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- Aboud, Said
(författare)
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Evaluation of HIV testing strategies and monitoring of immune responses in HIV-vaccinated individuals in Tanzania
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes studies on the evaluation of human immunodeficiency virus (HIV) enzyme-linked immunosorbent assays (ELISAs) and simple rapid HIV assays for use in HIV testing strategies in resource-limited settings and studies of HIV vaccine-induced immune responses. Peripheral blood mononuclear cell (PBMC) preparation techniques were also studied in preparation for use in the HIV vaccine trials. The performance of two antibody ELISAs (Vironostika Uni-Form II plus O and Enzygnost anti-HIV-1/2 Plus) and two new diagnostic HIV antigen/antibody combination ELISAs (Murex and Vironostika HIV Uni-Form II antigen/antibody) was evaluated using 1380 serum samples from Tanzanian individuals (paper I). The sensitivity at initial testing was 100% for all assays except Vironostika Uni-Form II plus O which showed one false negative sample at initial testing but 100% sensitivity after repeat testing. The initial specificity was 99.8% for Enzygnost, 98.9% for each of the antigen/antibody ELISAs and 97.0% for Vironostika Plus O ELISA. An alternative confirmatory HIV testing strategy based on initial testing on any of the two antigen/antibody assays followed by testing of reactive samples on the Enzygnost anti-HIV-1/2 Plus assay gave 100% specificity (95% CI; 99.7-100%). The performance of five simple rapid HIV antibody assays was evaluated using 1433 whole blood samples (paper II). The sensitivity at initial testing of Determine, SD Bioline and Uni-Gold was 100% while First Response and Stat-Pak had a sensitivity of 99.5% and 97.7%, respectively, which increased to 100% on repeat testing. The initial specificity of the Uni-Gold assay was 100% while the specificities were 99.6%, 99.4%, 99.6% and 99.8% for Determine, SD Bioline, First Response and Stat-Pak assays, respectively. An alternative confirmatory HIV testing strategy based on initial testing on SD Bioline followed by testing of reactive samples on the Determine gave 100% sensitivity (95% CI; 99.1-100) and 100% specificity (95% CI; 96-99.1) with Uni-Gold as tiebreaker for discordant results and was adopted as a national algorithm in Tanzania. Standard Ficoll-Paque gradient (FIP) centrifugation, BD vacutainer cell preparation tube (CPT) and Greiner Bio-One LeucoSep tube techniques for PBMC preparation were evaluated (paper III). No differences in mean recovery or mean viability of fresh PBMCs were observed between FIP centrifugation and CPT techniques used in Stockholm. In Dar es Salaam, recovery and viability of PBMCs isolated by FIP technique was higher compared to CPT purified cells. LeucoSep cell separation gave a higher yield and viability than FIP cell separation. The cells purified by the different techniques at the two sites performed equally well in interferon-gamma (IFN-γ) enzyme-linked immunospot (ELISpot) assays. In a phase 1 HIV-1 DNA prime MVA boost vaccine trial in Sweden (HIVIS01/02), HIV-specific lymphoproliferative responses were tested by a [3H]-thymidine uptake assay and a flow-cytometric assay using whole blood (FASCIA-WB) (paper IV). A FASCIA using PBMC (FASCIA-PBMC) was also employed (n=14).Two weeks after the HIV-MVA boost 35 of 38 (92%) vaccinees were reactive by the thymidine uptake assay. Thirty-two of 38 (84%) vaccinees were reactive by the CD4+ T-cell FASCIA-WB, and 7 of 38 (18%) also exhibited CD8+ T-cell responses. There was strong correlation between the proliferative responses measured by the thymidine uptake assay and CD4+ T-cell FASCIA-WB (r=0.68; P < 0.01). Fourteen vaccinees were analyzed using all three assays. Ten of 14 (71%) and 11/14 (79%) demonstrated CD4+ T-cell responses in FASCIA-WB and FASCIA-PBMC, respectively. CD8+ T-cell reactivity was observed in 3/14 (21%) and 7/14 (50%) using the FASCIA-WB and FASCIA-PBMC, respectively. All 14 were reactive by the thymidine uptake assay. A FASCIA-PBMC, which allows simultaneous phenotyping, may be an option to the [3H] thymidine uptake assay for assessment of vaccine-induced T-cell proliferation, especially in isotope-restricted settings. In the HIVIS03 phase I/II HIV vaccine trial in Tanzania, sixty HIV-uninfected volunteers randomised to three groups of 20, received DNA plasmid vaccine 1 mg intradermally (id) or 3.8 mg intramuscularly (im) or placebo using a needle-free injection device (paper V). DNA plasmids vectoring HIV-1 genes gp160 subtypes A, B, C; rev B; p17/p24 gag A, B and Rtmut B were given at weeks 0, 4 and 12. Recombinant MVA (10[8] pfu) expressing HIV-1 Env, Gag, Pol of CRF01_AE or placebo was administered im at month 9 and 21. The vaccines were well tolerated. Two weeks after the first HIV-MVA boost 35/35 (100%) vaccinees had IFN-γ ELISpot responses; 35 (100%) to Gag and 31 (89%) to Env. Two to four weeks after the second HIV-MVA boost, 28/29 (97%) vaccinees had IFN-γ responses. The id-primed recipients had significantly higher responses to Env than im recipients after HIV-MVA boost. Intracellular cytokine staining for Gag-specific IFN-γ/IL-2 production showed both CD8+ and CD4+ T-cell responses. All vaccinees had HIV-specific lymphoproliferative responses. All vaccinees reacted in diagnostic HIV serological tests and 26/29 (90%) had antibodies against gp160 after the second HIV-MVA boost. A high neutralizing antibody response rate (31-83% depending on the clade B or AE virus tested) was demonstrated using a PBMC assay. In conclusion, this vaccine approach was safe and highly immunogenic.
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| 2. |
- Msafiri, Frank, et al.
(författare)
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Vaccine-Induced Seroreactivity Impacts the Accuracy of HIV Testing Algorithms in Sub-Saharan Africa : An Exploratory Study
- 2022
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Ingår i: Vaccines. - : MDPI. - 2076-393X. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- The detection of vaccine-induced HIV antibody responses by rapid diagnostic tests (RDTs) may confound the interpretation of HIV testing results. We assessed the impact of vaccine-induced seroreactivity (VISR) on the diagnosis of HIV in sub-Saharan Africa. Samples collected from healthy participants of HIVIS and TaMoVac HIV vaccine trials after the final vaccination were analyzed for VISR using HIV testing algorithms used in Mozambique and Tanzania that employ two sequential RDTs. The samples were also tested for VISR using Enzygnost HIV Integral 4 ELISA and HIV western blot assays. Antibody titers to subtype C gp140 were determined using an in-house enzyme-linked immunosorbent assay (ELISA). The frequency of VISR was 93.4% (128/137) by Enzygnost HIV Integral 4 ELISA, and 66.4% (91/137) by western blot assay (WHO interpretation). The proportion of vaccine recipients that would have been misdiagnosed as HIV-positive in Mozambique was half of that in Tanzania: 26.3% (36/137) and 54.0% (74/137), respectively, p < 0.0001. In conclusion, the HIV RDTs and algorithms assessed here will potentially misclassify a large proportion of the HIV vaccine recipients if no other test is used. Increased efforts are needed to develop differential serological or molecular tools for use at the point of care.
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| 3. |
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| 4. |
- Smith, Emily R, et al.
(författare)
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Modifiers of the effect of maternal multiple micronutrient supplementation on stillbirth, birth outcomes, and infant mortality : a meta-analysis of individual patient data from 17 randomised trials in low-income and middle-income countries.
- 2017
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Ingår i: The Lancet Global Health. - 2214-109X. ; 5:11, s. e1090-e1100
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Micronutrient deficiencies are common among women in low-income and middle-income countries. Data from randomised trials suggest that maternal multiple micronutrient supplementation decreases the risk of low birthweight and potentially improves other infant health outcomes. However, heterogeneity across studies suggests influence from effect modifiers. We aimed to identify individual-level modifiers of the effect of multiple micronutrient supplements on stillbirth, birth outcomes, and infant mortality in low-income and middle-income countries.METHODS: This two-stage meta-analysis of individual patient included data from 17 randomised controlled trials done in 14 low-income and middle-income countries, which compared multiple micronutrient supplements containing iron-folic acid versus iron-folic acid alone in 112 953 pregnant women. We generated study-specific estimates and pooled subgroup estimates using fixed-effects models and assessed heterogeneity between subgroups with the χ(2) test for heterogeneity. We did sensitivity analyses using random-effects models, stratifying by iron-folic acid dose, and exploring individual study effect.FINDINGS: Multiple micronutrient supplements containing iron-folic acid provided significantly greater reductions in neonatal mortality for female neonates compared with male neonates than did iron-folic acid supplementation alone (RR 0·85, 95% CI 0·75-0·96 vs 1·06, 0·95-1·17; p value for interaction 0·007). Multiple micronutrient supplements resulted in greater reductions in low birthweight (RR 0·81, 95% CI 0·74-0·89; p value for interaction 0·049), small-for-gestational-age births (0·92, 0·87-0·97; p=0·03), and 6-month mortality (0·71, 0·60-0·86; p=0·04) in anaemic pregnant women (haemoglobin <110g/L) as compared with non-anaemic pregnant women. Multiple micronutrient supplements also had a greater effect on preterm births among underweight pregnant women (BMI <18·5 kg/m(2); RR 0·84, 95% CI 0·78-0·91; p=0·01). Initiation of multiple micronutrient supplements before 20 weeks gestation provided greater reductions in preterm birth (RR 0·89, 95% CI 0·85-0·93; p=0·03). Generally, the survival and birth outcome effects of multiple micronutrient supplementation were greater with high adherence (≥95%) to supplementation. Multiple micronutrient supplements did not significantly increase the risk of stillbirth or neonatal, 6-month, or infant mortality, neither overall or in any of the 26 examined subgroups.INTERPRETATION: Antenatal multiple micronutrient supplements improved survival for female neonates and provided greater birth-outcome benefits for infants born to undernourished and anaemic pregnant women. Early initiation in pregnancy and high adherence to multiple micronutrient supplements also provided greater overall benefits. Studies should now aim to elucidate the mechanisms accounting for differences in the effect of antenatal multiple micronutrient supplements on infant health by maternal nutrition status and sex.
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| 5. |
- Sylvester, Boniphace, et al.
(författare)
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Interferon-gamma and Interleukin-10 Responses during Clinical Malaria Episodes in Infants Aged 0-2 Years Prenatally Exposed to Plasmodium falciparum : Tanzanian Birth Cohort
- 2018
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Ingår i: Journal of Tropical Medicine. - : HINDAWI LTD. - 1687-9686 .- 1687-9694.
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Tidskriftsartikel (refereegranskat)abstract
- Background: Infants born to mothers with placental malaria are prenatally exposed to Plasmodium falciparum antigens. However, the effect of that exposure to subsequent immune responses has not been fully elucidated. This study aimed at determining the effect of prenatal exposure to P. falciparum on Interleukin-10 and Interferon-gamma responses during clinical malaria episodes in the first 24 months of life.Methods: This prospective cohort study involved 215 infants aged 0-2 years born to mothers with or without placental malaria. Enzyme-linked immunosorbent assay (ELISA) was used to determine levels of IL-10 and IFN-gamma in infants and detect IgM in cord blood. Data were analyzed using SPSS version 20.Findings: Geometric mean for IFN-gamma in exposed infants was 557.9 pg/ml (95% CI: 511.6-604.1) and in unexposed infants it was 634.4 pg/ml (95% CI: 618.2-668.5) (P=0.02). Mean IL-10 was 22.4 pg/ml (95% CI: 19.4-28.4) and 15.1 pg/ml (95% CI: 12.4-17.6), respectively (P=0.01).Conclusions: Prenatal exposure to P. falciparum antigens significantly affects IL-10 and IFN-gamma responses during clinical malaria episodes in the first two years of life.
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| 6. |
- Sylvester, Boniphace, et al.
(författare)
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Prenatal exposure to Plasmodium falciparum increases frequency and shortens time from birth to first clinical malaria episodes during the first two years of life : prospective birth cohort study
- 2016
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Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: Prenatal exposure to Plasmodium falciparum affects development of protective immunity and susceptibility to subsequent natural challenges with similar parasite antigens. However, the nature of these effects has not been fully elucidated. The aim of this study was to determine the effect of prenatal exposure to P. falciparum on susceptibility to natural malaria infection, with a focus on median time from birth to first clinical malaria episode and frequency of clinical malaria episodes in the first 2 years of life.Methods: A prospective birth cohort study was conducted in Rufiji district in Tanzania, between January 2013 and December 2015. Infants born to mothers with P. falciparum in the placenta at time of delivery were defined as exposed, and infants born to mothers without P. falciparum parasites in placenta were defined as unexposed. Placental infection was established by histological techniques. Out of 206 infants recruited, 41 were in utero exposed to P. falciparum and 165 infants were unexposed. All infants were monitored for onset of clinical malaria episodes in the first 2 years of life. The outcome measure was time from birth to first clinical malaria episode, defined by fever (>= 37 degrees C) and microscopically determined parasitaemia. Median time to first clinical malaria episode between exposed and unexposed infants was assessed using Kaplan-Meier survival analysis and comparison was done by log rank. Association of clinical malaria episodes with prenatal exposure to P. falciparum was assessed by multivariate binary logistic regression. Comparative analysis of mean number of clinical malaria episodes between exposed and unexposed infants was done using independent sample t test.Results: The effect of prenatal exposure to P. falciparum infection on clinical malaria episodes was statistically significant (Odds Ratio of 4.79, 95 % CI 2.21-10.38, p < 0.01) when compared to other confounding factors. Median time from birth to first clinical malaria episode for exposed and unexposed infants was 32 weeks (95 % CI 30.88-33.12) and 37 weeks (95 % CI 35.25-38.75), respectively, and the difference was statistically significant (p = 0.003). The mean number of clinical malaria episodes in exposed and unexposed infants was 0.51 and 0.30 episodes/infant, respectively, and the difference was statistically significant (p = 0.038).Conclusions: Prenatal exposure to P. falciparum shortens time from birth to first clinical malaria episode and increases frequency of clinical malaria episodes in the first 2 years of life.
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