The regulation of oxytocin and oxytocin receptor in human placenta according to gestational age.

Oxytocin (OXT) is a peptide hormone that plays a central role in the regulation of parturition and lactation. OXT signaling is mediated by OXT receptor (OXTR), which shows species- and tissue-specific expressions and gene regulation. In the present study, we examined the synthesis of OXT and OXTR in human placenta tissue according to gestational age. A total of 48 placentas were divided into early preterm, late preterm and term groups depending on gestational age, and expression of OXT and OXTR was evaluated. First, OXT and OXTR mRNA and protein were detected in normal placenta tissue via Q-PCR, Dot-blot and Western blot assay. Both OXT and OXTR levels in normal placenta increased gradually in the late stage of pregnancy, suggesting that local OXT may play a critical role in the function of the placenta. To determine the regulatory mechanism of OXT, placental BeWo cells were administrated estrogen (E2) or progesterone (P4), and expression of OXT and OXTR was tested. The mRNA and protein levels of OXT and OXTR were upregulated by E2 but blocked by co-treatment with P4 In order to confirm the estrogen receptor (ESR)-mediated signaling, we administrated ESR antagonists together with E2 to BeWo cells. As a result, both OXT and OXTR were significantly altered by ESR1 antagonist (MPP) while moderately regulated by ESR2 antagonist (PHTPP). These results suggest that OXT and OXTR are controlled mainly by E2 in the placenta via ESR1 and thus may play physiological functions in the human placenta during the late stage of pregnancy.

Expression of reproductive hormone receptors and contraction­associated genes in porcine uterus during the estrous cycle.

Contraction of uterus tissue frequently occurs throughout the estrous cycle and is regulated by several endogenous factors, including estradiol, progesterone, luteinizing hormone, follicle­stimulating hormone, oxytocin (OXT) and contraction­associated proteins (CAPs). Contraction activity of uterus tissue according to the estrous cycle is important, due to the fact that it is directly associated with balanced implantation and stable pregnancy. However, few studies have examined the mechanism of uterus contraction activity in a porcine model. In the current study, porcine uterus tissue was separated into the follicular and luteal phases by histological analysis. To investigate regulation of contraction­associated factors according to the estrous cycle, mRNA and protein expression levels of reproductive hormonal receptors, including estrogen receptors, progesterone receptor and luteinizing hormone/choriogonadotropin receptor in addition to CAPs including OXT, OXT receptor (OXTR), hydroxyprostaglandin dehydrogenase 15­(NAD) and gap junction α­1 protein, were examined in the porcine uterus according to the follicular and luteal phases. For the results, hormonal receptors and CAPs were dynamically regulated depending on the estrous cycle. In conclusion, genes associated with uterine contraction and its regulatory hormonal receptors in the porcine uterus were differently regulated in the follicular and luteal phases, suggesting that these genes are critically involved in the remodeling and contraction of uterine tissue and may be required to modulate the physiological status of the uterus.

Clinical outcomes of three- or five-day treatment with clomiphene citrate combined with gonadotropins and a timed intercourse cycle in polycystic ovary syndrome patients.

OBJECTIVE: This study aimed to investigate the effect of a new clomiphene citrate (CC) regimen on preventing thin endometrial lining in polycystic ovary syndrome (PCOS) patients receiving CC plus gonadotropin treatment with a timed intercourse cycle. METHODS: A total of 114 women with PCOS were included in this trial. Patients were divided into two groups and treated in accordance with the controlled ovarian stimulation (COS) protocol. In group A, 104 COS cycles in 67 patients were included, and in each cycle 150 mg CC was given for three days, starting from day 3. In group B, 69 COS cycles in 47 patients were included, in which 100 mg CC was given for five days, starting from day 3. The thickness of the endometrium was measured on the day of human chorionic gonadotropin (hCG) injection. Timed intercourse was recommended at 24 and 48 hours after the hCG injection. RESULTS: Additional doses of human menopausal gonadotropin and the number of days of hCG administration were not significantly different between the two groups. Endometrial thickness on the day of hCG administration was significantly larger in group A than group B (9.4±2.1 mm vs. 8.5±1.7 mm, p=0.004). The pregnancy rate was significantly higher in group A than in group B (38.4% vs. 21.7%, p=0.030). CONCLUSION: Three-day CC treatment resulted in a significantly higher pregnancy rate than the standard five-day CC treatment in a timed intercourse cycle in PCOS patients. Facilitating adequate endometrial growth via the early discontinuation of CC might be a crucial factor in achieving a higher pregnancy rate.

Ovarian Cavernous Hemangioma Presenting as a Large Growing Mass in a Postmenopausal Woman: A Case Report and Review of the Literature.

Ovarian hemangiomas are usually of the cavernous type, and are rarely encountered. A 73-year-old woman presented with lower abdominal discomfort. Subsequent physical examination depicted a palpable mass in the lower abdomen. Abdominopelvic computed tomography (CT) revealed a well-circumscribed mass with thin septa measuring 12.1 × 9.0 cm in the right ovary. Levels of the tumor markers cancer antigen (CA)-125 and CA 19-9 were within the normal range. At laparoscopy, the tumor was found to be confined to the right ovary and to have a smooth surface. The final histopathological result was ovarian cavernous hemangioma. Microscopically, the mass consisted of multiple, dilated, blood-filled vascular channels separated by loose connective tissue, and all were lined by a single layer of flattened endothelium. The authors present a case of ovarian cavernous hemangioma presenting as a large growing mass in a postmenopausal woman and review previously published literature.

Clinicopathological significance of atypical glandular cells on Pap smear.

OBJECTIVE: To investigate the clinical significance of atypical glandular cells (AGC) by analyzing the prevalence and histologic outcomes of patients with AGC according to Pap smear. METHODS: The medical records of 83 patients who were diagnosed AGC on Pap tests at the Pusan National University Hospital outpatient department and health care center from January 1998 to March 2006 were reviewed. RESULTS: The prevalence of AGC was 55 of 54,160 (0.10%) and 28 of 54,160 (0.05%) for AGC-not otherwise specified (NOS) and neoplastic associated AGC, respectively. The histopathologic results of the AGC-NOS group (n=55) were as follows: low-grade squamous intraepithelial lesion, 7 (12.7%); high-grade squamous intraepithelial lesion, 4 (7.2%); adenocarcinoma of cervix, 3 (5.4%); endometrial carcinoma, 2 (3.6%); and other malignancies including 2 ovarian cancer cases and 1 breast cancer case, 3 (5.4%). The histopathologic results for the AGC-associated neoplastic group (n=28) were as follows: low-grade squamous intraepithelial lesion, 1 (3.5%); high-grade squamous intraepithelial lesion, 3 (10.7%); adenocarcinoma of cervix, 5 (17.8%); endometrial carcinoma, 4 (4.8%); and additional malignancies including 3 stomach cancer cases, 2 ovarian cancer cases, and 2 breast cancer cases; 7 (25%). CONCLUSION: AGCs may represent a variety of benign and malignant lesions. AGC-associated neoplastic findings may be related to gynecological or extrauterine malignancies. Thus, when AGCs, especially neoplastic AGCs, are encountered, it is best to evaluate the cervix not only for typical maladies, but also for gynecological and non-gynecological malignancies.

A functional genomic screen identifies cellular cofactors of hepatitis C virus replication.

Hepatitis C virus (HCV) chronically infects 3% of the world's population, and complications from HCV are the leading indication for liver transplantation. Given the need for better anti-HCV therapies, one strategy is to identify and target cellular cofactors of the virus lifecycle. Using a genome-wide siRNA library, we identified 96 human genes that support HCV replication, with a significant number of them being involved in vesicle organization and biogenesis. Phosphatidylinositol 4-kinase PI4KA and multiple subunits of the COPI vesicle coat complex were among the genes identified. Consistent with this, pharmacologic inhibitors of COPI and PI4KA blocked HCV replication. Targeting hepcidin, a peptide critical for iron homeostasis, also affected HCV replication, which may explain the known dysregulation of iron homeostasis in HCV infection. The host cofactors for HCV replication identified in this study should serve as a useful resource in delineating new targets for anti-HCV therapies.

HIV increases HCV replication in a TGF-beta1-dependent manner.

BACKGROUND & AIMS: Human immunodeficiency virus (HIV) coinfection increases hepatitis C virus (HCV)-related progression of hepatic fibrosis, increases HCV persistence, and decreases response rates to interferon-based anti-HCV therapy. It has remained unclear how HIV, a nonhepatotropic virus, accelerates the progression of liver disease by HCV. METHODS: We explored the possibility that circulating HIV and/or its proteins contribute to the pathogenesis of HCV through engagement of extracellular coreceptors on hepatocytes. RESULTS: In this study, we found that inactivated HIV or gp120 increases HCV replication and enhances HCV-regulated transforming growth factor (TGF)-beta1 expression in both a replicon and an infectious model of HCV. This proviral effect of HIV and gp120 on HCV replication is neutralized by antibodies to CCR5 or CXCR4. However, HIV and gp120 did not alter type I interferon-mediated signaling in these HCV models, indicating that HIV regulates HCV replication through an alternative mechanism. Interestingly, we found that human TGF-beta1 also enhanced HCV replication. The effect of HIV on HCV replication was blocked by a neutralizing antibody to TGF-beta1, indicating that its effects on HCV replication are TGF-beta1 dependent. CONCLUSIONS: These results suggest a novel mechanism by which HIV not only enhances HCV replication but also contributes to progression of hepatic fibrosis.

Identification of novel epoxide inhibitors of hepatitis C virus replication using a high-throughput screen.

Using our high-throughput hepatitis C replicon assay to screen a library of over 8,000 novel diversity-oriented synthesis (DOS) compounds, we identified several novel compounds that regulate hepatitis C virus (HCV) replication, including two libraries of epoxides that inhibit HCV replication (best 50% effective concentration, < 0.5 microM). We then synthesized an analog of these compounds with optimized activity.

A cell-based, high-throughput screen for small molecule regulators of hepatitis C virus replication.

BACKGROUND & AIMS: Only half of patients with chronic hepatitis C virus (HCV) infection experience sustained virologic response to pegylated-interferon and ribavirin, which cause numerous side effects. Thus, the identification of more effective and better tolerated agents is a high priority. We applied chemical biology to screen small molecules that regulate HCV. METHODS: We first optimized the Huh7/Rep-Feo replicon cell line for the 384-well microplate format and used this line to screen a large library of well-characterized, known biologically active compounds using automated technology. After identifying several molecules capable of either stimulating or inhibiting HCV replication in this primary screen, we then validated our hit compounds using a full-length HCV replicon cell line in secondary screens. RESULTS: We identified and validated a number of antiviral and proviral agents, including HMG-CoA reductase inhibitors (antiviral) and corticosteroids (proviral). The finding of increased replication associated with corticosteroids suggests that these agents directly promote viral replication independent of their suppressive effects on the immune response. The finding of antiviral activity associated with the HMG-CoA reductase inhibitors implies an important role for lipid metabolism in the viral life cycle. CONCLUSIONS: We have developed a simple, reproducible, and reliable cell-based high-throughput screening assay system using an HCV replicon model to identify small molecules that regulate HCV replication. This method can be used to identify not only putative antiviral agents, but also cellular regulators of viral replication.

Hepatitis C virus core protein blocks interferon signaling by interaction with the STAT1 SH2 domain.

Emerging data have indicated that hepatitis C virus (HCV) subverts the host antiviral response to ensure its persistence. We previously demonstrated that HCV protein expression suppresses type I interferon (IFN) signaling by leading to the reduction of phosphorylated STAT1 (P-STAT1). We also demonstrated that HCV core protein directly bound to STAT1. However, the detailed mechanisms by which HCV core protein impacts IFN signaling components have not been fully clarified. In this report, we show that the STAT1 interaction domain resides in the N-terminal portion of HCV core (amino acids [aa] 1 to 23). This domain is also required to produce P-STAT1 reduction and inhibit IFN signaling transduction. Conversely, the C-terminal region of STAT1, specifically the SH2 domain (aa 577 to 684), is required for the interaction of HCV core with STAT1. The STAT1 SH2 domain is critical for STAT1 hetero- or homodimerization. We propose a model by which the binding of HCV core to STAT1 results in decreased P-STAT, blocked STAT1 heterodimerization to STAT2, and, therefore, reduced IFN-stimulated gene factor-3 binding to DNA and disrupted IFN-stimulated gene transcription.

Systemic chemotherapy with doxorubicin, cisplatin and capecitabine for metastatic hepatocellular carcinoma.

BACKGROUND: Although numerous chemotherapeutic agents have been tested, the role of systemic chemotherapy for hepatocellular carcinoma (HCC) has not been clarified. New therapeutic strategies are thus needed to improve outcomes, and we designed this study with new effective drug combination. METHODS: Twenty-nine patients with histologically-confirmed, metastatic HCC received a combination chemotherapy with doxorubicin 60 mg/m2 and cisplatin 60 mg/m2 on day 1, plus capecitabine 2000 mg/m2/day as an intermittent regimen of 2 weeks of treatment followed by a 1-week rest. RESULTS: The median age was 49 years (range, 32-64) and 19 patients were hepatitis B virus seropositive. Child-Pugh class was A in all patients and 4 had Zubrod performance status of 2. The objective response rate was 24% (95% CI 9-40) with 6 stable diseases. The chemotherapy was generally well tolerated despite one treatment-related death. CONCLUSION: Combination chemotherapy with doxorubicin, cisplatin and capecitabine produced modest antitumor activity with tolerable adverse effects in patients with metastatic HCC.

Thalidomide for treating metastatic hepatocellular carcinoma: a pilot study.

BACKGROUND: Thalidomide has been reported to have antitumor activity for treating metastatic hepatocellular carcinoma (HCC). We evaluated the safety and efficacy of using thalidomide for treating selected patients with unresectable or metastatic HCC, and their disease was refractory to systemic chemotherapy. METHODS: Eight patients with measurable and metastatic HCC that had progressed with prior systemic chemotherapy and who desired further active therapy were enrolled in this study. Thalidomide was given orally at bedtime and it was started at 200 mg/day with no further dose escalation. The response was measured at 2-month intervals. RESULTS: The median age was 44 years (range: 34-52 years) and all the patients had received doxorubicin-based systemic chemotherapy prior to their enrollment. Each patient received thalidomide for a median of 152 days (range: 5-422 days). One partial response was observed (12.5%, 95% CI; 0-42%) along with 4 cases of stable diseases. The most commonly encountered toxicity was somnolence; grade 3 somnolence was noted for one patient, which led to treatment discontinuation. Skin rash was observed in one responding patient. CONCLUSIONS: The results indicate that thalidomide may feasibly offer disease stabilization to metastatic HCC patients. Further dose escalation of thalidomide, or its combination with other chemotherapeutic agents, may be of interest and this should be investigated for treating patients with metastatic HCC.

[A case of colon obstruction developed during the recovery period of acute pancreatitis].

Complications of acute pancreatitis usually occur in pancreas and its contiguous organs. The prevalence of colonic invasion is rare, however, the consequence is fatal, with mortality above 50%. The initial symptoms and onset times are variable and major affected sites are transverse colon and splenic flexure. The spread of inflammatory exudates into the colon is the main mechanism of colonic invasion. If the colonic stenosis develops, it is necessary to manage it surgically. We report a case who arrived at the hospital with watery diarrhea and abdominal distension in the recovery period of acute alcoholic pancreatitis and was diagnosed as a colonic obstruction in the splenic flexure. The patient underwent loop ileostomy instead of the resection of the lesion because of severe adhesion around the splenic flexure. The patient died due to sepsis 5 days after the operation.

Acute exacerbation of chronic hepatitis B during thalidomide therapy for multiple myeloma: a case report.

We report a case of acute fatal exacerbation of chronic hepatitis B in a 50-year-old man with multiple myeloma being treated with thalidomide. The patient had a medical history of chronic hepatitis B and was diagnosed with stage IIIA multiple myeloma. He suffered two episodes of transient transaminitis of unknown origin after successive autologous stem cell transplantations. Spontaneous resolutions of the transaminitis were observed without special management. At that time, PCR of hepatitis B virus (HBV) were all-negative. After 5-months' administration of thalidomide for the second relapse of the multiple myeloma, he suddenly experienced dizziness and jaundice. The level of HBV DNA was 1,641 pg/mL and the serologic tests for other viruses were negative. Despite conventional supportive care, he expired due to septic shock caused by Klebsiella pneumonia. Based on the stable disease status of the multiple myeloma and exclusion of other hepatotoxic agents, it was assumed that the exacerbation of the hepatitis B virus during the thalidomide therapy preceded the bacterial sepsis. With the increased use of thalidomide in cancer treatment, cautious monitoring of the viral burden should be performed in patients with chronic hepatitis B.

Styrylquinazolines: a new class of inhibitors on prostaglandin E2 production in lipopolysaccharide-activated macrophage cells.

A series of styrylquinazoline derivatives (2a-k) were prepared and evaluated for their inhibiton of prostaglandin E(2) (PGE(2)) production by cyclooxygenase-2 (COX-2). The latter was induced by lipopolysaccharide-stimulated macrophage cells RAW264.7. 3', 4'-Dihydroxylated styrylquinazolines (2a-c), 3'-hydroxylated styrylquinazolines (2h, 2i), and 3'-acetoxy-styrylquinazolines (2j, 2k) exhibited good inhibitory effects of PGE(2) production by COX-2 with a range of IC(50) values of 1.19 approximately 3.56 microM. The potencies were comparable or better than that of the representative stilbene resveratrol (IC(50) = 3.07 microM). These results indicate that styrylquinazolines can be considered as potential resveratrol analogues in the modulation of prostaglandin production by COX-2.

[Helicobacter pylori infection in the remnant stomach after radical subtotal gastrectomy].

BACKGROUND/AIMS: It was reported that the prevalence of Helicobacter pylori (H. pylori) infection decreased after gastrectomy, but persistent H. pylori infection may cause residual gastritis or stump cancer. We studied the prevalence of H. pylori infection in patients who had undergone subtotal gastrectomy for the treatment of gastric cancer and the factors that influence H. pylori positivity in the remnant stomach. METHODS: Ninety-eight patients who had undergone radical subtotal gastrectomy (RSG group) for the treatment of gastric cancer and eighty-four patients diagnosed as having gastric cancer (GC group) were enrolled. H. pylori status was diagnosed by rapid urease test, histological examination, and 13C-urea breath test. We evaluated whether there were differences in various clinical characteristics according to the H. pylori status in the remnant stomach. RESULTS: The prevalences of H. pylori infection in RSG group and GC group were 55% and 69%, respectively. In RSG group, the prevalence of H. pylori was 76.9% in patients aged 49 or less, and it decreased with age. The prevalence of H. pylori within 3 years of gastrectomy was 59.5% and it decreased to 28.6% after 3 years of gastrectomy. CONCLUSIONS: The positive rate of H. pylori in RSG group is lower than that in GC group and decreases with age and time interval after operation.

[Polymorphism in codons 10 and 25 of the transforming growth factor-beta1 gene in Korean population and in patients with liver cirrhosis and hepatocellular carcinoma].

BACKGROUND/AIMS: The genetic polymorphism of transforming growth factor-beta1 (TGF-beta1) at codons 10 and 25 which influences the production of TGF-beta1 is related to fibrogenesis in the lung and liver. We evaluated the genetic polymorphism at codons 10 and 25 in controls and in patients with liver cirrhosis (LC) and hepatocellular carcinoma (HCC). METHODS: Blood samples were collected from controls (n=35), patients with LC (n=64), and HCC (n=49). Genomic DNA was isolated and polymerase chain reaction (PCR) was done for a segment including codons 10 and 25. The results of direct sequencing for PCR products were compared between the controls and the patients. RESULTS: There was no genetic polymorphism at codon 25 and three types of genetic polymorphism at codon 10. The leucine homozygous genotype (CTG/CTG) at codon 10 was more common in patients with LC than the controls (p=0.01) and especially in patients with LC caused by HBV (p=0.004). The polymorphism at codons 10 in patients with HCC was similar to the controls. However, leucine homozygous genotype was more common in patients with HCC of uninodular morphology than those of massive morphology (p=0.007). CONCLUSIONS: The genetic polymorphism of TGF-beta1 at codon 10 might be associated with LC and morphology of HCC. The potential usefulness of TGF-beta1 genotyping needs further studies in large scale.

[Clinical usefulness of plasma activities of gelatinase (matrix metalloproteinase-2 and 9) in chronic liver disease].

BACKGROUND/AIMS: Gelatinase (matrix metalloproteinase (MMP) -2 and 9) has an important role in the pathogenesis of liver cirrhosis (LC) and hepatocellular carcinoma (HCC). In this study, we evaluated the relationship of gelatinase to chronic liver disease. METHODS: Four groups of subjects were examined; healthy control (10 cases), chronic hepatitis (18 cases), LC (15 cases), and HCC (28 cases). The plasma of each subject was obtained, and the equal quantification of plasma protein was done. The plasma activities of MMP-2 and 9 were measured by zymography. RESULTS: The activities of plasma MMP-2 in patients with LC were significantly higher than those in controls (p=0.009) and in patients with chronic hepatitis (p=0.011), but not different from those in patients with HCC. The activities of plasma MMP-9 in patients with LC were significantly higher than those in controls, but not different from those in patients with chronic hepatitis or HCC. In patients with LC (regardless of having HCC), the activities of MMP-2 correlated with total bilirubin (r=0.323, p=0.048) and Child-Pugh score (r=0.414, p=0.012). The activities of MMP-2 and 9 were higher in patients with LC (regardless of having HCC) caused by alcohol than caused by HBV (p=0.009 and 0.002 for each one). CONCLUSIONS: The plasma activity of MMP-2 may be a useful marker for the diagnosis and determination of the severity of LC. The plasma activity of MMP-9 was not useful for HCC, but may be a marker for alcoholic LC. Further study is needed to determine why the plasma activity of gelatinase was higher in patients with LC caused by alcohol than by HBV.

Eugenol suppresses cyclooxygenase-2 expression in lipopolysaccharide-stimulated mouse macrophage RAW264.7 cells.

Inducible cyclooxygenase (COX-2) has been implicated in the processes of inflammation and carcinogenesis. Thus, the potential COX-2 inhibitors have been considered as anti-inflammatory or cancer chemopreventive agents. In this study, the methanolic extract of the cortex of Eugenia caryophyllata Thunberg (Myrtaceae) was found to potently inhibit the prostaglandin E(2) production in lipopolysaccharide (LPS)-activated mouse macrophage RAW264.7 cells (98.3% inhibition at the test concentration of 10 microg/ml). Further, hexane-soluble layer was the most active partition compared to ethyl acetate, n-butanol, and water-soluble parts. By bioassay-guided fractionation of hexane-soluble partition, eugenol was isolated and exhibited a significant inhibition of PGE(2) production (IC(50) = 0.37 microM). In addition, eugenol suppressed the cyclooxygenase-2 (COX-2) gene expression in LPS-stimulated mouse macrophage cells. On the line of COX-2 playing an important role in colon carcinogenesis further study was designed to investigate the effect of eugenol on the growth and COX-2 expression in HT-29 human colon cancer cells. Eugenol inhibited the proliferation of HT-29 cells and the mRNA expression of COX-2, but not COX-1. This result suggests that eugenol might be a plausible lead candidate for further developing the COX-2 inhibitor as an anti-inflammatory or cancer chemopreventive agent.

[Viral breakthrough in HBeAg-negative chronic hepatitis B patients receiving lamivudine therapy].

BACKGROUND/AIMS: Long-term efficacy and the rate of viral breakthrough in patients with HBeAg- negative chronic hepatitis B receiving lamivudine therapy is uncertain. This study was conducted to determine the rate of viral breakthrough according to the HBeAg status and the relation of viral breakthrough with YMDD mutants. METHODS: Two hundred and five patients with HBeAg-positive and 49 patients with HBeAg-negative chronic hepatitis B, who had received lamivudine for at least 9 months, were included. The mean durations of the lamivudine treatment were 176 months and 155 months in HBeAg-positive and negative patients, respectively. Analysis of HBV genome for YMDD mutations was performed by restriction-fragment-length polymorphism assay and direct sequencing. RESULTS: While the cumulative rates of viral breakthrough at 12th and 24th months of the lamivudine therapy were 0% and 7% in the HBeAg-negative group, they were 12% and 39% in the HBeAg-positive group. The cumulative rate of viral breakthrough in the HBeAg-negative group was significantly lower than in the HBeAg-positive group (p<0.01). In multivariate analysis, the only significant factor related to viral breakthrough was the HBeAg status (p<0.05). The YMDD mutants were detected in all patients with viral breakthrough irrespective of HBeAg status. However, in patients without viral breakthrough, the rate of YMDD mutants was significantly higher in the HBeAg-negative group than in the HBeAg-positive group (13.3% vs 5.1%; p<0.01). CONCLUSIONS: Lamivudine is expected to be more persistently effective in HBeAg-negative chronic hepatitis B because of a lower viral breakthrough rate than in HBeAg-positive chronic hepatitis B in spite of the emergence of YMDD mutants.