ObjectiveChronic HBV infection affects more than 250 million people worldwide and remains a global healthcare problem in part because we lack curative treatment. Sustained viral control requires HBV-specific T cells, but these become functionally impaired in chronic infection. Clinical evidence indicates that functional cure of HBV infection by the host immune response is feasible. Developing T cell-based therapies able to achieve functional cure will require identification of the requirements for a successful T cell response against HBV and the relative contribution of individual T cell specificities to HBV control.DesignThe phenotype and function of HBV-specific T cells were studied directly ex vivo using fluorochrome-labelled multimers. We studied multiple HBV-specific T cell specificities targeting different HBV proteins in individuals with either an acute self-limiting or chronic HBV infection.ResultsWe detected strong T cell responses targeting multiple HBV viral proteins in acute self-limiting and low-frequency core and polymerase-specific T cells in chronic infection. Expression of the T cell inhibitory receptor PD-1, as well as T cell differentiation, T cell function and T cell regulation differed by stages and outcomes of infection. In addition, these features differed significantly between T cells targeting different HBV specificities.ConclusionHBV-specific T cells with different target specificities are characterised by distinct phenotypical and functional profiles. These results have direct implications for the design of immunological studies in HBV infection, and are potentially relevant for informing immunotherapeutic approaches to induce functional cure.

T cell exhaustion is associated with failure to clear chronic infections and malignant cells. Defining the molecular mechanisms of T cell exhaustion and reinvigoration is essential to improving immunotherapeutic modalities. Here we confirmed pervasive phenotypic, functional, and transcriptional differences between memory and exhausted antigen-specific CD8+ T cells in human hepatitis C virus (HCV) infection before and after treatment. After viral cure, phenotypic changes in clonally stable exhausted T cell populations suggested differentiation towards a memory-like profile. However, functionally, the cells showed little improvement and critical transcriptional regulators remained in the exhaustion state. Notably, T cells from chronic HCV infection that were exposed to antigen for less time because of viral escape mutations were functionally and transcriptionally more similar to memory T cells from spontaneously resolved HCV infection. Thus, T cell stimulation duration impacts exhaustion recovery, with antigen removal after long-term exhaustion being insufficient for development of functional T cell memory.

Summary The role of the endogenous interferon (IFN) system has been well characterized during IFN‐based therapy for chronic hepatitis C virus (HCV) infection; less is known for direct‐acting antivirals (DAAs). In this phase 3b open‐label study, we assessed changes in IFN‐stimulated genes (ISGs) in non‐cirrhotic treatment‐naïve or pegIFN/RBV‐experienced HCV‐GT1a‐infected patients receiving paritaprevir/ritonavir/ombitasvir + dasabuvir + ribavirin (PrOD + R) for 12 weeks. ISG expression was quantified from peripheral blood mononuclear cells at baseline, treatment weeks (TW)2, TW4, TW8, end of treatment (EOT) and at post‐treatment week 12. Paired sera were used to assess IFN‐α/IFN‐related chemokines/cytokines. Twenty‐five patients were enrolled. Overall sustained virologic response (SVR)12 was 92% (no virologic failure [VF]) and 100% for those completing the study protocol. Two patients were excluded from the ISG analysis due to lack of post‐treatment samples. The majority of ISGs were downregulated at TW2‐TW4 (nadir TW4); however, a relative increase was observed at TW8‐EOT, although levels were lower than baseline. This downregulation was accompanied by increases in IFN‐α/IFN‐related chemokines, a finding not observed with TH1/2‐related cytokines. Following SVR, ISG expression returned to TW2 levels. In conclusion, PrOD + R for 12 weeks was well‐tolerated with no VF. Our data demonstrate dynamic alterations in innate immune profiles during highly potent IFN‐free DAA therapy. The downregulation of ISG post‐therapy suggests reversal of the “exhausted” ISG phenotype following SVR, and the rise in ISGs and IFN‐α/IFN‐responsive chemokines late during therapy suggests resetting of IFN responsiveness that may be relevant in determining duration of or immunological sequelae from DAA therapy, including HBV reactivation.