Gwynn Stevens

Imperial Valley College, London, Ohio, United States

Are you Gwynn Stevens?

Claim your profile

Publications (13)40.62 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Long-term safety is critical for the development and later use of a vaccine to prevent HIV/AIDS. Likewise, the persistence of vaccine-induced antibodies and their impact on HIV testing must be established. IAVI has sponsored several Phase I and IIA HIV vaccine trials enrolling healthy, HIV-seronegative African volunteers. Plasmid DNA and viral vector based vaccines were tested. No vaccine-related serious adverse events were reported. After completion of vaccine trials conducted between 2001-2007, both vaccine and placebo recipients were offered enrolment into an observational long-term follow-up study (LTFU) to monitor potential late health effects and persistence of immune responses. At scheduled 6-monthly clinic visits, a health questionnaire was administered; clinical events were recorded and graded for severity. Blood was drawn for HIV testing and cellular immune assays. 287 volunteers were enrolled; total follow-up after last vaccination was 1463 person years (median: 5.2 years). Ninety-three (93)% of volunteers reported good health at their last LTFU visit. Infectious diseases and injuries accounted for almost 50% of the 175 reported clinical events, of which over 95% were mild or moderate in severity. There were 30 six pregnancies, six incident HIV infections and 14 volunteers reported cases of social harm. Persistence of immune responses was rare. No safety signal was identified. No potentially vaccine related medical condition, no immune mediated disease, or malignancy was reported. HIV vaccines studied in these trials had a low potential of induction of persisting HIV antibodies.
    Human vaccines & immunotherapeutics. 12/2013; 10(3).
  • [Show abstract] [Hide abstract]
    ABSTRACT: To identify and describe populations at risk for HIV in 3 clinical research centers in Kenya and South Africa. Prospective cohort study. Volunteers reporting recent sexual activity, multiple partners, transactional sex, sex with an HIV-positive partner, or, if male, sex with men (MSM; in Kenya only) were enrolled. Sexually active minors were enrolled in South Africa only. Risk behavior, HIV testing, and clinical data were obtained at follow-up visits. From 2005 to 2008, 3023 volunteers were screened, 2113 enrolled, and 1834 contributed data on HIV incidence. MSM had the highest HIV incidence rate of 6.8 cases per 100 person-years [95% confidence interval (CI): 4.9 to 9.2] followed by women in Kilifi and Cape Town (2.7 cases per 100 person-years, 95% CI: 1.7 to 4.2). No seroconversions were observed in Nairobi women or men in Nairobi or Cape Town who were not MSM. In 327 MSM, predictors of HIV acquisition included report of genital ulcer (Hazard Ratio: 4.5, 95% CI: 1.7 to 11.6), not completing secondary school education (HR: 3.4, 95% CI: 1.6 to 7.2) and reporting receptive anal intercourse (HR: 8.2, 95% CI: 2.7 to 25.0). Paying for sex was inversely associated with HIV infection (HR: 0.2, 95% CI: 0.04 to 0.8). 279 (13.0%) volunteers did not return after the first visit; subsequent attrition rates ranged from 10.4 to 21.8 volunteers per 100 person-years across clinical research centers. Finding, enrolling, and retaining risk populations for HIV prevention trials is challenging in Africa. African MSM are not frequently engaged for research, have high HIV incidence, need urgent risk reduction counseling, and may represent a suitable population for future HIV prevention trials.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 02/2012; 59(2):185-93. · 4.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Acute HIV infection (prior to antibody seroconversion) represents a high-risk window for HIV transmission. Development of a test to detect acute infection at the point-of-care is urgent. Volunteers enrolled in a prospective study of HIV incidence in four African cities, Kigali in Rwanda and Ndola, Kitwe and Lusaka in Zambia, were tested regularly for HIV by rapid antibody test and p24 antigen ELISA. Five subgroups of samples were also tested by the Determine Ag/Ab Combo test 1) Antigen positive, antibody negative (acute infection); 2) Antigen positive, antibody positive; 3) Antigen negative, antibody positive; 4) Antigen negative, antibody negative; and 5) Antigen false positive, antibody negative (HIV uninfected). A sixth group included serial dilutions from a p24 antigen-positive control sample. Combo test results were reported as antigen positive, antibody positive, or both. Of 34 group 1 samples with VL between 5x105 and >1.5x107 copies/mL (median 3.5x106), 1 (2.9%) was detected by the Combo antigen component, 7 (20.6%) others were positive by the Combo antibody component. No group 2 samples were antigen positive by the Combo test (0/18). Sensitivity of the Combo antigen test was therefore 1.9% (1/52, 95% CI 0.0, 9.9). One false positive Combo antibody result (1/30, 3.3%) was observed in group 4. No false-positive Combo antigen results were observed. The Combo antigen test was positive in group 6 at concentrations of 80 pg/mL, faintly positive at 40 and 20 pg/mL, and negative thereafter. The p24 ELISA antigen test remained positive at 5 pg/mL. Although the antibody component of the Combo test detected antibodies to HIV earlier than the comparison antibody tests used, less than 2% of the cases of antigen-positive HIV infection were detected by the Combo antigen component. The development of a rapid point-of-care test to diagnose acute HIV infection remains an urgent goal.
    PLoS ONE 01/2012; 7(6):e37154. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To characterize WHO-defined transmitted HIV drug resistance mutation (TDRM) data from recently HIV-infected African volunteers, we sequenced HIV (pol) and evaluated for TDRM the earliest available specimens from ARV-naive volunteers diagnosed within 1 year of their estimated date of infection at eight research centers in sub-Saharan Africa. TDRMs were detected in 19/408 (5%) volunteers. The prevalence of TDRMs varied by research center, from 5/26 (19%) in Entebbe, 6/78 (8%) in Kigali, 2/49 (4%) in Kilifi, to 3/106 (3%) in Lusaka. One of five volunteers from Cape Town (20%) had TDRMs. Despite small numbers, our data suggest an increase in DRMs by year of infection in Zambia (pā€‰=ā€‰0.004). The prevalence observed in Entebbe was high across the entire study. ARV history data from 12 (63%) HIV-infected sexual partners were available; 3 reported ARV use prior to transmission. Among four partners with sequence data available, transmission linkage was confirmed and two had the same TDRMs as the newly infected volunteer (both K103N). As ARV therapy continues to increase in availability throughout Africa, monitoring incident virus strains for the presence of TDRMs should be a priority. Early HIV infection cohorts provide an excellent and important platform to monitor the development of TDRMs to inform treatment guidelines, drug choices, and strategies for secondary prevention of TDRM transmission.
    AIDS research and human retroviruses 01/2011; 27(1):5-12. · 2.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The recombinant vaccine, tgAAC09, based on an adeno-associated virus serotype 2 (AAV2) vector encoding HIV-1 subtype C Gag, protease, and part of reverse transcriptase, induced robust T cell and antibody responses in nonhuman primates. In a previous phase I study in 80 healthy HIV-seronegative European and Indian adults, the vaccine was generally safe, well tolerated, and modestly immunogenic when administered once at doses up to 3 x 10(11) DRP. This phase II double-blind, randomized, placebo-controlled trial tested two administrations and a higher dosage of tgAAC009. Ninety-one healthy HIV-seronegative adults from three African countries were given one of three dosage levels of tgAAC09 (3 x 10(10), 3 x 10(11), or 3 x 10(12) DRP) intramuscularly, either at a 6- or 12-month interval; follow-up was 18 months. Overall, 65% and 57% of vaccine recipients experienced local and systemic signs and symptoms, respectively, most being mild. Frequency and severity were not dose related and were similar to those in placebo recipients. No vaccine-related serious adverse events were reported. Overall, HIV-specific T cell responses were detected by IFN-gamma ELISPOT in 17/69 (25%) vaccine recipients with 38% (10/26) responders in the highest dosage group. The response rate improved significantly with boosting at 6, but not 12 months, in the 3 x 10(11) and 3 x 10(12) dosage groups only. Neutralizing antibody titers to the AAV2 did not alter the frequency of immune responses to HIV. Two doses of tgAAC09 were well tolerated at the dosage levels given. Fewer than half the recipients of the highest vaccine dosage, 3 x 10(12) DRP, had T cell responses to HIV.
    AIDS research and human retroviruses 08/2010; 26(8):933-42. · 2.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The introduction of antiretroviral (ARV) therapy in resource-poor settings is effective in suppressing HIV-1 replication and prolonging life of infected individuals. This has led to a demand for affordable HIV-1 drug resistance assays, since treatment failure due to development of drug resistance is common. This study developed and evaluated an affordable "in-house" genotyping assay to monitor HIV-1 drug resistance in Africa, particularly South Africa. An "in-house" assay using automated RNA extraction, and subtype C specific PCR and sequencing primers was developed and successfully evaluated 396 patient samples (viral load ranges 1000-1.6 million RNA copies/ml). The "in-house" assay was validated by comparing sequence data and drug resistance profiles from 90 patient and 10 external quality control samples to data from the ViroSeq HIV-1 Genotyping kit. The "in-house" assay was more efficient, amplifying all 100 samples, compared to 91 samples using Viroseq. The "in house" sequences were 99.2% homologous to the ViroSeq sequences, and identical drug resistance mutation profiles were observed in 96 samples. Furthermore, the "in-house" assay genotyped 260 of 295 samples from seven African sites, where 47% were non-subtype C. Overall, the newly validated "in-house" drug resistance assay is suited for use in Africa as it overcomes the obstacle of subtype diversity.
    Journal of virological methods 11/2009; 163(2):505-8. · 2.13 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Clinical laboratory reference intervals have not been established in many African countries, and non-local intervals are commonly used in clinical trials to screen and monitor adverse events (AEs) among African participants. Using laboratory reference intervals derived from other populations excludes potential trial volunteers in Africa and makes AE assessment challenging. The objective of this study was to establish clinical laboratory reference intervals for 25 hematology, immunology and biochemistry values among healthy African adults typical of those who might join a clinical trial. Equal proportions of men and women were invited to participate in a cross sectional study at seven clinical centers (Kigali, Rwanda; Masaka and Entebbe, Uganda; two in Nairobi and one in Kilifi, Kenya; and Lusaka, Zambia). All laboratories used hematology, immunology and biochemistry analyzers validated by an independent clinical laboratory. Clinical and Laboratory Standards Institute guidelines were followed to create study consensus intervals. For comparison, AE grading criteria published by the U.S. National Institute of Allergy and Infectious Diseases Division of AIDS (DAIDS) and other U.S. reference intervals were used. 2,990 potential volunteers were screened, and 2,105 (1,083 men and 1,022 women) were included in the analysis. While some significant gender and regional differences were observed, creating consensus African study intervals from the complete data was possible for 18 of the 25 analytes. Compared to reference intervals from the U.S., we found lower hematocrit and hemoglobin levels, particularly among women, lower white blood cell and neutrophil counts, and lower amylase. Both genders had elevated eosinophil counts, immunoglobulin G, total and direct bilirubin, lactate dehydrogenase and creatine phosphokinase, the latter being more pronounced among women. When graded against U.S. -derived DAIDS AE grading criteria, we observed 774 (35.3%) volunteers with grade one or higher results; 314 (14.9%) had elevated total bilirubin, and 201 (9.6%) had low neutrophil counts. These otherwise healthy volunteers would be excluded or would require special exemption to participate in many clinical trials. To accelerate clinical trials in Africa, and to improve their scientific validity, locally appropriate reference ranges should be used. This study provides ranges that will inform inclusion criteria and evaluation of adverse events for studies in these regions of Africa.
    PLoS ONE 02/2009; 4(2):e4401. · 3.53 Impact Factor
  • Source
    Retrovirology 01/2009; · 5.66 Impact Factor
  • Source
    Retrovirology 01/2009; · 5.66 Impact Factor
  • Source
    Retrovirology 01/2009; · 5.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: HIV rapid tests (RT) are a quick and non-technically demanding means to perform HIV voluntary counselling and testing (VCT) but understanding their limitations is vital to delivering quality VCT. To determine the sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing at four sites in East Africa. Cross-sectional study. Masaka District, Uganda; a sugar plantation in Kakira, Uganda; Coastal Villages in the Kilifi District of Kenya; and the Urban slum of Kangemi located West of Nairobi, Kenya. Six thousands two hundred and fifty five consenting volunteers were enrolled into the study, and 675 prevalent HIV infections were identified. The RT sensitivity tended to be high for all assays at all sites (97.63-100%) with the exception of the Uni-Gold assay (90.24% in Kangemi, 96.58% in Kilifi). Twenty four RT results were recorded as 'weak positives', 22 (92%) of which were negative by ELISA. There was a high rate of RT false positives in Uganda (positive predictive values ranging from 45.70% to 86.62%). The sensitivity and specificity of the RT varied significantly across sites. The rate of RT misclassification in Uganda suggests that a multiple test algorithm may be preferable to a single test as screener for HIV VCT.
    East African medical journal 11/2008; 85(10):500-4.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An understanding of the health of potential volunteers in Africa is essential for the safe and efficient conduct of clinical trials, particularly for trials of preventive technologies such as vaccines that enroll healthy individuals. Clinical safety laboratory values used for screening, enrolment and follow-up of African clinical trial volunteers have largely been based on values derived from industrialized countries in Europe and North America. This report describes baseline morbidity during recruitment for a multi-center, African laboratory reference intervals study. Asymptomatic persons, aged 18-60 years, were invited to participate in a cross-sectional study at seven sites (Kigali, Rwanda; Masaka and Entebbe, Uganda; Kangemi, Kenyatta National Hospital and Kilifi, Kenya; and Lusaka, Zambia). Gender equivalency was by design. Individuals who were acutely ill, pregnant, menstruating, or had significant clinical findings were not enrolled. Each volunteer provided blood for hematology, immunology, and biochemistry parameters and urine for urinalysis. Enrolled volunteers were excluded if found to be positive for HIV, syphilis or Hepatitis B and C. Laboratory assays were conducted under Good Clinical Laboratory Practices (GCLP). Of the 2990 volunteers who were screened, 2387 (80%) were enrolled, and 2107 (71%) were included in the analysis (52% men, 48% women). Major reasons for screening out volunteers included abnormal findings on physical examination (228/603, 38%), significant medical history (76, 13%) and inability to complete the informed consent process (73, 13%). Once enrolled, principle reasons for exclusion from analysis included detection of Hepatitis B surface antigen (106/280, 38%) and antibodies against Hepatitis C (95, 34%). This is the first large scale, multi-site study conducted to the standards of GCLP to describe African laboratory reference intervals applicable to potential volunteers in clinical trials. Approximately one-third of all potential volunteers screened were not eligible for analysis; the majority were excluded for medical reasons.
    PLoS ONE 02/2008; 3(4):e2043. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The oligonucleotide ligation assay (OLA) has been proposed as an affordable alternative to sequence-based HIV-1 drug resistance testing in resource poor settings. The aim was to evaluate OLA for detecting mutations K103N, Y181C, K65R, Q151M, M184V and T215Y/F in subtype C. Forty-four subtype C and 8 subtype B HIV-1 positive individuals were analysed using the ViroSeqtrade mark HIV-1 genotyping assay (Applied Biosystems, Foster City, CA). A one-step RT-PCR and nested PCR were performed using subtype B specific primers from the OLA kit (NIH AIDS Research and Reference Reagent Program). Seventy-eight subtype C sequences were used to design subtype C specific primers. Ligation and detection steps were followed according to OLA kit protocol. For codons, K103N, Y181C, K65R, Q151M, M184V and T215Y/F, four or more mismatches compared to the probe or mismatches less than four bases from the ligation site were not tolerated. Results revealed accurate identification of mutations in 2/10, 4/9 3/9, 6/7, 2/7 and 6/7 VQA samples and 5/20, 4/17 0/20, 18/24, 5/24 and 13/24 subtype C positive individuals, respectively. It was concluded that the probes and primers in the NIH reference kit would need modification to optimize detection of mutations in subtype C individuals.
    Journal of Virological Methods 06/2005; 125(2):99-109. · 1.90 Impact Factor