Hakan Bozkaya
Ankara University
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Featured researches published by Hakan Bozkaya.
The New England Journal of Medicine | 2011
Heiner Wedemeyer; Cihan Yurdaydin; George N. Dalekos; A. Erhardt; Yilmaz Cakaloglu; Halil Degertekin; Selim Gurel; Stefan Zeuzem; Kalliopi Zachou; Hakan Bozkaya; Armin Koch; Thomas Bock; Hans Peter Dienes; Michael P. Manns
BACKGROUND Chronic infection with hepatitis B virus and hepatitis delta virus (HDV) results in the most severe form of viral hepatitis. There is no currently approved treatment. We investigated the safety and efficacy of 48 weeks of treatment with peginterferon alfa-2a plus adefovir dipivoxil, peginterferon alfa-2a alone, and adefovir dipivoxil alone. METHODS We conducted a randomized trial in which 31 patients with HDV infection received treatment with 180 μg of peginterferon alfa-2a weekly plus 10 mg of adefovir daily, 29 received 180 μg of peginterferon alfa-2a weekly plus placebo, and 30 received 10 mg of adefovir alone weekly for 48 weeks. Follow-up was conducted for an additional 24 weeks. Efficacy end points included clearance of HDV RNA, normalization of alanine aminotransferase levels, and a decline in levels of hepatitis B surface antigen (HBsAg). RESULTS The primary end point--normalization of alanine aminotransferase levels and clearance of HDV RNA at week 48--was achieved in two patients in the group receiving peginterferon alfa-2a plus adefovir and two patients in the group receiving peginterferon alfa-2a plus placebo but in none of the patients in the group receiving adefovir alone. At week 48, the test for HDV RNA was negative in 23% of patients in the first group, 24% of patients in the second, and none of those in the third (P = 0.006 for the comparison of the first and third groups; P = 0.004 for the comparison of the second and third). The efficacy of peginterferon alfa-2a was sustained for 24 weeks after treatment, with 28% of the patients receiving peginterferon alfa-2a plus adefovir or peginterferon alfa-2a alone having negative results on HDV-RNA tests; none of the patients receiving adefovir alone had negative results. A decline in HBsAg levels of more than 1 log(10) IU per milliliter from baseline to week 48 was observed in 10 patients in the first group, 2 in the second, and none in the third (P<0.001 for the comparison of the first and third groups and P = 0.01 for the comparison of the first and second). CONCLUSIONS Treatment with peginterferon alfa-2a for 48 weeks, with or without adefovir, resulted in sustained HDV RNA clearance in about one quarter of patients with HDV infection. (Current Controlled Trials number, ISRCTN83587695.).
Archives of Virology | 2004
A.M. Bozdayi; N. Aslan; Gulendam Bozdayi; Ahmet R Turkyilmaz; T. Sengezer; U. Wend; Ö. Erkan; F. Aydemir; S. Zakirhodjaev; Ş. Orucov; Hakan Bozkaya; Wolfram H. Gerlich; Selim Karayalcin; Cihan Yurdaydin; Ozden Uzunalimoglu
Summary.Different genotypes of the hepatitis viruses may influence the clinical outcome of the disease. The distribution of genotypes may vary according to geographical regions. The aim of this study was to evaluate hepatitis B virus (HBV), hepatitis C virus (HCV) and hepatitis D virus (HDV) genotypes in Turkish patients with chronic hepatitis in a large cohort of patients. Genotyping was performed in 41, 59 and 365 patients with chronic hepatitis B, D and C, respectively, and 36 hemodialysis patients with chronic hepatitis C. Genotypes were determined by direct sequencing in hepatitis B and by polymerase chain reaction-restriction fragment length polymorphism in hepatitis C and D patients. In addition, HBV subtyping by multiplex PCR and subtype specific ELISA were performed in 83 and 71 HBsAg (+) blood donors, respectively. All hepatitis B (100%) and hepatitis D (100%) patients had genotype D and type I, respectively. HBsAg subtyping by two methods yielded that 99% of the patients were subtype ayw. S gene amino acid sequence in the 41 patients included for HBV genotyping revealed the ayw2 subtype. Genotype distribution of 365 patients with chronic C hepatitis were as follows: 306 (84%) patients genotype 1b, 43 (11%) patients genotype 1a, 10 (3%) patients genotype 2, 3 (1%) patients genotype 3, 3 (1%) patients genotype 4. Among 36 patients receiving hemodialysis, 28 (78%) patients had genotype 1b and 8 (22%) patients had genotype 1a. The study indicates that Turkish patients with chronic viral hepatitis show very little genotypic heterogeneity. Subtype ayw and the genotype D of HBV DNA, and the type I of HDV RNA represent almost 100% of related infections. The genotype 1b of HCV RNA was found to be significantly dominant in Turkish patients.
Journal of Viral Hepatitis | 2008
Cihan Yurdaydin; Hakan Bozkaya; Fatih Oguz Onder; H. Şentürk; H. Karaaslan; Meral Akdogan; Hülya Çetinkaya; Esra Erden; Ö. Erkan-Esin; K. Yalçın; A.M. Bozdayi; Raymond F. Schinazi; J. L. Gerin; Ozden Uzunalimoglu; Ali Özden
Summary. Chronic delta hepatitis is the most severe form of chronic viral hepatitis for which interferon (IFN) is the only available treatment. In 39 patients (25 were treatment‐naïve, 14 had previously used IFN), efficacy of 1‐year treatment with IFN (9 MU, t.i.w.) or lamivudine (LAM; 100 mg, q.d.) alone was compared with IFN and LAM combination (2 months of LAM to be followed by combination treatment). IFN monotherapy was given only to treatment‐naïve patients. In both treatment‐naïve and previous IFN users, end of treatment virological and biochemical responses were similar with IFN–LAM combination and superior to LAM monotherapy (P < 0.05). Improvement in liver histology occurred more often with IFN ± LAM than with LAM alone (P < 0.05). In treatment‐naïve patients, combination treatment was not superior to IFN monotherapy. After treatment discontinuation, virological and biochemical response rates decreased in LAM and IFN combination and IFN monotherapy. On treatment virological response at month 6 of treatment predicted sustained virological response. The results of this study suggest that addition of LAM to IFN for the treatment of delta hepatitis is of no additional value and that both treatment modalities are superior to LAM monotherapy.
Journal of Viral Hepatitis | 2006
N. Aslan; Cihan Yurdaydin; J. Wiegand; T. Greten; A. Ciner; M. F. Meyer; H. Heiken; B. Kuhlmann; T. Kaiser; Hakan Bozkaya; Hans L. Tillmann; A.M. Bozdayi; Michael P. Manns; Heiner Wedemeyer
Summary. CD4+ T cells are thought to contribute to antiviral immune responses by secretion of cytokines thereby providing help to CD8+ T and B cells. However, perforin‐positive cytotoxic CD4+ T cells have been described in human immunodeficiency virus‐positive patients suggesting a role not only of CD8+ but also of CD4+ T cells for killing virus‐infected cells. We investigated 76 patients with viral hepatitis [15 hepatitis B virus (HBV), 22 HBV/hepatitis D virus and 17 hepatitis C virus (HCV)] for cytotoxic CD4+ T cells. The frequency of perforin‐positive CD4+ T cells in viral hepatitis was highly variable ranging from <1% to more than 25%. Perforin‐positive CD4+ T cells displayed the phenotype of terminally differentiated effector cells (CD28−, CD27−). The highest frequencies of CD4+ cytotoxic T lymphocytes (CTLs) were found in patients with delta hepatitis (P = 0.04 vs HBV and HCV patients), and the presence of CD4+ CTLs was associated with elevated aspartate aminotransferase levels (P = 0.01) and decreased platelet counts (P = 0.03). Perforin‐positive CD4+ T cells decreased in two individuals during spontaneous clearance of acute hepatitis C. Significant associations were found between the frequency of perforin‐expressing CD4+ cells and age (P = 0.04), perforin‐positive CD8+ cells (P < 0.001) and perforin‐positive CD4−/CD8− lymphoid cells (P = 0.002). Differentiated CD27− effector CD4+ CTLs can be detected in patients with viral hepatitis. In particular in patients with more advanced liver disease, the accumulation of perforin‐positive T cells with age could be one correlate for the more severe course of viral hepatitis in elderly individuals.
Journal of Hepatology | 2002
Cihan Yurdaydin; Hakan Bozkaya; Selim Gurel; Hans L. Tillmann; N. Aslan; A. Okcu-Heper; Esra Erden; Kendal Yalçin; Nevzat Iliman; Ozden Uzunalimoglu; Michael P. Manns; A. Mithat Bozdayi
BACKGROUND/AIMS Interferon is the only established therapy for chronic delta hepatitis and alternative treatment options are an urgent need. Since successful treatment of a case of post-transplant delta hepatitis with the nucleoside analogue famciclovir had been reported, a pilot study was undertaken to evaluate the use of famciclovir in the treatment of chronic delta hepatitis. METHODS A total of 15 adult patients, 13 men, two women, ages 20-52 years, with chronic delta hepatitis were treated with famciclovir, 500 mg, three times a day for 6 months and were then followed-up for 6 months posttreatment. All patients had compensated chronic liver disease, elevated liver enzymes and were hepatitis delta virus (HDV) RNA positive by polymerase chain reaction at baseline. Patients were monitored and tested for HBsAg, hepatitis B virus (HBV) DNA and HDV RNA levels. Liver biopsies were obtained before starting famciclovir and within 1 month of completion of treatment. RESULTS HBV DNA levels decreased in nine of the 15 patients and levels rose again after treatment (P<0.05). Famciclovir had no effect on alanine aminotransferase (ALT) and HBsAg levels or on serum HDV RNA and overall, there was no improvement in liver histology. CONCLUSIONS Treatment of chronic delta hepatitis with famciclovir has no effect on disease activity and HDV RNA levels.
Liver International | 2010
Kalliopi Zachou; Cihan Yurdaydin; Uta Drebber; George N. Dalekos; A. Erhardt; Yilmaz Cakaloglu; Halil Degertekin; Selim Gurel; Stefan Zeuzem; Hakan Bozkaya; Verena Schlaphoff; Hans Peter Dienes; Thomas Bock; Michael P. Manns; Heiner Wedemeyer
Background: Hepatitis delta virus (HDV) causes severe liver disease.
Journal of Viral Hepatitis | 2010
Cihan Yurdaydin; Ramazan Idilman; Hakan Bozkaya; A.M. Bozdayi
Summary. Chronic delta hepatitis (CDH) represents a severe form of chronic viral hepatitis, induced by the hepatitis delta virus (HDV) in conjunction with the hepatitis B virus (HBV). Delta hepatitis may lead to disease in humans through co‐infection. The former leads to acute hepatitis which clinically can range from mild hepatitis to fulminant hepatitis and death. Severe or fulminant hepatitis is more often observed with HBV‐HDV co‐infection compared to HBV mono‐infection. Chronic infection after acute hepatitis B + D co‐infection is infrequent and similar to the rate in mono‐infected patients. CDH develops in 70–90% of patients with superinfection. CDH runs a more progressive course than chronic hepatitis B and may lead to cirrhosis within 2 years in 10–15% of patients. However, as with any immune‐mediated disease, different patterns of progression, ranging from mild to severe progressive disease, are observed. Active replication of both HBV and HDV may be associated with a more progressive disease pattern. Further, different HDV and HBV genotypes may contribute to various disease outcomes. CDH may be frequently associated with hepatocellular carcinoma development although recent studies provided conflicting results. The only established therapy for CDH is treatment with interferons for a duration of at least 1 year. On treatment, 6 month HDV RNA assessment may give clues as to whether to stop treatment at 1 year or continue beyond 1 year. New approaches to treatment of CDH are an urgent need of which the use of prenylation inhibitors appears the most promising.
Journal of Viral Hepatitis | 2003
A.M. Bozdayi; Ozden Uzunalimoglu; Ahmet R Turkyilmaz; N. Aslan; Sezgin O; Sahin T; Bozdayi G; Kubilay Çinar; Pai Sb; Pai R; Hakan Bozkaya; Selim Karayalcin; Cihan Yurdaydin; Raymond F. Schinazi
Summary. The emergence of drug‐resistant virus in hepatitis B virus (HBV) patients treated with lamivudine is well documented. In this study, we determined the mutations occurring in the tyrosine–methionine–aspartate–aspartate (YMDD) amino acid motif of the HBV DNA polymerase gene, as well as upstream and downstream of this region, in patients with breakthrough virus during lamivudine therapy. Thirty‐one Turkish patients (20 patients HBeAg positive, 11 patients HBeAg negative and anti‐HBe positive) with chronic HBV infection who completed at least 104 weeks of lamivudine treatment were investigated. All patients received lamivudine, (150 mg/day), for 104 weeks, with or without 4 months of interferon (IFN) combination. HBV‐specific sequences were amplified by polymerase chain reaction (PCR) from sera of patients with breakthrough virus, and the PCR products were directly analysed by sequencing. Breakthrough virus was detected in seven of the 31 patients (22.6%) between 9 and 18 months of therapy. Of the seven patients, six were HBeAg positive at baseline, and four had a double mutation consisting of rtM204V and rtL180M, while two had an rtM204I change. In one patient, two base substitutions at rt204 (ATG → AGT; T to G and G to T) lead to a methionine to serine change (YMDD → YSDD). This novel DNA pol mutation was detected at month 18 of lamivudine treatment. In addition, this new variant had the rtL180M mutation and a 12 base pair deletion in the pre‐S1 region between nucleotides 43–54. The YSDD mutation was still present 6 months after lamivudine discontinuation.In vitro transfection studies also confirmed that the YSDD strain is resistant to lamivudine. In conclusion, the results indicate that, in addition to a Met → Val and Met → Ile change in YMDD, a Met → Ser change at rt204 (YMDD → YSDD) associated with the rtL180M change can also emerge during lamivudine treatment, which confers lamivudine resistance in vivo and in vitro, leading to virological breakthrough and ALT increases.
European Journal of Gastroenterology & Hepatology | 2005
Ozlem Erkan; A.M. Bozdayi; Selcuk Disibeyaz; Dilek Oguz; Muhit Ozcan; Kadir Bahar; Selim Karayalcin; Ali Özden; Hakan Bozkaya; Cihan Yurdaydin; Ozden Uzunalimoglu
Objective Thrombophilic gene mutations have been reported to be associated with the formation of portal vein thrombosis (PVT). This study aimed to investigate the role of thrombophilic gene mutations in cirrhotic patients with PVT. Patients and methods A total of 74 cirrhotic patients (17 with PVT, 57 without PVT), and 19 non-cirrhotic patients with PVT and 80 healthy controls were included. Factor V Leiden G1691A, prothrombin G20210A and methylenetetrahydrofolate reductase C677T mutations were analysed by restriction fragment length polymorphism. Results Aetiologies and Child–Pugh distribution of cirrhotic patients with and without PVT were similar. Five of 17 (29%) of cirrhotic patients with PVT but only two of 57 (3.5%) of cirrhotics without PVT, five of 80 (6%) of controls and none of the 19 non-cirrhotic patients with PVT had factor V Leiden G1691A mutation (P<0.05). Prothrombin G20210A mutation was found in five (29%) cirrhotic patients with PVT while only two (3.5%) cirrhotic patients without PVT, one (5%) non-cirrhotic patient with PVT and two (2.5%) controls had this mutation (P<0.05). The frequency of the homozygote methylenetetrahydrofolate reductase 677C-T mutation was similar in all four groups. Conclusions Inherited thrombophilic gene mutations appear to increase the risk of PVT formation in cirrhotic patients but not in patients without liver disease in a cohort of Turkish patients.
Digestive Diseases and Sciences | 2001
Ozden Uzunalimoglu; Cihan Yurdaydin; Hülya Çetinkaya; Hakan Bozkaya; Tülin Sahin; S. Colakoglu; Ethem Tankurt; Mustafa Sarioglu; Seren Ozenirler; Hikmet Akkiz; Nurdan Tozun; Halil Degertekin; Atilla Ökten
The contribution of hepatitis B, hepatitis C, and excess alcohol intake to the development of hepatocellular carcinoma in Turkey was assessed. The study was conducted through a questionnaire sent to seven major medical referral centers in different regions of Turkey and is based on 207 patients seen in the period 1994–1997. Of the seven centers, two were located in West Turkey (54 patients), two were in Central Turkey (85 patients), and two were in south and southeast Turkey (68 patients). In 196 of the 207 patients (94.7%), there was a history of chronic liver disease, and in 180 patients (87%) liver cirrhosis was documented. Of the 207 patients, 116 (56%) had hepatitis B, 48 (23.2%) had hepatitis C, and 33 (15.9%) had a history of excess alcohol intake. Anti-delta testing was available in 69 of 116 patients with hepatitis B, and anti-HDV was positive in 13 of these patients (13/69, 18.8%). Of the 33 patients with a history of heavy alcohol intake, 18 had concomitant chronic viral hepatitis infection, and alcohol alone was the etiology of hepatocellular carcinoma in only 15 cases (7.2%). The distribution of etiologic factors was not homogenous in different geographical regions in Turkey. In central, south, and southeastern Turkey, the predominant etiology of hepatocellular carcinoma was hepatitis B, whereas in western Turkey the impact of hepatitis B, hepatitis C, and alcohol was similar. This study indicates that hepatitis B virus infection is the leading cause of hepatocellular carcinoma in Turkey, followed by hepatitis C infection and alcoholic liver disease.