During the first 18 months of the project, the activities have focused on the setup of a cross-sectional, multicenter cohort of 750 HDV infected patients in Stockholm (Sweden), Bucharest (Romania), Milan (Italy) and Hannover (Germany). In addition to a detailed clinical characterization, we established a centralized biobanking in order to share plasma/ serum, immune cells, liver cells and liver tissue within the consortium. In the first period of the project, we achieved to establish the so far world's largest HDV cohort with almost 650 HDV infected patients and an extensive biosample collection. We harmonized sample processing and established protocols for the innovative, minimal-invasive fine needle aspiration procedure and the preparation of historical biopsies. Important progress has also been made with the development of a clinical study protocol for a structured bulevirtide discontinuation study. In total, in the first period the establishment of appropriate clinical cohorts, the setup of a harmonized biobanking and the establishment of the multi-omics approach formed the basis of the comprehensive and unbiased biomarker screening in well-defined HDV-infected patients and following mechanistic studies.
We successfully engrafted and infected chimeric mice with HBV and HDV/HBV and conducted ChIP-seq and RNA-seq from the livers of these animals. We identified a unique HDV-specific transcriptional signature of 748 genes, which associated with an epigenetic imprinting on gene enhancer-associated histone marks, and which is largely independent from a repressive histone mark. Among these epigenetically coded HDV signature genes are potentially secreted biomarker candidates, which are currently being validated in the blood of infected mice and patients. A second batch of 11 chimeric mice have been successfully transplanted and are currently infected with HDV/HBV for Bulevirtide treatment of 3 months compared to vehicle control.