HBV Suppression by Nucleos(t)ide Analogues Reduces PD-1 Expression on Liver-Resident T Cells.

BACKGROUND AND AIM: PD-1-expressing T cells within the HBV-infected liver constitute a target of novel immunotherapeutics. Our aim was to investigate the impact of viral suppression on PD-1 expression on intrahepatic versus circulating lymphocyte populations from chronic hepatitis B (CHB) patients.

METHODS

Twenty-two CHB patients, nine of them on nucleos(t)ide analogues (NUCs), had paired blood, liver fine needle aspirations (FNAs) and biopsies. A subset had a follow-up FNA after treatment initiation (n = 4) or discontinuation (n = 4). Intrahepatic (iHBV-DNA and cccDNA) and serum (HBV-DNA, HBsAg, HBcrAg and cirB-RNA) viral markers were quantified. Flow cytometry was used for immunophenotyping PBMCs and intrahepatic lymphocytes. An independent liver FNA scRNAseq dataset was used to consolidate our results.

RESULTS

PD-1 expression on tissue-resident memory CD8 T cells (TRM) correlated with both iHBV-DNA and cccDNA, as well as surrogate markers of cccDNA transcriptional activity (cirB-RNA and HBcrAg) in CHB patients with mild hepatitis. These associations were not reflected in circulating T cells. PD-1 expression intensity on CD8 TRM was lower in NUC-treated than in naive patients, changes that were again not detectable in the circulation. Longitudinal analysis showed that viral load rebound induced by NUC discontinuation had the potential to drive re-expression of high levels of PD-1 on CD8 TRM. Conversely, therapy initiation and subsequent viral suppression reversed these changes. scRNAseq results further extended the profiling of these PD-1 + CD8 TRM, showing a phenotype consistent with bystander activation in response to subclinical liver damage.

CONCLUSIONS

Intrahepatic viral markers correlate with PD-1 expression on global liver-resident T cells of CHB patients with mild hepatitis, with a reduction after prolonged NUC therapy and re-expression following treatment withdrawal.