A Rapid Point-of-Care Test for the Serodiagnosis of Hepatitis Delta Virus Infection

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.

Hepatitis Delta Virus Surveillance Practice among Clinicians in Nigeria: A Cross-Sectional Survey

BACKGROUND

The near total absence of routine Hepatitis Delta Virus (HDV) screening in many countries in sub-Saharan Africa is a major challenge to understanding the burden of HDV in the region.

AIM

To evaluate Hepatitis Delta Virus screening practices and associated factors among clinicians in Nigeria.

METHODS

A cross-sectional study was conducted in June-July 2022, in which a self-administered questionnaire that inquired about HDV awareness, screening practices, and treatment options was shared electronically with consenting clinicians practicing in Nigeria. At the end of the survey, data was analyzed using descriptive and inferential statistics. The level of significance was set at 0.05.

RESULTS

At the end of the survey, 210 of the 213 responses retrieved from respondents were analyzed. The respondent's mean age was 38.60 ± 7.27 years with a male-to-female ratio of 1:2.5. They comprised 13.8% gastroenterologists and 86.2% respondents in other areas of clinical medicine. The study showed that 89.5% of the respondents knew that HDV infection occurs only in hepatitis B virus (HBV)-infected individuals. Most (91.4%) respondents do not screen for HDV in chronic HBV patients, mainly due to the non-availability of screening tools and lack of awareness of any screening test for HDV. Research interest was reported as the reason for screening among clinicians who had ever screened for HDV. Pegylated interferon was the main regimen used for treatment by 87.5% of respondents. About 2% did not know treatment options for HDV. A significant association between knowledge of HDV infection and area of specialty, as well as the nature of medical practice was noted (P = 0.008 and 0.013, respectively).

CONCLUSION

The study showed a high level of awareness of HDV dependency on HBV, for natural infection to occur. However, it documented very minimal HDV screening in clinical settings and factors affecting screening among clinicians.

The Prevalence and Molecular Epidemiology of Hepatitis Delta Virus in Nigeria: The Results of a Nationwide Study

Hepatitis delta virus (HDV) is a satellite of hepatitis B virus (HBV), which requires the HBV surface antigen (HBsAg) for its assembly and propagation. Although countries affected by HBV infection in Africa are well identified, data on HDV infection are still scarce, like in Nigeria, where HBV infection is endemic. In this study, we aimed to determine the prevalence of HDV infection and identify the circulating genotypes/strains in the country. A nationwide study was performed on 1281 HBsAg-positive samples collected from patients across eleven sites drawn from the six geopolitical zones in Nigeria. Anti-HDV antibody (HDV-Ab) screening and HDV-RNA viral load quantification were performed using a commercial ELISA assay and real-time RT-PCR kit, respectively. HDV genotyping was performed by the Sanger sequencing of amplicons from the so-called R0 region of the viral genome, followed by phylogenetic analyses. Of the 1281 HBsAg-positive samples, 61 (4.8%) were HDV-Ab positive, among which, 12 (19.7%) were HDV-RNA positive. Genotypes were obtained for nine of them: seven "African" HDV-1, one "Asian/European" HDV-1 and one HDV-6. This study shows that Nigeria is a country of low HDV prevalence where mainly "African" genotype-1 strains are circulating.

Costs of Community-Based Viral Hepatitis Screening in Cameroon Using Point-of-Care Technologies

This cost analysis of a community-based viral hepatitis screening program in Cameroon found an investment of $3.52 per person screened, $50.63 per new diagnosis of hepatitis B, $159.45 per new diagnosis of hepatitis C, and $47.97 per new diagnosis of either hepatitis B or C.

Advances and Challenges in Managing Hepatitis D Virus: Evolving Strategies

Purpose of Review

Hepatitis D Virus (HDV), although a small defective virus, poses a substantial public health challenge due to lack of awareness, underrecognized prevalence, and limited treatment options. Universal HDV screening within hepatitis B virus (HBV) cohorts is essential to address this issue. Despite its aggressive nature, effective HDV therapies have remained elusive for over four decades.

Recent Findings

Advances in understanding HDV's biology and clinical behavior offer potential therapeutic breakthroughs, fostering optimism. As insights grow, effective and targeted therapies are being developed to improve HDV management.

Summary

This review delves into HDV's intricate structure and biology, highlighting formidable hurdles in antiviral development. It emphasizes the importance of widespread screening, exploring noninvasive diagnostics, and examining current and emerging innovative therapeutic strategies. Moreover, the review explores models for monitoring treatment response. In essence, this review simplifies the complexities of effectively combating HDV.

CRISPR/Cas13a-Assisted accurate and portable hepatitis D virus RNA detection

BACKGROUND & AIMS

Hepatitis delta virus (HDV) infection accelerates the progression of chronic hepatitis B virus (HBV) infection, posing a large economic and health burden to patients. At present, there remains a lack of accurate and portable detection methods for HDV RNA. Here, we aim to establish a convenient, rapid, highly sensitive and specific method to detect HDV RNA using CRISPR-Cas13a technology.

METHODS

We established fluorescence (F) and lateral flow strip (L) assays based on CRISPR-Cas13a combined with RT-PCR and RT-RAA for HDV RNA detection, respectively. we conducted a cohort study of 144 patients with HDV-IgG positive to evaluate the CRISPR-Cas13a diagnostic performance for identifying HDV in clinical samples, compared to RT-qPCR and RT-ddPCR.

RESULTS

For synthetic HDV RNA plasmids, the sensitivity of RT-PCR-CRISPR-based fluorescence assays was 1 copy/μL, higher than that of RT-qPCR (10 copies/μL) and RT-ddPCR (10 copies/μL); for HDV RNA-positive samples, the sensitivity of RT-RAA-CRISPR-based fluorescence and lateral flow strip assays was 10 copies/μL, as low as that of RT-qPCR and RT-ddPCR, and the assay took only approximately 85 min. Additionally, the positivity rates of anti-HDV IgG-positive samples detected by the RT-qPCR, RT-ddPCR, RT-PCR-CRISPR fluorescence and RT-RAA-CRISPR lateral flow strip methods were 66.7% (96/144), 76.4% (110/144), 81.9% (118/144), and 72.2% (104/144), respectively.

CONCLUSIONS

We developed a highly sensitive and specific, as well as a portable and easy CRISPR-based assay for the detection of HDV RNA, which could be a prospective measure for monitoring the development of HDV infection and evaluating the therapeutic effect.

Point-of-Care Testing for Hepatitis Viruses: A Growing Need

Viral hepatitis, caused by hepatitis A virus (HAV), hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV), or hepatitis E virus (HEV), is a major global public health problem. These viruses cause millions of infections each year, and chronic infections with HBV, HCV, or HDV can lead to severe liver complications; however, they are underdiagnosed. Achieving the World Health Organization's viral hepatitis elimination goals by 2030 will require access to simpler, faster, and less expensive diagnostics. The development and implementation of point-of-care (POC) testing methods that can be performed outside of a laboratory for the diagnosis of viral hepatitis infections is a promising approach to facilitate and expedite WHO's elimination targets. While a few markers of viral hepatitis are already available in POC formats, tests for additional markers or using novel technologies need to be developed and validated for clinical use. Potential methods and uses for the POC testing of antibodies, antigens, and nucleic acids that relate to the diagnosis, monitoring, or surveillance of viral hepatitis infections are discussed here. Unmet needs and areas where additional research is needed are also described.

State of the Art: Test all for Anti-Hepatitis D Virus and Reflex to Hepatitis D Virus RNA Polymerase Chain Reaction Quantification

Diagnosis of HDV exposure is based on clinical assays of anti-hepatitis D antibody and current infection with hepatitis D RNA PCR. The role of hepatitis D antigen testing is not yet defined. RT-qPCR is the gold standard for measuring HDV RNA viral load, which is used to assess response to the treatment of HDV infection. Gaps in testing include poor sensitivity of antigen testing and quantitative HDV RNA accuracy can be affected by the genotypic variability of the virus and variation in laboratory techniques. There is also a limitation in HDV testing due to access, cost, and limited knowledge of testing indications. Droplet digital PCR promises to be a more accurate method to quantify HDV RNA. Also, the recent development of a rapid HDV detection test could prove useful in resource-limited areas.

Hepatitis delta: Epidemiology to recent advances in therapeutic agents

Hepatitis D virus (HDV) was first described in 1977 and is dependent on the presence of hepatitis B surface antigen (HBsAg) for its entry into cells and on the human host for replication. Due to the envelopment with the hepatitis B virus (HBV) envelope, early phases of HDV entry resemble HBV infection. Unlike HBV, HDV activates innate immune responses. The global prevalence of HDV is estimated to be about 5% of HBsAg positive individuals. However, recent studies have described a wide range of prevalence between 12 to 72 million individuals. Infection can occur as super-infection or co-infection. The diagnosis of active HDV infection involves screening with anti HDV antibodies followed by quantitative PCR testing for HDV RNA in those who are HBsAg positive. The diagnostic studies have evolved over the years improving the validity and reliability of the tests performed. HDV infection is considered the most severe form of viral hepatitis and the HDV genotype may influence the disease course. There are eight major HDV genotypes with prevalence varying by geographic region. HDV treatment has been challenging as HDV strongly depends on the host cell for replication and provides few, if any viral targets. Better understanding of HDV virology has led to the development of several therapeutic agents currently being studied in different phase II and III clinical trials. There is increasing promise of effective therapies that will ameliorate the course of this devastating disease.

Hepatitis D double reflex testing of all hepatitis B carriers in low-HBV- and high-HBV/HDV-prevalence countries

Hepatitis D virus (HDV) infection occurs as a coinfection with hepatitis B and increases the risk of hepatocellular carcinoma, decompensated cirrhosis, and mortality compared to hepatitis B virus (HBV) monoinfection. Reliable estimates of the prevalence of HDV infection and disease burden are essential to formulate strategies to find coinfected individuals more effectively and efficiently. The global prevalence of HBV infections was estimated to be 262,240,000 in 2021. Only 1,994,000 of the HBV infections were newly diagnosed in 2021, with more than half of the new diagnoses made in China. Our initial estimates indicated a much lower prevalence of HDV antibody (anti-HDV) and HDV RNA positivity than previously reported in published studies. Accurate estimates of HDV prevalence are needed. The most effective method to generate estimates of the prevalence of anti-HDV and HDV RNA positivity and to find undiagnosed individuals at the national level is to implement double reflex testing. This requires anti-HDV testing of all hepatitis B surface antigen-positive individuals and HDV RNA testing of all anti-HDV-positive individuals. This strategy is manageable for healthcare systems since the number of newly diagnosed HBV cases is low. At the global level, a comprehensive HDV screening strategy would require only 1,994,000 HDV antibody tests and less than 89,000 HDV PCR tests. Double reflex testing is the preferred strategy in countries with a low prevalence of HBV and those with a high prevalence of both HBV and HDV. For example, in the European Union and North America only 35,000 and 22,000 cases, respectively, will require anti-HDV testing annually.

Epidemiology, presentation, and therapeutic approaches for hepatitis D infections

INTRODUCTION

Chronic Hepatitis D virus (HDV) infection remains an important global public health problem, with a changing epidemiological landscape over the past decade along with widespread implementation of hepatitis B vaccination and human migration. The landscape of HDV treatments has been changing, with therapies that have been under development for the last decade now in late stage clinical trials. The anticipated availability of these new therapies will hopefully replace the current therapies which are minimally effective.

AREAS COVERED

This narrative review discusses the clinical course, screening and diagnosis, transmission risk factors, epidemiology, current and investigational therapies, and liver transplantation in HDV. Literature review was performed using PubMed and ClinicalTrials.gov and includes relevant articles from 1977 to 2022.

EXPERT OPINION

HDV infection is an important global public health issue with a true prevalence that is still unknown. The distribution of HDV infection has changed globally with the availability of HBV vaccination and patterns of human migration. As HDV infection is associated with accelerated disease courses and poor outcomes, the global community needs to agree upon a uniform HDV screening strategy to understand the truth of global prevalence such that new therapies can target appropriate individuals as they become available in the future.

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.

Silent Antibodies Start Talking: Enhanced Lateral Flow Serodiagnosis with Two-Stage Incorporation of Labels into Immune Complexes

The presence of pathogen-specific antibodies in the blood is widely controlled by a serodiagnostic technique based on the lateral flow immunoassay (LFIA). However, its common one-stage format with an antigen immobilized in the binding zone of a test strip and a nanodispersed label conjugated with immunoglobulin-binding proteins is associated with risks of very low analytical signals. In this study, the first stage of the immunochromatographic serodiagnosis was carried out in its traditional format using a conjugate of gold nanoparticles with staphylococcal immunoglobulin-binding protein A and an antigen immobilized on a working membrane. At the second stage, a labeled immunoglobulin-binding protein was added, which enhanced the coloration of the bound immune complexes. The use of two separated steps, binding of specific antibodies, and further coloration of the formed complexes, allowed for a significant reduction of the influence of non-specific immunoglobulins on the assay results. The proposed approach was applied for the serodiagnosis using a recombinant RBD protein of SARS-CoV-2. As a result, an increase in the intensity of test zone coloration by more than two orders of magnitude was demonstrated, which enabled the significant reduction of false-negative results. The diagnostic sensitivity of the LFIA was 62.5% for the common format and 100% for the enhanced format. Moreover, the diagnostic specificity of both variants was 100%.

Silicon Nanowires Length and Numbers Dependence on Sensitivity of the Field-Effect Transistor Sensor for Hepatitis B Virus Surface Antigen Detection

Silicon nanowire field effect transistor (NWFET) sensors have been demonstrated to have high sensitivity, are label free, and offer specific detection. This study explored the effect of nanowire dimensions on sensors’ sensitivity. We used sidewall spacer etching to fabricate polycrystalline silicon NWFET sensors. This method does not require expensive nanoscale exposure systems and reduces fabrication costs. We designed transistor sensors with nanowires of various lengths and numbers. Hepatitis B surface antigen (HBsAg) was used as the sensing target to explore the relationships of nanowire length and number with biomolecule detection. The experimental results revealed that the sensor with a 3 µm nanowire exhibited high sensitivity in detecting low concentrations of HBsAg. However, the sensor reached saturation when the biomolecule concentration exceeded 800 fg/mL. Sensors with 1.6 and 5 µm nanowires exhibited favorable linear sensing ranges at concentrations from 800 ag/mL to 800 pg/mL. The results regarding the number of nanowires revealed that the use of few nanowires in transistor sensors increases sensitivity. The results demonstrate the effects of nanowire dimensions on the silicon NWFET biosensors.