In vitro resistance to interferon of hepatitis B virus with precore mutation

AIM: Chronic hepatitis B virus (HBV) infection is predominantly treated with interferon alpha (IFN-α), which results in an efficient reduction of the viral load only in 20-40% of treated patients. Mutations at HBV precore prevail in different clinical status of HBV infection. The roles of precore mutation in the progression of chronic hepatitis and interferon sensitivity are still unknown. The aim of this study was to explore if there was any relationship between HBV precore mutation and sensitivity to interferon in vitro. METHODS: HBV replication-competent recombinant constructs with different patterns of precore mutations were developed. Then the recombinants were transiently transfected into hepatoma cell line (Huh7) by calcium phosphate transfection method. With or without IFN, viral products in culture medium were collected and quantified 3 d after transfection. RESULTS: We obtained 4 recombinant constructs by orientation-cloning 1.2-fold-overlength HBV genome into pUC18 vector via the EcoRI and Hind lll and PCR mediated site-directed mutagenesis method. All the recombinants contained mutations within precore region. Huh7 cells transfected with recombinants secreted HBsAg and HBV particles into the cell culture medium, indicating that all the recombinants were replication-competent. By comparing the amount of HBV DNA in the medium, we found that HBV DNA in medium reflecting HBV replication efficiency was different in different recombinants. Recombinants containing precore mutation had fewer HBV DNAs in culture medium than wild type. This result: showed that recombinants containing precore mutation had lower replication efficiency than wild type. HBV DNA was decreased in pUC18-HBV1.2-WT recombinants after IFN was added while others with precore mutations were not, indicating that HBV harboring precore mutation was less sensitive to IFN in cell culture system. CONCLUSION: These data indicate that HBV harboring precore mutation may be resistant to IFN in vitro.

Relationship of human leukocyte antigen class II genes with the susceptibility to hepatitis B virus infection and the response to interferon in HBV-infected patients

AIM： To study the relationship of human leukocyte antigen （HLA）-DRB1 and -DQB1 alleles with the genetic susceptibility to HBV infection and the response to interferon （IFN） in HBV-infected patients. METHODS： Low-resolution DNA typing kit was used to determine HLA-DR-1 and -DQB1 genes in 72 patients with chronic hepatitis B （CHB） and HLA-DRB1 in 200 healthy people ready to donate their bone marrow in Shanghai. Among CHB patients, 35 were treated with IFNα-1b for 24 wk. RESULTS： The frequencies of HLA-DRBI＊06, DRBI＊08 and DRB1＊16 alleles in 72 patients were higher than in 200 healthy people （2.08% vs0%, OR = 3.837, P= 0.018; 11.11% vs5.50%, OR = 2.148, P= 0.034; and 6.94% vs 3.00%, OR = 0.625, P = 0.049, respectively）; whereas that of DRBI＊07 allele was lower （2.78% vs 7.75%, OR = 0.340, P= 0.046）. The frequency of HLA-DRBI＊ 14 allele was higher in 11 responders to IFN compared with 24 non-responders （18.18% vs2.08%, OR = 10.444, P = 0.031）, whereas that of DQBI＊07 allele was inverse （9.09% vs37.50%, OR = 0.167, P= 0.021）. CONCLUSION： The polymorphism of HLA class II may influence the susceptibility to HBV infection and the response to IFN in studied CHB patients. Compared with other HLA-DRB1 alleles, HLA-DRBI＊06, DRBI＊08, and DRB1＊16 may be associated with chronicity of HBV infection, HLA-DRBI＊07 with protection against HBV infection, and HLA-DRB1＊14 allele may be associated with a high rate of the response of CHB patients to IFN treatment. Compared with other HLA-DQB1 alleles, HLA-DQBI＊07 may be associated with low response rate to IFN. 2005 The WJG Press and Elsevier Inc. All rights reserved

Quantitation of HBsAg predicts response to entecavir therapy in HBV genotype C patients

AIM： To analysis the factors that predict the response to entecavir therapy in chronic hepatitis patients with hepatitis B virus （HBV） genotype C. METHODS： Fifty patients [hepatitis B e antigen （HBeAg）- negative：HBeAg-positive = 26：24] with HBV genotype C, who received nalve entecavir therapy for 〉 2 years, were analyzed. Patients who showed HBV DNA levels ≥ 3.0 log viral copies/mL after 2 years of entecavir ther- apy were designated as slow-responders, while those that showed 〈 3.0 log copies/mL were termed rapid- responders. Quantitative hepatitis B surface antigen （HBsAg） levels （qHBsAg） were determined by the Archi- tect HBsAg QT immunoassay. Hepatitis B core-related antigen was detected by enzyme immunoassay. Pre-C and Core promoter mutations were determined using by polymerase chain reaction （PCR）. Drug-resistance muta- tions were detected by the PCR-Invader method. RESULTS： At year 2, HBV DNA levels in all patients in the HBeAg-negative group were 〈 3.0 log copies/mL. In contrast, in the HBeAg-positive group, 41.7% were slow-responders, while 58.3% were rapid-responders. No entecavir-resistant mutants were detected in the slow-responders. When the pretreatment factors were compared between the slow- and rapid-responders; the median qHBsAg in the slow-responders was 4.57 log IU/mL, compared with 3.63 log IU/mL in the rapid- responders （P 〈 0.01）. When the pretreatment factors predictive of HBV DNA-negative status at year 2 in all 50 patients were analyzed, HBeAg-negative status, low HBV DNA levels, and low qHBsAg levels were signifi- cant （P 〈 0.01）. Multivariate analysis revealed that the low qHBsAg level was the most significant predictive factor （P = 0.03）. CONCLUSION： Quantitation of HBsAg could be a use- ful indicator to predict response to entecavir therapy.

Quantification of HBsAg:Basic virology for clinical practice

Hepatitis B surface antigen (HBsAg) is produced and secreted through a complex mechanism that is still not fully understood. In clinical fields, HBsAg has long served as a qualitative diagnostic marker for hepatitis B virus infection. Notably, advances have been made in the development of quantitative HBsAg assays, which have allowed viral replication monitoring, and there is an opportunity to make maximal use of quantitative HBsAg to elucidate its role in clinical fields. Yet, it needs to be underscored that a further understanding of HBsAg, not only from clinical point of view but also from a virologic point of view, would enable us to deepen our insights, so that we could more widely expand and apply its utility. It is also important to be familiar with HBsAg variants and their clinical consequences in terms of immune escape mutants, issues resulting from overlap with corresponding mutation in the P gene, and detection problems for the HBsAg variants. In this article, we review current concepts and issues on the quantification of HBsAg titers with respect to their biologic nature, method principles, and clinically relevant topics.

Cytotoxic T-lymphocyte antigen 4 gene polymorphisms and susceptibility to chronic hepatitis B

AIM： To assess the three polymorphJsm regions within cytotoxic T-lymphocyte antigen 4 （CTLA-4） gene, a C/T base exchange in the promoter region-318 （CTLA-4 -318C/T）, an A/G substitution in the exon 1 position 49 （CTLA-4 49A/G）, a T/C substitution in 1172 （CTLA-4 -1172T/C） in patients with chronic hepatitis B. METHODS： Fifty-one patients with chronic hepatitis B virus infection and 150 healthy subjects were recruited sequentially as they presented to the hepatic clinic. Classification of chronic hepatitis B virus （HBV）-infected patients was as asymptomatic carrier state （26 patients） and chronic hepatitis B （25 patients）. Genomic DNA was isolated from anti-coagulated peripheral blood Bully coat using Miller＇s salting-out method. The presence of the CTLA-4 gene polymorphisms was determined using polymerase chain reaction amplification refractory mutation system （ARMS）. RESULTS： We observed a significant association between -318 genotypes frequency （T＋C-, T＋C＋, T-C＋） and susceptibility to chronic hepatitis B （P=0.012, OR=0.49, 95%CI： 0.206-1.162）. However, we did not observe a significant association for ＋49 genotype frequency （T＋C＋, T＋C- T-C＋） and -1172 genotype frequency （C＋T＋, T＋C- C＋T-） and state of disease. CONCLUSION： Our results suggest that CTLA-4 gene polymorphisms may partially be involved in the susceptibility to chronic hepatitis B.

Adenovirus-expressed preS2 antibody inhibits hepatitis B virus infection and hepatic carcinogenesis

AIM:To investigate the inhibitory effect of hepatitis B virus (HBV) preS2 antibody (preS2Ab) against HBV in-fection and HBV-associated hepatic carcinogenesis.METHODS:An adenoviral vector carrying the full-length light and heavy chains of the HBV preS2Ab gene,Ad315-preS2Ab,was constructed.Enzyme linked immunosorbent assay (ELISA) and Western blotting analyses were used to determine the preS2Ab expres-sion levels in vitro.Immunofluorescent techniques were used to examine the binding affinity between the expressed HBV preS2Ab and HBV-positive liver cells.ELISAs were also used to determine hepatitis B surface antigen (HBsAg) levels to assess the inhibitory effect of the preS2Ab against HBV infection in L02 cells.The inhibitory effect of preS2Ab against hepatic carcinogen-esis was studied with diethylnitrosamine (DEN)-induced hepatocellular carcinomas (HCCs) in HBV transgenic mice.RESULTS:The expression of HBV preS2Ab increased with increases in the multiplicity of infection (MOI) of Ad315-preS2Ab in L02 cells,with 350.87 ± 17.37 μg/L of preS2Ab when the MOI was 100 plaque forming units (pfu)/cell.The expressed preS2Abs could recog-nize liver cells from HBV transgenic mice.ELISA results showed that L02 cells expressing preS2Ab produced less HBsAg after treatment with the serum of HBV pa-tients than parental L02 cells expressing no preS2Ab.HBV transgenic mice treated with Ad315-preS2Ab had fewer and smaller cancerous nodes after induction with DEN than mice treated with a blank Ad315 vec-tor or untreated mice.Additionally,the administration of Ad315-preS2Ab could alleviate hepatic cirrhosis and decrease the serum levels of alanine transaminase and aspartate transaminase.CONCLUSION:Adenovirus-mediated HBV preS2Ab expression could inhibit HBV infection in L02 cells,and then inhibit DEN-induced hepatocellular carcinogenesis and protect hepatic function in HBV transgenic mice.