The use of the hydrodynamic HBV animal model to study HBV biology and anti-viral therapy.

A simple reproducible and versatile small animal model for hepatitis B virus (HBV) infection is still unavailable. We have generated a simple transient liver-targeted transgenic mouse. Hydrodynamics tail vein injection of a head-to-tail dimer of adw HBV genome (pHBVadwHTD) into immunocompetent mice generated HBsAg and HBeAg expression in both serum and hepatocytes, followed by seroconversion. The injection of pHBVadwHTD into SCID mice generated prolonged HBsAg and HBeAg antigenemia and HBV viremia. Our results demonstrate that hydrodynamic injection of naked DNA could support the generation of HBV particles. We used this model for the assessment of anti-viral agents. Administration of our human monoclonal antibodies, HBV-Ab17(XTL) and HBV-Ab19(XTL), as well as Lamivudine (3TC) treatment suppressed HBV viremia. The model presented herein supports long and stable expression of HBV and will enable determination of various biological questions related to HBV life cycle, mutants and could enhance the development of anti-viral reagents.

Preclinical evaluation of two neutralizing human monoclonal antibodies against hepatitis C virus (HCV): a potential treatment to prevent HCV reinfection in liver transplant patients.

Passive immunotherapy is potentially effective in preventing reinfection of liver grafts in hepatitis C virus (HCV)-associated liver transplant patients. A combination of monoclonal antibodies directed against different epitopes may be advantageous against a highly mutating virus such as HCV. Two human monoclonal antibodies (HumAbs) against the E2 envelope protein of HCV were developed and tested for the ability to neutralize the virus and prevent human liver infection. These antibodies, designated HCV-AB 68 and HCV-AB 65, recognize different conformational epitopes on E2. They were characterized in vitro biochemically and functionally. Both HumAbs are immunoglobulin G1 and have affinity constants to recombinant E2 constructs in the range of 10(-10) M. They are able to immunoprecipitate HCV particles from infected patients' sera from diverse genotypes and to stain HCV-infected human liver tissue. Both antibodies can fix complement and form immune complexes, but they do not activate complement-dependent or antibody-dependent cytotoxicity. Upon complement fixation, the monoclonal antibodies induce phagocytosis of the immune complexes by neutrophils, suggesting that the mechanism of viral clearance includes endocytosis. In vivo, in the HCV-Trimera model, both HumAbs were capable of inhibiting HCV infection of human liver fragments and of reducing the mean viral load in HCV-positive animals. The demonstrated neutralizing activities of HCV-AB 68 and HCV-AB 65 suggest that they have the potential to prevent reinfection in liver transplant patients and to serve as prophylactic treatment in postexposure events.

Oligonucleotide-assisted cleavage and ligation: a novel directional DNA cloning technology to capture cDNAs. Application in the construction of a human immune antibody phage-display library.

The use of oligonucleotide-assisted cleavage and ligation (ONCL), a novel approach to the capture of gene repertoires, in the construction of a phage-display immune antibody library is described. ONCL begins with rapid amplification of cDNA ends to amplify all members equally. A single, specific cut near 5' and/or 3' end of each gene fragment (in single stranded form) is facilitated by hybridization with an appropriate oligonucleotide adapter. Directional cloning of targeted DNA is accomplished by ligation of a partially duplex DNA molecule (containing suitable restriction sites) and amplification with primers in constant regions. To demonstrate utility and reliability of ONCL, a human antibody repertoire was cloned from IgG mRNA extracted from human B-lymphocytes engrafted in Trimera mice. These mice were transplanted with peripheral blood lymphocytes from Candida albicans infected individuals and subsequently immunized with C.albicans glyceraldehyde-3-phosphate dehydrogenase (GAPDH). DNA sequencing showed that ONCL resulted in efficient capture of gene repertoires. Indeed, full representation of all V(H) families/segments was observed showing that ONCL did not introduce cloning biases for or against any V(H) family. We validated the efficiency of ONCL by creating a functional Fab phage-display library with a size of 3.3 x 10(10) and by selecting five unique Fabs against GAPDH antigen.

The Trimera mouse: a system for generating human monoclonal antibodies and modeling human diseases.

A Trimera mouse is constructed through a three-step process. Firstly, a normal mouse host is rendered immuno-incompetent by a lethal split-dose total body irradiation. Secondly, the myeloid and erythroid lineages are reconstituted by transplantation of bone marrow cells from a genetically immune-deficient mouse donor. Thirdly. the resulting preconditioned mouse is transplanted with human cells or tissues that can be maintained in the foreign, yet supporting, environment for a considerable period of time. Immunization of Trimera mice, engrafted with human immune cells, induces a strong human immune response, thereby enabling generation of human therapeutic monoclonal antibodies (mAbs) via hybridoma technology. Transplantation of infected human tissue into the preconditioned mice results in the creation of Trimera mouse models for human diseases.

The hepatitis C virus (HCV)-Trimera mouse: a model for evaluation of agents against HCV.

The lack of small-animal models that are suitable for evaluation of agents used to treat infection with hepatitis C virus (HCV) severely hinders the assessment of potential new therapies for the disease. This study created such a model, termed the "HCV-Trimera" model. The HCV-Trimera model was developed by using lethally irradiated mice, reconstituted with SCID mouse bone marrow cells, in which human liver fragments infected ex vivo with HCV had been transplanted. Viremia (positive-strand HCV RNA levels) in HCV-Trimera mice peaked at approximately day 18 after liver transplantation, and an infection rate of 85% was reached. Viral replication in liver grafts was evidenced by the presence of specific negative-strand HCV RNA. The usefulness of this model for evaluation of anti-HCV agents was demonstrated by the ability of a small molecule (an HCV internal ribosomal entry site inhibitor) and an anti-HCV human monoclonal antibody (HCV AB(XTL)68) to reduce virus loads in HCV-Trimera mice in a dose-dependent manner.