epidemic, most southern Thai IDUs still occasionally engaged in needle sharing although they reported reductions in sharing frequency. Withdrawal symptoms and craving were most commonly cited as compelling reasons to share. Misconceptions about how to determine "healthy" from the "sick" was another key factor underlying sharing. Pooling money for drugs (with subsequent cost-savings) was given priority over purchasing new needles/syringes among disadvantaged IDUs. Receiving HIV voluntary counseling and testing (VCT), however, promotes reduced sharing. Our findings suggest that southern Thai IDUs remain at high risk of acquiring HIV infection, primarily through needle sharing. Harm reduction strategies, such as, providing VCT to all IDUs and promoting needle exchange programs might be beneficial approaches to curbing the rapid spread of HIV.

Social harms in injecting drug users participating in the first phase III HIV vaccine trial in Thailand

OBJECTIVE

To study related social harms due to identification with a group of participants in an HIV-1 vaccine trial who are potentially high risk for HIV/AIDS.

MATERIAL AND METHOD

Two thousand five hundred forty six injecting drug users (IDU) were enrolled in a 36-month vaccine trial. Volunteers received education and risk reduction counseling at every six-month study visit. Social harms were not actively solicited, but volunteers were encouraged to report any during the process of counseling at every six-month visit. If a social harm was reported, a questionnaire was administered and the harm was tracked If necessary, clinic staff assisted in resolving the social harm.

RESULTS

Thirty-nine social harms were reported by 37 participants; 33 (84.6%) were disturbances in personal relationships, three (7.7%) in employment, one (2.6%) was medically related, one (2.6%) was related to admission in the military and one (2.6%) was related with misbelieve about the vaccine. The most common reason for disturbances in personal relationships was suspicion of HIV infection (n=20). The impact of these harms on quality of life was characterized as minimal by 31 (79.5%) participants, as moderate by seven (17.9%), and as major by one (2.6%). All social harms were documented to be resolved by the end of the study.

CONCLUSION

A few participants reported study-related social harms during the course of the trial. Most harm had minimal impact and all could be resolved by the end of the present study.

The spread of HIV-1 subtypes B and CRF01_AE among injecting drug users in Bangkok, Thailand

The HIV epidemic among injecting drug users (IDUs) in Bangkok was initially dominated by HIV subtype B and later by the recombinant CRF01_AE. The present study investigates the distribution of the 2 variants in time and how it is affected by changes in injecting risk behavior and treatment. A mathematic model describing the spread of HIV subtype B and CRF01_AE among IDUs was developed, and data from the AIDSVAX B/E cohort of IDUs in Bangkok were used. From the model, it was calculated that during 1999 to 2003, the annual incidence of HIV was around 0.6 and 2.7 to 3.9 infections per 100 person-years for subtype B and CRF01_AE, respectively. Of the new infections, 18% and 72% are first infections with subtype B and CRF01_AE, respectively, and 9% are superinfections. With increases in risk behavior, the fraction of superinfections rises. If treatment reduces the infectivity of CRF01_AE more than that of subtype B, the fraction of subtype B infections should increase. Subtype B should remain prevalent in a small but considerable fraction of the population for a long time. Changes in risk behavior and the introduction of treatment may alter the distribution of subtypes, but CRF01_AE should remain dominant.

Sexual risk reduction in a cohort of injecting drug users in Bangkok, Thailand

OBJECTIVE

Interventions to reduce sexual risk behavior among injecting drug users (IDUs) have generally had very modest effects, but almost all such interventions have been conducted within short time frames. This study assessed whether long-term participation in interventions to reduce sexual risk behavior was associated with reduced sexual risk behavior.

METHODS

A total of 806 IDUs participated in the Bangkok HIV Vaccine Trial Preparatory Cohort Study from 1995-1998 and remained in the study for at least 4 follow-up visits (approximately 16 months). Participants received HIV counseling and testing every 4 months and free condoms were provided. Structured interviews including questions on sexual behavior were administered every 4 months.

RESULTS

Approximately 40% of participants reported engaging in unprotected sex (vaginal intercourse without always using a condom) with a regular partner at each study visit, without any decline over time in this behavior. There were declines in the proportions of participants reporting unprotected sex with casual partners and with paid partners (men only) over time, but the declines were confined to the early period of the study. Unprotected sex with casual partners was associated with amphetamine use. Condom use increased substantially among participants who seroconverted for HIV during the study.

CONCLUSIONS

Interventions to reduce sexual risk behavior among HIV-seronegative IDUs over extended periods were no more likely to be effective than shorter interventions. New programs are needed to reduce sexual risk behavior among amphetamine users and among IDUs who are currently seronegative but are engaging in injection risk behaviors and in unprotected sex with regular partners.

Early markers of HIV-1 disease progression in a prospective cohort of seroconverters in Bangkok, Thailand: implications for vaccine trials

BACKGROUND

Some candidate HIV-1 vaccines may not prevent HIV-1 infection but may alter the course of disease. Surrogate endpoints based on early laboratory makers in HIV-1-infected persons who are antiretroviral therapy (ART)-naive will be useful for evaluating vaccine efficacy in slowing disease progression (VEp). We examined pretreatment HIV-1 viral loads and CD4 cell counts in recent HIV-1 seroconverters to inform selection of these endpoints.

METHODS

We studied 130 newly HIV-1-infected injection drug users identified from a prospective cohort of initially uninfected persons in Bangkok during 1995 through 1998. We analyzed trends in HIV-1 viral loads and CD4 cell counts as well as progression to the surrogate endpoint, defined as 2 consecutive CD4 cell counts of fewer than 350 cells/mm, during 24 months after the first HIV-1 seropositive (FP) visit.

RESULTS

Median HIV-1 RNA copies/mL with interquartile ranges were 43,693 (14,320-94,767) at the FP visit, 46,924 (16,273-104,314) at 6 months, 28,446 (11,292-54,325) at 12 months, and 18,080 (8713-54,059) at 18 months. HIV-1 viral loads at the FP visit and at 18 months were positively correlated (r = 0.53, P < 0.0001). Of 130 participants, 12% reached the surrogate endpoint by 6 months, 16% by 12 months, and 27% by 18 months. In Cox regression analyses, HIV-1 viral loads of more than 50,000 copies/mL at the FP visit (hazard ratio [HR] = 2.3, 95% confidence interval [CI]: 1.1-4.8) and first CD4 cell count of 500 or fewer cells/mm (HR = 7.6, 95% CI: 3.2-17.6) were independently associated with faster progression to the surrogate endpoint.

CONCLUSIONS

Participants with high HIV-1 RNA levels and low CD4 cell counts close to the time of seroconversion were more likely to experience early immunologic progression. Approximately one quarter of seroconverters reached the surrogate immunologic endpoint within 18 months of their FP visit and before starting ART, suggesting the utility of this endpoint for analyses of VEp in some ongoing and planned HIV-1 vaccine efficacy trials.

CDC international HIV prevention research activities among injection drug users in Thailand and Russia

The Centers for Disease Control and Prevention (CDC) has participated in collaborative HIV prevention research activities in injection drug users (IDUs) with the Bangkok Metropolitan Administration (BMA) in Bangkok, Thailand, from 1995 to the present and with the Orel AIDS Center in Orel Oblast, Russia, from 2001 to 2003. Studies in Bangkok have included an HIV prevention trial preparatory cohort from 1995 to 1998, a seroconverter cohort from 1998 to the present, a phase III trial of the AIDSVAX B/E gp120 HIV vaccine from 1999 to 2003, and a phase II/III HIV prophylaxis trial with tenofovir scheduled to begin in 2005. Activities in Orel included a review of HIV surveillance data in 2001, focus group discussions and a case-control study with HIV-infected and -uninfected IDUs in 2001, a cross-sectional study with the female sex partners of male IDUs in 2002, and a community outreach intervention in 2002-2003. In Bangkok, 1,209 IDUs were enrolled in the preparatory cohort which revealed an HIV incidence of 5.8% per 100 person-years; 133 HIV-infected IDUs have been followed in the seroconverter cohort with >85% follow-up and HIV and tuberculosis care provided; 2,546 IDUs were enrolled in the HIV vaccine efficacy trial which was successfully completed with a follow-up rate of >95%, although the vaccine was not shown to be effective at reducing HIV incidence; and 1,600 IDUs will be enrolled in the daily tenofovir HIV prophylaxis trial in 2005. In Orel, initial focus group discussions and epidemiologic studies revealed low HIV knowledge and high rates of unsafe injecting and sexual practices among IDUs and their female sex partners; and educational campaigns and the community outreach intervention were developed and implemented. A steady decline in new HIV infections in IDUs was then observed in Orel in 2002-2003. CDC has participated in the conduct of successful collaborative HIV prevention research activities in Thailand and Russia over the past decade. The establishment of long-term relationships with in-country public health and community partners has been instrumental in the success of these efforts.

Frequency of HIV-1 dual subtype infections, including intersubtype superinfections, among injection drug users in Bangkok, Thailand

OBJECTIVES

To estimate the frequency and incidence of dual HIV-1 subtype infections, including superinfections, among recent seroconvertors from a cohort of injection drug users (IDUs).

METHODS

A total of 1209 HIV-negative IDUs were followed in a prospective cohort study at 15 methadone clinics in Bangkok, Thailand. After 2308 person-years (PY) of follow-up, 133 seroconverted to HIV-1, of which approximately 20% were subtype B and 80% were CRF01_AE (formerly called subtype E). Specimens from 126 individuals were available at time of first seropositive test and specimens from 80 of these 126 individuals were also available more than 12 months later. For each infected participant, we calculated the amount of time to superinfection, loss to follow-up, or to the closest visit more than 12 months after the time of initial seropositivity.

RESULTS

Of all 126 seroconverters seen at the time of the first seropositive test result, there was no apparent case of concurrent dual subtype infection detected despite 2301 PY of observation. Overall, the incidence of superinfection was 2.2 per 100 PY [95% confidence interval (CI), 0.3-7.8]. The 1-year incidence of CRF01_AE superinfection following subtype B primary infection was 3.9 per 100 PY (95% CI, 0.1-21.9) and the incidence of subtype B superinfection following CRF01_AE primary infection was 1.5 per 100 PY (95% CI, 0.04-8.3).

CONCLUSIONS

Determination of the frequency and incidence of dual HIV-1 subtype infection demonstrates that HIV-1 superinfection is not uncommon in a population with high HIV-1 incidence with more than one circulating strain.

Frequent Human Leukocyte Antigen Class I Alleles Are Associated With Higher Viral Load Among HIV Type 1 Seroconverters in Thailand

The loss of viral control by the host may be due to the evolution of viruses with mutations that limit presentation by human leukocyte antigen (HLA) to cytotoxic T cells. The authors hypothesized that the consequence of such evolution might be that persons with common HLA class I alleles would be less able to control viremia, on average, than would those with rare alleles. HLA class I typing was completed for 128 injection drug users who seroconverted in a prospective cohort study in Bangkok, Thailand. Logistic regression was used to model viral load (greater than or equal to the median) at 9 and 12 months after seroconversion with an HLA score that profiled the relative prevalence of each individual's alleles. At 12 months after seroconversion, injection drug users with the most common HLA alleles (highest quartile HLA score) had an almost 4-fold increased risk for higher viral load (> or = 32,055 copies/mL) than injection drug users with less common HLA alleles (adjusted odds ratio, 3.92; 95% confidence interval, 1.3-11.8). These findings support the importance of frequency-dependent effects of host genes on HIV type 1 evolution in different populations and suggest that HLA-driven viral evolution critically influences control of viremia in early HIV type 1 infection.

CCR5 promoter human haplogroups associated with HIV-1 disease progression in Thai injection drug users

BACKGROUND

An evolutionary-based analysis of the CC chemokine receptor 5 gene (CCR5) promoter region has identified nine stable human haplogroups, within which certain haplogroups appear to influence HIV-1 disease progression differentially among Caucasians and African-Americans.

OBJECTIVE

To assess the influence of CCR5 haplogroups on HIV-1 disease progression in a Thai population.

DESIGN

Haplogroup analysis of HIV-1-seropositive injection drug users (IDU) participating in a prospective cohort study in Bangkok. All were documented seroconverters with a median follow-up time of 3.5 years (range, 0.2-7.0).

METHODS

From a cohort of 130 IDU, 106 (81.5%) were genotyped for the CCR2b-64I, CCR5-delta32 and seven CCR5 promoter alleles constituting the CCR5 haplogroups. Survival curves and adjusted Cox proportional hazards models were used to assess the effect of haplogroups on the time from HIV-1 infection until CD4 count < 200 x 10(6) cells/l.

RESULTS

The most common CCR5 haplogroups were HHC (61.8%), followed by HHE (15.6%) and HHF*2 (14.6%). HHE was associated with an accelerated CD4 count decline to < 200 x 10(6) cells/l (adjusted relative hazard, 1.88; 95% confidence interval, 1.05-3.36; P = 0.02).

CONCLUSIONS

This is the first evidence that the CCR5 haplogroup E speeds the decline of the CD4 cell count and may lead to accelerated disease progression among HIV-infected Thais. These new observations highlight the need for additional studies involving populations in Asia.

Lack of increased HIV risk behavior among injection drug users participating in the AIDSVAX B/E HIV vaccine trial in Bangkok, Thailand

OBJECTIVE

To determine whether HIV vaccine trial participation leads to increased risk behavior through beliefs about vaccine protection against infection.

METHODS

Changes in risk behavior were evaluated among 2545 injection drug users participating in the AIDSVAX B/E vaccine trial in Bangkok, enrolled from March 1999 to August 2000. Demographic characteristics, beliefs and risk behavior were assessed at baseline and every 6 months thereafter. Risk-reduction counseling was provided at every study visit. Generalized estimation-equation logistic regression analysis was used to study trends in risk behavior and associated factors.

RESULTS

Participants were 93.4% male, their median age was 26 years, and 67.2% had at least secondary education. At baseline, 61.3% were receiving methadone detoxification and 20.9% were receiving methadone maintenance. From baseline to the 12-month follow-up visit, injection drug use decreased from 93.8% to 66.5% (P < 0.001) and needle sharing from 33.0% to 17.5% (P < 0.001). Multivariate analyses showed earlier follow-up time (at baseline and 6 months) and believing the vaccine to be efficacious associated with more-frequent injecting; younger age and lower education associated with less-frequent injecting. Earlier follow-up time (at baseline), younger age, and injection of methamphetamine and midazolam were associated with more-frequent needle sharing; methadone treatment and injecting less than weekly were associated with less-frequent needle sharing.

CONCLUSIONS

Injection drug use and needle sharing decreased during the first 12 months of the trial. No increases in risk behavior in relation to beliefs about vaccine protection against HIV infection could be identified.

Recruitment, screening and characteristics of injection drug users participating in the AIDSVAX B/E HIV vaccine trial, Bangkok, Thailand

OBJECTIVES

To describe recruitment, screening and baseline characteristics of injection drug users (IDU) participating in a phase III HIV vaccine (AIDSVAX B/E; VaxGen, USA) trial and to compare enrollment characteristics between trial participants and 1209 IDU from a 1995-1998 vaccine trial preparatory cohort for changes that might impact trial design assumptions.

METHODS

Enrollment for both studies was conducted at Bangkok narcotic treatment clinics, where a standardized questionnaire was administered on demographics, risk behavior and incarceration history over the previous 6 months.

RESULTS

During 1999-2000, 4943 IDU were screened for enrollment; successful sources of recruitment included clinic attendees (43.4%), an IDU referral program (20.4%) and preparatory cohort participants (14.7%). Of those screened, 1689 (34%) were HIV seropositive (HIV subtype B 23.6%; subtype E 76.4%). Of the 2545 enrolled, 93.4% were male. Compared with cohort IDU, trial IDU were younger (mean age: 28.8 versus 31.3 years), better educated (secondary level or higher: 67.2% versus 58.7%), and less likely to inject drugs daily (39.4% versus 90.4%); they were more likely to have been incarcerated (78.4% versus 65.7%), have recently injected stimulants (14.8% versus 5.8%) and tranquilizers (11.5% versus 2.3%), and obtained needles/syringes from a source other than a pharmacist (7.2% versus 3.9%) (all P < or = 0.003).

CONCLUSIONS

IDU at high risk for HIV have been successfully enrolled in the AIDSVAX B/E efficacy trial. Only minor epidemiologic differences were found at enrollment between trial and preparatory cohort IDU. The latter has proven critical in guiding trial design; results are expected in late 2003.

HIV type 1 incidence estimates by detection of recent infection from a cross-sectional sampling of injection drug users in Bangkok: use of the IgG capture BED enzyme immunoassay

Development of serologic tests to detect recent HIV-1 infection has generated worldwide interest in applying this approach to estimate incidence. We previously devised an IgG-capture BED-EIA (or BED-CEIA) that detects increasing levels of anti-HIV IgG following seroconversion to identify recent infection and to estimate incidence among persons infected with diverse HIV-1 subtypes worldwide. Injection drug users (IDUs; n = 1969) were screened in 1996 for participation in a prospective cohort study. Serum specimens from 594 IDUs were HIV-1 seropositive (30.2%) and were tested with the BED-CEIA. The proportion of recent infections and estimated incidence by different epidemiological risk factors were compared with incidence data measured from the prospective cohort. Of 594 HIV-1-seropositive specimens, 113 (19%) were identified as recent infections. Overall, the estimated annual incidence among persons screened was 17.3%/year (95% CI, 12.8-24.2%/year) compared with 9.0%/year (95% CI, 6.7-11.9%/year) measured from the prospective cohort during the same time period. Estimated incidence was higher among younger aged and unemployed IDUs as well as among those who injected more frequently, confirming previously reported risk factors from this prospective cohort. As persons screened from a cross-sectional sampling probably have higher risk for HIV than selected uninfected individuals who choose to participate and receive risk reduction counseling in a longitudinal cohort study, use of this or other serologic testing strategies to identify populations with high incidence (such as for HIV vaccine trials) may overestimate incidence measured from prospective cohorts.

New HIV type 1 CRF01_AE/B recombinants displaying unique distribution of breakpoints from incident infections among injecting drug users in Thailand

The goals of this study were to identify and characterize recombinant human immunodeficiency virus type 1 (HIV-1) genomes among incident infections in a prospective cohort study of injecting drug users (IDUs) in Bangkok, Thailand. Through cross-sectional, comparative phylogenetic analysis of the protease and env (C2-V4) gene regions, subtype discordance was observed in HIV-1 sequences from 4 of 111 IDUs (3.5%). Near-full-length HIV-1 genome sequences of the four strains revealed that in all four, the gp120 sequences clustered with a CRF01_AE prototype, while the remainder of the genomes displayed distinct mosaic patterns, with multiple breakpoints between HIV-1 CRF01_AE and subtype B-like regions. Two of the four HIV-1 recombinant strains displayed a nearly identical mosaic structure, suggesting the possible emergence and spread of a potentially new circulating recombinant form of HIV-1. Further characterization of these and other recombinant genomes through long-term follow-up will be important in understanding the generation of viral diversity and escape from the hosts immune responses. This information will be especially important for vaccine development.

Evaluation of a sensitive/less sensitive testing algorithm using the bioMérieux Vironostika-LS assay for detecting recent HIV-1 subtype B' or E infection in Thailand

The performance of the bioMérieux Vironostika-LS EIA (less sensitive enzyme immunoassay) was assessed to detect recent seroconversion among injecting drug users (IDUs) in Bangkok, Thailand who were infected with either HIV-1 subtypes B' or E (also known as circulating recombinant form CRF01_AE). To evaluate the Vironostika-LS EIA in non-B subtypes, we collected longitudinal specimens (n = 796) from 115 IDUs (subtype B' infection, n = 24; subtype E infection, n = 91). After testing HIV-positive specimens with the Vironostika-LS EIA, standardized optical densities (SODs) were calculated using median values to determine the window period, which is the time from seroconversion on a standard EIA to seroconversion on the Vironostika-LS EIA for a given SOD, for either subtype. For an SOD cutoff of 1.0, Vironostika-LS EIA results showed a mean window period of 239 days (95% confidence interval [95% CI], 208-287 days) for subtype B' and 356 days (95% CI, 318-402 days) for subtype E in Thailand. This outcome demonstrates that the Vironostika-LS EIA has significantly different performance characteristics in detecting recent seroconversion between different HIV-1 subtypes. Accurate identification of recent infection and estimation of incidence for HIV-1 strains other than North American subtype B, using the Vironostika-LS EIA, requires knowledge of specimen subtype and use of appropriate cutoffs and mean window periods.

HIV risk reduction in a cohort of injecting drug users in Bangkok, Thailand

OBJECTIVE

To determine changes in risk behavior in relation to study participation among injecting drug users (IDUs) in Bangkok, Thailand.

METHODS

During 1995-1996, 1,209 HIV-seronegative IDUs were recruited from Bangkok Metropolitan Administration drug abuse treatment programs to participate in a prospective cohort study. Study visits occurred every 4 months, at which the participants underwent an interview to assess risk behavior and HIV counseling and testing. Eight hundred nine of the IDUs were considered "long-term" participants, who remained in the study through at least the first four scheduled follow-up visits (16 months). Injection risk behavior at each study visit was measured on a four-point scale strongly associated with incident HIV infections in the cohort. Individual regression slopes were used to assess changes in injection risk behavior (risk increase, no change, or risk reduction).

RESULTS

Of the 806 long-term study participants, 79% showed declines, 4% showed no change, and 17% showed increases in injection risk behavior. The percentage of participants in the highest-risk category (injecting daily or more frequently and sharing needles and syringes) declined from 42% at baseline to 3% at the final follow-up visit. Being in methadone maintenance treatment was associated with stable low rates of injection risk behavior, while recruitment from the 45-day detoxification treatment was associated with reductions in injection risk behavior. The risk reduction was independent of decline in risk behavior among IDUs in the community at large.

CONCLUSIONS

Participation in this cohort study was associated with substantial declines in injection risk behavior. This information is important in the evaluation of possible adverse behavioral effects of participation in future preventive HIV vaccine trials including IDUs, particularly in developing country settings.

Intersubtype human immunodeficiency virus type 1 superinfection following seroconversion to primary infection in two injection drug users

In this study, we describe two cases of human immunodeficiency virus type 1 (HIV-1) intersubtype superinfection with CRF01_AE and subtype B strains, which occurred in two injection drug users participating in a prospective cohort study in Bangkok, Thailand. In both cases, the superinfecting strain was detected by molecular and serologic analyses several weeks after complete seroconversion to the primary infection with a strain belonging to a different subtype. Superinfection occurred despite specific T-cell and humoral antibody responses to the primary virus. In both cases, cross-subtype immune responses were limited or absent prior to the second infection. These data show that, in some individuals, the quality and quantity of the immune response elicited by primary HIV-1 infection may not protect against superinfection. This finding has important implications for vaccine design. HIV-1 vaccines, at a minimum, will need to include potent, broadly protective, conserved immunogens derived from several group M subtypes.

Higher viral loads and other risk factors associated with HIV-1 seroconversion during a period of high incidence among injection drug users in Bangkok

We analyzed data from a prospective cohort study of injection drug users (IDUs) attending methadone treatment clinics in Bangkok, Thailand, during 1995-1998 to characterize factors associated with a period of high incidence (PHI) from July 1996 through January 1997 compared with periods of lower incidence. Sociobehavioral characteristics were similar for all participants during and outside the PHI except for the following: there was more reported drug injection while IDUs were incarcerated during the PHI (odds ratio, 1.67; p =.02) and significantly higher proportions of persons reported heroin injection (91% vs. 75%, respectively; p =.02) and higher frequencies of daily injection and sharing of injection equipment (40% vs. 25%, respectively; p =.05) during the PHI than outside the PHI. Through most of the first year after seroconversion, plasma HIV-1 loads were significantly higher in persons who seroconverted during the PHI than in those who seroconverted outside the PHI. Higher viral loads may potentially contribute to faster disease progression and increased infectiousness or transmissibility to subsequent contacts. Our findings suggest that prevention efforts to reduce the effective size and turnover within IDU sharing networks may have a significant impact on the epidemic by disrupting the rapid transmission of HIV-1 from recently infected, highly infectious individuals.

Genetic analysis of incident HIV-1 strains among injection drug users in Bangkok: evidence for multiple transmission clusters during a period of high incidence

During 1995-1996, 1,209 HIV-1-negative injection drug users (IDUs) attending methadone treatment clinics operated by the Bangkok Metropolitan Administration in Bangkok, Thailand, were enrolled in a prospective cohort study. Through 1998, 133 of these IDUs had seroconverted to HIV-1; 130 of these seroconverters were included in this study. HIV-1 CRF01_AE and subtype B strains accounted for 79% and 21% of the incident infections, respectively. To examine phylogenetic relationships among these incident HIV-1 strains, we used several phylogenetic inference methodologies to analyze the env (C2-V4) sequences in blood samples collected soon after seroconversion. These analyses consistently revealed eight phylogenetic clusters comprising 21 incident strains (bootstrap method, >80%; six CRF01_AE and two subtype B clusters). Two factors were found to be associated with the eight clusters. The first factor was temporal: seven of the eight clusters comprised 17 sequences from IDUs whose estimated dates of seroconversion were within a period of high incidence from July 1996 through January 1997. The second factor was a possible geographic association: four clusters were observed among IDUs who had attended the same methadone treatment clinics. These phylogenetic clusters likely represent subgroups within larger HIV transmission networks among IDUs in Bangkok. Despite prevention efforts, the incidence of HIV-1 infection among the Bangkok IDU population continues to be high. A better understanding of transmission networks and factors associated with such networks can help guide prevention efforts.

Quantitative detection of increasing HIV type 1 antibodies after seroconversion: a simple assay for detecting recent HIV infection and estimating incidence

We have devised a simple enzyme immunoassay (EIA) that detects increasing levels of anti-HIV IgG after seroconversion and can be used for detecting recent HIV-1 infection. Use of a branched peptide that included gp41 immunodominant sequences from HIV-1 subtypes B, E, and D allowed similar detection of HIV-specific antibodies among various subtypes. Because of the competitive nature of the capture EIA, a gradual increase in the proportion of HIV-1-specific IgG in total IgG was observed for 2 years after seroconversion. This was in contrast to results obtained with the conventional EIA using the same antigen in solid phase, which plateaus soon after seroconversion. The assay was used to test 622 longitudinal specimens from 139 incident infections in the United States (subtype B) and in Thailand (subtypes B and E). The assay was also performed with an additional 8 M urea incubation step to assess the contribution of high-avidity antibodies. Normalized optical density (OD-n) was calculated (ODspecimen/ODcalibrator), using a calibrator specimen. An incremental analysis indicated that a cutoff of 1.0 OD-n and a seroconversion period of 160 days offered the best combination of sensitivity and specificity for classifying incident or long-term infections. The urea step increased the seroconversion period to 180 days with similar sensitivity and specificity. Separate analysis of B and E subtype specimens yielded the same optimal OD-n threshold and similar seroconversion periods. The assay was further validated in African specimens (subtypes A, C, and D) where the observed incidence was within 10% of the expected incidence. This assay should be useful for detecting recent HIV-1 infection and for estimating incidence among diverse HIV-1 subtypes worldwide.

Subtype-specific transmission probabilities for human immunodeficiency virus type 1 among injecting drug users in Bangkok, Thailand

The Bangkok (Thailand) Metropolitan Administration cohort of injecting drug users (IDUs) consisted of 1,209 IDUs initially seronegative for human immunodeficiency virus (HIV) who were followed from 1995 to 1998 at 15 Administration drug treatment clinics. At enrollment and approximately every 4 months thereafter, participants were assessed for HIV seropositivity. As of December 1998, there were 133 HIV type 1 seroconversions and approximately 2,300 person-years of follow-up. Of the 133 observed seroconversions, specimens from 126 persons were available for subtyping (27 subtype B, 99 subtype E). In this analysis, the authors assessed differences in subtype-specific transmission while controlling for important risk factors. The methodology used accounts for left truncation, interval censoring, and competing risks as well as for time-varying covariates such as each IDU's history of reported frequency of injection and of incarceration. Using plausible epidemiologic assumptions and controlling for behavioral risks, the authors found that a significantly higher transmission probability was associated with subtype E compared with subtype B in this population. Since many epidemiologic, virologic, and host factors can influence HIV transmission, it was difficult to conclude whether these differences in transmission probabilities were due to biologic properties associated with subtype.

Incarceration and risk for HIV infection among injection drug users in Bangkok

OBJECTIVE

To assess potential multiple relationships between incarceration and HIV infection among injecting drug users (IDUs) in Bangkok. Previous cross-sectional studies have shown strong relationships between incarceration and HIV infection but have not been able to assess potential causal pathways.

METHODS

Injection drug users seen at methadone treatment programs in Bangkok were screened during 1995 to 1996 for enrollment into the study. With informed consent, 1,209 seronegative IDUs were enrolled in a cohort study to determine HIV incidence and identify factors associated with incident infections. Follow-up visits were conducted every 4 months, with HIV testing and assessment of risk behaviors.

RESULTS

Overall incidence rate was 5.8 per 100 person-years (95% confidence interval [CI], 4.8-6.8) of follow-up. A four-step "injection risk" scale was constructed that included less frequent than daily injection, daily injection, daily injection with reported sharing of injection equipment, and injection while incarcerated. This scale was strongly related to HIV incidence, with incidence approximately doubling for each step in the scale. Incidence rate for follow-up periods that contained drug injection while incarcerated was 35/100 person-years at risk. In multivariate analyses, incarceration was related to incident HIV infection in multiple ways: previous incarceration and recent incarceration without drug injection, and the injection risk scale were all independently predictors of incident HIV infection.

CONCLUSIONS

Incarceration is related to incident HIV infection through multiple pathways. Previous incarcerations are likely to serve as markers for unmeasured high-risk behaviors, and it is also highly likely that HIV is transmitted during periods of incarceration. Programs to reduce HIV transmission in jails and prisons, including drug abuse treatment of inmates and programs to reduce the likelihood of incarceration of IDUs, are needed urgently. Given the current diffusion of injecting drug use, of HIV infection among drug injectors, and of the common policy of incarcerating drug users, it is very likely that the problem of HIV transmission in jails and prisons is increasing in many countries throughout the world.

Viral load differences in early infection with two HIV-1 subtypes

OBJECTIVES

Information on early HIV-1 infection has come primarily from studies of persons infected with subtype B in North America and Europe; much less is known about other subtypes. The purpose of the present study was to compare the virologic and immunologic parameters following seroconversion among recently-infected persons infected with either of two different HIV-1 subtypes.

METHOD

A prospective cohort study was carried out at methadone treatment clinics administered by the Bangkok Metropolitan Administration, Thailand. A total of 130 HIV-1-infected seroconverters (103 with HIV-1 subtype E and 27 with subtype B) were included in the study. The main outcome measures were serial HIV-1 RNA viral load, natural killer cell percentage, CD4 and CD8 lymphocyte counts since seroconversion.

RESULTS

The demographic and behavioral characteristics of persons with either subtype were similar. Median RNA viral levels at the earliest time within 3 months of seroconversion were more than three times higher for persons infected with subtype E than subtype B (63 100 versus 18 050 copies/ml, P = 0.001). However, this difference decreased over time such that viral loads were similar at 12, 18, and 24 months following seroconversion. The CD4 and CD8 lymphocyte counts were similar in infections with either subtype during the entire period up to 24 months post-seroconversion.

CONCLUSIONS

Higher viral loads associated with subtype E may result from inter-subtype biological differences; however, the epidemiological dynamics of transmission in Bangkok may have also contributed to this phenomenon.

Evaluation of a sensitive/less-sensitive testing algorithm using the 3A11-LS assay for detecting recent HIV seroconversion among individuals with HIV-1 subtype B or E infection in Thailand

The development of a serologic algorithm to determine recent HIV seroconversion, using sensitive/less-sensitive testing strategies, has generated widespread interest in applying this approach to estimate HIV-1 incidence in various populations around the world. To evaluate this approach in non-B subtypes, longitudinal specimens (n = 522) collected from 90 incident infections among injecting drug users in Bangkok (subtype B infection, n = 18; subtype E infection, n = 72) were tested by the 3A11-LS assay. Standardized optical density (SOD) was calculated, using median values, and the window period between seroconversion as determined by sensitive and less sensitive tests was estimated by a maximum-likelihood model described previously. Our results show that the mean window period of the 3A11-LS assay was 155 days (95% CI, 128-189 days) for subtype B but was 270 days (95% CI, 187-349 days) for subtype E specimens from Thailand. About 4% of individuals with incident subtype E infections remained below the threshold (SOD of 0.75), even 2 years after seroconversion. Among the patients with clinical AIDS and declining antibodies, none of the 7 individuals with subtype B, but 10 (8.7%) of 115 with subtype E infections, were misclassified as recent infections. Lowering the cutoff to an SOD of 0.45 for subtype E specimens resulted in a mean window period of 185 days (95% CI, 154-211 days), with all individuals seroconverting, and reduced the number of subtype E-infected patients with AIDS who were misclassified as having recent infection to 2.6%. Our results demonstrate that the 3A11-LS assay has different performance characteristics in detecting recent infections among individuals infected with subtypes B or E. Determining appropriate cutoffs and mean window periods for other HIV-1 subtypes will be necessary before this approach can be reliably implemented in settings where non-B subtypes are common.

Continued high HIV-1 incidence in a vaccine trial preparatory cohort of injection drug users in Bangkok, Thailand

BACKGROUND

A large epidemic of HIV-1 subtype B began among injection drug users (IDUs) in Bangkok in 1988. Despite ongoing prevention efforts, HIV-1 prevalence among IDUs remained at 30-50% through the 1990s.

OBJECTIVES

To measure the incidence of HIV-1 infection and related risk factors to guide prevention efforts and to evaluate the feasibility of conducting an HIV vaccine efficacy trial.

DESIGN AND METHODS

A prospective cohort study in which IDUs attending methadone treatment programs in Bangkok were screened during 1995-1996 for enrollment into the study. IDUs found to be HIV-seronegative on two occasions were offered enrollment with follow-up visits every 4 months. On each visit participants were evaluated with a questionnaire and serologic testing.

RESULTS

A total of 1209 HIV-negative IDUs were enrolled. Through the end of 1998, the overall HIV-1 incidence rate was 5.8 (95% confidence interval, 4.8-6.8) per 100 person-years of follow-up. HIV-1 subtypes E and B accounted for 79 and 21% of infections, respectively. On multivariate analysis, HIV-1 seroconversion was primarily associated with the frequency of heroin injection, the sharing of injection equipment, and incarceration, especially with drug injection. Sexual behavior was not associated with increased risk for HIV-1. Risk factors for infection with HIV-1 subtypes E and B were similar.

CONCLUSION

HIV-1 transmission risk remains high among Bangkok IDUs despite methadone treatment and other current prevention strategies. There is an urgent need to address this ongoing epidemic, especially in jails and prisons. This study led to the initiation in 1999 of a phase III HIV-1 vaccine efficacy trial in this population.

A comparison of full-length glycoprotein 120 from incident HIV type 1 subtype E and B infections in Bangkok injecting drug users with prototype E and B strains that are components of a candidate vaccine

Complete gp120 sequence information was obtained from eight persons with incident HIV-1 infections (four subtype E and four subtype B) who were part of a prospective injecting drug user (IDU) cohort in Bangkok, Thailand, during 1996-1998. The incident subtype E strains were similar to the prototype subtype E strain CM244 isolated in 1992 in northern Thailand. The incident subtype B strains displayed divergence, in both overall genetic distance and other significant gp120 characteristics, from the prototype North American subtype B strain HIV-MN. Recombinant gp120s derived from CM244 and HIV-MN strains are components of a vaccine that is undergoing phase III efficacy testing, begun in March 1999, among Bangkok area IDUs. The information presented here will be important in the evaluation of any breakthrough HIV-1 infections occurring among vaccinees during the vaccine trial and in ongoing vaccine development efforts in Thailand.

Genetic characterization of incident HIV type 1 subtype E and B strains from a prospective cohort of injecting drug users in Bangkok, Thailand

We obtained specimens from 128 HIV-1 seroconverters identified from 1995 through 1998 in a prospective cohort study of 1,209 HIV-negative injecting drug users (IDUs) in Bangkok, Thailand. Epidemiologic data indicated that parenteral transmission accounted for nearly all infections. HIV-1 DNA from the C2-V4 env region was sequenced, and phylogenetic analyses determined that 102 (79.7%) of the specimens were subtype E and 26 (20.3%) subtype B strains. All subtype B strains clustered with strains often referred to in previous studies as Thai B or B'. The interstrain nucleotide distance (C2-V4) within subtype E strains was low (mean, 6.8%), and pairwise comparisons with a prototype subtype E strain, CM244, showed limited divergence (mean, 5.6%). The subtype B stains showed greater interstrain divergence (mean, 9.2%) and were significantly divergent from the prototype B strain HIV-MN (mean, 13.0%; p < 0.0001). The subtype E strains had significantly lower mean V3 loop charge than did subtype B strains (p = 0.017) and, on the basis of analysis of amino acid sequences, were predicted to be predominantly (91%) non-syncytium-inducing (NSI), chemokine coreceptor CCR5-using (CCR5+) viruses. The subtype B strains had a higher mean V3 loop charge, and a smaller proportion (23%) were predicted to be NSI/CCR5+ viruses. This study demonstrates that most incident HIV1 infections among Bangkok IDUs are due to subtype E viruses, with a narrow spectrum of genetic diversity. The characterization of incident HIV-1 strains from 1995 to 1998 will provide important baseline information for comparison with any breakthrough infections that occur among IDUs in Bangkok who are participating in an HIV-1 vaccine efficacy trial initiated in 1999.

AIDSVAX (MN) in Bangkok injecting drug users: a report on safety and immunogenicity, including macrophage-tropic virus neutralization

A randomized, double-blind, placebo-controlled phase I/II study of AIDSVAX (MN) was conducted among injecting drug users in Bangkok, Thailand. Four doses of vaccine (300 microg of MN-rgp120 in alum) or placebo (alum) were given at study entry and at 1, 6, and 12 months. The objectives of the study were to evaluate (1) the feasibility of conducting vaccine trials in this population; (2) the safety of this candidate AIDS vaccine; and (3) the immunogenicity of this vaccine. Thirty-three volunteers (22 vaccine and 11 placebo recipients) were recruited. None were lost to follow-up during the 18-month study. Mild reactogenicity was noted, which was similar in both vaccine and placebo recipients. The vaccine induced anti-HIV-1 antibody in all vaccine recipients. Maximal titers of binding antibodies of MN-rgp120 and the V3 domain of MN-rgp120 were induced after the third (6 month) dose while maximal neutralizing antibodies followed the fourth (12 month) dose. The vaccine-induced antibodies from several volunteers were capable of neutralizing macrophage-tropic, subtype B viruses (301660 and JRCSF) detected in a PBMC-based assay. Binding and neutralizing antibodies declined about 10-fold in the 6 months after the last boost. Two vaccinees became infected during the trial, both with subtype E viruses. A phase III efficacy trial, using a bivalent gp120 vaccine containing antigens from a subtype B virus (MN) and a subtype E virus (A244), was initiated in March 1999 in injecting drug users in Bangkok.

Willingness of injection drug users to participate in an HIV vaccine efficacy trial in Bangkok, Thailand

We assessed willingness to participate in an HIV recombinant gp120 bivalent subtypes B/E candidate vaccine efficacy trial among 193 injection drug users (IDUs) attending drug treatment clinics in Bangkok, Thailand. IDUs previously enrolled in a prospective cohort study were invited to group sessions describing a potential trial, then completed questionnaires assessing comprehension and willingness to participate. A week later, they completed a follow-up questionnaire that again assessed comprehension and willingness to participate, as well as barriers to and positive motives for participation, with whom (if anyone) they talked about the information, and whether others thought participation was a good, bad, or neutral idea. At baseline, 51% were definitely willing to participate, and at follow-up 54%; only 3% were not willing to participate at either time. Comprehension was high at baseline and improved at follow-up. Participants who viewed altruism, regular HIV tests, and family support for participation as important were more willing to volunteer. Frequency of incarceration and concerns about the length of the trial, possible vaccine-induced accelerated disease progression, and lack of family support were negatively associated with willingness. Overall, IDUs comprehended the information needed to make a fully informed decision about participating in an rgp120 vaccine efficacy trial and expressed a high level of willingness to participate in such a trial.

Infection with HIV-1 subtypes B and E in injecting drug users screened for enrollment into a prospective cohort in Bangkok, Thailand

From May through August 1995, a cross-sectional survey was conducted among injecting drug users (IDUs) drawn from 15 drug treatment clinics in Bangkok and who were not known to be HIV-seropositive, to determine the prevalence of HIV-1 subtypes B and E and related risk behaviors, and to offer enrollment in a prospective cohort study. IDUs who voluntarily consented were interviewed, and blood specimens were tested for the presence of HIV antibodies. HIV-1-seropositive specimens were tested for subtypes B' (Thai B) and E by using V3 loop peptide enzyme immunoassays specific for these HIV-1 genetic subtypes. Of 1674 IDUs studied, the mean age was 31.2 years (interquartile range, 25-37 years), 94.8% were men, and 29.3% were HIV-1-seropositive. On multiple logistic regression analysis, HIV-1 seropositivity was associated with older age, not being married, less education, needle sharing, and incarceration. HIV-1 subtype B' accounted for 65% of prevalent infections and subtype E, 35%. Infection with subtype E was associated with younger age and did not seem to be associated with sexual risk behaviors, which were uncommon in general. Bangkok IDUs continue to be at high risk for HIV-1 infection related to needle sharing and incarceration. Although HIV-1 subtype B' accounts for most prevalent infections, subtype E seems to be more prevalent among younger IDUs, and most infections seem likely to result from parenteral transmission.