Characterization of T cell responses after stopping HBV therapy with nucleos(t)ide analogues (NA) in HBeAg-negative patients

Introduction: In a prospective study we showed that stopping NA treatment in HBeAg-negative patients is safe and leads to a significant decline in HBsAg levels. Patients with high HBV-DNA and HBcrAg rebound showed the highest decrease in HBsAg levels at week 48. Interestingly, we could show that plasma cytokines/chemokine levels of IL-10, IL-12 and TNF were significantly increased early (4 weeks) and IP-10 at week 8 after treatment stop (presented at GASL 2016). This induction of cytokines could be an indicator for activation of immune responses.

Objectives: In order to understand the mechanisms leading to HBsAg decline, T cell responses were analysed before and after stop of NA therapy.

Patients & Methods: In a prospective trial, 15 chronically HBeAg-negative patients stopped NA treatment. Multicolor flow cytometry was performed to characterize the ex-vivo immune cell phenotype at stop of treatment and 4, 8 and 12 weeks after stop. Additionally, HBV core-specific T cell responses were studied after in-vitro stimulation of PBMCs with core-specific overlapping peptides for 10 days and following restimulation.

Results: HLA-DR was upregulated on T cells compared to healthy controls. Additionally, Ki-67 was increased on T cells at week 12 for those patients who had the strongest HBsAg decline. At stop of NA therapy, hardly any HBV-specific CD4+ and CD8+ IFNγ+ T cell responses were detectable. However, this changed in some, but not all patients after stop of treatment, when a virological relapse occurred. Overall increases of CD4+ T cell responses in 10/12 patients (SI> 2) and of CD8+ T cell responses in 9 out of 12 (SI> 2) were visible. In some patients, blocking PD-L1 could further augment this response.

Conclusion: Stop of NA therapy and virological rebound led to changes in the peripheral blood T cell phenotype. HBV-specific T cell responses after stop of therapy could be induced after in vitro stimulation and the cells were more sensitive to in vitro checkpoint inhibition. The current data are relevant in relation to the discussion of new treatment concepts, i.e. combining NA treatment cessation with immunmodulatory therapies.