Browsing by Author "Ronacher, Katharina"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Open Access
    A semi-automatic technique to quantify complex tuberculous lung lesions on 18F-fluorodeoxyglucose positron emission tomography/computerised tomography images
    (Springer Berlin Heidelberg, 2018-06-25) Malherbe, Stephanus T; Dupont, Patrick; Kant, Ilse; Ahlers, Petri; Kriel, Magdalena; Loxton, André G; Chen, Ray Y; Via, Laura E; Thienemann, Friedrich; Wilkinson, Robert J; Barry, Clifton E; Griffith-Richards, Stephanie; Ellman, Annare; Ronacher, Katharina; Winter, Jill; Walzl, Gerhard; Warwick, James M
    Background There is a growing interest in the use of 18F-FDG PET-CT to monitor tuberculosis (TB) treatment response. However, TB causes complex and widespread pathology, which is challenging to segment and quantify in a reproducible manner. To address this, we developed a technique to standardise uptake (Z-score), segment and quantify tuberculous lung lesions on PET and CT concurrently, in order to track changes over time. We used open source tools and created a MATLAB script. The technique was optimised on a training set of five pulmonary tuberculosis (PTB) cases after standard TB therapy and 15 control patients with lesion-free lungs. Results We compared the proposed method to a fixed threshold (SUV > 1) and manual segmentation by two readers and piloted the technique successfully on scans of five control patients and five PTB cases (four cured and one failed treatment case), at diagnosis and after 1 and 6 months of treatment. There was a better correlation between the Z-score-based segmentation and manual segmentation than SUV > 1 and manual segmentation in terms of overall spatial overlap (measured in Dice similarity coefficient) and specificity (1 minus false positive volume fraction). However, SUV > 1 segmentation appeared more sensitive. Both the Z-score and SUV > 1 showed very low variability when measuring change over time. In addition, total glycolytic activity, calculated using segmentation by Z-score and lesion-to-background ratio, correlated well with traditional total glycolytic activity calculations. The technique quantified various PET and CT parameters, including the total glycolytic activity index, metabolic lesion volume, lesion volumes at different CT densities and combined PET and CT parameters. The quantified metrics showed a marked decrease in the cured cases, with changes already apparent at month one, but remained largely unchanged in the failed treatment case. Conclusions Our technique is promising to segment and quantify the lung scans of pulmonary tuberculosis patients in a semi-automatic manner, appropriate for measuring treatment response. Further validation is required in larger cohorts.
  • Thumbnail Image
    Item
    Open Access
    Bacterial loads measured by the Xpert MTB/RIF assay as markers of culture conversion and bacteriological cure in pulmonary TB
    (Public Library of Science, 2016) Shenai, Shubhada; Ronacher, Katharina; Malherbe, Stefanus; Stanley, Kim; Kriel, Magdalena; Winter, Jill; Peppard, Thomas; Barry, Charles E; Wang, Jing; Dodd, Lori E; Via, Laura E; Walzl, Gerhard; Alland, David
    Introduction Biomarkers are needed to monitor tuberculosis (TB) treatment and predict treatment outcomes. We evaluated the Xpert MTB/RIF (Xpert) assay as a biomarker for TB treatment during and at the end of the 24 weeks therapy. METHODS: Sputum from 108 HIV-negative, culture-positive pulmonary TB patients was analyzed using Xpert at time points before and during anti-TB therapy. Results were compared against culture. Direct Xpert cycle-threshold (Ct), a change in the Ct (delta Ct), or a novel "percent closing of baseline Ct deficit" (percent closing) were evaluated as classifiers of same-day and end-of-treatment culture and therapeutic outcomes. RESULTS: Xpert was positive in 29/95 (30.5%) of subjects at week 24; and positive one year after treatment in 8/64 (12.5%) successfully-treated patients who remained free of tuberculosis. We identified a relationship between initial bacterial load measured by baseline Xpert Ct and time to culture conversion (hazard ratio 1.06, p = 0.0023), and to the likelihood of being among the 8 treatment failures at week 24 (AUC = 72.8%). Xpert Ct was even more strongly associated with culture conversion on the day the test was performed with AUCs 96.7%, 99.2%, 86.0% and 90.2%, at Day 7, Week 4, 8 and 24, respectively. Compared to baseline Ct measures alone, a combined measure of baseline Ct plus either Delta Ct or percent closing improved the classification of treatment failure status to a 75% sensitivity and 88.9% specificity. CONCLUSIONS: Genome loads measured by Xpert provide a potentially-useful biomarker for classifying same day culture status and predicting response to therapy.
  • Thumbnail Image
    Item
    Open Access
    Effect of standard tuberculosis treatment on plasma cytokine levels in patients with active pulmonary tuberculosis
    (Public Library of Science, 2012) Riou, Catherine; Peixoto, Blas Perez; Roberts, Lindi; Ronacher, Katharina; Walzl, Gerhard; Manca, Claudia; Rustomjee, Roxana; Mthiyane, Thuli; Fallows, Dorothy; Gray, Clive M
    BACKGROUND: Sputum Mycobacterium tuberculosis (Mtb) culture is commonly used to assess response to antibiotic treatment in individuals with pulmonary tuberculosis (TB). Such techniques are constrained by the slow growth rate of Mtb, and more sensitive methods to monitor Mtb clearance are needed. The goal of this study was to evaluate changes in plasma cytokines in patients undergoing treatment for TB as a means of identifying candidate host markers associated with microbiologic response to therapy. METHODS: Twenty-four plasma cytokines/chemokines were measured in 42 individuals diagnosed with active pulmonary TB, 52% were HIV co-infected. Individuals, undergoing a 26-week standard TB treatment, were followed longitudinally over 18 months and measurements were associated with HIV status and rates of sputum culture conversion. RESULTS: Plasma concentrations of interferon-inducible protein-10 (IP-10) and vascular endothelial growth factor (VEGF) were significantly reduced upon TB treatment, regardless of HIV status. By the end of treatment, IP-10 concentrations were significantly lower in HIV negative individuals when compared to HIV-positive individuals (p = 0.02). Moreover, in HIV negative patients, plasma VEGF concentrations, measured as early as 2-weeks post TB treatment initiation, positively correlated with the time of sputum conversion (p = 0.0017). No significant changes were observed in other studied immune mediators. CONCLUSIONS: These data suggest that VEGF plasma concentration, measured during early TB treatment, could represent a surrogate marker to monitor sputum culture conversion in HIV uninfected individuals.
  • Thumbnail Image
    Item
    Open Access
    Internalisation of the type II gonadotropin-releasing hormone receptor of marmoset monkey
    (2003) Ronacher, Katharina
    The mammalian type II GnRH receptor has a C-terminal tail unlike the mammalian type I GnRH receptor, which uniquely lacks the cytoptasmic C- terminal domain. lnternalisation of a mammalian type ll GnRH receptor has never been investigated, therefore this thesis studies the internalisation pathway of the type ll GnRH receptor. As the C-terminal tail mediates rapid internalisation of many G protein-coupled receptors this research investigates the functional role of the C-terminal tail and intracellular loop in receptor internalisation. The internalisation pathway of the type ll GnRH receptor in COS-1 cells was investigated by co expressing dominant negative mutants and wild- type constructs of G protein-coupled receptor kinases (GRKs), dynamin-1 and β-arrestin 1 and 2 with the type II GnRH receptor. The results show that internatisation of the receptor requires GRK 2 and dynamin but does not require β-arrestin 1 and 2. Furthermore, inhibitors to both the caveolae pathway as well as the clathrin coated vesicle endocytosis abolished receptor internalisation indicating that both structures are involved in internalisation of the receptor. Even though in COS-1 cells the type ll GnRH receptor internatises in a β-arrestin independent manner, internalisation of this receptor can be enhanced by over-expression of wild type β-arrestin. This indicates that the type ll GnRH receptor is able to utilise a β-arrestin mediated internaltsation pathway if high levels of β-arrestin are present in the cell. The mammalian type ll GnRH receptor internalises with enhanced rate and extent compared to the tail-less human type I GHRH receptor. The role of the C-terminal tail of the type ll GnRH receptor in internalisation was investigated by measuring internalisation of C-terminally truncated mutants. It was found that the region between Gly 343 and Ser 335 within the C-terminal domain is important for receptor internalisation. Substitution of putative phosphorylation sites within this region revealed that Ser 338 and Ser 339 are critical for rapid receptor internalisation. Furthermore a serine residue in intracellular loop three (Ser 251) was shown to play a role in signalling as well as in internalisation. Since dominant negative GRK 2 could not inhibit internalisation of a mutant lacking all three serine residues, but could reduce internalisation of the wild-type receptor, we suggest that Ser 251, 338 and 339 are target of phosphorylation by GRK. However these phosphorylation sites as well as the C-terminal tail are not necessary for β-arrestin dependent internalisation. Taken together this thesis elucidates the internalisation pathway of a mammalian type lI GnRH receptor and identified residues within the C-terminal tail and intracellular loop three that are critical for rapid internalisation.
  • Thumbnail Image
    Item
    Open Access
    Quantitative 18F-FDG PET-CT scan characteristics correlate with tuberculosis treatment response
    (2020-02-10) Malherbe, Stephanus T; Chen, Ray Y; Dupont, Patrick; Kant, Ilse; Kriel, Magdalena; Loxton, André G; Smith, Bronwyn; Beltran, Caroline G G; van Zyl, Susan; McAnda, Shirely; Abrahams, Charmaine; Maasdorp, Elizna; Doruyter, Alex; Via, Laura E; Barry, Clifton E; Alland, David; Richards, Stephanie G; Ellman, Annare; Peppard, Thomas; Belisle, John; Tromp, Gerard; Ronacher, Katharina; Warwick, James M; Winter, Jill; Walzl, Gerhard
    Abstract Background There is a growing interest in the use of F-18 FDG PET-CT to monitor tuberculosis (TB) treatment response. Tuberculosis lung lesions are often complex and diffuse, with dynamic changes during treatment and persisting metabolic activity after apparent clinical cure. This poses a challenge in quantifying scan-based markers of burden of disease and disease activity. We used semi-automated, whole lung quantification of lung lesions to analyse serial FDG PET-CT scans from the Catalysis TB Treatment Response Cohort to identify characteristics that best correlated with clinical and microbiological outcomes. Results Quantified scan metrics were already associated with clinical outcomes at diagnosis and 1 month after treatment, with further improved accuracy to differentiate clinical outcomes after standard treatment duration (month 6). A high cavity volume showed the strongest association with a risk of treatment failure (AUC 0.81 to predict failure at diagnosis), while a suboptimal reduction of the total glycolytic activity in lung lesions during treatment had the strongest association with recurrent disease (AUC 0.8 to predict pooled unfavourable outcomes). During the first year after TB treatment lesion burden reduced; but for many patients, there were continued dynamic changes of individual lesions. Conclusions Quantification of FDG PET-CT images better characterised TB treatment outcomes than qualitative scan patterns and robustly measured the burden of disease. In future, validated metrics may be used to stratify patients and help evaluate the effectiveness of TB treatment modalities.