Establishment of transgenic mouse harboring hepatitis B virus (adr subtype) genomes

Modeling Hepatotropic Viral Infections: Cells vs. Animals

The lack of an appropriate platform for a better understanding of the molecular basis of hepatitis viruses and the absence of reliable models to identify novel therapeutic agents for a targeted treatment are the two major obstacles for launching efficient clinical protocols in different types of viral hepatitis. Viruses are obligate intracellular parasites, and the development of model systems for efficient viral replication is necessary for basic and applied studies. Viral hepatitis is a major health issue and a leading cause of morbidity and mortality. Despite the extensive efforts that have been made on fundamental and translational research, traditional models are not effective in representing this viral infection in a laboratory. In this review, we discuss in vitro cell-based models and in vivo animal models, with their strengths and weaknesses. In addition, the most important findings that have been retrieved from each model are described.

In Vivo Model Systems for Hepatitis B Virus Research

Hepatitis B virus (HBV) affects more than 257 million people globally, resulting in progressively worsening liver disease, manifesting as fibrosis, cirrhosis, and hepatocellular carcinoma. The exceptionally narrow species tropism of HBV restricts its natural hosts to humans and non-human primates, including chimpanzees, gorillas, gibbons, and orangutans. The unavailability of completely immunocompetent small-animal models has contributed to the lack of curative therapeutic interventions. Even though surrogates allow the study of closely related viruses, their host genetic backgrounds, immune responses, and molecular virology differ from those of HBV. Various different models, based on either pure murine or xenotransplantation systems, have been introduced over the past years, often making the choice of the optimal model for any given question challenging. Here, we offer a concise review of in vivo model systems employed to study HBV infection and steps in the HBV life cycle or pathogenesis.

Inhibitory effect of emodin and Astragalus polysaccharide on the replication of HBV

AIM

To evaluate the anti-viral effect of emodin plus Astragalus polysaccharide (APS) in hepatitis B virus (HBV) transgenic mice.

METHODS

Sixty HBV transgenic mice (HBV TGM) whose weight varied between 18 and 24 g were randomly divided into 3 groups, with 20 mice in each group. Group A was the normal control, where the mice were treated with physiological saline; group B was the positive control where the mice were treated with lamivudine solution (100 mL/kg per day). Group C was the experimental group where the mice were treated with physiological saline containing emodin and APS (57.59 mg/kg per day and 287.95 mg/kg per day, respectively). The mice were treated daily for 3 wk. After 1 wk recovery time, the mice were sacrificed and serum as well as liver tissues were collected for ELISA and histological examination.

RESULTS

After 21 d treatment, HBV DNA levels in group B and group C significantly declined when compared with group A (P < 0.05). However, a significant increase in HBV DNA content was observed in group B, whereas this phenomenon was not observed in group C. A reduction in the contents of HBsAg, HBeAg and HBcAg in the mice from group B and C was observed when compared with group A.

CONCLUSION

Emodin and APS have a weak but persistent inhibitory effect on HBV replication in vivo, which may function as a supplementary modality in the treatment of hepatitis B infection.

Long-term persistence of hepatitis B surface antigen and antibody induced by DNA-mediated immunization results in liver and kidney lesions in mice

DNA-mediated immunization has been recognized as a new approach for prevention and treatment of hepatitis B virus (HBV) infection. However, the side effects of this approach have not been well described. Here we report that DNA-mediated immunization by intramuscular injection of plasmid DNA encoding HBV surface antigen (HBsAg) induced long-term persistence of HBsAg and HBsAg-specific antibody (anti-HBs) in the sera of the immunized BALB/c mice and resulted in liver and kidney lesions. The lesions persisted for 6 months after injection. Lesions were also found in normal mice injected with the sera from immunized mice, and in HBV-transgenic mice injected with anti-HBs antibody, or sera from immunized mice. Furthermore, lesions were accompanied by deposition of circulating immune complex (CIC) of HBsAg and anti-HBs antibody in the damaged organs. These results indicate that long-term persistence of HBsAg and anti-HBs in the immunized mice can result in deposited CIC in liver and kidney, and in development of lesions. The use of DNA containing mammalian replication origins, such as the plasmids used in this study, is not appropriate for human vaccines due to safety concerns relating to persistence of DNA; nevertheless, the safety of DNA-mediated immunization protocols still needs to be carefully evaluated before practical application.

Down-regulating effect of orosomucoid 2 on preS1 promoter of hepatitis B virus

AIM: To investigate activity of orosomucoid 2 (ORM2) on preS1 promoter (SP Ⅰ) of hepatitis B virus (HBV).

METHODS: Yeast one-hybrid system was employed in screening of DNA-binding proteins specifically recognizing HBV-SP I sequence, in which ORM2 was identified in GenBank by bioinformatics. For further studying the interaction between ORM2 and HBV-SP Ⅰ, the sequence of ORM2 was amplified from HepG2 genome by polymerase chain reaction (PCR) technique, which was then cloned into pcDNA3.1(-) expression vector. The HepG2 cell line was transfected by pCAT3- SP Ⅰ, and co-transfected by pCAT3-SP Ⅰ and pcDNA3.1(-)-ORM2, respectively. The chloramphenicol acetyltransferase (CAT) activity was detected by an enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS: pCAT3-SP Ⅰ had higher activity of CAT than pCAT3-basic by ELISA kit. The expression of CAT from pCAT3-SP Ⅰ was increased 81.9%, as compared with that in the co-transfection of pCAT3-SP Ⅰ and pcDNA3.1(-)-ORM2.

CONCLUSION: Cell transfection and ELISA technology are successfully used to prove the results from yeast one-hybrid system, which brings some new clues for studying the specific binding proteins of HBV- SP Ⅰ and its transcriptional regulation mechanism.

Effect of HBeAg on the hepatitis B virus vertical transmission in neonates

AIM: To investigate the effect of HBeAg on the hepatitis B virus vertical transmission in neonates.

METHODS: HBsAg positive pregnant women were enrolled,and ELISA or Abbott was employed to detect the HBeAg and HBsAg in the peripheral blood of neonates and their mothers.

RESULTS: Fifty-seven HBsAg positive pregnant women were reconfirmed as HBsAg positive. Fifteen of them were detected as HBeAg positive. Eleven of 16 neonates born to 15 HBeAg positive mother were detected as HBeAg positive. Three neonates diagnosed as HBsAg positive by ELISA or Abbott reagents were detected as HBeAg positive. Statistic analysis indicated that HBeAg in newborns was an important risk factor.

CONCLUSION: HBeAg in neonates played an important role during HBV vertical transmission.

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Genetic polymorphisms in IL-10 and IL-12b allele promoter regions in Chinese patients of Han nationality with HBV infection

AIM

To investigate the association of genetic susceptibility to hepatitis B virus infection and disease progression with the allelic polymorphisms of IL-10 and IL-12b promoter regions in Chinese Han population.

METHODS

Two groups of indigenous Chinese subjects (314 subjects in total) were recruited in this study. Group 1 included 104 unrelated patients with chronic hepatitis B virus infection and 76 unrelated healthy donors. Group 2 contained 134 related subjects from seven HBV-infected pedigrees of Han ethnic origin. Total genomic DNA samples were purified from the 1.5 ml of peripheral blood of all participated individuals by using the QIAgen purification DNA kit. Genotyping of IL10-5'A and IL12-5'C alleles was performed by means of PCR-RFLP (restriction fragment length polymorphism) and further proved by direct DNA sequencing. All data were statistically analyzed by using SAS software.

RESULTS

IL10-5'A mutant frequency in unrelated healthy subjects was 41.9% compared with 42.1% in unrelated HBV-infected patients, while IL12-5'C mutant frequency was 64.6% and 55.8% among healthy individuals and HBV-infected patients, respectively. No significant difference was found among the unrelated healthy individuals and unrelated HBV-infected patients. In related individuals from the seven HBV-infected pedigrees, the mutant frequency of IL12-5'C allele was found to be identical to that in unrelated healthy and HBV-infected patients, but the mutant frequency of IL10-5'A allele(19.5%) was significantly different from that(42.0%) in unrelated group (P<0.01).

CONCLUSION

The polymorphisms of IL10-5'A and IL12-5'C allele promoter regions were not correlated with hepatitis B virus infection and disease progression among unrelated subjects, but there was a significantly lower mutant frequency of IL10-5'A allele among related subjects.

Effect of thymosin-α1 on immune function with chronic hepatitis B

AIM

To realize effect of thymosin-α1 (Tα1) on immune function with chronic hepatitis B (CHB) and to evaluate the efficacy of Tα1 in the treatment of CHB.

METHODS

Sixty patients with CHB were randomly chosen. Twenty-five cases were received Tα1 (1.6 mg, sc, twice a week, 3-6mo) and thirty-five were received Tα1 combined with Lamivudine (0.1 g, po, once a day, 3-6 mo). Hepatic function, virological analyses (HBeAg, HBsAg, HBV-DNA) and immunological analyses (periperal blood T lymphocytes subset, IFN-α and IL-4 levels) from patients in pretreatment and posttreatment were observed.

RESULTS

At the end of treatment, ALT and T-Bil were decreased in the group of Tα1 combined with Lamivudine (P<0.01), HBeAg/HBsAg remained negative (n = 9) and HBV-DNA levels were also low (n = 14) in the group of Tα1 combined with Lamivudine (P<0.01 and P<0.05, respectively) as compared with healthy individuals. CD₄⁺ T Cell (from 31.3±2.4 to 36.1±2.5), the level of IFN-α(from 71.3±21.0 to 83.7±21.4) and Th1/Th2 (from 0.79±0.2 to 0.98±0.3) increased in the group of Tα1 (P<0.01, P<0.05 and P<0.05, respectively).

CONCLUSION

Tα1 is efficient to treat patients with CHB because it can elevate the level of cellular immunity, which is beneficial to viral clearance.

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Expression of hepatitis B virus X protein in transgenic mice

AIM: To establish a mice model harboring hepatitis B virus x gene (adr subtype) for studying the function of hepatitis B virus X protein, a transactivator of viral and cellular promoter/enhancer elements.

METHODS: Expression vector pcDNA3-HBx, containing CMV promoter and hepatitis B virus x gene open reading fragment, was constructed by recombination DNA technique. Hela cells were cultured in DMEM and transfected with pcDNA3-HBx or control pcDNA3 plasmids using FuGENE6 Transfection Reagent. Expression of pcDNA3-HBx vectors in the transfected Hela cells was confirmed by Western blotting. After restriction endonuclease digestion, the coding elements were microinjected into male pronuclei of mice zygotes. The pups were evaluated by multiplex polymerase chain reaction (PCR) at genomic DNA level. The x gene transgenic mice founders were confirmed at protein level by Western blotting, immunohistochemistry and immunogold transmission electron microscopy.

RESULTS: Expression vector pcDNA3-HBx was constructed by recombination DNA technique and identified right by restriction endonuclease digestion and DNA direct sequencing. With Western blotting, hepatitis X protein was detected in Hela cells transfected with pcDNA3-HBx plasmids, suggesting pcDNA3-HBx plasmids could express in eukaryotic cells. Following microinjection of coding sequence of pcDNA3-HBx, the embryos were transferred to oviducts of psedopregnant females. Four pups were born and survived. Two of them were verified to have the HBx gene integrated in their genomic DNA by multiplex PCR assay, and named C57-TgN (HBx)S MMU1 and C57-TgN (HB x) SMMU3 respectively. They expressed 17KD X protein in liver tissue by Western blotting assay. With the immunohistochemistry, X protein was detected mainly in hepatocytes cytoplasm of transgenic mice, which was furthermore confirmed by immunogold transmission electon microscopy.

CONCLUSION: We have constructed the expression vector pcDNA3-HBx that can be used to study the function of HBx gene in eukaryotic cells in vitro. We also established HBx gene (adr subtype) transgenic mice named C57-TgN (HBx) SMMU harboring HBx gene in their genome and express X protein in hepatocytes, Which might be a valuable animal system for studying the roles of HBx gene in hepatitis B virus life cycle and development of hepatocellular carcinoma in vivo.

Pharmacokinetics of radioimmunotherapeutic agent of direct labeling mAb 188Re-HAb18

AIM: To label anti-hepatoma monoclonal antibody (mAb) fragment HAb18 F(ab’)₂ was labeled with ¹⁸⁸Re for the pharmacokinetic model of ¹⁸⁸Re-HAb18 F(ab’)₂ and to evaluate its pharmacokinetic parameters in hepatoma-bearing nude mice.

METHODS: HAb18 F(ab’)₂ was directly labeled with ¹⁸⁸Re using 2-mercaptoethanol (2-ME) as reducing agents. Labeling efficiency and immunoreactivity of ¹⁸⁸Re-HAb18 F(ab’)₂ were evaluated by Whatman 3MM paper chromatography and live cell assay, respectively. Biodistribution analysis was also conducted in nude mice bearing human hepatoma in which animals were sacrificed at different time points (1, 4, 18, 24 and 24 h) after ¹⁸⁸Re-HAb18 F (ab’)₂ was injected through tail-vein into hepatoma-bearing nude mice. The blood and radioactivity of organs and mass were measured. The concentrations of ¹⁸⁸Re-HAb18 F(ab’)₂ were evaluated with apharmacokinetic 3P97 software.

RESULTS: The optimum labeling efficiency and immunoreactive fraction were 91.7% and 0.78% respectively. The parameters of ¹⁸⁸Re-HAb18 F(ab’)₂ were: T_1/2, 2.29 h; Vd,1.49 × 10^-9 L·Bq^-1; AUC, 20. 49 × 10⁹ Bq·h·L^-1;CL, 0.45 × 10^-3 L·h^-1. ¹⁸⁸Re-HAb18 F(ab’)₂ could locate specially in hepatoma with high selective reactivity of HAb18 F(ab’)₂. ¹⁸⁸Re-HAb18 F(ab’)₂ was mainly eliminated by kidney. The maximal tumor to blood ratio was at 48 h, and maximal tumor to liver ratio was at 18 h.

CONCLUTION: The pharmacokinetics of ¹⁸⁸Re-HAb18 F (ab’)₂ fital-compartment model.¹⁸⁸Re-HAb18 F(ab’)₂ can be uptaken selectively at the hepatoma site.

TECA hybrid artificial liver support system in treatment of acute liver failure

AIM: To assess the efficacy and safety of TECA type hybr id artificial liver support system (TECA-HALSS) in providing liver function of detoxification, metabolism and physiology by treating the patients with acute liv er failure (ALF).

METHODS: The porcine liver cells (1-2) × 10¹⁰ were separated from the Chinese small swine and cultured in the bioreactor of TECA-BALSS at 37.0 °C and circulated through the outer space of the hollow fiber tubes in BALSS. The six liver failure patients with various degree of hepatic coma were treated by TECA-HALSS and with conventional medicines. The venous plasma of the patients was separated by a plasma separator and treated by charcoal adsorbent or plasma exchange. The plasma circulated through the inner space of the hollow fiber tubes of BALSS and mixed with the patients’ blood cells and flew back to their blood circulation. Some small molecular weight substances were exchanged between the plasma and porcine liver cells. Each treatment lasted 6.0-7.0 h. Physiological and biochemical parameters were measured before, during and after the treatment.

RESULTS: The average of porcine liver cells was (1.0-3.0) × 10¹⁰ obtained from each swine liver using our modified enzymatic digestion method. The survival rate of the cells was 85%-93% by trypan blue stain and AO/PI fluorescent stain. After cultured in TECA-BALSS bioreactor for 6 h, the survival rate of cells still remained 70%-85%. At the end of TECA-HALSS treatment, the levels of plasma NH₃, ALT, TB and DB were significantly decreased. The patients who were in the state of drowsiness or coma before the treatment improved their appetite significantly and regained consciousness, some patients resumed light physical work on a short period after the treatment. One to two days after the treatment, the ratio of PTA increased warkedly. During the treatment, the heart rates, blood pressure, respiration condition and serum electrolytes (K⁺, Na⁺ and Cl^-) were stable without thrombosis and bleeding in all the six patients.

CONCLUSION: TECA-HALSS treatment could be a rapid, safe and efficacious method to provide temporary liver support for patients with ALF.