Development and assessment of a novel real-time PCR assay for quantitation of hepatitis D virus RNA to study viral kinetics in chronic hepatitis D

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.

Diagnosis of HDV: From virology to non-invasive markers of fibrosis

Hepatitis D viral infection in humans is a disease that requires the establishment of hepatitis B, relying on hepatitis B surface Ag and host cellular machinery to replicate and propagate the infection. Since its discovery in 1977, substantial progress has been made to better understand the hepatitis D viral life cycle, pathogenesis and modes of transmission along with expanding on clinical knowledge related to prevention, diagnosis, monitoring and treatment. The availability of serologic diagnostic assays for hepatitis D infection has evolved over time with current widespread availability, improved detection and standardized reporting. With human migration, the epidemiology of hepatitis D infection has changed over time. Thus, the ability to use diagnostic assays remains essential to monitor the global impact of hepatitis D infection. Separately, while liver biopsy remains the gold standard for the staging of this rapidly progressive and severe form of chronic viral hepatitis, there is an unmet need for clinical monitoring of chronic hepatitis D infection for management of progressive disease. Thus, exploration of the utility of non-invasive fibrosis markers in hepatitis D is ongoing. In this review, we discuss the virology, the evolution of diagnostics and the development of non-invasive markers for the detection and monitoring of fibrosis in patients with hepatitis D infection.

Viral Diagnosis of Hepatitis B and Delta: What We Know and What Is Still Required? Specific Focus on Low- and Middle-Income Countries

To achieve the World Health Organization's (WHO) goals of eradicating viral hepatitis globally by 2030, the regional prevalence and epidemiology of hepatitis B virus (HBV) and hepatitis delta virus (HDV) coinfection must be known in order to implement preventiveon and treatment strategies. HBV/HDV coinfection is considered the most severe form of vira l hepatitis due to it's rapid progression towards cirrhosis, hepatocellular carcinoma, and liver-related death. The role of simplified diagnosticsis tools for screening and monitoring HBV/HDV-coinfected patients is crucial. Many sophisticated tools for diagnoses have been developed for detection of HBV alone as well as HBV/HDV coinfection. However, these advanced techniques are not widely available in low-income countries and there is no standardization for HDV detection assays, which are used for monitoring the response to antiviral therapy. More accessible and affordable alternative methods, such as rapid diagnostic tests (RDTs), are being developed and validated for equipment-free and specific detection of HBV and HDV. This review will provide some insight into both existing and diagnosis tools under development, their applicability in developing countries and how they could increase screening, patient monitoring and treatment eligibility.

Hepatitis D: challenges in the estimation of true prevalence and laboratory diagnosis

Hepatitis delta virus (HDV) is a defective single negative chain RNA virus, as its envelope protein synthesis is dependent on hepatitis B virus (HBV). Studies have consistently shown that coinfection of HBV and HDV is the most serious form of viral hepatitis, with accelerated progression to liver cirrhosis and hepatocellular carcinoma. About 74 million of HBV surface antigen (HBsAg) positive patients worldwide are also co-infected with HDV. Besides, patients with intravenous drug use and high-risk sexual behavior are at higher risk of HDV infection. Therapeutic schedules for HDV are limited, and relapse of HDV has been observed after treatment with pegylated interferon alpha. To reduce the transmission of HDV, all people infected with HBV should be screened for HDV. At present, several serological and molecular detection methods are widely used in the diagnosis of HDV. However, due to the lack of international standards diagnostic results from different laboratories are often not comparable. Therefore, the true prevalence of HDV is still unclear. In this manuscript, we have analyzed various factors influencing the estimation of HDV prevalence. We have also discussed about the advantages and disadvantages of currently available HDV laboratory diagnostic methods, in order to provide some ideas for improving the detection of HDV.

Hepatitis delta virus: From infection to new therapeutic strategies

The hepatitis delta virus (HDV) is a small RNA virus that encodes a single protein and which requires the hepatitis B virus (HBV)-encoded hepatitis B surface antigen (HBsAg) for its assembly and transmission. HBV/HDV co-infections exist worldwide and show a higher prevalence among selected groups of HBV-infected populations, specifically intravenous drug users, practitioners of high-risk sexual behaviours, and patients with cirrhosis and hepatocellular carcinoma. The chronic form of HDV-related hepatitis is usually severe and rapidly progressive. Patterns of the viral infection itself, including the status of co-infection or super-infection, virus genotypes (both for HBV and HDV), and persistence of the virus’ replication, influence the outcome of the accompanying and manifested liver disease. Unfortunately, disease severity is burdened by the lack of an effective cure for either virus type. For decades, the main treatment option has been interferon, administered as mono-therapy or in combination with nucleos(t)ide analogues. While its efficacy has been reported for different doses, durations and courses, only a minority of patients achieve a sustained response, which is the foundation of eventual improvement in related liver fibrosis. The need for an efficient therapeutic alternative remains. Research efforts towards this end have led to new treatment options that target specific steps in the HDV life cycle; the most promising among these are myrcludex B, which inhibits virus entry into hepatocytes, lonafarnib, which inhibits farnesylation of the viral-encoded L-HDAg large hepatitis D antigen, and REP-2139, which interferes with HBsAg release and assembly.

First international external quality assessment for hepatitis delta virus RNA quantification in plasma

Infection by the hepatitis delta virus (HDV), a satellite of the hepatitis B virus (HBV), increases viral liver disease severity. Its diagnosis is thus vital for HBV-infected patients. HDV-RNA load (HDVL) should be assessed and monitored in plasma using real-time reverse-transcriptase polymerase chain reaction assays. Taking advantage of the recently-developed World Health Organization (WHO) HDV international standard (WHO-HDV-IS), the first international external quality control for HDVL quantification was performed. Two panels of samples were sent to 28 laboratories in 17 countries worldwide. Panel A comprised 20 clinical samples of various genotypes (1, 2, and 5-8) and viral loads, including two negative controls. Panel B, composed of dilutions of the WHO-HDV-IS, allowed the conversion of results from copies/mL into IU/mL for HDVL standardization and interlaboratory comparisons. Comprehensive analysis revealed a very high heterogeneity of assay characteristics, including their technical steps and technologies. Thirteen labs (46.3%) properly quantified all 18 positive samples; 16 (57.1%) failed to detect one to up to 10 samples, and several others underestimated (>3 log IU/mL) HDVL of African genotype strains (1 and 5-8). Discrepancies were mainly attributed to either primers or probe mismatches related to the high genetic variability of HDV and, possibly, to the complex secondary structure of the target genomic RNA. The labs were grouped in four clusters by the statistical analysis of their performances. The best clusters comprised the 17 labs that obtained the expected HDVL values, including five that otherwise failed to quantify one or two samples.

CONCLUSION

The results of this international quality-control study underline the urgent need to improve methods used to monitor HDV viremia and will be instrumental in achieving that goal. (Hepatology 2016;64:1483-1494).

Dynamics of in vivo hepatitis D virus infection

Hepatitis-D virus (HDV) is a satellite virus of hepatitis-B virus (HBV) whose intracellular products are required for the completion of the HDV life cycle. HDV can replicate in a cell without the presence of HBV but needs hepatitis B surface antigen (HBsAg) to complete virus assembly and packaging. In order to better understand HDV dynamics, we developed a mathematical model and successfully simulated HBV and HDV data under a range of scenarios. Compared to HBV mono-infection, dual HDV infection resulted in lower chronic HBV DNA levels, with more marked suppression for coinfection (1 logs HBV DNA copies/ml lower) compared to superinfection (0.6 logs HBV DNA copies/ml). Although they have no effect on HBV, prenylation inhibitors may provide the best therapy for reducing HDV viremia irrespective of the stage in which they are commenced. We found that highly effective long term pegylated interferon (IFN) therapy (99.99%) eliminates HBV and HDV viremia while less effective long term IFN therapy (99%) will only produce approximately 2.03 logs and no decrease in HBV and HDV viremia respectively in both coinfection and superinfection settings. Our study also suggests that there is a substantial difference in the outcome of therapies depending upon the time of commencement.

CONCLUSION

Mathematical modeling of HDV infection can describe the complex interplay between this virus and HBV. Simulations suggest that HDV impacts on the feedback mechanisms that maintain cccDNA levels and that targeting these mechanisms may result in new therapeutic agents for both viruses.

Hepatitis D in Children

Hepatitis D virus (HDV) is an uncommon, defective, single-stranded circular RNA virus that is dependent on the hepatitis B virus' surface antigen envelope proteins for transmission. It is highly pathogenic and associated with high rates of progression to cirrhosis and associated complications. HDV continues to ravage endemic parts of Asia and Europe, and its prevalence in the United States, although low, has not decreased in frequency, despite universal hepatitis B virus vaccination, because of lack of testing and underrecognition. There are few reports on the prevalence and characteristics of HDV infection in the pediatric population. We present 2 patients with HDV infection at our institution; both were from eastern Europe and were treated with pegylated interferon-α. The present standard of care treatment for HDV yields suboptimal results, but insights into the virology of hepatitis D are stimulating the search for novel therapeutic approaches, particularly the development of prenylation inhibitors and viral entry inhibitors.

Relevance of a full-length genomic RNA standard and a thermal-shock step for optimal hepatitis delta virus quantification

Hepatitis D virus (HDV) is a defective RNA virus that requires the surface antigens of hepatitis B virus (HBV) (HBsAg) for viral assembly and replication. Several commercial and in-house techniques have been described for HDV RNA quantification, but the methodologies differ widely, making a comparison of the results between studies difficult. In this study, a full-length genomic RNA standard was developed and used for HDV quantification by two different real-time PCR approaches (fluorescence resonance energy transfer [FRET] and TaqMan probes). Three experiments were performed. First, the stability of the standard was determined by analyzing the effect of thawing and freezing. Second, because of the strong internal base pairing of the HDV genome, which leads to a rod-like structure, the effect of intense thermal shock (95°C for 10 min and immediate cooling to -80°C) was tested to confirm the importance of this treatment in the reverse transcription step. Lastly, to investigate the differences between the DNA and RNA standards, the two types were quantified in parallel with the following results: the full-length genomic RNA standard was stable and reliably mimicked the behavior of HDV-RNA-positive samples, thermal shock enhanced the sensitivity of HDV RNA quantification, and the DNA standard underquantified the HDV RNA standard. These findings indicate the importance of using complete full-length genomic RNA and a strong thermal-shock step for optimal HDV RNA quantification.

Considerations for accurate gene expression measurement by reverse transcription quantitative PCR when analysing clinical samples

Reverse transcription quantitative PCR is an established, simple and effective method for RNA measurement. However, technical standardisation challenges combined with frequent insufficient experimental detail render replication of many published findings challenging. Consequently, without adequate consideration of experimental standardisation, such findings may be sufficient for a given publication but cannot be translated to wider clinical application. This article builds on earlier standardisation work and the MIQE guidelines, discussing processes that need consideration for accurate, reproducible analysis when dealing with patient samples. By applying considerations common to the science of measurement (metrology), one can maximise the impact of gene expression studies, increasing the likelihood of their translation to clinical tools.

Serological and molecular diagnosis of hepatitis delta virus infection: results of a French national quality control study

A French national quality control study for the serological and molecular diagnosis of hepatitis delta virus (HDV) was organized. Total HDV antibodies were properly detected by all laboratories; 8/14 laboratories failed to detect low titers of IgM, and 6/11 failed to quantify and/or underestimated the RNA viral load in several samples. These discrepancies are likely related to the molecular diversity of HDV.

Hepatitis delta: epidemiology, diagnosis and management 36 years after discovery

With recent studies showing increased prevalence of hepatitis delta (HDV) even in the US, Australia, and some countries in Europe, and very high prevalence in endemic regions, HDV infection is far from being a disappearing disease. Although immigrants from endemic countries have been shown to have increased risk, studies have clearly shown that the disease is not solely appearing in traditional high-risk groups. Recent studies provide increasing evidence that sexual transmission may be an important factor in HDV infection spread. Based on the totality of evidence showing increased disease progression and substantially increased risk of cirrhosis in HDV-infected CHB patients, and the current studies showing higher than expected prevalence, it is time to call for HDV screening of all CHB patients. HDV viral load detection and measurement should be considered in all patients whether or not they are anti-HDV-positive. With universal screening of CHB patients for HDV, earlier diagnosis and consideration of treatment would be possible. Current treatment of HDV is IFN-based therapy with or without HBV antivirals, but current research indicates the possibility that prenylation inhibitors, entry inhibitors, HBsAg release inhibitors, or other therapies currently in the pipeline may provide more effective therapy in the future. In addition, universal screening would serve the important public health goal of allowing patients to be educated on their status and on the need for HDV-negative patients to protect themselves against superinfection and for HDV-infected patients to protect against transmission to others. Further studies and global awareness of HDV infection are needed.

One-step real-time PCR assay for detection and quantitation of hepatitis D virus RNA

Hepatitis D virus (HDV) is a defective virus which requires hepatitis B virus (HBV) surface antigen (HBsAg) for its assembly. Hepatitis B infected individuals co-infected or superinfected with HDV often present with more severe hepatitis, progress faster to liver disease, and have a higher mortality rate than individuals infected with HBV alone. Currently, there are no commercially available clinical tests for the detection and quantitation of HDV RNA in the United States. A one-step TaqMan quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was developed for detection of HDV RNA, designing primers located in the region just downstream from the HDV antigen gene. The assay has the potential to detect all eight HDV genotypes. A quantifiable synthetic RNA control was also developed for use in the determination of HDV RNA titers in clinical samples. The limit of detection of this assay is 7.5×10(2) HDV RNA copies/ml with a dynamic range of six logs. Most clinical specimens tested (40/41) fell within the linear range of the assay. The median HDV RNA titer of the tested specimens was 6.24×10(6) copies/ml, with a range of 8.52×10(3)-1.79×10(9) copies/ml. Out of 132 anti-HDV-positive specimens 41 (31.1%) were positive for HDV RNA.