Regensburg, Univ., Diss., 2009.

Hepatitis B virus infection (HBV) is an important health problem worldwide, with a significant rate of chronic infection, which can lead to cirrhosis and hepatocellular carcinoma (HCC). Increased age is an important determinant of progression to cirrhosis and HCC, possibly because age is a crude measure of the duration of HBV infection. Increasing age is associated with changes in liver structure, blood flow and function and with reduced response to injury, impaired regeneration and increased mortality in acute liver disease. Age has been identified as a co‐factor in several chronic liver diseases including chronic hepatitis C infection (HCV). Available evidence suggests differential ageing of various intrahepatic cell types in different liver diseases and the ageing process may be more complex in the liver than originally thought. Telomeres are DNA structures located at the end of each chromosome, which protect the underlying coding DNA from breaks and fusions and shorten with increasing age. Both DNA damage and cell proliferation lead to progressive telomere shortening, which ultimately leads to cell cycle arrest and a state of replicative senescence. Persistent HCV and HBV infections lead to cell cycle arrest, providing a favourable environment for viral replication. Evidence suggests that progressive telomere shortening occurs with advancing stage of liver disease in HBV and specifically from cirrhosis through large cell dysplasia to small cell dysplasia and to HCC. Whether cell cycle arrest leads to a senescent‐like state or whether this is the result of oxidative stress is unknown. Unpublished data using cell cycle phase markers in chronic HBV infection reveal that hepatocytes, which support HBV replication, are arrested in G1, which is mediated by hepatocyte p21 expression. I hypothesise that: 1. In normal liver tissue, different cell types age at different rates and this is altered during disease; 2. Hepatocyte senescence plays a significant role in the natural course of chronic HBV infection and underlies HBV antigen expression. I developed and optimised large volume Q‐FISH methodology to measure telomere length and nuclear size in a variety of intrahepatic cell lineages. In normal liver tissue, cholangiocytes had longer telomeres compared with all other intrahepatic lineages over a wide age range. Hepatocytes did not show any age‐related telomere shortening, in contrast to Kupffer and hepatic stellate cells. In chronic HBV infection, all hepatocytes had shortened telomeres when compared to age and sex‐matched controls consistent with accelerated ageing. HBV replication was confined to those hepatocytes with longer telomeres, suggesting that HBV entry or replication is less efficient in older hepatocytes and compatible with the fall in serum HBV DNA and HBsAg titre seen with advancing age. There may be two populations of hepatocytes in chronic HBV infection; hepatocytes that are growth arrested with short telomeres not supporting HBV replication and biologically 'younger' hepatocytes with longer telomeres that do support HBV replication. The change in cellular HBV antigen localisation with disease progression is also explained by age related changes in HBV expression. Nuclear Hepatitis B core antigen expression (HBcAg), characteristic of the early immune tolerant phase of infection, was associated with the longest telomeres, while cytoplasmic HBcAg expression was associated with shorter telomeres. Furthermore, the total number of hepatocyte telomeres fell with increasing fibrosis stage. Hepatocyte nuclear size, a marker of senescence, increased as HBcAg expression shifted from nucleus to cytoplasm; and p21, another senescence marker, never co‐localised with HBcAg expression. These results suggest that the location and production of HBV antigens are related to increased functional hepatocyte age and the onset of cellular senescence.

Eine chronische Infektion mit dem Hepatitis B Virus (HBV) ist ein wichtiges, jedoch vernachlässigtes Problem der globalen Gesundheit. Weltweit sind ungefähr 257 Millionen Personen chronisch mit dem Virus infiziert. Eine Impfung gegen diese Erkrankung ist seit 1982 verfügbar. Impfprogramme haben dort, wo die Impfung ausreichend verfügbar ist, einen durchschlagenden Erfolg in der Reduktion von chronischer Hepatitis B gezeigt. Es gibt jedoch Teile der Welt, in denen die Impfung nicht zu einem ausreichenden Schutz führt, da die Infektion schon vor der Gabe der ersten Impfdosis geschieht oder die Impfung nicht oder nur unvollständig verabreicht wird. In Ländern mit einer hohen Prävalenz von Hepatitis B wird das Virus vor allem von Müttern auf Kinder übertragen. Kinder, die sich innerhalb ihres ersten Lebensjahres infizieren, haben hohes Risiko eine chronische Infektion zu entwickeln. Tansania, mit einer Prävalenz der chronischen Hepatitis B von 7,2% in der Allgemeinbevölkerung, gilt als Hochendemiegebiet der Erkrankung. Die Weltgesundheitsorganisation (WHO) nennt in ihrer globalen Strategie zur Elimination von viralen Hepatitiden die Prävention von Mutter-Kind-Übertragung als eine zentrale Aufgabe. Das beinhaltet unter anderem die Testung von schwangeren Frauen und die Impfung von Neugeborenen gegen HBV innerhalb von 24 Stunden nach der Geburt. Diese Maßnahmen sind jedoch in Tansania nicht implementiert. Zudem lagen zum Durchführungszeitraum der Studie nur wenige Daten zu der Prävalenz von HBV in schwangeren Frauen vor. Aus diesem Grund untersuchte die Studie die Prävalenz von Hepatitis B unter schwangeren Frauen in einem Krankenhaus der tertiären Versorgungsstufe in Mwanza, Tansania, sowie den sozio-ökonomischen Hintergrund und mögliche Risikofaktoren für eine Infektion seitens der Mütter. Ergänzend wurden verschiedene serologische und virologische Analysen des Blutes der Mütter und ihrer Kinder durchgeführt. / Chronic hepatitis B virus (HBV) infection is an important but neglected global health problem. Approximately 257 million people worldwide are chronically infected with the virus. Vaccination against this disease has been available since 1982 and vaccination programs have shown resounding success in reducing chronic hepatitis B where vaccination is sufficiently available. However, there are parts of the world where vaccination does not result in adequate protection because infection occurs before the first dose of vaccine is administered or because vaccination is not administered or is incomplete. In countries with a high prevalence of hepatitis B, the virus is transmitted primarily from mothers to their children. Children who become infected within their first year of life are at high risk of developing chronic infection. Tanzania, with a prevalence of chronic hepatitis B of 7.2% in the general population, is considered a high-endemic area for the disease. In its global strategy for the elimination of viral hepatitis, the World Health Organization (WHO) identifies prevention of mother-to-child transmission as a key task. This includes, among others, testing pregnant women and vaccinating newborns against HBV within 24 hours after birth. However, these measures have not been implemented in Tanzania. In addition, few data were available on the actual prevalence of HBV in pregnant women at the time the study was conducted. For this reason, the following study investigated the prevalence of hepatitis B among pregnant women in a tertiary care hospital in Mwanza, Tanzania, as well as the socioeconomic background and possible risk factors for infection on the part of the mothers. In addition, various serological and virological analyses of the blood of the mothers and their children were performed.

No description available.

Mathematical modeling of biological systems has improved the knowledge of scientists for many years. In virology, particularly in the study of hepatitis B virus, mathematical models were used to explain interactions between hepatitis B virus and the human host in the absence and presence of interventions such as drug therapy and vaccines. This thesis seeks to explain the role of e-Antigen, a particle produced by hepatitis B virus, in the pathogenesis of hepatitis B infection. To accomplish this goal, I will provide biological background as well as previous modeling work on the role of e-Antigen in hepatitis B virus infection, before finally developing a new model adapted specifically for connecting hepatitis B progression with e-Antigen and drug therapy. I will analyze the model both analytically and numerically, fit it to virus data from humans chronically infected with hepatitis B that undergo drug therapy, and draw conclusions about the relation between drugs, immune activation, and loss of e-Antigen. / Master of Science

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / The development of non-replicating vaccines is an emerging option for safe, effective vaccines, several of which contain virus-like particles (VLPs). Many recombinant expression systems have been evaluated as hosts for VLP production for the prevention of infectious diseases. The filamentous fungi Aspergillus niger has emerged as a potential alternative expression system for cost effective VLP vaccine production. Hepatitis B surface antigen (HBsAg) was used as a model VLP product to benchmark A. niger’s production capacity with those of Saccharomyces cerevisiae, Pichia pastoris and Hansenula polymorpha. Bioprocessing strategies were used to optimise VLP production by recombinant A. niger in batch culture. In particular, the effect of the parameters culture temperature, inoculum concentration, agitation intensity, dissolved oxygen (dO2) concentration and culture pH on biomass formation, morphology and VLP (HBsAg) production concentration was quantified. At an optimum agitation of 100 rpm and optimum dO2 concentration of 50 %, HBsAg production levels were increased 9-fold compared to yields obtained in shakeflask cultivation. Highest HBsAg production levels of 3.6 mg.ℓculture -1 and 350 μg.gDW -1 were recorded, at a biomass concentration of 10.5 gDW.ℓculture -1. These production levels compare favourable with those obtained by other production systems under similar conditions. HBsAg VLPs mostly accumulated intracellularly, although under optimum bioreactor conditions significant HBsAg accumulation in the cytoplasm and culture supernatant was also observed. The impact of these process parameters on VLP production and cell morphology was attributed to environmental stress conditions. Volumetric biomass and HBsAg production levels were maximised under conditions of lowest environmental stress, resulting in the most optimal small-pelleted morphology. These results indicate a substantial potential for further engineering of the A. niger production system for the high level of intracellular and extracellular VLP production.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / abstract / Surgery / Doctoral / Doctor of Philosophy

<p>Adekvatni nadzor nad zaraznim bolestima predstavlja aktuelni izazov ne samo kod nas već i u razvijenim zemljama. Savremeni epidemiolo&scaron;ki nadzor nad zaraznim bolestima zasniva se na odgovarajućim definicijama slučaja. Njihova osnovna funkcija je olak&scaron;avanje prepoznavanja određenih bolesti i njihovo registrovanje na jednoobrazan način. Definisanje slučajeva zaraznih bolesti nije jednostavno, jer uključuje kliničke, epidemiolo&scaron;ke i laboratorijske parametre, uz istovremeno očekivanje visoke senzitivnosti i specifičnosti. Ciljevi istraživanja su bili da se utvrdi primenljivost definicija slučaja hepatitisa B i C na Klinici za infektivne bolesti Kliničkog centra Vojvodine, te da se utvrdi senzitivnost i specifičnost primenjenih definicija slučaja hepatitisa B i C. Uz postojeći dijagnostički algoritam Klinike za infektivne bolesti Kliničkog centra Vojvodine, uvedena su tri seta definicija hepatitisa B i C: Evropskog centra za prevenciju i kontrolu bolesti (ECDC) iz 2008. i 2012.godine kao i američkih Centara za kontrolu bolesti (CDC) iz 2012. godine. Istraživanje je sprovedeno na Klinici za infektivne bolesti Kliničkog centra Vojvodine i tokom 12 meseci, u skladu sa predloženim definicijama slučaja, identifikovano je 150 ispitanika obolelih od hepatitisa B i C. Utvrđene su sledeće činjenice: preporučene definicije slučaja su primenljive u Republici Srbiji za laboratorijske i kliničke kriterijume, dok uključivanje epidemiolo&scaron;ke povezanosti u definicije slučaja ima malo praktičnog značaja za prijavljivanje hepatitisa; definicije slučaja koje uključuju i obavezno prisustvo kliničkih kriterijuma (najče&scaron;će definicije verovatnog slučaja) imaju nisku senzitivnost, a visoku specifičnost, kao posledica prisustva infekcije i u odsustvu bilo kakvih kliničkih manifestacija; definicije slučaja koje se zasnivaju samo na laboratorijskim kriterijumima imaju maksimalnu senzitivnost i specifičnost.</p> / <p>Adequate surveillance of communicable diseases is the actual challenge, not only in our country but also in developed countries. Modern epidemiological surveillance of communicable diseases is based on the appropriate case definitions. Their main purpose of them is to facilitate the recognition of certain diseases and their registration in a uniform manner. Case definition of communicable diseases is not easy, because it involves clinical, epidemiological and laboratory parameters, along with the expectated high sensitivity and specificity.The objectives of the study were to determine the applicability of the casedefinitions for hepatitis B and C in the Clinic for Infectious Diseases of the Clinical Center of Vojvodina and to determine the sensitivity and specificity of the applied definition of cases of hepatitis B and C. In addition to existing diagnostic algorithm of the Clinic for Infectious Diseases, three sets of hepatitis B and C case definitions were introduced: the European Centre for Disease Prevention and Control in 2008 and 2012 as well as the US Centers for Disease Control in 2012. The study was conducted at the Clinic for Infectious Diseases Clinical Center of Vojvodina over 12 months, and in accordance with the proposed case definitions, 150 patients suffering from hepatitis B and C were identified. We found following facts: recommended case definitions are applicable in the Republic of Serbia for laboratory and clinical criteria, while the inclusion of epidemiological connection between the case definition has little practical significance for reporting hepatitis; case definitions that include the obligatory presence of clinical criteria (most common definition of probable cases) have low sensitivity and high specificity, as a result of the presence of infection in the absence of any clinical manifestations; case definitions that are based solely on laboratory criteria showed maximum sensitivity and specificity.</p>

In conclusion, two new methods of cccDNA quantitation were developed and validated. The two assays are complementary to each other and may be used in patients with extreme HBV DNA levels. These cccDNA assays should be further validated in larger studies and may become important tests for diagnostic, prognostic and treatment monitoring purposes. / Over 350 million people worldwide suffer from chronic hepatitis B virus (HBV) infection, which leads to many cases of cirrhosis and hepatocellular carcinoma. HBV covalently closed circular DNA (cccDNA) is a critical intracellular replicative intermediate and cannot be eliminated during antiviral therapy. Current methods for cccDNA detection are limited by false positive detection due to the interference by HBV relaxed circular DNA (rcDNA). The tests also have limited sensitivity to detect cccDNA at low concentrations. Hence, we aimed to develop a highly sensitive and highly specific assay for cccDNA detection with wide linear range. / The modified Bowden's assay had the highest intrahepatic cccDNA detection rate (60 positive results out of 61 cases). The detection rate of the modified Bowden's assay is significantly higher than that of the Bowden's assay. On the other hand, the cccDNA detection rate in serum samples was low at 20--27% by all 3 assays. In 5 samples in which cccDNA was undetectable by the Bowden's assay but detectable by the other two assays, a point mutation in the HBV genome was found in the forward primer binding site of the Bowden's assay. This partly explained the false negative results. / The quantification result of cccDNA by the bisulfite conversion assay was significantly lower than that by the Bowden's assay assay (P=0.001) and the modified Bowden's assay (P=0.003). When the total HBV DNA was higher than 107 copies/ml, the serum cccDNA level detected by the bisulfite conversion assay was significantly lower than that detected by the Bowden's assay (P=0.008) and the modified Bowden's assay (P=0.046). When the total HBV DNA is less than 107 copies/ml, there were no significant differences. This suggests that the bisulfite conversion assay was less affected by rcDNA even in samples containing a high viral load. / With this background, two new cccDNA assays were developed and optimized. Bowden's assay was used as a standard to evaluate the performance of new assays. The first new assay (modified Bowden's assay) involved the use of new primers and probes that targeted more conserved regions in the HBV genome. The second assay adopted the bisulfite conversion method, which introduced gene sequence changes into the HBV genome and thereby enhance the specificity of the assay. Capillary sequencing was performed to find mutations in primers and probe range of different assays. / Yu, Ling. / Advisers: Vincent Wai-Sun Wang; Joseph Jao-Yiu Sung. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 105-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.