Modeling the Interplay between HDV and HBV in Chronic HDV/HBV Patients

Molecular Epidemiology of Hepatitis D Virus in the North-East Region of Romania

The hepatitis D virus (HDV) superinfection of individuals with chronic hepatitis B virus (HBV) infection causes severe liver damage and the poorest long-term prognosis among viral hepatitis. This is attributed to the unique pathogenic mechanisms of HDV characterized by a direct cytopathic effect on hepatocytes and a significant impairment of the host immune response. The HDV genotype largely influences the extent of the pathogenic mechanisms with consequences on disease progression towards cirrhosis, liver decompensation, or hepatocellular carcinoma. In this context, identifying the circulating HDV genotypes in European regions with high prevalence, such as Romania, is crucial for effectively managing the long-term liver health. Here, we report the first comprehensive HDV study in Romania that clinically characterizes 82 patients and performs HDV genotyping by combining the nested-PCR reaction with sequencing analysis in 49 samples with an HDV-RNA load higher than 5000 IU/mL. While all isolates in our study belong to the HDV-1 genotype, the phylogenetic analysis based on sequence data from GenBank reveals the presence of the following potential three groups: (i) Italy and France; (ii) Spain; and (iii) Turkey, Iran, Pakistan, and Germany. This broad clustering highlights the recent surge in migration to and from Western Europe and the Middle East. Equally important, no differences in viral markers, clinical and paraclinical parameters, or treatment options were observed between these identified clusters. Nevertheless, this study considerably advances the understanding of hepatitis D epidemiology and clinical aspects in Romania.

Incorporating Intracellular Processes in Virus Dynamics Models

In-host models have been essential for understanding the dynamics of virus infection inside an infected individual. When used together with biological data, they provide insight into viral life cycle, intracellular and cellular virus-host interactions, and the role, efficacy, and mode of action of therapeutics. In this review, we present the standard model of virus dynamics and highlight situations where added model complexity accounting for intracellular processes is needed. We present several examples from acute and chronic viral infections where such inclusion in explicit and implicit manner has led to improvement in parameter estimates, unification of conclusions, guidance for targeted therapeutics, and crossover among model systems. We also discuss trade-offs between model realism and predictive power and highlight the need of increased data collection at finer scale of resolution to better validate complex models.

Hepatitis D Virus and HBsAg Dynamics in the era of new Antiviral Treatments

PURPOSE OF REVIEW

Hepatitis D virus (HDV) infection is the most severe form of chronic viral hepatitis, with no FDA-approved therapy. Progress in the development of effective HDV treatments is accelerating. This review highlights how mathematical modeling is improving understanding of HDV-HBsAg-host dynamics during antiviral therapy and generating insights into the efficacy and modes of action (MOA) of new antiviral agents.

RECENT FINDINGS

Clinical trials with pegylated-interferon-λ, bulevertide, nucleic acid polymers, and/or lonafarnib against various steps of the HDV-life cycle have revealed new viral-kinetic patterns that were not observed under standard treatment with pegylated-interferon-α. Modeling indicated that the half-lives of circulating HDV and HBsAg are ~ 1.7 d and ~ 1.3 d, respectively, estimated the relative response of HDV and HBsAg during different antiviral therapies, and provided insights into the efficacy and MOA of drugs in development for treating HDV, which can inform response-guided therapy to individualize treatment duration. Mathematical modeling of HDV and HBsAg kinetics provides a window into the HDV virus lifecycle, HDV-HBsAg-host dynamics during antiviral therapy, and the MOA of new drugs for HDV.

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.