Revisiting the estimation of hepatitis D global prevalence

Addressing hepatitis delta in primary care practices in the US: a narrative review

OBJECTIVE

Infection with the hepatitis delta virus (HDV), a unique RNA virus that requires hepatitis B virus (HBV) antigens for its assembly, replication, and transmission, causes severe viral hepatitis. Compared to HBV monoinfection, HDV infection increases the risk of severe liver disease, necessity for liver transplant, and mortality. Global HDV prevalence estimates vary from 5% to 15% among persons with HBV, but screening guidelines for HDV are inconsistent; some recommend risk-based screening, while others recommend universal screening for all people with HBV. Among primary care providers (PCPs) in the US, there is a lack of awareness and/or insufficient adherence to current recommendations for the screening of HDV infection and management of chronic HDV.

METHODS

Publications were obtained by conducting literature searches between July and August 2022 using the PubMed database and by manual searches of the retrieved literature for additional references. Information was synthesized to highlight HDV screening and management strategies for PCPs. Best practices for PCPs based on current guidelines and comanagement strategies for patients with HBV and HDV infection were summarized.

RESULTS

We recommend universal screening for HDV in patients positive for hepatitis B surface antigen. Confirmed HDV infection should prompt evaluation by a liver specialist, if available, with whom the PCP can comanage the patient. PCPs should counsel patients on the expected course of the disease, lifestyle factors that may influence liver health, need for consistent disease monitoring and follow-up, and risk of disease transmission. Screening is suggested for sexual partners, household contacts, and family members, with HBV immunization recommended for those found to be susceptible. There are currently no US Food and Drug Administration-approved therapies for HDV infection; thus, management is limited to treatments for chronic HBV infection plus long-term monitoring of liver health.

CONCLUSIONS

PCPs can be a valuable point of care for patients to access HDV/HBV screening, HBV immunization, and education, and can comanage patients with HBV and/or HDV infection.

Adjusted estimate of the prevalence of hepatitis delta virus in 25 countries and territories

BACKGROUND & AIMS

Hepatitis delta virus (HDV) is a satellite RNA virus that requires the hepatitis B virus (HBV) for assembly and propagation. Individuals infected with HDV progress to advanced liver disease faster than HBV-monoinfected individuals. Recent studies have estimated the global prevalence of anti-HDV antibodies among the HBV-infected population to be 5-15%. This study aimed to better understand HDV prevalence at the population level in 25 countries/territories.

METHODS

We conducted a literature review to determine the prevalence of anti-HDV and HDV RNA in hepatitis B surface antigen (HBsAg)-positive individuals in 25 countries/territories. Virtual meetings were held with experts from each setting to discuss the findings and collect unpublished data. Data were weighted for patient segments and regional heterogeneity to estimate the prevalence in the HBV-infected population. The findings were then combined with The Polaris Observatory HBV data to estimate the anti-HDV and HDV RNA prevalence in each country/territory at the population level.

RESULTS

After adjusting for geographical distribution, disease stage and special populations, the anti-HDV prevalence among the HBsAg+ population changed from the literature estimate in 19 countries. The highest anti-HDV prevalence was 60.1% in Mongolia. Once adjusted for the size of the HBsAg+ population and HDV RNA positivity rate, China had the highest absolute number of HDV RNA+ cases.

CONCLUSIONS

We found substantially lower HDV prevalence than previously reported, as prior meta-analyses primarily focused on studies conducted in groups/regions that have a higher probability of HBV infection: tertiary care centers, specific risk groups or geographical regions. There is large uncertainty in HDV prevalence estimates. The implementation of reflex testing would improve estimates, while also allowing earlier linkage to care for HDV RNA+ individuals. The logistical and economic burden of reflex testing on the health system would be limited, as only HBsAg+ cases would be screened.

IMPACT AND IMPLICATIONS

There is a great deal of uncertainty surrounding the prevalence of hepatitis delta virus among people living with hepatitis B virus at the population level. In this study, we aimed to better understand the burden in 25 countries and territories, to refine techniques that can be used in future analyses. We found a lower prevalence in the majority of places studied than had been previously reported. These data can help inform policy makers on the need to screen people living with hepatitis B virus to find those coinfected with hepatitis delta virus and at high risk of progression, while also highlighting the pitfalls that other researchers have often fallen into.

Triple Threat: HDV, HBV, HIV Coinfection

Hepatitis delta virus (HDV) only infects patients with hepatitis B virus (HBV) due to its reliance on HBV surface proteins to form its envelope. With shared routes of transmission, HDV coinfection is estimated to occur in 15% of patients with HIV and HBV. However, HDV is often underdiagnosed and may be missed particularly in people living with HIV (PLWH) who are already on antiretroviral therapy with anti-HBV activity and coincidental HBV suppression. At the same time, HDV causes the most severe form of chronic viral hepatitis and leads to faster progression of liver disease and hepatocellular carcinoma. Thus, increased recognition and effective treatment are paramount, and as novel treatment options approach global markets, the study of their efficacy in PLWH should be pursued.

Hepatitis Delta Infection: A Clinical Review

First discovered over 40 years ago, the hepatitis delta virus (HDV) is a unique RNA virus, requiring hepatitis B virus (HBV) antigens for its assembly, replication, and transmission. HBV and HDV can be acquired at the same time (coinfection) or HDV infection can occur in persons with chronic HBV (superinfection). Screening guidelines for HDV are inconsistent. While some guidelines recommend universal screening for all people with HBV, others recommend risk-based screening. Estimates of the global HDV prevalence range from 4.5 to 14.6% among persons with HBV; thus, there may be up to 72 million individuals with HDV worldwide. HDV is the most severe form of viral hepatitis. Compared to HBV monoinfection, HDV coinfection increases the risk of cirrhosis, hepatocellular carcinoma, hepatic decompensation, mortality, and necessity for liver transplant. Despite the severity of HDV, there are few treatment options. Pegylated interferon (off-label use) has long been the only available treatment, although bulevirtide is conditionally approved in some European countries. There are many potential treatments in development, but as yet, there are few effective and safe therapies for HDV infection. In conclusion, given the severity of HDV disease and the paucity of treatments, there is a great unmet need for HDV therapies.

Future anti-HDV treatment strategies, including those aimed at HBV functional cure

HDV is a defective virus that uses the HBV surface antigen to enter hepatocytes. It is associated with an accelerated course of liver fibrosis progression and an increased risk of hepatocellular carcinoma. Negative HDV RNA 24 weeks after the end of therapy has been proposed as an endpoint but late relapses make this endpoint suboptimal, hence HBsAg loss appears to be more appropriate. Current HBV antiviral agents have poor activity against HDV hence the search for improved therapy. Drugs only active against HDV, such as lonafarnib, have shown efficacy in combination with nucleoside analogues and peginterferon, but do not lead to HBsAg loss. HBsAg loss sustained 24 weeks after the end of therapy with negative HBV DNA is termed functional cure. Agents that are being investigated for functional cure include those that inhibit replication such as entry inhibitors, polymerase inhibitors and capsid assembly modulators but seldom lead to functional cure. Agents that reduce HBV antigen load such as RNA interference and inhibitors of HBsAg secretion are promising. Immunomodulators on their own seldom achieve functional cure, hence these agents in combination to assess the optimal combination are being investigated. Consequently, agents leading to functional cure of HBV are ideal for both HBV and HDV.

Hepatitis D: advances and challenges

Hepatitis D virus (HDV) infection causes the most severe form of viral hepatitis with rapid progression to cirrhosis, hepatic decompensation, and hepatocellular carcinoma. Although discovered > 40 years ago, little attention has been paid to this pathogen from both scientific and public communities. However, effectively combating hepatitis D requires advanced scientific knowledge and joint efforts from multi-stakeholders. In this review, we emphasized the recent advances in HDV virology, epidemiology, clinical feature, treatment, and prevention. We not only highlighted the remaining challenges but also the opportunities that can move the field forward.

Hepatitis delta in patients hospitalized in Spain (1997-2018)

BACKGROUND

Hepatitis delta is the most aggressive form of chronic viral hepatitis. We examined the clinical burden, epidemiological features and time trends for hepatitis delta patients hospitalized in Spain during the last two decades.

METHODS

Retrospective, observational study using the Spanish National Registry of Hospital Discharges. Information was retrieved since 1997 to 2018.

RESULTS

From a total of 79 647 783 nationwide hospital admissions recorded during the study period, 5179 included hepatitis delta as diagnosis. The overall hospitalization rate because of hepatitis delta was 6.5/105, without significant yearly changes. In-hospital death occurred in 335 (6.6%) patients. Acute hepatitis and cirrhosis were recorded in 46.5 and 33.5% of hepatitis delta hospitalizations, respectively. Acute hepatitis delta predominated until 2007 (55.9%) whereas cirrhosis increased since then (39.4%). Hepatic decompensation events and liver cancer accounted on average for 16 and 8% of hospitalizations, increasing significantly over time. Coinfection with HIV and hepatitis C virus (HCV) were recognized in 24 and 31.2% of hepatitis delta patients, respectively. All hepatitis C, HIV and injection drug use declined significantly since 2008.

CONCLUSION

The rate of hepatitis delta in patients hospitalized in Spain is low and has remained stable over two decades. However, hepatitis delta-related decompensation events and liver cancer are on the rise. The association of hepatitis delta with injection drug use, HIV and HCV has declined among recently hospitalized hepatitis delta patients.

Prevalence of hepatitis delta virus among chronic hepatitis B carriers in a large tertiary center in the Netherlands

BACKGROUND & AIMS

Hepatitis D virus infection (HDV) is considered the most severe form of viral hepatitis. In this study, we aimed to evaluate the prevalence of HDV infection in a tertiary center of a large, multi-ethnic city in the Netherlands. Moreover, we validate the reliability of a novel anti-HDV CLIA assay.

METHODS

All HBsAg-positive patients visiting the outpatient clinic between 2017 and 2019 were tested for HDV serology. Seropositive serum samples were further assessed by HDV RNA PCR and Sanger sequencing to identify the HDV genotype.

RESULTS

The CLIA assay was 100% sensitive and 98% specific. Out of 925 patients 3.7% tested seropositive for HDV, and HDV viremia was confirmed in 2.0%. The majority of patients had a non-Dutch background and did not speak English or Dutch. We detected HDV genotype 5 (N = 3), and genotype 1 (N = 15). Phylogenetic analysis demonstrated HDV1 clusters composed of sub-Saharan Africa isolates, central Asian, Turkish, Iranian and European isolates.

CONCLUSIONS

The prevalence of HDV infection in a tertiary center in the Netherlands was 2.0% among HBsAg-positive individuals, and mainly in non-Dutch individuals. Only HDV genotype 1 and 5 isolates were detected, which was found to match with the patient's country of origin.

Is hepatitis delta underestimated?

Hepatitis D virus may be underestimated because it is a significant problem in HBsAg-positive patients, especially those who inject drugs, have HIV or HCV co-infections and/or live in certain endemic regions. In the past few decades, the prevalence of HDV was expected to have decreased as a result of improvements in public healthcare policies and universal HBV vaccination programs. However, HDV has continued to spread in low-income countries, with local outbreaks and migration to less endemic areas, so that its prevalence has remained stable or even increased in certain regions. As a result, research has been focused on the epidemiology of HDV. Contradicting data from three large recent meta-analyses have reported that the prevalence of HDV may be between 0.16% and 1.00% in the global general population, and 4.5% and 14.6% in HBsAg-positive patients, with an estimated 12 to 70 million HDV patients worldwide. The exact prevalence and estimated number of HDV patients is still a subject of debate for several reasons, including the unreliable assessment of the infection and a lack of real-world screening. HDV infection is associated with an increased risk of progression to cirrhosis and the development of HCC compared to patients with HBV mono-infection, a risk which is even higher in patients with HIV co-infection. Morbidity and mortality from HDV-related cirrhosis should not be overlooked. In conclusion, hepatitis D virus is probably underestimated and certainly underdiagnosed, and screening for HDV should be performed in all HBsAg-positive patients in clinical practice.

Human hepatitis D virus-specific T cell epitopes

HDV is a small, defective RNA virus that requires the HBsAg of HBV for its assembly, release, and transmission. Chronic HBV/HDV infection often has a severe clinical outcome and is difficult to treat. The important role of a robust virus-specific T cell response for natural viral control has been established for many other chronic viral infections, but the exact role of the T cell response in the control and progression of chronic HDV infection is far less clear. Several recent studies have characterised HDV-specific CD4+ and CD8+ T cell responses on a peptide level. This review comprehensively summarises all HDV-specific T cell epitopes described to date and describes our current knowledge of the role of T cells in HDV infection. While we now have better tools to study the adaptive anti-HDV-specific T cell response, further efforts are needed to define the HLA restriction of additional HDV-specific T cell epitopes, establish additional HDV-specific MHC tetramers, understand the degree of cross HDV genotype reactivity of individual epitopes and understand the correlation of the HBV- and HDV-specific T cell response, as well as the breadth and specificity of the intrahepatic HDV-specific T cell response.

Current status of hepatitis delta

Hepatitis D virus (HDV) infection in patients chronically infected with hepatitis B virus (HBV) causes the most severe form of chronic viral hepatitis and continues to represent a major health problem. The latest data show that the global prevalence is much higher than previously considered. Therefore, screening with the detection of anti-HDV antibodies is mandatory for all chronic HBV patients. In spite of the severity of liver disease, the only recommended treatment today is pegylated interferon-alpha, which has limited efficacy. Novel host-targeting molecules are now under investigation. The current phase 2 clinical trials include pegylated interferon-lambda, bulevirtide, lonafarnib, and REP-2139. This review focuses on the current status of epidemiology, diagnosis, and treatment of HDV infection.