Publications by authors named "Samuel Darko"

Migration is associated with a substantial change in environmental exposures and health outcomes. We aimed to investigate the shift in gut microbiota composition and the associations with cardiometabolic outcomes in the RODAM-Pros cohort spanning multiple research sites across continents. We determined gut microbiota composition of 1,177 Ghanaian participants in rural Ghana, urban Ghana, and Amsterdam, the Netherlands, using 16S rRNA sequencing.

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Aim: To characterize clinically relevant subgroups of patients with type-2 diabetes mellitus (T2DM) based on adiposity, insulin secretion, and resistance indices.

Methods: A cross-sectional study was conducted at Eastern Regional Hospital in Ghana from July to October 2021 to investigate long-term patients with T2DM. To select participants, a systematic random sampling method was employed.

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Background: Limited longitudinal data exist on chronic kidney disease (CKD) in African populations undergoing epidemiological transitions. We investigated incidence, long-term predictors and progression of CKD among Ghanaians residing in Ghana and Ghanaian migrants in the Netherlands (Amsterdam).

Methods And Findings: We analysed data from 2183 participants in the transcontinental population-based prospective Research on Obesity and Diabetes among African Migrants cohort, followed for approximately 7 years.

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Human immunodeficiency virus 1 (HIV-1) infection is characterized by a dynamic and persistent state of viral replication that overwhelms the host immune system in the absence of antiretroviral therapy (ART). The impact of prolonged treatment on the antiviral efficacy of HIV-1-specific CD8 T cells has nonetheless remained unknown. Here, we used single-cell technologies to address this issue in a cohort of aging individuals infected early during the pandemic and subsequently treated with continuous ART.

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Xylene is the commonest clearing agent even though it is hazardous and costly. This study evaluated the clearing properties of coconut oil as an alternative cost-effective clearing agent for histological processes. Ten (10) prostate samples fixed in formalin were taken and each one was cut into 4 before randomly separating them into four groups (A, B, C and D).

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We describe humans with rare biallelic loss-of-function variants impairing pre-α T cell receptor (pre-TCRα) expression. Low circulating naive αβ T cell counts at birth persisted over time, with normal memory αβ and high γδ T cell counts. Their TCRα repertoire was biased, which suggests that noncanonical thymic differentiation pathways can rescue αβ T cell development.

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The environmental impacts of global warming driven by methane (CH) emissions have catalyzed significant research initiatives in developing novel technologies that enable proactive and rapid detection of CH. Several data-driven machine learning (ML) models were tested to determine how well they identified fugitive CH and its related intensity in the affected areas. Various meteorological characteristics, including wind speed, temperature, pressure, relative humidity, water vapor, and heat flux, were included in the simulation.

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Key Clinical Message: and manages mild COVID-19 in 7 days.

Abstract: Coronavirus Disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can lead to severe complications and deaths. The search for phytotherapeutic agents to augment the fight against the current COVID-19 pandemic is therefore of highest priority.

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Norovirus infection can cause gastrointestinal disease in humans. Development of therapies and vaccines against norovirus have been limited by the lack of a suitable and reliable animal model. Here we established rhesus macaques as an animal model for human norovirus infection.

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Article Synopsis
  • SARS-CoV-2 variants are evolving, making it crucial to test updated vaccines on non-human primates to improve human clinical practice.
  • Researchers conducted a study on mRNA-1273 vaccination in rhesus macaques, examining both innate and adaptive immune responses using single-cell sequencing.
  • They found that the second vaccine dose increased specific immune cells and gene expression linked to better antibody production, highlighting the interaction between innate and adaptive immunity.
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Article Synopsis
  • - The study focuses on Th17 cells, which are known for their role in autoimmune diseases; however, the differentiation pathways and memory structure of these cells in humans are still not fully understood.
  • - Researchers utilized surface markers like CCR6 to examine human type 17 memory cells, revealing a continuum of cell types influenced by RORγt levels that reflects early activation preferences.
  • - While the properties of CCR6+ cells remain stable under non-inflammatory conditions, varying activation environments can further alter their functions, showcasing both adaptability and a complex memory in type 17 cells.
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Article Synopsis
  • Th17 cells have mostly been studied in mice for their role in autoimmune diseases, but their differentiation and memory structures in humans remain poorly understood.
  • Researchers used varying levels of surface CCR6 to show that human type 17 memory cells exist in a continuum that reflects their developmental pathways, influenced by the protein RORγt.
  • The phenotypes and epigenomes of these CCR6 cells are stable, but different activation conditions can lead to new functionalities, demonstrating the unique adaptability of type 17 cells.
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Modifications to vaccine delivery that increase serum antibody longevity are of great interest for maximizing efficacy. We have previously shown that a delayed fractional (DFx) dosing schedule (0-1-6 month) - using AS01B-adjuvanted RH5.1 malaria antigen - substantially improves serum IgG durability as compared with monthly dosing (0-1-2 month; NCT02927145).

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Rare CD4 T cells that contain HIV under antiretroviral therapy represent an important barrier to HIV cure, but the infeasibility of isolating and characterizing these cells in their natural state has led to uncertainty about whether they possess distinctive attributes that HIV cure-directed therapies might exploit. Here we address this challenge using a microfluidic technology that isolates the transcriptomes of HIV-infected cells based solely on the detection of HIV DNA. HIV-DNA memory CD4 T cells in the blood from people receiving antiretroviral therapy showed inhibition of six transcriptomic pathways, including death receptor signalling, necroptosis signalling and antiproliferative Gα12/13 signalling.

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Although combination antiretroviral therapy (ART) blocks HIV replication, it is not curative because infected CD4+ T cells that carry intact, infectious proviruses persist. Understanding the behavior of clones of infected T cells is important for understanding the stability of the reservoir; however, the stabilities of clones of infected T cells in persons on long-term ART are not well defined. We determined the relative stabilities of clones of infected and uninfected CD4+ T cells over time intervals of one to four years in three individuals who had been on ART for 9-19 years.

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The dynamics of T-cell receptor (TCR)selection in chronic HIV-1 infection, and its association with clinical outcome, is well documented for an array of MHC-peptide complexes and disease stages. However, the factors that may contribute to the selection and expansion of CD8+ T-cells in chronic HIV-2 infection, especially at the clonal level remain unclear. To address this question, we undertook a detailed molecular characterization of the clonotypic architecture of an HLA-B*3501 restricted Gag-specific CD8+ T-cell response in donors chronically infected with HIV-2 using a combination of flow cytometry, tetramer-specific CD8+ TCR clonotyping, and in vitro assays.

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The emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identified four receptor binding domain-targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 23 variants, including the B.1.

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The development of follicular helper CD4 T (TFH) cells is a dynamic process resulting in a heterogenous pool of TFH subsets. However, the cellular and molecular determinants of this heterogeneity and the possible mechanistic links between them is not clear. We found that human TFH differentiation is associated with significant changes in phenotypic, chemokine, functional, metabolic and transcriptional profile.

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An effective vaccine for respiratory syncytial virus (RSV) is an unrealized public health goal. A single dose of the prefusion-stabilized fusion (F) glycoprotein subunit vaccine (DS-Cav1) substantially increases serum-neutralizing activity in healthy adults. We sought to determine whether DS-Cav1 vaccination induces a repertoire mirroring the pre-existing diversity from natural infection or whether antibody lineages targeting specific epitopes predominate.

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αβ and γδ T cell receptors (TCRs) are highly diverse antigen receptors that define two evolutionarily conserved T cell lineages. We describe a population of γμTCRs found exclusively in non-eutherian mammals that consist of a two-domain (Vγ-Cγ) γ-chain paired to a three-domain (Vμ-Vμj-Cμ) μ-chain. γμTCRs were characterized by restricted diversity in the Vγ and Vμj domains and a highly diverse unpaired Vμ domain.

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The epidemic spread of Zika virus (ZIKV), associated with devastating neurologic syndromes, has driven the development of multiple ZIKV vaccines candidates. An effective vaccine should induce ZIKV-specific T cell responses, which are shown to improve the establishment of humoral immunity and contribute to viral clearance. Here we investigated how previous immunization against Japanese encephalitis virus (JEV) and yellow fever virus (YFV) influences T cell responses elicited by a Zika purified-inactivated virus (ZPIV) vaccine.

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The emergence of highly transmissible SARS-CoV-2 variants of concern (VOC) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identify four receptor-binding domain targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 12 variants including the B.1.

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Aims: To compare body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR) as determinants of type 2 diabetes (T2DM) and determine optimal cut-offs in a sub-Saharan African population.

Methods: Data from the RODAM study including Ghanaians aged 25-70 living in rural Ghana, urban Ghana and Europe were used. Logistic regression was used to assess associations between BMI, WC, WHR and T2DM status, by sex and site.

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Lymphocyte migration is essential for adaptive immune surveillance. However, our current understanding of this process is rudimentary, because most human studies have been restricted to immunological analyses of blood and various tissues. To address this knowledge gap, we used an integrated approach to characterize tissue-emigrant lineages in thoracic duct lymph (TDL).

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