Browsing by Author "Kaplan, Gilla"
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- ItemOpen AccessAssociation of human TLR1 and TLR6 deficiency with altered immune responses to BCG vaccination in South African infants(Public Library of Science, 2011) Randhawa, April Kaur; Shey, Muki S; Keyser, Alana; Peixoto, Blas; Wells, Richard D; de Kock, Marwou; Lerumo, Lesedi; Hughes, Jane; Hussey, Gregory; Hawkridge, Anthony; Kaplan, Gilla; Hanekom, Willem A; Hawn, Thomas RThe development of effective immunoprophylaxis against tuberculosis (TB) remains a global priority, but is hampered by a partially protective Bacillus Calmette-Guérin (BCG) vaccine and an incomplete understanding of the mechanisms of immunity to Mycobacterium tuberculosis. Although host genetic factors may be a primary reason for BCG's variable and inadequate efficacy, this possibility has not been intensively examined. We hypothesized that Toll-like receptor (TLR) variation is associated with altered in vivo immune responses to BCG. We examined whether functionally defined TLR pathway polymorphisms were associated with T cell cytokine responses in whole blood stimulated ex vivo with BCG 10 weeks after newborn BCG vaccination of South African infants. In the primary analysis, polymorphism TLR6_C745T (P249S) was associated with increased BCG-induced IFN-γ in both discovery (n = 240) and validation (n = 240) cohorts. In secondary analyses of the combined cohort, TLR1_T1805G (I602S) and TLR6_G1083C (synonymous) were associated with increased IFN-γ, TLR6_G1083C and TLR6_C745T were associated with increased IL-2, and TLR1_A1188T was associated with increased IFN-γ and IL-2. For each of these polymorphisms, the hypo-responsive allele, as defined by innate immunity signaling assays, was associated with increased production of TH1-type T cell cytokines (IFN-γ or IL-2). After stimulation with TLR1/6 lipopeptide ligands, PBMCs from TLR1/6-deficient individuals (stratified by TLR1_T1805G and TLR6_C745T hyporesponsive genotypes) secreted lower amounts of IL-6 and IL-10 compared to those with responsive TLR1/6 genotypes. In contrast, no IL-12p70 was secreted by PBMCs or monocytes. These data support a mechanism where TLR1/6 polymorphisms modulate TH1 T-cell polarization through genetic regulation of monocyte IL-10 secretion in the absence of IL-12. These studies provide evidence that functionally defined innate immune gene variants are associated with the development of adaptive immune responses after in vivo vaccination against a bacterial pathogen in humans. These findings could potentially guide novel adjuvant vaccine strategies as well as have implications for IFN-γ-based diagnostic testing for TB.
- ItemOpen AccessCellular immunity of naïve and BCG vaccinated neonates(2010) Watkins, Marcia Linda Vivienne; Kaplan, GillaDespite more than 95% vaccination coverage with Mycobacterium bovis Bacille Calmette-Guérin (BCG), tuberculosis (TB) remains epidemic in South Africa. The dichotomy that successful pregnancy is usually associated with a type 2 (Th2) cytokine profile in the newborn child, whereas immunity to Mycobacterium tuberculosis (Mtb) is associated with the development of a type 1 helper (Th1) cytokine response, could impact on the subsequent adaptive immune response to BCG vaccination. Previous studies have suggested that immune responses in early life may be defective and related to the immaturity of antigen-presenting cells and/or T cells.
- ItemOpen AccessGenetic variation in TLR genes in Ugandan and South African populations and comparison with HapMap data(Public Library of Science, 2012) Baker, Allison R; Qiu, Feiyou; Randhawa, April Kaur; Horne, David J; Adams, Mark D; Shey, Muki; Barnholtz-Sloan, Jill; Mayanja-Kizza, Harriet; Kaplan, Gilla; Hanekom, Willem A; Boom, W Henry; Hawn, Thomas R; Stein, Catherine MGenetic epidemiological studies of complex diseases often rely on data from the International HapMap Consortium for identification of single nucleotide polymorphisms (SNPs), particularly those that tag haplotypes. However, little is known about the relevance of the African populations used to collect HapMap data for study populations conducted elsewhere in Africa. Toll-like receptor (TLR) genes play a key role in susceptibility to various infectious diseases, including tuberculosis. We conducted full-exon sequencing in samples obtained from Uganda (n = 48) and South Africa (n = 48), in four genes in the TLR pathway: TLR2, TLR4, TLR6, and TIRAP. We identified one novel TIRAP SNP (with minor allele frequency [MAF] 3.2%) and a novel TLR6 SNP (MAF 8%) in the Ugandan population, and a TLR6 SNP that is unique to the South African population (MAF 14%). These SNPs were also not present in the 1000 Genomes data. Genotype and haplotype frequencies and linkage disequilibrium patterns in Uganda and South Africa were similar to African populations in the HapMap datasets. Multidimensional scaling analysis of polymorphisms in all four genes suggested broad overlap of all of the examined African populations. Based on these data, we propose that there is enough similarity among African populations represented in the HapMap database to justify initial SNP selection for genetic epidemiological studies in Uganda and South Africa. We also discovered three novel polymorphisms that appear to be population-specific and would only be detected by sequencing efforts.
- ItemOpen AccessInduction of ER stress in macrophages of tuberculosis granulomas(Public Library of Science, 2010) Seimon, Tracie A; Kim, Mi-Jeong; Blumenthal, Antje; Koo, Jovanka; Ehrt, Sabine; Wainwright, Helen; Bekker, Linda-Gail; Kaplan, Gilla; Nathan, Carl; Tabas, IraBACKGROUND: The endoplasmic reticulum (ER) stress pathway known as the Unfolded Protein Response (UPR) is an adaptive survival pathway that protects cells from the buildup of misfolded proteins, but under certain circumstances it can lead to apoptosis. ER stress has been causally associated with macrophage apoptosis in advanced atherosclerosis of mice and humans. Because atherosclerosis shares certain features with tuberculosis (TB) with regard to lesional macrophage accumulation, foam cell formation, and apoptosis, we investigated if the ER stress pathway is activated during TB infection. Principal FINDINGS: Here we show that ER stress markers such as C/EBP homologous protein (CHOP; also known as GADD153), phosphorylated inositol-requiring enzyme 1 alpha (Ire1α) and eukaryotic initiation factor 2 alpha (eIF2α), and activating transcription factor 3 (ATF3) are expressed in macrophage-rich areas of granulomas in lungs of mice infected with virulent Mycobacterium tuberculosis (Mtb) . These areas were also positive for numerous apoptotic cells as assayed by TUNEL. Microarray analysis of human caseous TB granulomas isolated by laser capture microdissection reveal that 73% of genes involved in the UPR are upregulated at the mRNA transcript level. The expression of two ER stress markers, ATF3 and CHOP, were also increased in macrophages of human TB granulomas when assayed by immunohistochemistry. CHOP has been causally associated with ER stress-induced macrophage apoptosis. We found that apoptosis was more abundant in granulomas as compared to non-granulomatous tissue isolated from patients with pulmonary TB, and apoptosis correlated with CHOP expression in areas surrounding the centralized areas of caseation. CONCLUSIONS: In summary, ER stress is induced in macrophages of TB granulomas in areas where apoptotic cells accumulate in mice and humans. Although macrophage apoptosis is generally thought to be beneficial in initially protecting the host from Mtb infection, death of infected macrophages in advanced granulomas might favor dissemination of the bacteria. Therefore future work is needed to determine if ER-stress is causative for apoptosis and plays a role in the host response to infection.
- ItemOpen AccessMycobacterial strain diversity : impact on the host immune response(2003) Post, Frank A; Kaplan, Gilla
- ItemOpen AccessTranscriptional profiling of mycobacterial antigen-induced responses in infants vaccinated with BCG at birth(BioMed Central Ltd, 2009) Fletcher, Helen; Keyser, Alana; Bowmaker, Mark; Sayles, Peter; Kaplan, Gilla; Hussey, Greg; Hill, Adrian; Hanekom, WillemBACKGROUND:Novel tuberculosis (TB) vaccines recently tested in humans have been designed to boost immunity induced by the current vaccine, Mycobacterium bovis Bacille Calmette-Guerin (BCG). Because BCG vaccination is used extensively in infants, this population group is likely to be the first in which efficacy trials of new vaccines will be conducted. However, our understanding of the complexity of immunity to BCG in infants is inadequate, making interpretation of vaccine-induced immune responses difficult. METHODS: To better understand BCG-induced immunity, we performed gene expression profiling in five 10-week old infants routinely vaccinated with BCG at birth. RNA was extracted from 12 hour BCG-stimulated or purified protein derivative of tuberculin (PPD)-stimulated PBMC, isolated from neonatal blood collected 10 weeks after vaccination. RNA was hybridised to the Sentrix(R) HumanRef-8 Expression BeadChip (Illumina) to measure expression of >16,000 genes. RESULTS: We found that ex vivo stimulation of PBMC with PPD and BCG induced largely similar gene expression profiles, except that BCG induced greater macrophage activation. The peroxisome proliferator-activated receptor (PPAR) signaling pathway, including PPAR-gamma, involved in activation of the alternative, anti-inflammatory macrophage response was down-regulated following stimulation with both antigens. In contrast, up-regulation of genes associated with the classic, pro-inflammatory macrophage response was noted. Further analysis revealed a decrease in the expression of cell adhesion molecules (CAMs), including integrin alpha M (ITGAM), which is known to be important for entry of mycobacteria into the macrophage. Interestingly, more leukocyte genes were down-regulated than up-regulated. CONCLUSION: Our results suggest that a combination of suppressed and up-regulated genes may be key in determining development of protective immunity to TB induced by vaccination with BCG.
- ItemOpen AccessTranslational research for tuberculosis elimination: priorities, challenges, and actions(Public Library of Science, 2016) Lienhardt, Christian; Lönnroth, Knut; Menzies, Dick; Balasegaram, Manica; Chakaya, Jeremiah; Cobelens, Frank; Cohn, Jennifer; Denkinger, Claudia M; Evans, Thomas G; Källenius, Gunilla; Kaplan, Gilla; Kumar, Ajay M V; Matthiessen, Line; Mgone, Charles S; Mizrahi, Valerie; Mukadi, Ya-diul; Nguyen, Viet Nhung; Nordström, Anders; Sizemore, Christine F; Spigelman, Melvin; Squire, S Bertel; Swaminathan, Soumya; Helden, Paul D Van; Zumla, Alimuddin; Weyer, Karin; Weil, Diana; Raviglione, MarioChristian Lienhardt and colleagues describe the research efforts needed to end the global tuberculosis epidemic by 2035.