HDV RNA assays: Performance characteristics, clinical utility, and challenges

Coinfection with HBV and HDV results in hepatitis D, the most severe form of chronic viral hepatitis, frequently leading to liver decompensation and HCC. Pegylated interferon alpha, the only treatment option for chronic hepatitis D for many years, has limited efficacy. New treatments are in advanced clinical development, with one recent approval. Diagnosis and antiviral treatment response monitoring are based on detection and quantification of HDV RNA. However, the development of reliable HDV RNA assays is challenged by viral heterogeneity (at least 8 different genotypes and several subgenotypes), intrahost viral diversity, rapid viral evolution, and distinct secondary structure features of HDV RNA. Different RNA extraction methodologies, primer/probe design for nucleic acid tests, lack of automation, and overall dearth of standardization across testing laboratories contribute to substantial variability in performance characteristics of research-based and commercial HDV RNA assays. A World Health Organization (WHO) standard for HDV RNA, available for about 10 years, has been used by many laboratories to determine the limit of detection of their assays and facilitates comparisons of RNA levels across study centers. Here we review challenges for robust pan genotype HDV RNA quantification, discuss particular clinical needs and the importance of reliable HDV RNA quantification in the context of drug development and patient monitoring. We summarize distinct technical features and performance characteristics of available HDV RNA assays. Finally, we provide considerations for the use of HDV RNA assays in the context of drug development and patient monitoring.

An Insight Into the Factors Affecting the Prevalence and Natural History of Hepatitis D

Epidemiological studies and recent metanalyses addressing hepatitis D have reported a wide variation in the prevalence of the disease. Between 4.5% to 15% of all hepatitis B surface antigen (HBsAg) positive patients are thought to harbor the hepatitis D virus. The emergent variation in prevalence can be attributed to several factors. Unsurprisingly, published literature shows that the prevalence of the disease is higher in areas where aggregate viral hepatitis infections are endemic and amongst groups with high-risk practices facilitating the horizontal transfer. Meanwhile, the natural history of the disease is influenced by the genotype of the virus, the hepatitis D virus (HDV) RNA levels, HBV-HDV codominance, HBsAg titers, HBV genotype, nutritional status, HIV co-infection, and prior treatment. Together these factors contribute to the accelerated development of fibrosis and the increased risk of hepatocellular carcinoma. Superinfection with genotype 1 results in rapid progression to cirrhosis with lower rates of remission. Genotype 3 follows an aggressive course but shows a good response to interferon therapy. Other genotypes have better outcomes. The course of the disease leading to these outcomes can be tracked by HDV-specific models integrating clinical surrogate markers and epidemiological factors such as age, region, alanine aminotransferase (ALT), gamma-glutamyl transferase, albumin, platelets and cholinesterase, and liver stiffness.

Emerging drugs for hepatitis D

INTRODUCTION

Chronic hepatitis delta (CHD) is the most severe form of chronic viral hepatitis. Until recently, its treatment consisted of pegylated interferon alfa (pegIFN) use.

AREAS COVERED

Current and new drugs for treating CHD. Virus entry inhibitor bulevirtide has received conditional approval by the European Medicines Agency. Prenylation inhibitor lonafarnib and pegIFN lambda are in phase 3 and nucleic acid polymers in phase 2 of drug development.

EXPERT OPINION

Bulevirtide appears to be safe. Its antiviral efficacy increases with treatment duration. Combining bulevirtide with pegIFN has the highest antiviral efficacy short-term. The prenylation inhibitor lonafarnib prevents hepatitis D virus assembly. It is associated with dose dependent gastrointestinal toxicity and is better used with ritonavir which increases liver lonafarnib concentrations. Lonafarnib also possesses immune modulatory properties which explains some post-treatment beneficial flare cases. Combining lonafarnib/ritonavir with pegIFN has superior antiviral efficacy. Nucleic acid polymers are amphipathic oligonucleotides whose effect appears to be a consequence of phosphorothioate modification of internucleotide linkages. These compounds led to HBsAg clearance in a sizeable proportion of patients. PegIFN lambda is associated with less IFN typical side effects. In a phase 2 study it led to 6 months off treatment viral response in one third of patients.

What does quantitative HBsAg level mean in chronic hepatitis D infection?

OBJECTIVE

In hepatitis delta virus (HDV) infection, which is an important etiological cause of chronic liver disease, the relationship between serum quantitative HBsAg level and fibrosis and histological activity was investigated.

METHODS

Between 2014 and 2020, 98 patients with chronic HDV infection (53 noncirrhotic, 45 cirrhotic) participated in this prospectively designed study. Quantitative HBsAg levels of the patients were measured and their relationship with the stage of chronic liver disease was compared with histological activity index (HAI), fibrosis score and HDV RNA, model for end-stage liver disease score and other biochemical parameters.

RESULTS

All patients were infected with genotype 1 (100%). HBeAg was positive in 8 (8.1%) of the patients. A correlation was found between quantitative HBsAg level and HDV RNA level in patients with both cirrhotic (r = 0.568; P < 0.001) and noncirrhotic (r = 0.644; P < 0.001) HDV infection. Alanine transaminase (P = 0.001; r = 0.495) and aspartate transaminase (P = 0.001; r = 0.511) levels correlated with quantitative HBsAg levels, more prominently in noncirrhotic patients. There was a correlation between quantitative HBsAg level and histological activity index (HAI) in patients with noncirrhotic HDV infection (P < 0.001; r = 0.664). In receiver operating characteristic analysis, both quantitative HBsAg (for cutoff: 1000; sensitivity 76%; specificity 17%; P = 0.335) and HDV RNA (for cutoff: 100000; sensitivity 2%; specificity 98%; P = 0.096) were not predictive markers for cirrhosis.

CONCLUSION

Quantitative HBsAg level can be evaluated as an indicator of viral replication and histological activity in patients with chronic delta hepatitis without cirrhosis. We think that quantitative HBsAg level will be useful in the management of chronic HDV infection, especially in noncirrhotic patients.

Hepatitis B and Hepatitis D Viruses: A Comprehensive Update with an Immunological Focus

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) are highly prevalent viruses estimated to infect approximately 300 million people and 12-72 million people worldwide, respectively. HDV requires the HBV envelope to establish a successful infection. Concurrent infection with HBV and HDV can result in more severe disease outcomes than infection with HBV alone. These viruses can cause significant hepatic disease, including cirrhosis, fulminant hepatitis, and hepatocellular carcinoma, and represent a significant cause of global mortality. Therefore, a thorough understanding of these viruses and the immune response they generate is essential to enhance disease management. This review includes an overview of the HBV and HDV viruses, including life cycle, structure, natural course of infection, and histopathology. A discussion of the interplay between HDV RNA and HBV DNA during chronic infection is also included. It then discusses characteristics of the immune response with a focus on reactions to the antigenic hepatitis B surface antigen, including small, middle, and large surface antigens. This paper also reviews characteristics of the immune response to the hepatitis D antigen (including small and large antigens), the only protein expressed by hepatitis D. Lastly, we conclude with a discussion of recent therapeutic advances pertaining to these viruses.

Hepatitis delta virus: Disease assessment and stratification

Hepatitis D virus (HDV) causes one of the most severe forms of hepatitis in people with chronic hepatitis B (CHB) infection. Timely and accurate assessment of hepatitis delta virus (HDV) and disease stratification is mandatory for thorough pre-therapeutic evaluation for prioritizing treatment and outcome prediction. Viral biomarkers associated with HDV and hepatitis B virus (HBV) are crucial to aid in diagnosis, and monitoring of serum viral nucleic acids for both viruses is recommended. Liver biopsy remains the gold standard for staging of liver fibrosis and grading of histological activity and should remain central for diagnostic purposes, but is also of importance for research to enhance our understanding of HDV. The emergence of novel non-invasive tests for the assessment of liver fibrosis in HDV patients coupled with the well-recognized potential complications of liver biopsy has resulted in reduced utility of liver biopsy in clinical practice. Preliminary data suggest that these emerging non-invasive modalities appear to be reliable, and their use is supported, similar to other viral hepatitis. Nevertheless, further validation is required before their widespread adoption into clinical practice.

Hepatitis D infection: from initial discovery to current investigational therapies

Hepatitis D is the most severe form of viral hepatitis associated with a more rapid progression to cirrhosis and an increased risk of hepatocellular carcinoma and mortality compared with hepatitis B mono-infection. Although once thought of as a disappearing disease, hepatitis D is now becoming recognized as a serious worldwide issue due to improvement in diagnostic testing and immigration from endemic countries. Despite these concerns, there is currently only one accepted medical therapy (pegylated-interferon-α) for the treatment of hepatitis D with less than desirable efficacy and significant side effects. Due to these reasons, many patients never undergo treatment. However, increasing knowledge about the virus and its life cycle has led to the clinical development of multiple promising new therapies that hope to alter the natural history of this disease and improve patient outcome. In this article, we will review the literature from discovery to the current investigational therapies.

New treatment options for delta virus: Is a cure in sight?

Current treatment of chronic hepatitis D viral infection with interferons is poorly tolerated and effective only in a minority of patients. Despite delta virus causing the most severe form of chronic viral hepatitis, no other treatments are available. After many years of inactivity, there is now hope for new treatment approaches for delta virus and some are likely to enter clinical practice in the near future. Four new treatment approaches are currently being evaluated in phase 2 studies. These involve the hepatocyte entry inhibitor myrcludex B, the farnesyl transferase inhibitor lonafarnib, the nucleic acid inhibitor REP 2139 Ca and pegylated interferon lambda. Results obtained so far are promising, and phase 3 studies are expected shortly. This review summarizes the available data on the efficacy and safety of these new drugs.

Hepatitis B Virus-Hepatitis D Virus mother-to-child co-transmission: A retrospective study in a developed country

BACKGROUND & AIMS

Hepatitis B Virus (HBV) DNA during chronic infection can reach levels at which mother-to-child (MTC) transmission frequently occurs despite passive-active immunization of newborns. Hepatitis D Virus (HDV) RNA can reach high levels, we assessed HBV/HDV MTC co-transmission.

METHODS

Monocentric retrospective study (registered in ClinicalTrials.gov (NCT02044055)), after informed consent in HBV/HDV co-infected women pregnant between 01/01/2004 and 01/01/2015 in Paris, France. The children were tested when 24 months of age or older.

RESULTS

Twenty-two (3%) of 742 HBV infected women, HDV co-infected, gave birth to 54 children during the study period. HBV DNA was above 5 Log₁₀ I.U/mL in 10 pregnancies previous any treatment, with HDV RNA of less than 2.3 Log₁₀ I.U/mL. HDV RNA was above 5 Log₁₀ I.U/mL in eight pregnancies previous any treatment, with HBV DNA of less than 1.5 Log₁₀ I.U/mL. Inverse patterns of HBV DNA and HDV RNA were observed in 17 of 35 (49%) pregnancies: 13 (76%) received no HBV treatment; four (24%) were treated. HBV DNA was under 5 Log₁₀ I.U/mL in 46 of the 50 assessed women (92%) at birth. Of the 36 assessed children, given passive-active immunization, 24 (66%) were protected, 10 (28%) were neither infected nor protected, one was chronically HBV infected, and one had a past HBV infection. HDV Ab was negative in the 36 children.

CONCLUSIONS

These results suggest that HBV/HDV MTC co-transmission is exceptional. Studies are needed, mainly in developing countries.

Recent advances in managing hepatitis D

Hepatitis D virus (HDV) infection leads to the most severe form of chronic viral hepatitis and requires the attention of a liver specialist. In this review, I will recapitulate recent advances in the management of HDV, present background information on HDV infection as well as current chronic hepatitis D treatment, briefly examine the HDV life cycle and discuss new management strategies.

The role of quantitative hepatitis B surface antigen revisited

In the past 10years, there has been a lot of enthusiasm surrounding the use of serum hepatitis B surface antigen (HBsAg) quantification to predict disease activity and monitor treatment response in chronic hepatitis B. The measurement of HBsAg levels have been standardized in IU/ml, and nowadays it is almost a mandatory measurement due to the development of new antiviral treatments aiming at HBsAg seroclearance, i.e., functional cure of hepatitis B. Recently, there has been an improved understanding of the molecular virology of HBsAg, and particularly the relative roles of covalently closed circular DNA and integrated hepatitis B virus (HBV) DNA. This has shed new light on the interpretation of HBsAg levels in different phases of chronic hepatitis B. HBsAg level can assist the differentiation of immune tolerance and immune clearance in hepatitis B e antigen (HBeAg)-positive patients, and it can predict inactive disease and spontaneous HBsAg seroclearance in HBeAg-negative patients. The determination of HBsAg level is pivotal to individualize pegylated interferon (PegIFN) treatment; it is the key investigation to decide early termination of PegIFN among non-responders. Among patients treated by nucleos(t)ide analogues, responders tend to have dramatic reduction of HBsAg to low levels, which may be followed by HBsAg seroclearance. With newer data on combination treatment of PegIFN and nucleos(t)ide analogues as well as emerging new antiviral agents, HBsAg quantification is expected to become increasingly important to monitor and guide antiviral therapy for chronic hepatitis B.

Performance Characteristics of a New Consensus Commercial Kit for Hepatitis D Virus RNA Viral Load Quantification

Hepatitis D virus (HDV) is responsible for fulminant hepatitis and liver failure and accelerates evolution toward cirrhosis and hepatocellular carcinoma in hepatitis B virus (HBV)-infected patients. To date, treatment relies upon long-term administration of pegylated alpha-interferon with a sustained virological response in 30% of the patients. Very recently, new, promising anti-HDV therapies have been developed and are already being used in clinical trials. HDV RNA viral load (HDVL) monitoring must be an integral part of the management of the infected patients. However, HDV genus is characterized by a high genetic variability into eight genotypes (HDV-1 to -8), and most available in-house or commercial assays are useful for only a limited subset of genotypes. Results of a comparison of the performance of a new kit for HDVL quantification with the consensus in-house assay of the French National Reference Laboratory for HDV developed in 2005 are reported here. A total of 611 clinical samples of all HDV genotypes with various HDVL values, including several consecutive samples over several years from 36 patients, were studied. A specificity, sensitivity, and reproducibility evaluation was conducted using HDV-positive clinical samples, hepatitis A, B, C and E (HAV, HBV, HCV, and HEV, respectively) and HIV mono-infected samples, and the WHO HDV RNA international standard. Overall results were strictly comparable between the two assays (median difference, 0.07 log IU/ml), with high diagnosis precision and capacity. In summary, this new kit showed high performance in detection/quantification of HDVL, regardless of the genotype of the infecting strain used, and seems to be a suitable tool for patient management.

HBsAg kinetics in chronic hepatitis D during interferon therapy: on-treatment prediction of response

BACKGROUND

Therapy of chronic hepatitis D with Interferon is successful when testing for HDV-RNA turns negative. This end-point is disputed.

AIM

To assess the role of serum hepatitis B surface antigen (HBsAg) in the clearance of HDV-RNA in pegylated interferon (Peg-IFN)-treated chronic hepatitis D (CHD).

METHODS

Sixty-two patients with CHD, treated with Peg-IFN, were considered. The patients belonged to three groups: 14 patients cleared the HBsAg and HDV-RNA (responders, R), 12 cleared the HDV-RNA remaining positive for HBsAg (partial responders, PR) and 36 cleared neither the HBsAg nor the HDV-RNA (nonresponders, NR).

RESULTS

In responders, at baseline the median value (mv) of HBsAg and HDV-RNA was 1187 and 188 663 IU/mL. By month 6 of therapy, HBsAg declined to less than 1000 IU/mL and HDV-RNA was undetectable in 12 patients. In NR, the pre-therapy median value of HBsAg and HDV viremia was 6577 and 676 319 IU/mL. There was no significant reduction of antigen at month 6; after a decline, HDV-RNA rebounded to baseline levels. In PR, the median value of baseline HBsAg was 7031 IU/mL; it declined at month 6 in the majority. HDV-RNA progressively declined from an initial median value of 171 405 IU/mL. HBsAg <1000 IU/mL at month 6 discriminated responders and PR from NR (P < 0.001). By ROC curve, the threshold of 0.105 log reduction of HBsAg associated with 1.610 log reduction of HDV-RNA from baseline to month 6 predicted the clearance of this marker.

CONCLUSIONS

A reduction of serum HBsAg is mandatory for the definitive clearance of the HDV-RNA. Quantitative HBsAg may predict the long-term response to Peg-IFN therapy and provide a guide to prolong or stop treatment.

Pegylated Interferon α Therapy in Chronic Delta Hepatitis: A One-Center Experience

BACKGROUND

The only established therapy for chronic viral delta hepatitis, the most severe form of viral hepatitis is treatment with pegylated-interferon α (Peg IFN α).

OBJECTIVES

In this study, we aimed to determine the efficacy of pegylated-interferon α 2a (Peg-IFN α 2a) and 2b (Peg IFN α 2b) in the treatment of patients infected with chronic delta hepatitis virus.

PATIENTS AND METHODS

The sample size was based on available patients potentially to be recruited. Data of 63 patients receiving either Peg IFN alpha 2a or Peg IFN alpha 2b were retrospectively assessed in the present cohort study performed in Turkey. Of 56 patients completed the study, 41 received Peg IFN α 2a and 15 received Peg IFN α 2b for 12 months. Patients were evaluated for biochemical and virological responses at the end of given treatment and six months after the treatment.

RESULTS

Stage of fibrosis was found high in both groups (85.4% vs. 86.7%), while cirrhosis was higher in the group of Peg IFN α 2b (53.3% vs. 34.1%). At the end of treatment, either hepatitis delta virus RNA (HDV RNA) alone or both HDV RNA and hepatitis b virus DNA (HBV DNA) had negative results in 32% of patients. Although HDV RNA negativity was sustained in 30.3% of patients, negativity of both HDV RNA and HBV DNA was decreased to 19.6% six months after completion of the treatment. HBV DNA became positive in one third of patients with response at six months after completion of the treatment (10.7% of all patients). HDV RNA negativity at month six was found as a predictor of positive response. No significant difference was found between Peg IFN α 2a and Peg IFN α 2b for virological response rate.

CONCLUSIONS

Treatment with Peg IFN α achieved a sustained negativity of HDV RNA in about one third of patients. Duration of Peg IFN α therapy might be prolonged to at least 24 months or more to prevent the occurrence of Hepatitis B virus (HBV) relapse encountered six months after completion of the treatment.

Clinical utility of hepatitis B surface antigen quantitation in patients with chronic hepatitis B: a review

This clinically relevant review focuses on recent findings concerning hepatitis B surface antigen (HBsAg) quantitation in untreated patients and treated patients with chronic hepatitis B. Recent studies and emerging data have shown that both HBsAg and hepatitis B virus (HBV) DNA levels decline during the natural course of a chronic HBV infection; they are lowest in the inactive phase, which is also characterized by the highest HBsAg/HBV DNA ratio. It has been demonstrated that the combined use of HBsAg and HBV DNA levels might help in the identification of true inactive carriers with high accuracy. Retrospective analyses of HBsAg levels in patients undergoing therapy have suggested a role for HBsAg quantitation in monitoring the response to therapy. In comparison with nucleos(t)ide analogues (NAs), interferon-based therapy results in greater overall declines in serum HBsAg levels. A rapid on-treatment decline in HBsAg levels appears to be predictive of a sustained response. With the aid of HBsAg quantitation, it appears that we can anticipate an individualized approach to tailoring the treatment duration. The proposal of early stopping rules for patients not responding to pegylated interferon (according to a lack of any HBsAg decline) represents a step toward a response-guided approach. The development of stopping rules for patients treated with NAs is desirable for reducing the need for lifelong therapy. However, before stopping rules for antiviral therapy can be applied, we need to learn more about the kinetics of HBsAg declines during the natural history of the infection and as a response to therapy so that we can better define the best timing, the relevant HBsAg cutoff levels, and the best ways to apply these rules in clinical practice.

Six-Year Follow-Up of Hepatitis B Surface Antigen Concentrations in Tenofovir Disoproxil Fumarate Treated HIV–Hbv-Coinfected Patients

Background

Quantitative measurement of hepatitis B surface antigen (HBsAg) has been proposed as a surrogate marker of treatment efficacy when HBV DNA load becomes undetectable. Our main objective was to study the kinetics of HBsAg level in HIV–HBV-coinfected patients with undetectable HBV DNA load under treatment containing tenofovir disoproxil fumarate (TDF).

Methods

A retrospective analysis was performed on frozen serum samples of 33 HIV–HBV-coinfected patients who were treated with TDF and had undetectable HBV DNA for ≥1 year. Baseline and serial follow-up samples were assayed for HBsAg levels.

Results

The characteristics of the patients at TDF initiation were median age 43.6 years, median HBV DNA load 2 log10 IU/ml and median HBsAg concentration 3.4 log10 IU/ml. Ten patients were positive for hepatitis B e antigen. Baseline median HBsAg concentration, defined 1 year after HBV DNA became undetectable, was 3.1 log10 IU/ml. Overall, from years 1 to 6 and a median duration of TDF treatment of 2.6 years, the median HBsAg concentration decreased slowly. Notably, only 13 (39%) patients presented a constant decrease of HBsAg concentration, whereas the remaining had fluctuating or increasing HBsAg concentrations. The slope was not influenced by HBeAg status, HIV infection duration and CD4+ T-cell count at baseline or at nadir.

Conclusions

Despite control of HBV DNA replication under efficient TDF treatment, HBsAg levels persistently decreased in only 39% of HIV–HBV-coinfected patients. Larger follow-up studies are needed to determine whether HBsAg concentration monitoring under analogue treatment can be used as a reliable marker for HBV clearance.

Quantitative Analysis of Hepatitis D Virus RNA and Hepatitis B Surface Antigen Serum Levels in Chronic Delta Hepatitis Improves Treatment Monitoring

Background/aims

Treatment of chronic delta hepatitis is long and difficult and better monitoring is needed.

Methods

In this study, hepatitis delta virus (HDV) RNA, hepatitis B surface antigen (HBsAg) and hepatitis B virus (HBV) DNA were retrospectively quantified in 53 patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis delta. Twenty-one had received 28 courses of 3–5 MU interferon-α2b (IFN-α2b) thrice weekly for a median of 12.6 months (interquartile range [IQR]: 7.3–31.6), five had received eight courses of 100 mg lamivudine (LAM) daily for 23.6 months (IQR: 8.4–61.5) and 27 were untreated. The controls were 54 untreated, randomly selected, HBeAg-negative chronic hepatitis B patients without delta infection. Quantification of serum HDV RNA, HBsAg and HBV DNA were performed at baseline, during and at the end of treatment and end of follow up.

Results

Untreated patients had significantly higher median HBsAg levels than controls (5,872 vs 3,501 IU/ml; P=0.046), but lower median HBV DNA levels (2.933 vs 6.459 log10 copies/ml; P<0.001). Median baseline HDV RNA (6.374 log10 copies/ml) was similar in IFN-α2b-treated, LAM-treated and untreated patients. At the end of treatment, IFN-α2b significantly suppressed in paired measurements HDV RNA ( P=0.012) and HBsAg ( P=0.043), but LAM was inefficient. In IFN-α2b-treated patients, HDV RNA became undetectable in five patients within a median of 30 months (IQR: 8–90), followed by a slower decrease in HBsAg.

Conclusions

In untreated chronic delta hepatitis, suppressed HBV replication is associated with significantly increased HBsAg serum levels. IFN-α2b significantly suppresses both HDV RNA and HBsAg, but LAM has no effect. Long-term IFN-α2b treatment (IQR: 1.5–5.0 years) appears necessary for undetectable serum HDV RNA and further treatment is required for HBsAg loss. Monitoring of HDV RNA and HBsAg serum levels in patients with chronic delta hepatitis provides insight during treatment.