IL-12 rather than immune checkpoint inhibitors contribute to the functional restoration of hepatitis D virus-specific T-cells

Hepatitis D virus (HDV) infection affects 15 – 20 million individuals world-wide and causes severely progressive hepatitis. It is unknown to what extent cellular immune responses contribute to liver disease and why immune responses fail to control viral replication in persistent HDV infection. This study aimed to analyse the mechanisms behind poor immune responses in hepatitis delta.

Frequencies of immune cells and specific markers were determined by cell surface stainings of PBMCs, derived from chronic HDV patients and from healthy controls (HDV n = 49; Healthy n = 18). Cell proliferative capacity was characterized by 3 H thymidine assays (n = 45) while functionality was determined by intracellular cytokine stainings. Samples were stimulated with 15mer peptide sequences derived from the large hepatitis delta antigen overlapping by 11 amino acids. To restore T cell responses, either blocking antibodies (CTLA-4, PDL-1) or pro-inflammatory cytokines (IL-12) were used.

We show that T-cell subsets were not altered in HDV patients compared to healthy controls. However, the senescence marker CD57 was significantly upregulated on CD8+ T-cells in hepatitis delta patients. Subsequently, weak and very infrequent HDV-specific T-cell proliferative and cytokine responses were observed by in vitro stimulation with overlapping peptides covering the entire HDV antigen. Blocking the co-inhibitory molecule PD1 and to a lesser extent also CTLA-4 slightly restored HDV-specific T-cell immunity in some cases. In contrast, a more robust and consistent increase in both HDV-specific CD4+ and CD8+ T-cell responses was evident when the third signal cytokine IL-12 was added in vitro.

Conclusions: This so far largest investigation of virus-specific T-cell immunity in patients with hepatitis delta revealed premature aging of immune cells associated with largely impaired T-cell functionality in chronic HDV infections. However, weak proliferation and cytokine production could be restored by blocking inhibitory pathways and in particular supplementation of third-signal cytokines. Overall, these data give new insights into the immunopathogenesis of hepatitis delta and supports the development of immunomodulatory treatment strategies.

Corresponding author: Schirdewahn, Thomas

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