Transbody against virus core protein potently inhibits hepadnavirus replication in vivo: evidence from a duck model of hepatitis B virus

Interferon and interferon-stimulated genes in HBV treatment

Human hepatitis B virus (HBV) is a small enveloped DNA virus with a complex life cycle. It is the causative agent of acute and chronic hepatitis. HBV can resist immune system responses and often causes persistent chronic infections. HBV is the leading cause of liver cancer and cirrhosis. Interferons (IFNs) are cytokines with antiviral, immunomodulatory, and antitumor properties. IFNs are glycoproteins with a strong antiviral activity that plays an important role in adaptive and innate immune responses. They are classified into three categories (type I, II, and III) based on the structure of their cell-surface receptors. As an effective drug for controlling chronic viral infections, Type I IFNs are approved to be clinically used for the treatment of HBV infection. The therapeutic effect of interferon will be enhanced when combined with other drugs. IFNs play a biological function by inducing the expression of hundreds of IFN-stimulated genes (ISGs) in the host cells, which are responsible for the inhibiting of HBV replication, transcription, and other important processes. Animal models of HBV, such as chimpanzees, are also important tools for studying IFN treatment and ISG regulation. In the present review, we summarized the recent progress in IFN-HBV treatment and focused on its mechanism through the interaction between HBV and ISGs.

Anti-HBc IgG Responses Occurring at the Early Phase of Infection Correlate Negatively with HBV Replication in a Mouse Model

Anti-HBc IgG is usually recognized as a diagnostic marker of hepatitis B, while the functional role anti-HBc IgG in HBV infection has not been fully elucidated. In this study, we firstly investigated the relationship between the anti-HBc IgG responses and the replication of HBV using AAV8-1.3HBV infected C57BL/6N mice. Our data showed that the anti-HBc IgG responses at the early phase of infection correlated negatively with the concentrations of circulating HBsAg and HBV DNA at both the early and chronic phases of infection. This observation was confirmed by an independent experiment using AAV8-1.3HBV infected C57BL/6J mice. Furthermore, to comprehend the potential causal relationship between the anti-HBc IgG responses and HBV infection, mice were treated with an anti-HBc monoclonal antibody at three days post AAV8-1.3HBV infection. Our data showed that the anti-HBc mAb significantly suppressed the fold increase of circulating HBsAg level, and the protective effect was not affected by NK cell depletion. Collectively, our study demonstrated that anti-HBc antibodies occurring at the early phase of HBV infection may contribute to the constraint of the virus replication, which might be developed as an immunotherapy for hepatitis B.

Potential of cell-penetrating peptides (CPPs) in delivery of antiviral therapeutics and vaccines

Viral infections are a great threat to human health. Currently, there are no effective vaccines and antiviral drugs against the majority of viral diseases, suggesting the need to develop novel and effective antiviral agents. Since the intracellular delivery of antiviral agents, particularly the impermeable molecules, such as peptides, proteins, and nucleic acids, are essential to exert their therapeutic effects, using a delivery system is highly required. Among various delivery systems, cell-penetrating peptides (CPPs), a group of short peptides with the unique ability of crossing cell membrane, offer great potential for the intracellular delivery of various biologically active cargoes. The results of numerous in vitro and in vivo studies with CPP conjugates demonstrate their promise as therapeutic agents in various medical fields including antiviral therapy. The CPP-mediated delivery of various antiviral agents including peptides, proteins, nucleic acids, and nanocarriers have been associated with therapeutic efficacy both in vitro and in vivo. This review describes various aspects of viruses including their biology, pathogenesis, and therapy and briefly discusses the concept of CPP and its potential in drug delivery. Particularly, it will highlight a variety of CPP applications in the management of viral infections.

Targeted Intracellular Delivery of Antibodies: The State of the Art

A dominant area of antibody research is the extension of the use of this mighty experimental and therapeutic tool for the specific detection of molecules for diagnostics, visualization, and activity blocking. Despite the ability to raise antibodies against different proteins, numerous applications of antibodies in basic research fields, clinical practice, and biotechnology are restricted to permeabilized cells or extracellular antigens, such as membrane or secreted proteins. With the exception of small groups of autoantibodies, natural antibodies to intracellular targets cannot be used within living cells. This excludes the scope of a major class of intracellular targets, including some infamous cancer-associated molecules. Some of these targets are still not druggable via small molecules because of large flat contact areas and the absence of deep hydrophobic pockets in which small molecules can insert and perturb their activity. Thus, the development of technologies for the targeted intracellular delivery of antibodies, their fragments, or antibody-like molecules is extremely important. Various strategies for intracellular targeting of antibodies via protein-transduction domains or their mimics, liposomes, polymer vesicles, and viral envelopes, are reviewed in this article. The pitfalls, challenges, and perspectives of these technologies are discussed.

Transbody against virus core protein potently inhibits hepadnavirus replication in vivo: evidence from a duck model of hepatitis B virus

BACKGROUND AND PURPOSE

The therapeutic management of hepatitis B virus (HBV) infections remains challenging, and novel antiviral strategies are urgently required. The HBV transbody, a monoclonal antibody (MAb) against human HBcAg coupled with the trans-activator of transcription protein transduction domain (TAT PTD), was previously shown to possess cell-penetrating ability and potent antiviral activity in vitro. The purpose of the present study was to evaluate the antiviral activity of the HBcMAb-TAT PTD conjugate in vivo in a duck model of HBV.

EXPERIMENTAL APPROACH

Female Peking ducks were injected i.p. with 0.03-0.3 mg·kg^-1 ·day^-1 of the DHBV transbody (DHBcMAb-TAT PTD conjugate) for 30 days. Serum DHBV DNA levels and liver DHBV DNA and covalently closed circular DNA (cccDNA) loads were determined at scheduled time points. Immunohistological examination of DHBcAg in the duck liver was also performed.

KEY RESULTS

The DHBV transbody significantly reduced the serum and liver DHBV DNA levels at doses of 0.1 and 0.3 mg·kg^-1 ·day^-1 and liver cccDNA levels at a dose of 0.3 mg·kg^-1 ·day^-1 after 30 days of treatment. The suppressive effects of the DHBV transbody at 0.3 mg·kg^-1 ·day^-1 on the serum and liver DHBV DNA and liver cccDNA levels remained significant, even at 15 days after treatment cessation. Similarly, immunohistochemistry of liver sections revealed decreased DHBcAg levels within hepatocytes 15 days after treatment termination.

CONCLUSIONS AND IMPLICATIONS

The DHBV transbody inhibits DHBV replication and possesses potent anti-DHBV activities in vivo. The cell-permeable antibody against the virus core antigen may be developed as a novel treatment for patients with hepadnavirus infections.