Hepatitis D virus in Bulgaria: virology, epidemiology and pathogenesis in chronic HBV carriers with liver dysfunction

Inroduction: Hepatitis D (HDV) is the most interesting and unique among animal viruses. It causes viral hepatitis D only in individuals already infected with HBV (hepatitis B). This dual    infection leads to the most aggressive hepatic dysfunction of all human viral hepatitis. Aim: This study was made to outline the hepatitis D virus among patients with chronic liver disorders in northeastern Bulgaria, in the sight of virus epidemiology, pathogenicity and viral genotype. Materials and methods: This is a retrospective study conducted between 2013-2019 at St. Marina University Hospital,Varna, Bulgaria. We have analyzed 418 serum samples from 391 patients with chronic liver disease using ELISA, PCR and HDV sequencing and genotyping. Results and Discussion: From 391 patients with chronic liver abnormalities, 16.6% (95% CI: 15.9% - 23.8%, n = 65) had an etiological association with HDV in ELISA. We found HDV RNA positive results in 63 out of all 65 anti-HDV Ab (antibody) positive patients (96.9%). Twenty-four of them, or 38.1% (95% CI: 26.1% - 51.2%, n = 24), were on antiviral HBV/HDV therapy. For five of them, or 20.8% (95% CI: 7.1% - 42.2%, n = 5), HDV genotype I was found. Conclusion: HDV infection has still many mysteries to discover - in terms of pathogenesis, clinical outcome in chronic HBV/HDV-infected individuals, as well as genotype variations and their role in avoiding immune elimination of the virus. All these unanswered questions pose a great challenge to the scientific thought and efforts of humankind to reduce and gradually eliminate viral hepatitis D.