RNA interference inhibits hepatitis B virus gene expression and replication in HepG2-N10 cells

TCR-like bispecific antibodies toward eliminating infected hepatocytes in HBV mouse models

Therapeutics for eradicating hepatitis B virus (HBV) infection are still limited and current nucleos(t)ide analogs (NAs) and interferon are effective in controlling viral replication and improving liver health, but they cannot completely eradicate the hepatitis B virus and only a very small number of patients are cured of it. The TCR-like antibodies recognizing viral peptides presented on human leukocyte antigens (HLA) provide possible tools for targeting and eliminating HBV-infected hepatocytes. Here, we generated three TCR-like antibodies targeting three different HLA-A2.1-presented peptides derived from HBV core and surface proteins. Bispecific antibodies (BsAbs) were developed by fuzing variable fragments of these TCR-like mAbs with an anti-CD3ϵ antibody. Our data demonstrate that the BsAbs could act as T cell engagers, effectively redirecting and activating T cells to target HBV-infected hepatocytes in vitro and in vivo. In HBV-persistent mice expressing human HLA-A2.1, two infusions of BsAbs induced marked and sustained suppression in serum HBsAg levels and also reduced the numbers of HBV-positive hepatocytes. These findings highlighted the therapeutic potential of TCR-like BsAbs as a new strategy to cure hepatitis B.

Epigallocatechin gallate inhibits hepatitis B virus via farnesoid X receptor alpha

Plants possess various natural antiviral properties. Epigallocatechin-3-gallate (EGCG), a major component of green tea, inhibits a variety of viruses. However, the clinical application of EGCG is currently hindered by a scarcity of information on its molecular mechanism of action. In the present study, we examined the anti-HBV (hepatitis B virus) effects of catechins from green tea at the transcriptional and antigen-expression levels, as well as the associated molecular mechanisms, because HBV-associated liver diseases have become a key public health issue due to their serious impact on human physical and mental health. By using fluorescence quenching and affinity binding, we demonstrated that EGCG is an important transcriptional regulator of the HBV genome, which it achieves by interacting with farnesoid X receptor alpha (FXRα). Luciferase assay showed that EGCG effectively inhibited the transcription of the HBV promoter dose-dependently when expression plasmids of FXRα and retinoid X receptor α (RXRα) were co-transfected into HEK293 cells. These results indicate that the downregulation of the HBV antigen and the decrease in the transcriptional activation of the HBV EnhII/core promoter by FXRα/RXRα are mainly due to the interaction between EGCG and FXRα. Therefore, EGCG, an antagonist of FXRα in liver cells, has the potential to be employed as an effective anti-HBV agent.

Inhibition of matrix metalloproteinase 9 expression in rat dermal fibroblasts using small interfering RNA

BACKGROUND

Matrix metalloproteinases (MMPs) degrade extracellular matrix components. Increased MMP-9 content in diabetic skin contributes to skin vulnerability and refractory foot ulcers. To identify ways to decrease MMP-9 levels in skin, inhibition of MMP-9 expression in dermal fibroblasts using small interfering RNA was investigated in vitro.

METHODS

A full-thickness wound was created on the midback of streptozotocin-induced diabetic rats; skin biopsies were performed 3 days later. Skin MMP-9 expression was observed by immunohistochemical analysis. Dermal fibroblasts from 1-day-old normal Sprague Dawley rats cultured with high glucose and homocysteine concentrations were transfected with small interfering RNA complexes. Cells were collected 30, 48, and 72 hours after transfection, and reverse transcription-polymerase chain reaction, Western blot analysis, and gelatin zymography for MMP-9 were performed.

RESULTS

Expression of MMP-9 was increased in diabetic rat skin, especially around wounds. After 30-, 48-, and 72-hour transfection with each MMP-9-specific small interfering RNA, reverse transcription-polymerase chain reaction showed markedly decreased MMP-9 messenger RNA expression, protein abundance, and activity. Of four MMP-9 small interfering RNAs, one sequence had a stable high inhibition rate (>70% at 30 and 48 hours after transfection).

CONCLUSIONS

Expression of MMP-9 was increased in diabetic rat skin, especially around wounds, and was markedly inhibited after MMP-9 small interfering RNA transfection in vitro (P < .05). These findings may provide new treatments for diabetic skin wounds.

Stringent testing identifies highly potent and escape-proof anti-HIV short hairpin RNAs

BACKGROUND

RNA interference (RNAi) is a cellular mechanism that can be induced by small interfering RNAs to mediate sequence-specific gene silencing by cleavage of the targeted mRNA. RNAi can be used as an antiviral approach to silence the human immunodeficiency virus type 1 (HIV-1) through stable expression of short hairpin RNAs (shRNAs). Previously, we used a co-transfection assay in which shRNA constructs were transfected with an HIV-1 molecular clone to identify 20 shRNA inhibitors that target highly conserved HIV-1 sequences.

METHODS

In the present study, we selected the most potent shRNAs to formulate a combinatorial shRNA therapy and determine the best and easiest method for antiviral shRNA selection. We performed transient inhibition assays with either a luciferase reporter or HIV-1 molecular clone and also infected shRNA-expressing T cell lines with HIV-1 and monitored virus replication. The latter assay allows detection of viral escape. In addition, we also tested shRNA-expressing T cells upon challenge with increasing dosages of HIV-1, and measured the dose required to result in massive virus-induced syncytia formation in this 2-week assay.

RESULTS

Extended culturing selected three highly effective shRNAs that do not allow viral replication for more than 100 days. This difference in potency was not observed in the transient co-transfection assays. The use of increased dosages of HIV-1 selected the same highly potent shRNAs as the laborious and extended escape study.

CONCLUSIONS

These highly potent shRNAs could be used for a clinical vector and the comparison of the developed assays might help other researchers in their search for antiviral shRNAs.

Human immunodeficiency virus type 1 escape is restricted when conserved genome sequences are targeted by RNA interference

RNA interference (RNAi) is a cellular mechanism in which small interfering RNAs (siRNAs) mediate sequence-specific gene silencing by cleaving the targeted mRNA. RNAi can be used as an antiviral approach to silence the human immunodeficiency virus type 1 (HIV-1) through stable expression of short-hairpin RNAs (shRNAs). We previously reported efficient HIV-1 inhibition by an shRNA against the nonessential nef gene but also described viral escape by mutation or deletion of the nef target sequence. The objective of this study was to obtain insight in the viral escape routes when essential and highly conserved sequences are targeted in the Gag, protease, integrase, and Tat-Rev regions of HIV-1. Target sequences were analyzed of more than 500 escape viruses that were selected in T cells expressing individual shRNAs. Viruses acquired single point mutations, occasionally secondary mutations, but-in contrast to what is observed with nef-no deletions were detected. Mutations occurred predominantly at target positions 6, 8, 9, 14, and 15, whereas none were selected at positions 1, 2, 5, 18, and 19. We also analyzed the type of mismatch in the siRNA-target RNA duplex, and G-U base pairs were frequently selected. These results provide insight into the sequence requirements for optimal RNAi inhibition. This knowledge on RNAi escape may guide the design and selection of shRNAs for the development of an effective RNAi therapy for HIV-1 infections.