Evaluation of Interfering RNA Efficacy in Treating Hepatitis B: Is It Promising?

Abstract

Background: Despite an existing safe and effective vaccine for hepatitis B virus (HBV), it is still a major public health concern. Nowadays, several drugs are used to treat chronic hepatitis B; however, full healing remains controversial. The viral covalently closed circular DNA (cccDNA) formed by HBV forms a major challenge in its treatment, as does the ability of HBV to integrate itself into the host genome, which enables infection reactivation. Interfering RNA (RNAi) is a gene-silencing post-transcriptional mechanism which forms as a promising alternative to treat chronic hepatitis B. The aim of the present review is to assess the evolution of hepatitis B treatment approaches based on using RNA interference.

Methods: Data published between 2016 and 2023 in scientific databases (PubMed, PMC, LILACS, and Bireme) were assessed.

Results: In total, 76,949 articles were initially identified and quality-checked, and 226 eligible reports were analyzed in depth. The main genomic targets, delivery systems, and major HBV therapy innovations are discussed in this review. This review reinforces the therapeutic potential of RNAi and identifies the need for conducting further studies to fill the remaining gaps between bench and clinical practice.

Keywords: RNA interference (RNAi); chronic hepatitis; covalently closed circular DNA (cccDNA); gene therapy; hepatitis B virus (HBV).

Figure 1

HBV replication cycle model. The viral particle enters the cytoplasm by binding to the sodium taurocholate receptor cotransporting polypeptide (hepatocyte membrane receptor); the capsid is transported to the nucleus, wherein the HBV DNA is released. The HBV genome is converted to covalently closed DNA (cccDNA) which is used sequentially as transcriptional template for genomic and sub-genomic RNAs. Transcripts are exported to cytosol, and they can be used as messenger RNAs (mRNAs). Pre-genomic RNA (pgRNA) works as replication template. The new viral particle is formed at the transition between the endoplasmatic reticulum and the Golgi complex, and it is then secreted. Created at Biorender.com (accessed on 2 August 2024).

Figure 2

Hepatitis B virus (HBV) genome map. The HBV genome is a double-stranded DNA (3.2 kb) comprising four overlapping open reading frames (ORFs) coding the viral envelope (pre-S1/pre-S2/S) (blue arrow), core proteins (pre-C/C) (purple arrow), viral polymerase (green arrow), and HBx protein (orange arrow). Overlapping regions are highlighted by red arrows. Created at Biorender.com (accessed on 2 August 2024).

Figure 3

(1) The DICER enzyme recognizes and processes exogenous HBV mRNA (pre-shRNA) into small RNA fragments upon initial contact with a eukaryotic cell. (2) These small RNA fragments are subsequently incorporated into the RNA-induced silencing complex (RISC) as guide strands. (3) Upon subsequent interaction with exogenous mRNA, the guide strand within the RISC recognizes the complementary sequence. This recognition induces conformational changes in the RISC, leading to the cleavage of the target mRNA. Cellular endonucleases then degrade the mRNA residues, thereby preventing the synthesis of encoded proteins. (4) The RISC, utilizing the interfering RNA, cleaves HBV pre-genomic RNA and mRNA, thereby silencing viral replication and protein production. The HBV replication process involves the following steps: (A) viral entry into hepatocytes via endocytosis; (B) release and transport of the nucleocapsid to the nucleus, where the HBV genome is converted into covalently closed circular DNA (cccDNA); (C) transcription of cccDNA, resulting in the production of pre-genomic RNA and mRNAs necessary for viral protein synthesis and replication; and (D) RNA interference (RNAi) that targets pre-genomic RNA (pgRNA) and mRNAs, thereby halting viral protein synthesis and replication. Created at Biorender.com (accessed on 2 August 2024).