Publications (9)62.38 Total impact
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Article: Safety and adherence to intermittent pre-exposure prophylaxis (PrEP) for HIV-1 in African men who have sex with men and female sex workers.
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ABSTRACT: Little is known about safety of and adherence to intermittent HIV PrEP regimens, which may be more feasible than daily dosing in some settings. We present safety and adherence data from the first trial of an intermittent PrEP regimen among Kenyan men who have sex with men (MSM) and female sex workers (FSW). MSM and FSW were randomized to daily oral FTC/TDF or placebo, or intermittent (Monday, Friday and within 2 hours after sex, not to exceed one dose per day) oral FTC/TDF or placebo in a 2:1:2:1 ratio; volunteers were followed monthly for 4 months. Adherence was assessed with the medication event monitoring system (MEMS). Sexual activity data were collected via daily text message (SMS) queries and timeline followback interviews with a one-month recall period. Sixty-seven men and 5 women were randomized into the study. Safety was similar among all groups. Median MEMS adherence rates were 83% [IQR: 63-92] for daily dosing and 55% [IQR:28-78] for fixed intermittent dosing (p = 0.003), while adherence to any post-coital doses was 26% [IQR:14-50]. SMS response rates were low, which may have impaired measurement of post-coital dosing adherence. Acceptability of PrEP was high, regardless of dosing regimen. Adherence to intermittent dosing regimens, fixed doses, and in particular coitally-dependent doses, may be more difficult than adherence to daily dosing. However, intermittent dosing may still be appropriate for PrEP if intracellular drug levels, which correlate with prevention of HIV acquisition, can be attained with less than daily dosing and if barriers to adherence can be addressed. Additional drug level data, qualitative data on adherence barriers, and better methods to measure sexual activity are necessary to determine whether adherence to post-coital PrEP could be comparable to more standard regimens. ClinicalTrials.gov NCT00971230.PLoS ONE 01/2012; 7(4):e33103. · 4.09 Impact Factor -
Article: Anal sex, vaginal practices, and HIV incidence in female sex workers in urban Kenya: implications for the development of intravaginal HIV prevention methods.
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ABSTRACT: Multiple intravaginal HIV prevention methods, including microbicide gels, barriers, and intravaginal rings, are in clinical development in Africa. Development of intravaginal HIV prevention products requires an understanding of sexual behavior, sexually transmitted infection (STI), and vaginitis prevalences, and sexual and vaginal practices in potential target populations. We assessed these factors in a cohort of Kenyan female sex workers (FSW). Women who reported exchanging sex for money/gifts at least three times in the past month and who were HIV uninfected were enrolled and followed for 6 months. STI prevalence and HIV incidence were analyzed by multivariate logistic regression analysis, controlling for demographic and behavioral factors. Thirty-seven percent (74/200) reported having had anal sex. Frequency of anal sex was higher with regular and casual partners than with primary partners. Women were less likely to use condoms for anal sex than for vaginal sex with regular or casual partners. Vaginal washing was universal (100%). HIV incidence was 5.6 per 100 person-years (95% CI 1.62, 11.67). HIV incidence was not associated with any demographic or risk behavior. The relatively high rate of anal sex and universal vaginal washing may complicate both safety and efficacy evaluation of intravaginal products and should be taken into account in trial design. This FSW population had significant HIV incidence and needs continued HIV prevention interventions.AIDS research and human retroviruses 03/2011; 27(10):1067-72. · 2.18 Impact Factor -
Article: AIDS vaccines and preexposure prophylaxis: is synergy possible?
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ABSTRACT: While the long-term goal is to develop highly effective AIDS vaccines, first generation vaccines may be only partially effective. Other HIV prevention modalities such as preexposure prophylaxis with antiretrovirals (PrEP) may have limited efficacy as well. The combined administration of vaccine and PrEP (VAXPREP), however, may have a synergistic effect leading to an overall benefit that is greater than the sum of the individual effects. We propose two test-of-concept trial designs for an AIDS vaccine plus oral or topical ARV. In one design, evidence that PrEP reduces the risk of HIV acquisition is assumed to justify offering it to all participants. A two-arm study comparing PrEP alone to VAXPREP is proposed in which 30 to 60 incident infections are observed to assess the additional benefit of vaccination on risk of infection and setpoint viral load. The demonstrated superiority of VAXPREP does not imply vaccine alone is efficacious. Similarly, the lack of superiority does not imply vaccine alone is ineffective, as antagonism could exist between vaccine and PrEP. In the other design, PrEP is assumed not to be in general use. A 2 × 2 factorial design is proposed in which high-risk individuals are randomized to one of four arms: placebo vaccine given with placebo PrEP, placebo vaccine given with PrEP, vaccine given with placebo PrEP, or VAXPREP. Between 60 and 210 infections are required to detect a benefit of vaccination with or without PrEP on risk of HIV acquisition or setpoint viral load, with fewer infections needed when synergy is present.AIDS research and human retroviruses 11/2010; 27(6):669-80. · 2.18 Impact Factor -
Article: Broad and potent neutralizing antibodies from an African donor reveal a new HIV-1 vaccine target.
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ABSTRACT: Broadly neutralizing antibodies (bNAbs), which develop over time in some HIV-1-infected individuals, define critical epitopes for HIV vaccine design. Using a systematic approach, we have examined neutralization breadth in the sera of about 1800 HIV-1-infected individuals, primarily infected with non-clade B viruses, and have selected donors for monoclonal antibody (mAb) generation. We then used a high-throughput neutralization screen of antibody-containing culture supernatants from about 30,000 activated memory B cells from a clade A-infected African donor to isolate two potent mAbs that target a broadly neutralizing epitope. This epitope is preferentially expressed on trimeric Envelope protein and spans conserved regions of variable loops of the gp120 subunit. The results provide a framework for the design of new vaccine candidates for the elicitation of bNAb responses.Science 10/2009; 326(5950):285-9. · 31.20 Impact Factor -
Article: Human immunodeficiency virus type 1 elite neutralizers: individuals with broad and potent neutralizing activity identified by using a high-throughput neutralization assay together with an analytical selection algorithm.
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ABSTRACT: The development of a rapid and efficient system to identify human immunodeficiency virus type 1 (HIV-1)-infected individuals with broad and potent HIV-1-specific neutralizing antibody responses is an important step toward the discovery of critical neutralization targets for rational AIDS vaccine design. In this study, samples from HIV-1-infected volunteers from diverse epidemiological regions were screened for neutralization responses using pseudovirus panels composed of clades A, B, C, and D and circulating recombinant forms (CRFs). Initially, 463 serum and plasma samples from Australia, Rwanda, Uganda, the United Kingdom, and Zambia were screened to explore neutralization patterns and selection ranking algorithms. Samples were identified that neutralized representative isolates from at least four clade/CRF groups with titers above prespecified thresholds and ranked based on a weighted average of their log-transformed neutralization titers. Linear regression methods selected a five-pseudovirus subset, representing clades A, B, and C and one CRF01_AE, that could identify top-ranking samples with 50% inhibitory concentration (IC(50)) neutralization titers of >or=100 to multiple isolates within at least four clade groups. This reduced panel was then used to screen 1,234 new samples from the Ivory Coast, Kenya, South Africa, Thailand, and the United States, and 1% were identified as elite neutralizers. Elite activity is defined as the ability to neutralize, on average, more than one pseudovirus at an IC(50) titer of 300 within a clade group and across at least four clade groups. These elite neutralizers provide promising starting material for the isolation of broadly neutralizing monoclonal antibodies to assist in HIV-1 vaccine design.Journal of Virology 05/2009; 83(14):7337-48. · 5.40 Impact Factor -
Article: Safety and immunogenicity of adenovirus-vectored near-consensus HIV type 1 clade B gag vaccines in healthy adults.
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ABSTRACT: Vaccines inducing pathogen-specific cell-mediated immunity are being developed using attenuated adenoviral (Ad) vectors. We report the results of two independent Phase I trials of similar replication-deficient Ad5 vaccines containing a near-consensus HIV-1 clade B gag transgene. Healthy HIV-uninfected adults were enrolled in two separate, multicenter, dose-escalating, blinded, placebo-controlled studies to assess the safety and immunogenicity of a three-dose homologous regimen of Ad5 and MRKAd5 HIV-1 gag vaccines given on day 1, week 4, and week 26. Adverse events were collected for 29 days following each intradeltoid injection. The primary immunogenicity endpoint was the proportion of subjects with a positive unfractionated Gag-specific IFN-gamma ELISPOT response measured 4 weeks after the last dose (week 30). Analyses were performed after combining data for each dose group from both protocols, stratifying by baseline Ad5 titers. Overall, 252 subjects were randomized to receive either vaccine or placebo, including 229 subjects (91%) who completed the study through week 30. Tolerability and immunogenicity did not appear to differ between the Ad5 and MRKAd5 vaccines. The frequency of injection-site reactions was dose dependent. Systemic adverse events were also dose dependent and more frequent in subjects with baseline Ad5 titers <200 versus > or =200, especially after the first dose. The percent of ELISPOT responders and the ELISPOT geometric means overall were significantly higher for all four vaccine doses studied compared to placebo, and were generally higher in vaccine recipients with baseline Ad5 titers <200 versus > or = 200. Ad5 titers increased after vaccination in a dose-dependent fashion. Both Ad5-vectored HIV-1 vaccines were generally well tolerated and induced cell-mediated immune responses against HIV Gag-peptides in the majority of healthy adults with baseline Ad5 titers <200. Preexistent and/or vaccine-induced immunity to the Ad5 vector may dampen the CMI response to HIV Gag.AIDS research and human retroviruses 12/2008; 25(1):103-14. · 2.18 Impact Factor -
Article: Safety and immunogenicity of a replication-incompetent adenovirus type 5 HIV-1 clade B gag/pol/nef vaccine in healthy adults.
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ABSTRACT: The safety and immunogenicity of the MRK adenovirus type 5 human immunodeficiency virus type 1 clade B gag/pol/nef vaccine, a replication-incompetent adenovirus type 5-vectored vaccine designed to elicit cell-mediated immunity against conserved human immunodeficiency virus proteins, was assessed in a phase 1 trial. Healthy adults not infected with human immunodeficiency virus were enrolled in a multicenter, dose-escalating, blind, placebo-controlled study to evaluate a 3-dose homologous prime-boost regimen of the trivalent MRK adenovirus type 5 human immunodeficiency virus type 1 vaccine containing from 3 x 10(6) to 1 x 10(11) viral particles per 1-mL dose administered on day 1, during week 4 and during week 26. Adverse events were recorded for 29 days after each intradeltoid injection. The primary immunogenicity end point was the proportion of study participants with a positive unfractionated Gag-, Pol-, or Nef-specific interferon-gamma enzyme-linked immunosorbent spot response measured 4 weeks after administration of the last dose. Of 259 randomized individuals, 257 (99%) received > or = 1 dose of vaccine or placebo and were included in the safety analyses. Enzyme-linked immunosorbent spot results were available for 217 study participants (84%) at week 30. No serious vaccine-related adverse events occurred. No study participant discontinued participation because of vaccine-related adverse events. The frequency of injection-site reactions was dose dependent. Vaccine doses of > or = 3 x 10(9) viral particles elicited positive enzyme-linked immunosorbent spot responses to > or = 1 vaccine component in > 60% of recipients. High baseline antibody titers against adenovirus type 5 diminished enzyme-linked immunosorbent spot responses at all doses except the 3 x 10(10) viral particle dose. The vaccine was generally well tolerated and induced cell-mediated immune responses against human immunodeficiency virus type 1 peptides in most healthy adults. Despite these findings, vaccination in a proof-of-concept trial with use of this vaccine was discontinued because of lack of efficacy.Clinical Infectious Diseases 06/2008; 46(11):1769-81. · 9.15 Impact Factor -
Article: Detection of acute HIV infections in an urban HIV counseling and testing population in the United States.
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ABSTRACT: The southeastern United States has an increasing burden of HIV, particularly among blacks, women, and men who have sex with men. To evaluate HIV nucleic acid amplification testing (NAAT) and antibody-based algorithms in determination of HIV incidence, detection of acute HIV infections, and surveillance of drug-resistant virus transmission in the urban southeastern United States, we conducted a cross-sectional analysis of prospectively collected data from 2202 adults receiving HIV testing and counseling at 3 sites in Atlanta, GA from October 2002 through January 2004. After standard testing with an HIV enzyme immunoassay (EIA) and Western blot confirmation, HIV-positive specimens were tested with 2 standardized assays to detect recent infection. HIV antibody-negative specimens were pooled and screened for HIV using NAAT. Seventy (3.2%) of 2202 subjects were HIV infected. Only 66 were positive on the standard HIV antibody test; 4 were antibody-negative but acutely HIV infected. The overall annual HIV incidence was 1.1% (95% confidence interval [CI]: 0.4 to 1.8) based on the Vironostika-LS assay and 1.3% (95% CI: 0.6 to 2.1) based on the BED Incidence Enzyme Immunoassay (EIA). The prevalence of acute HIV infection was 1.8 per 1000 persons (95% CI: 0.7 to 4.6). The sensitivity of the current testing algorithm using an EIA and Western blot test for detectable infections was only 94.3% (95% CI: 86.2 to 97.8). All 3 of the acutely infected subjects genotyped had drug resistance mutations, and 1 had multiclass resistance. Adding NAAT-based screening to standard HIV antibody testing increased case identification by 6% and uncovered the first evidence of multidrug-resistant HIV transmission in Atlanta. Antibody tests alone are insufficient for public health practice in high-risk urban HIV testing settings.JAIDS Journal of Acquired Immune Deficiency Syndromes 03/2007; 44(2):196-202. · 4.43 Impact Factor -
Article: An evaluation of intravaginal rings as a potential HIV prevention device in urban Kenya: behaviors and attitudes that might influence uptake within a high-risk population.
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ABSTRACT: We sought to assess the potential acceptability of intravaginal rings (IVRs) as an HIV prevention method among at-risk women and men. We conducted a qualitative assessment of initial attitudes toward IVRs, current HIV prevention methods, and common behavioral practices among female sex workers (FSWs) and men who frequent FSWs in Mukuru, an urban slum community in Nairobi, Kenya. Nineteen women and 21 men took part in six focus group discussions. Most participants, both male and female, responded positively to the concept of an IVR as a device for delivering microbicides. Women particularly liked the convenience offered by its slow-release capacity. Some female respondents raised concerns about whether male customers would discover the ring and respond negatively, whereas others thought it unlikely that their clients would feel the ring. Focus groups conducted with male clients of FSWs suggested that many would be enthusiastic about women, and particularly sex workers, using a microbicide ring, but that women's fears about negative responses to covert use were well founded. Overall, this high-risk population of FSWs and male clients in Nairobi was very open to the IVR as a potential HIV prevention device. Themes that emerged from the focus groups highlight the importance of understanding attitudes toward IVRs as well as cultural practices that may impact IVR use in high-risk populations when pursuing clinical development of this potential HIV prevention device.Journal of Women s Health 17(6):1025-34. · 1.57 Impact Factor
Top co-authors
Top Journals
Institutions
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2012
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University of Nairobi
Nairobi, Nairobi Province, Kenya
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2007–2011
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Emory University
- • School of Medicine
- • Department of Internal Medicine
Atlanta, GA, USA
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