Publications by authors named "Gita Parekh"

6 Publications

  • Page 1 of 1

Measurement of innate immune response biomarkers in peritoneal dialysis effluent using a rapid diagnostic point-of-care device as a diagnostic indicator of peritonitis.

Kidney Int 2020 06 6;97(6):1253-1259. Epub 2020 Mar 6.

Department of Nephrology, Royal Free Hospital, London, UK; Centre for Nephrology, University College London, London, UK.

Peritonitis is the commonest complication of peritoneal dialysis and a major reason for treatment failure. Current diagnosis is based on clinical symptoms, cloudy effluent and a dialysate white cell count (over 100 cells/μl). A rapid point-of-care diagnostic test would accelerate diagnosis and potentially improve outcomes from infection. Here, in a clinical audit project, we used PERiPLEX®, a point-of-care device which detects when levels of matrix metalloproteinase-8 and interleukin-6 are elevated above a threshold within minutes in dialysis effluent, to assess whether it could confirm or exclude peritonitis in 107 patients undergoing peritoneal dialysis. Mean patient age was 64.6 years with a median duration of peritoneal dialysis of 13.3 months (interquartile range 6.3 - 33.5 months). Presence of peritonitis was confirmed by clinical criteria. There were 49 positive tests of which 41 patients had peritonitis, three had other causes of intra-peritoneal inflammation, three had severe urosepsis and two patients required no treatment. Fifty-eight tests were negative with one patient having a false negative result. The positive predictive value of the test was 83.7% (95% confidence interval 72.8 - 90.8) and the negative predictive value was 98.3% (89.1 - 99.8). Sensitivity and specificity were 97.6% (87.4 - 99.9) and 87.7% (77.2 - 94.5) respectively. Thus, PERiPLEX® could be used as a rapid point-of-care test that can aid the diagnosis or exclusion of peritonitis with a high negative predictive value.
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http://dx.doi.org/10.1016/j.kint.2020.01.044DOI Listing
June 2020

Control of neutrophil influx during peritonitis by transcriptional cross-regulation of chemokine CXCL1 by IL-17 and IFN-γ.

J Pathol 2020 06 13;251(2):175-186. Epub 2020 May 13.

Department of Nephrology and Medical Intensive Care, Charité-Universitätsmedizin, Berlin, Germany.

Neutrophil infiltration is a hallmark of peritoneal inflammation, but mechanisms regulating neutrophil recruitment in patients with peritoneal dialysis (PD)-related peritonitis are not fully defined. We examined 104 samples of PD effluent collected during acute peritonitis for correspondence between a broad range of soluble parameters and neutrophil counts. We observed an association between peritoneal IL-17 and neutrophil levels. This relationship was evident in effluent samples with low but not high IFN-γ levels, suggesting a differential effect of IFN-γ concentration on neutrophil infiltration. Surprisingly, there was no association of neutrophil numbers with the level of CXCL1, a key IL-17-induced neutrophil chemoattractant. We investigated therefore the production of CXCL1 by human peritoneal mesothelial cells (HPMCs) under in vitro conditions mimicking clinical peritonitis. Stimulation of HPMCs with IL-17 increased CXCL1 production through induction of transcription factor SP1 and activation of the SP1-binding region of the CXCL1 promoter. These effects were amplified by TNFα. In contrast, IFN-γ dose-dependently suppressed IL-17-induced SP1 activation and CXCL1 production through a transcriptional mechanism involving STAT1. The SP1-mediated induction of CXCL1 was also observed in HPMCs exposed to PD effluent collected during peritonitis and containing IL-17 and TNFα, but not IFN-γ. Supplementation of the effluent with IFN-γ led to a dose-dependent activation of STAT1 and a resultant inhibition of SP1-induced CXCL1 expression. Transmesothelial migration of neutrophils in vitro increased upon stimulation of HPMCs with IL-17 and was reduced by IFN-γ. In addition, HPMCs were capable of binding CXCL1 at their apical cell surface. These observations indicate that changes in relative peritoneal concentrations of IL-17 and IFN-γ can differently engage SP1-STAT1, impacting on mesothelial cell transcription of CXCL1, whose release and binding to HPMC surface may determine optimal neutrophil recruitment and retention during peritonitis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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http://dx.doi.org/10.1002/path.5438DOI Listing
June 2020

Identification of clinical and urine biomarkers for uncomplicated urinary tract infection using machine learning algorithms.

Sci Rep 2019 12 23;9(1):19694. Epub 2019 Dec 23.

Division of Population Medicine, School of Medicine, College of Biomedical and Life Sciences, Cardiff University, Cardiff, United Kingdom.

Women with uncomplicated urinary tract infection (UTI) symptoms are commonly treated with empirical antibiotics, resulting in overuse of antibiotics, which promotes antimicrobial resistance. Available diagnostic tools are either not cost-effective or diagnostically sub-optimal. Here, we identified clinical and urinary immunological predictors for UTI diagnosis. We explored 17 clinical and 42 immunological potential predictors for bacterial culture among women with uncomplicated UTI symptoms using random forest or support vector machine coupled with recursive feature elimination. Urine cloudiness was the best performing clinical predictor to rule out (negative likelihood ratio [LR-] = 0.4) and rule in (LR+ = 2.6) UTI. Using a more discriminatory scale to assess cloudiness (turbidity) increased the accuracy of UTI prediction further (LR+ = 4.4). Urinary levels of MMP9, NGAL, CXCL8 and IL-1β together had a higher LR+ (6.1) and similar LR- (0.4), compared to cloudiness. Varying the bacterial count thresholds for urine culture positivity did not alter best clinical predictor selection, but did affect the number of immunological predictors required for reaching an optimal prediction. We conclude that urine cloudiness is particularly helpful in ruling out negative UTI cases. The identified urinary biomarkers could be used to develop a point of care test for UTI but require further validation.
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http://dx.doi.org/10.1038/s41598-019-55523-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6928162PMC
December 2019

Machine-learning algorithms define pathogen-specific local immune fingerprints in peritoneal dialysis patients with bacterial infections.

Kidney Int 2017 07 17;92(1):179-191. Epub 2017 Mar 17.

Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK; Systems Immunity Research Institute, Cardiff University, Cardiff, UK. Electronic address:

The immune system has evolved to sense invading pathogens, control infection, and restore tissue integrity. Despite symptomatic variability in patients, unequivocal evidence that an individual's immune system distinguishes between different organisms and mounts an appropriate response is lacking. We here used a systematic approach to characterize responses to microbiologically well-defined infection in a total of 83 peritoneal dialysis patients on the day of presentation with acute peritonitis. A broad range of cellular and soluble parameters was determined in peritoneal effluents, covering the majority of local immune cells, inflammatory and regulatory cytokines and chemokines as well as tissue damage-related factors. Our analyses, utilizing machine-learning algorithms, demonstrate that different groups of bacteria induce qualitatively distinct local immune fingerprints, with specific biomarker signatures associated with Gram-negative and Gram-positive organisms, and with culture-negative episodes of unclear etiology. Even more, within the Gram-positive group, unique immune biomarker combinations identified streptococcal and non-streptococcal species including coagulase-negative Staphylococcus spp. These findings have diagnostic and prognostic implications by informing patient management and treatment choice at the point of care. Thus, our data establish the power of non-linear mathematical models to analyze complex biomedical datasets and highlight key pathways involved in pathogen-specific immune responses.
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http://dx.doi.org/10.1016/j.kint.2017.01.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484022PMC
July 2017

Mapping nitro-tyrosine modifications in fibrinogen by mass spectrometry as a biomarker for inflammatory disease.

Free Radic Biol Med 2014 Oct 10;75 Suppl 1:S50. Epub 2014 Dec 10.

Aston University (Birmingham), School of Life and Health Sciences, UK. Electronic address:

There is a growing awareness that inflammatory diseases have an oxidative pathology, which can result in specific oxidation of amino acids within proteins. It is known that patients with inflammatory disease have higher levels of plasma protein nitro-tyrosine than healthy controls. Fibrinogen is an abundant plasma protein, highly susceptible to such oxidative modifications, and is therefore a potential marker for oxidative protein damage. The aim of this study was to map tyrosine nitration in fibrinogen under oxidative conditions and identify susceptible residues. Fibrinogen was oxidised with 0.25mM and 1mM SIN-1, a peroxynitrite generator, and methionine was used to quench excess oxidant in the samples. The carbonyl assay was used to confirm oxidation in the samples. The carbonyl levels were 2.3, 8.72 and 11.5nmol/mg protein in 0, 0.25mM and 1mM SIN-1 samples respectively. The samples were run on a SDS-PAGE gel and tryptically digested before analysis by HPLC MS-MS. All 3 chains of fibrinogen were observed for all treatment conditions. The overall sequence coverage for fibrinogen determined by Mascot was between 60-75%. The oxidised samples showed increases in oxidative modifications in both alpha and beta chains, commonly methionine sulfoxide and tyrosine nitration, correlating with increasing SIN-1 treatment. Tyrosines that were most susceptible were Tyr135 (tryptic peptide YLQEIYNSNNQK) and Tyr277 (tryptic peptide GGSTSYGTGSETESPR), but several other nitrated tyrosines were also identified with high confidence. Identification of these susceptible peptides will allow design of sequences-specific biomarkers of oxidative and nitrative damage to plasma protein in inflammatory conditions.
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http://dx.doi.org/10.1016/j.freeradbiomed.2014.10.819DOI Listing
October 2014