Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 112-133). Also available in electronic version.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

No description available.

Introduction: In pediatrics, ninety-eight percent of all chest pain complaints are non-cardiac in origin, with the leading cause being muscular skeletal pain. Of the two percent that are cardiac in origin, troponin levels are helpful in detecting cardiac muscle ischemia, most commonly present in myocardial infarction, pulmonary embolism, pericarditis, myocarditis, aortic dissection, heart failure, and cardiac contusion. There are multiple different troponin assays that detect troponin, usually using a two-site immunoezematic assay. Although values obtained may differ slightly between assays, there is not a statistically significant difference between assays. Several endogenous substances, such as rheumatoid factor, excess fibrin, alkaline phosphatase, and heterophile antibodies can cause statistically significant, though falsely increased troponin levels that do not rise and fall in the typical pattern seen in cardiac ischemia due to cross reactivity with the assays. We present the case of a fifteen-year-old male with chest pain and elevated troponins, but otherwise benign workup. It highlights the falsely elevated troponin levels seen with the cross-reactivity of heterophile antibodies and various troponin assays. Case Presentation: A 15-year-old male presents with a two-day history of intermittent, stabbing, 5/10 left sided chest pain, as well as substernal chest pressure that radiates to his left upper chest and shoulder. He is unable to identify any triggers of the pain or alleviating factors. Review of systems is negative for nausea, vomiting, diaphoresis, and shortness of breath. His past medical history is significant for pectus excavatum that has been corrected with Nuss bar procedure. He also reports being treated for strep pharyngitis two weeks prior. The patient presents to emergency department after having an irregular heart rate noted by the school nurse’s office. His vital signs are stable, and his physical exam is notable for a regular heart rate and rhythm. Pectus excavatum with well healed midline scar is present. A basic metabolic panel is normal. In the emergency department, serum troponins are elevated between 0.24-0.25 ng/ml (normal range 0.00-0.02), and a D-dimer is elevated at 500 ng/ml (normal range 0-230). Cardiology is consulted, and following an algorithm for chest pain in pediatric patients,1 a series of additional tests are performed. His electrocardiogram shows a normal sinus rhythm with minimal left axis deviation. Chest x-ray shows intact Nuss bars and is, otherwise, normal. Ventilation-Perfusion (VQ) scan is normal. An echocardiogram shows normal ventricular output and valvular function with an incidental finding of slight angulation of aortic arch with no significant gradient. Cardiology recommends trending troponins every 6 hours. A repeat EKG the following day shows normal sinus rhythm without evidence of ischemia or arrhythmia. Serial troponins remain elevated for the following 48 hours ranging 0.22-0.24 ng/ml. The patient denies any further cardiac symptoms despite the persistently elevated troponins, and he is discharged home with close follow-up with pediatric cardiology as well as a thirty-day looping event monitor. One week after discharge, in the cardiology clinic, troponin levels are still 0.23ng/ml. Creatine kinase MB level is obtained and is within normal limits. Due to persistently elevated troponins within a narrow range, a literature search is performed to determine if there are other causes for elevated troponins that neither rise nor fall. Several articles are found confirming cross reactivity between various antibodies and troponin assays that lead to falsely elevated troponin levels.2,3 Rheumatoid factor, antinucleic antibodies, and Epstein-Barr virus antibody titers are obtained. RF and ANA levels return within normal limits. However, EBV IgM levels are elevated , while EBV IgG levels are within normal limits, supporting the theory that the patient has a current infection of mononucleosis. The thirty day looping event monitor is uneventful, showing no dysrhythmia or ectopy. Serial echocardiograms continue to remain unchanged from the initial echo during the patient’s hospitalization. Serum samples are analyzed on four different troponin assays, and a vast variation in troponin levels is found, ranging from < 0.015 ng/ml (normal value) on the Siemens Vista/ cTnl to 0.23 ng/ml (significantly elevated) on Beckman Access/ AccuTnI+3. Serial dilution studies are performed on a Beckman Dxi800 instrument and reveal decreasing troponin values with increasingly diluted serum samples. Discussion: In pediatrics, ninety-eight percent of all chest pain complaints are non-cardiac in origin, with the leading cause being muscular skeletal pain.4 Of the two percent that are cardiac in origin, troponin levels are helpful in detecting cardiac muscle ischemia, most commonly present in myocardial infarct, pulmonary embolism, pericarditis, myocarditis, aortic dissection, heart failure, and cardiac contusion, over exertion, and rhabdomyolysis. Most troponin assays use a two-site immunoenzymatic assay. One study in 2016 found that various assays reported different troponin levels; however the 99th percentile cutoff values were in agreeance with each other.5 Heterophilie antibodies in the serum have been found to falsely elevate troponin levels due to cross-reactivity between the antibodies and troponin assays. Rheumatoid factor, fibrin, and alkaline phosphatase can also cause false positive results.2 Conclusions: Elevated troponins are commonly interpreted as a sign of myocardial injury that prompts an extensive cardiac evaluation. This case illustrates that a common pediatric illness, infection with Epstein-Barr virus, can cause a false elevation in serum troponins. Infectious mononucleosis, as well as autoimmune diseases, should be considered in the differential of patients who present with elevated troponins without an apparent cardiac source.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2010-2011 / Le TLR2 et le TLR9 sont membres de la famille des ±Toll-like receptors¿ (TLRs), récepteurs de l'immunité innée, pouvant reconnaître divers motifs de microorganismes. Il est connu que ces deux récepteurs peuvent lier différentes composantes de certains virus de la famille des Herpesviridae. Le TLR2, exprimé à la surface de la cellule, peut reconnaître l'herpès simplex, le cytomegalovirus et varicella zoster. Quant au TLR9, il est exprimé dans les vésicules intracellulaires et peut lier l'ADN double brin étranger présent notamment chez les virus herpétiques. Ces données nous ont poussés à vérifier si une telle interaction était observée entre ces récepteurs et le virus Epstein-Barr (EBV). Nous avons tout d'abord établi, dans un modèle in vitro de cellules HEK293 transfectées avec le TLR2 et un plasmide rapporteur NF[kabba]B-LUC, qu'EBV pouvait activer la voie NF-[kabba]B et ce, dépendamment du TLR2. En effet, l'initiation de la voie NF-[kabba]B par le virus peut être abolie par l'utilisation d'anticorps bloquant/neutralisant contre le TLR2 ou la glycoprotéine 350 (gp350) virale. De plus, nous avons aussi démontré que'EBV pouvait activer la sécrétion de MCP-1 par les monocytes primaires humains, un processus pouvant être inhibé par l'utilisation d'ARNs bloquants contre le TLR2 (SiRNA TLR2). Dans un deuxième temps, nous avons examiné si le génome d'EBV pouvait être reconnu par le TLR9. Les résultats indiquent clairement que les particules intactes d'EBV, ainsi son génome purifié, peuvent induire la sécrétion d'IL-8 par les monocytes humains. Cette induction par l'ADN viral semble de plus être dépendante de l'acidification des endosomes. Le traitement des cellules par un SiRNA TLR2, un ODN inhibiteur du TLR9 ou une combinaison des deux diminue la production d'IL-8, ceci indiquant une coopération probable de ces récepteurs lors de la détection d'EBV. Concernant les cellules dendritiques plasmacytoïdes (pDCs), qui expriment majoritairement le TLR7 et le TLR9, la stimulation avec EBV ou l'ADN viral purifié induit la production d'IFN-α. Une combinaison d'antagonistes du TLR7 et du TLR9 élimine complètement la sécrétion d'IFN-α, supportant ainsi notre hypothèse voulant que le TLR7 puisse aussi contribuer à cette réponse. En conclusion, les résultats présentés dans ce manuscrit démontrent que la famille des TLRs joue un rôle important dans le déclenchement d'une réponse pro-inflammatoire et antivirale suite à la reconnaissance d'EBV, et que l'activation de multiples TLRs par diverses composantes virales permet probablement de potentialiser l'efficacité de celle-ci.

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

Infection with Epstein-Barr virus (EBV) during adolescence results in an immunopathological disease, Infectious Mononucleosis (IM), in around 25% of cases. A role for Regulatory T cells (Treg) in IM has yet to be established. These suppressive cells may affect the well-characterised cytotoxic T cell (CTL) response to EBV and thus the level of viral persistence and reactivation, potentially creating an environment conducive to the outgrowth of EBV-infected cells and tumour development. The work in this thesis examines the frequency and functional capacity of Treg in primary EBV infection. The results show that the frequency of Treg within the CD4+ T cell population of IM patients was reduced with borderline significance (p=0.05) compared with healthy controls as revealed by fluorescence activated cell sorting. Treg function was confirmed using suppression assays on peripheral blood mononuclear cells (PBMC) from healthy controls but could not be assessed in IM patients due to low cell numbers. EBV-specific Treg function was analysed using Interferon (IFN)-γ ELISPOT assays in which PBMC from IM patients and healthy controls were stimulated with phytohaemagglutinin (PHA) and EBV peptides in the presence or absence of Treg. The IFN-gamma response of PBMC to PHA stimulation was significantly reduced in IM patients compared to healthy controls (p=0.009) but the IFN-gamma response to EBV peptides did not alter, irrespective of the presence or absence of Treg. Investigation of FOXP3 expression by immunohistochemistry provided evidence of Treg presence and preliminary data indicated an increased expression in IM tonsil sections compared with healthy tonsil sections. The proliferative responses and cytokine profiles of healthy controls, as measured by proliferation assays and ELISAs, in response to stimulation with the recall antigen PPD did not significantly alter upon the addition of latent membrane protein (LMP)-1 peptide. In IM patients, the same treatment resulted in a significant reduction in IFN-gamma (p=0.026) but no significant differences in IL-10 production or cell proliferation. The significantly reduced frequency of Treg in peripheral blood of IM patients and abundant FOXP3 expression in IM tonsils provides evidence for a Treg role in primary EBV infection. One plausible explanation is the recruitment of Treg to the site of primary infection by an as yet unidentified EBV-specific mechanism. Clarification of Treg activity in IM may expose opportunities for immunomanipulation during early stages of infection.