The hepatitis delta virus and chronic hepatitis D

Hepatitis B Virus DNA integration: Implications for diagnostics, therapy, and outcome

HBV DNA integration originally recognized as a non-functional byproduct of the HBV life cycle has now been accepted as a significant contributor to HBV pathogenesis and HDV persistence. Integrated HBV DNA is derived from linear genomic DNA present in virus particles or produced from aberrantly processed relaxed circular genomic DNA following an infection, and can drive expression of HBsAg and HBx. DNA integration events accumulate over the course of viral infection ranging from a few percent during early phases to nearly 100 percent of infected cells after prolonged chronic infection. HBV DNA integration events have primarily been investigated in the context of HCC development where they can activate known oncogenes and other growth promoting genes, cause chromosomal instability and presumably epigenetic alterations promoting tumor growth. More recent evidence suggests that HBsAg expression from integrated DNA might contribute to HBV pathogenesis by attenuating the immune response. Integrated DNA provides a source for envelope proteins required for HDV replication and hence represents a means for HDV persistence. Because integrated DNA is responsible for persistence of HBsAg in the absence of viral replication it impacts established criteria for the resolution of HBV infection which relies on HBsAg as a diagnostic marker. Integrated HBV DNA has been useful in assessing the turnover of infected hepatocytes which occurs during all phases of chronic hepatitis B including the initial phase of infection historically termed immune tolerant. HBV DNA integration was also shown to impact the development of novel therapies targeting viral RNAs.

Blocking viral entry with bulevirtide reduces the number of HDV-infected hepatocytes in human liver biopsies

BACKGROUND & AIMS

Bulevirtide (BLV) is a first-in-class entry inhibitor and the only approved treatment for patients chronically infected with HDV in Europe. We aimed to investigate the efficacy of BLV treatment in paired liver biopsies obtained at baseline and after 24 or 48 weeks of treatment.

METHODS

We performed a combined analysis of 126 paired liver biopsies derived from three clinical trials. In the phase II clinical trial MYR202, patients with chronic hepatitis D were randomised to receive 24 weeks of BLV at 2 mg, 5 mg or 10 mg/day. Patients in MYR203 (phase II) and MYR301 (phase III) received 48 weeks of BLV at 2 mg or 10 mg/day. Tenofovir disoproxil fumarate monotherapy or delayed treatment served as comparators. Virological parameters and infection-related host genes were assessed by qPCR and immunohistochemistry.

RESULTS

At week 24, median intrahepatic HDV RNA decline from baseline was 0.9Log10 with 2 mg (n = 7), 1.1Log10 with 5 mg (n = 5) and 1.4 Log10 with 10 mg (n = 7) of BLV. At week 48, median reductions were 2.2Log10 with 2 mg (n = 27) and 2.7Log10 with 10 mg (n = 37) of BLV, while HDV RNA levels did not change in the comparator arms. Notably, a drastic decline in the number of hepatitis delta antigen-positive hepatocytes and a concomitant decrease in transcriptional levels of inflammatory chemokines and interferon-stimulated genes was determined in all BLV-treatment arms. Despite the abundance of HBsAg-positive hepatocytes, replication and covalently closed circular DNA levels of the helper virus HBV were low and remained unaffected by BLV treatment.

CONCLUSION

Blocking viral entry diminishes signs of liver inflammation and promotes a strong reduction of HDV infection within the liver, thus suggesting that some patients may achieve HDV cure with long-term treatment.

IMPACT AND IMPLICATIONS

Chronic infection with HDV causes the most severe form of viral hepatitis, affecting approximately 12 million people worldwide. The entry inhibitor bulevirtide (BLV) is the only recently approved anti-HDV drug, which has proven efficacious and safe in clinical trials and real-word data. Here, we investigated paired liver biopsies at baseline and after 24 or 48 weeks of treatment from three clinical trials to understand the effect of the drug on viral and host parameters in the liver, the site of viral replication. We found that BLV treatment strongly reduces the number of HDV-infected cells and signs of liver inflammation. This data implies that blocking viral entry ameliorates liver inflammation and that prolonged treatment regimens might lead to HDV cure in some patients. This concept will guide the further development of therapeutic strategies and combination treatments for patients with CHD.

CLINICAL TRIAL NUMBERS

NCT03546621, NCT02888106, NCT03852719.

ICTV Virus Taxonomy Profile: Kolmioviridae 2024

Kolmioviridae is a family for negative-sense RNA viruses with circular, viroid-like genomes of about 1.5-1.7 kb that are maintained in mammals, amphibians, birds, fish, insects and reptiles. Deltaviruses, for instance, can cause severe hepatitis in humans. Kolmiovirids encode delta antigen (DAg) and replicate using host-cell DNA-directed RNA polymerase II and ribozymes encoded in their genome and antigenome. They require evolutionary unrelated helper viruses to provide envelopes and incorporate helper virus proteins for infectious particle formation. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Kolmioviridae, which is available at ictv.global/report/kolmioviridae.

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Non-organ-specific autoantibodies with unspecific patterns are a frequent para-infectious feature of chronic hepatitis D

Infections with hepatotropic viruses are associated with various immune phenomena. Hepatitis D virus (HDV) causes the most severe form of viral hepatitis. However, few recent data are available on non-disease-specific and non-organ-specific antibody (NOSA) titers and immunoglobulin G (IgG) levels in chronic hepatitis D (CHD) patients. Here, we examined the NOSA titers and IgG levels of 40 patients with CHD and different disease courses and compared them to 70 patients with chronic hepatitis B (CHB) infection. 43% of CHD patients had previously undergone treatment with pegylated interferon-α (IFN-α). The antibody display of 46 untreated patients diagnosed with autoimmune hepatitis (AIH) was used as a reference. The frequency of elevated NOSA titers (CHD 69% vs. CHB 43%, p < 0.01), and the median IgG levels (CHD 16.9 g/L vs. CHB 12.7 g/L, p < 0.01) were significantly higher in CHD patients than in patients with CHB, and highest in patients with AIH (96%, 19.5 g/L). Also, the antinuclear antibody pattern was homogeneous in many patients with AIH and unspecific in patients with viral hepatitis. Additionally, f-actin autoantibodies were only detectable in patients with AIH (39% of SMA). In CHD patients, IgG levels correlated with higher HDV viral loads, transaminases, and liver stiffness values. IgG levels and NOSA were similar in CHD patients irrespective of a previous IFN-α treatment. In summary, autoantibodies with an unspecific pattern are frequently detected in CHD patients with unclear clinical relevance.

Strain-specific responsiveness of hepatitis D virus to interferon-alpha treatment

Background & Aims

Pegylated interferon alpha (pegIFNα) is commonly used for the treatment of people infected with HDV. However, its mode of action in HDV-infected cells remains elusive and only a minority of people respond to pegIFNα therapy. Herein, we aimed to assess the responsiveness of three different cloned HDV strains to pegIFNα. We used a previously cloned HDV genotype 1 strain (dubbed HDV-1a) that appeared insensitive to interferon-α in vitro, a new HDV strain (HDV-1p) we isolated from an individual achieving later sustained response to IFNα therapy, and one phylogenetically distant genotype 3 strain (HDV-3).

Methods

PegIFNα was administered to human liver chimeric mice infected with HBV and the different HDV strains or to HBV/HDV infected human hepatocytes isolated from chimeric mice. Virological parameters and host responses were analysed by qPCR, sequencing, immunoblotting, RNA in situ hybridisation and immunofluorescence staining.

Results

PegIFNα treatment efficiently reduced HDV RNA viraemia (∼2-log) and intrahepatic HDV markers both in mice infected with HBV/HDV-1p and HBV/HDV-3. In contrast, HDV parameters remained unaffected by pegIFNα treatment both in mice (up to 9 weeks) and in isolated cells infected with HBV/HDV-1a. Notably, HBV viraemia was efficiently lowered (∼2-log) and human interferon-stimulated genes similarly induced in all three HBV/HDV-infected mouse groups receiving pegIFNα. Genome sequencing revealed highly conserved ribozyme and L-hepatitis D antigen post-translational modification sites among all three isolates.

Conclusions

Our comparative study indicates the ability of pegIFNα to lower HDV loads in stably infected human hepatocytes in vivo and the existence of complex virus-specific determinants of IFNα responsiveness.

Impact and implications

Understanding factors counteracting HDV infections is paramount to develop curative therapies. We compared the responsiveness of three different cloned HDV strains to pegylated interferon alpha in chronically infected mice. The different responsiveness of these HDV isolates to treatment highlights a previously underestimated heterogeneity among HDV strains.