Chau-Ting Yeh

Hepatitis C Virus Variants Circumventing Cytotoxic T Lymphocyte Activity as a Mechanism of Chronicity

BACKGROUND & AIMS High rate of chronicity after acute hepatitis C virus (HCV) infection cannot be explained in the presence of a multispecific cytotoxic T lymphocyte (CTL) response. The aim of this study was to investigate the effect of virus variants on CTL activity in patients in whom chronicity developed. METHODS CTL clones specific to a decapeptide epitope derived from hypervariable region 1 were generated from 5 HLA-A2-positive patients with acute hepatitis C by in vitro stimulation with synthetic peptides. The sequential change of this CTL epitope and its influence on the CTL recognition were examined. RESULTS Virus variants did not appear in 3 patients with recovery, whereas variants with altered peptide ligands capable of antagonizing CTL activity emerged rapidly in the remaining 2 patients in whom chronicity developed. Importantly, these HLA-A2-restricted, hypervariable region 1-specific CTL clones shared the use of T-cell receptor (TCR) genes AV6 and BV17. CONCLUSIONS These data suggest that there is only a narrow T-cell repertoire responding to a single viral peptide/HLA ligand. The emergence of HCV variants with altered peptide ligands as TCR antagonists accompanied by a limited TCR repertoire may provide a mechanism for HCV chronicity.

Age, gender, and local geographic variations of viral etiology of hepatocellular carcinoma in a hyperendemic area for hepatitis B virus infection

There are etiologic variations of hepatocellular carcinoma (HCC) in different geographic areas. Taiwan is a hyperendemic area for hepatitis B virus (HBV) infection. Hepatitis C virus (HCV) infection also plays an important role in HCC development in Taiwan. Identification of local HCV‐endemic areas is important to keep HCV from spreading. This study investigated the etiologic variations of HCC in different geographic areas of Taiwan.

Prevalence and significance of thyroid autoantibodies in patients with chronic hepatitis C virus infection: a prospective controlled study

To clarify controversies on the prevalence and clinical significance of thyroid autoimmunity in hepatitis C virus (HCV) infection.

Precore Stop Mutant in HBeAg-Positive Patients with Chronic Hepatitis B: Clinical Characteristics and Correlation with the Course of HBeAg-to-Anti-HBe Seroconversion

ABSTRACT This study aimed to investigate the ratios of precore stop mutant (codon 28; TGG to TAG) to total viremia in 53 HBeAg-positive patients with chronic hepatitis B by amplification-created restriction site assays along the course of HBeAg-to-anti-HBe seroconversion. At baseline, 11% had exclusive wild-type hepatitis B virus (HBV), 15% had exclusively precore mutant, and 74% had mixed viral strains. Precore mutant ratios correlated little with age, sex, or HBV DNA levels (all P > 0.1), but correlated modestly with alanine aminotransferase (ALT) levels (P = 0.05). The intervals from presentation to anti-HBe seroconversion correlated significantly with ALT and precore mutant ratios in univariate analysis but with only precore mutant ratios in multivariate analysis (P = 0.003). Precore mutant ratios at baseline were significantly higher (P < 0.001) in six patients with persistent high viremia and ALT elevation after anti-HBe seroconversion (group 1) than in 47 with remission (group 2). All group 1 patients had exclusive precore mutant after anti-HBe seroconversion, as did only 14 (30%) of the group 2 patients (P = 0.003). Among group 2 patients, precore mutant ratios at baseline or after anti-HBe seroconversion showed no significant difference between 34 patients with sustained remission and 13 with relapse. Cirrhosis developed in 50% (5 of 10) of patients with precore mutant ratios >50% at baseline but only in 12% (5 of 43) of those with precore mutant ratios of <50% at baseline (P < 0.05). In conclusion, precore mutant of variable ratios was frequently detected in HBeAg-positive patients with chronic hepatitis B. Precore mutant ratios tended to correlate with ALT levels and anti-HBe seroconversion, but high precore mutant ratios were associated with persistent hepatitis after anti-HBe seroconversion and increased risk of cirrhosis.

IMPACT OF ACUTE HEPATITIS B VIRUS SUPERINFECTION ON CHRONIC HEPATITIS C VIRUS INFECTION

Hepatitis B virus (HBV) and hepatitis C virus (HCV) dual infection is not uncommon, but the impact of acute HBV superinfection in patients with chronic HCV infection is still unknown. Two patients with well documented chronic HCV infection were hospitalized for acute hepatitis, which was serologically confirmed to be acute HBV superinfection. One patient who was seropositive for both HBV-DNA and HCV-RNA upon admission died of hepatic failure. The other became seronegative for HCV-RNA and recovered with alanine aminotransferase normalization, seroclearance of HBsAg, and antibodies to HCV. These findings confirm that acute superinfection in patients with chronic hepatitis may increase the risk for severe hepatitis, and suggest that HBV as the newcomer may suppress the pre-existing HCV. Together with the earlier observation that acute HCV superinfection suppresses pre-existing HBV, it seems that the timing or sequence of infection is a factor influencing the outcome of viral interactions.

Detection and partial sequence analysis of Helicobacter pylori DNA in the bile samples

The existence ofhelicobacter pylori in the biliary tract was investigated. Seven bile samples were included in this study. Among them, six bile samples were collected by percutaneous transhepatic cholangiodrainage and the other by needle aspiration during cholecystectomy. Using nested PCR with two sets of primers homologous to the urease A gene,Helicobacter pylori DNA was detected. Three samples, one from a patient with advanced gastric cancer involving the pancreatic head and two from patients with pancreatic head tumor, were found to be positive forHelicobacter pylori DNA. On the other hand, three samples from patients with cholangiocarcinoma and one from a patient with chronic cholecystitis were all negative. To further verify the specificity of our PCR analysis, partial sequences of the PCR products from the three positive samples were analyzed by direct sequencing. Several silent mutations and a missense mutation (AAA to AGA; Lys-164 to Arg-164) were identified in the urease A gene. We conclude thatHelicobacter pylori DNA can be easily detected in the bile samples. The possibility of asymptomatic cholangitis caused by this organism requires further investigation.

Purification and characterization of a naturally processed hepatitis B virus peptide recognized by CD8+ cytotoxic T lymphocytes.

In vitro studies in patients with hepatitis B virus (HBV) infection have suggested that hepatocytolysis induced by CD8+ cytotoxic T lymphocytes (CTLs) is the most important effector pathway in eliminating infected cells. The recognition is implicated in the endogenously processed HBV antigens in the context of HLA class I molecules presented on the liver cell membrane. However, the naturally occurring HBV peptide antigens have not yet been demonstrated. We report here that a naturally processed peptide antigen P2 was isolated from HLA class I molecules of HBV-infected liver cell membrane. The P2 peptide exhibited the activity of sensitizing target cells for lysis by CD8+ CTLs. The P2 sequence (YVNVNMGLK) purified from liver tissue was in concordance with that encoded by the viral genome for the HBV nucleocapsid antigen or HBcAg 88-96. P2 peptide could also be isolated from the EBV-transformed B cells that were transfected by HBcAg-expressing vector. The P2 epitope, sharing the HLA-A11 binding motifs, was recognized by HLA-A11-restricted CD8+ CTLs. The data provided direct evidence that, in hepatitis B patients, antigenic peptides of HBV were processed by hepatocytes, presented with the class I MHC molecules, and recognized by CD8+ CTLs.

Tumor-Derived Chemokine CCL5 Enhances TGF-β–Mediated Killing of CD8+ T Cells in Colon Cancer by T-Regulatory Cells

Chemokine CCL5/RANTES is highly expressed in cancer where it contributes to inflammation and malignant progression. In this study, we show that CCL5 plays a critical role in immune escape in colorectal cancer. We found that higher levels of CCL5 expression in human and murine colon tumor cells correlated with higher levels of apoptosis of CD8+ T cells and infiltration of T-regulatory cells (T(reg)). In mouse cells, RNA interference (RNAi)-mediated knockdown of CCL5 delayed tumor growth in immunocompetent syngeneic hosts but had no effect on tumor growth in immunodeficient hosts. Reduced tumor growth was correlated with a reduction in T(reg) infiltration and CD8(+) T-cell apoptosis in tumors. Notably, we found that CCL5 enhanced the cytotoxicity of T(reg) against CD8(+) T cells. We also found tumor growth to be diminished in mice lacking CCR5, a CCL5 receptor, where a similar decrease in both T(reg) cell infiltration and CD8(+) T-cell apoptosis was noted. TGF-β signaling blockade diminished apoptosis of CD8(+) T cells, implicating TGF-β as an effector of CCL5 action. In support of this concept, CCL5 failed to enhance the production of TGF-β by CCR5-deficient T(reg) or to enhance their cytotoxic effects against CD8(+) T cells. CCR5 signaling blockade also diminished the in vivo suppressive capacity of T(reg) in inhibiting the antitumor responses of CD8(+) T cells, in the same way as CCL5 signaling blockade. Together, our findings establish that CCL5/CCR5 signaling recruits T(reg) to tumors and enhances their ability to kill antitumor CD8(+) T cells, thereby defining a novel mechanism of immune escape in colorectal cancer.

Subcellular localization of hepatitis B core antigen in relation to hepatocyte regeneration in chronic hepatitis B

BACKGROUND & AIMS To test whether the dominant cytoplasmic expression of hepatitis B core antigen (HBcAg) in active chronic hepatitis B is secondary to liver damage and regeneration, the relationship between subcellular localization of HBcAg, liver inflammatory activity, and hepatocyte regeneration in chronic hepatitis B was studied. METHODS Correlation of the clinical and laboratory data with the topographical distribution of HBcAg was studied in 30 patients. The subcellular localization of HBcAg in relation to hepatocyte cell cycles was studied by double immunostaining of HBcAg and proliferating cell nuclear antigen. RESULTS Patients with predominant cytoplasmic HBcAg had significantly higher levels of biochemical and histological activities and proliferating cell nuclear antigen expression than patients with predominant nuclear HBcAg. The levels of proliferating cell nuclear antigen expression correlated positively with biochemical and histological activities and degrees of cytoplasmic HBcAg expression but negatively with degrees of nuclear HbcAg expression. Proliferating cell nuclear antigen expression was shown in 49% of hepatocytes with cytoplasmic HBcAg but in only 2% of hepatocytes with nuclear HBcAg. CONCLUSIONS These findings suggested that, following liver damage, the regeneration of surviving hepatocytes might cause the shift of intracellular HBcAg from nucleus to cytoplasm. As a result, the extent of nuclear HBcAg expression reduces with concomitant increase in cytoplasmic HBcAg expression.

Identification and characterization of a prevalent hepatitis B virus X protein mutant in Taiwanese patients with hepatocellular carcinoma

The aim of this study was to investigate whether there was a particular hepatitis B virus (HBV) X protein (HBx) mutant associated with Taiwanese patients with hepatocellular carcinoma (HCC). Initially, the entire coding region of HBx gene from the serum samples of 14 Taiwanese patients were sequenced. A novel mutant, HBx-A31, was preferentially found in patients with HCC. Sera from 67 patients with HCC and 100 patients with chronic hepatitis B were thus subjected for codon 31 analysis using a dual amplification created restriction site method. HBx-A31 was detected more frequently in patients with HCC (52% versus 12%; P<0.001) and in patients with liver cirrhosis (44% versus 6%; P<0.001). Site directed mutagenesis experiment revealed that HBx-A31 was less effective in transactivating HBV enhancer I-X promoter complex, less efficient in supporting HBV replication, and less potent in enhancing TNF-α induced increment of CPP32/caspase 3 activities in HepG2 cells. In conclusion, a prevalent HBx mutant was identified in Taiwanese patients with hepatocellular carcinoma. Development of this mutant might represent a strategy of the virus to escape immune surveillance and thus contribute to the process of multiple-step hepatocarcinogenesis.