CD3(bright)CD56(+) T cells associate with pegylated interferon-alpha treatment nonresponse in chronic hepatitis B patients.

The hepatitis B virus (HBV) infects more than 350 million people worldwide and is a major cause of chronic liver disease1. Both the innate and adaptive immune responses in the host regulate HBV infection2. In the innate immune response, hepatic natural killer (NK) cells exert their antiviral function against HBV infection by killing infected cells and producing high cytokine levels, which both promote the pathogenesis of viral hepatitis3. In the adaptive immune response, HBV-specific CD8+ T cells lyse infected hepatocytes and control viral infection; indeed, impaired CD8+ T cell activity is associated with the establishment of chronic HBV infection4. In addition, regulatory T cells are increased and have an immunosuppressive effect on HBV-specific T helper cells in chronic hepatitis B (CHB) patients5. The findings described above provide valuable information for understanding HBV pathogenesis and immune-evasion mechanisms. However, immune indexes that reflect the therapeutic efficacy of HBV treatments have not been so reliable, and other ways to evaluate therapeutic efficacy are needed. Thus far, only three major clinical regimens to treat HBV are available: peg-IFNα, nucleoside/nucleotide analogues (NA), and the combination of peg-IFNα plus NA therapy6. Unlike HCV treatment that has yielded encouraging results, the effect of various therapies on HBV has been rather poor regardless of the treatment strategy. For instance, loss of hepatitis B e antigen (HBeAg)—a readout of reduced viral infectivity after treatment—occurs in only 30% of HBeAg-positive CHB patients treated with peg-IFNα, while the remaining 70% do not respond to treatment7. However, the underlying reason for this treatment resistance in HBV patients remains unknown. A subset of the human T cell population expresses CD56, an NK cell surface marker. Generally, CD56+ T cells constitute approximately 10% of peripheral blood T cells and nearly 50% of liver T cells8,9. Upon stimulation, CD56+ T cells are activated, proliferate, and exhibit cytotoxicity in an MHC-unrestricted manner10,11. Notably, CD56+ T cells are a superior latent source of IFN-γ, which is considered to be a main mediator of antiviral responses12. As an abundant T cell subset in the liver, CD56+ T cells inhibit hepatic viral infection and replication, including HBV and HCV13,14. Moreover, CD56+ T cells are competent to treat a number of various infectious diseases15,16,17,18,19. Despite this observed antiviral function, however, effector immune cells are always weaker in the context of HBV infection. We previously reported that TGFβ1 enrichment in HBV-persistent patients reduced NKG2D/2B4 expression on NK cells, leading to NK cell suppression20. In CHB patients, high NKG2A expression on NK cells decreased NK cell cytotoxicity21. Additionally, CHB patients reportedly harbor CD56+ T cells that display significantly increased inhibitory T cell immunoglobulin mucin-3 (Tim-3) expression over those from healthy controls, and this expression is further upregulated in patients with acute-on-chronic liver failure22. Tim-3 expression on CD56+ T cells also closely correlated with elevated serum ALT levels (a readout of liver injury) in CHB patients. Taken together, we speculate that CD56+ T cells may be in diminished antiviral status in CHB patients. In order to understand the state of the immune system in CHB patients during HBV therapy, we evaluated new cases of untreated CHB patients who were systematically treated with peg-IFNα for 48 weeks. We identified that CHB patients could be classified into the following two different groups based on the intensity of CD3 expression on their CD56+ T cells: the CD3brightCD56+ T cell– and CD3dimCD56+ T cell–harboring CHB patient groups. Interestingly, a higher percentage of CHB patients (55/85, 64.7%) preferentially harbored the CD3brightCD56+ T cells than healthy controls (10/33, 30.3%). We further found that CD56+ T cells played an important role in the host response to peg-IFNα therapy and that the presence of peripheral CD3brightCD56+ T cells counted against host control of HBV and predicted poor therapeutic response. Indeed, CD3brightCD56+ T cells appeared to be both phenotypically and functionally inhibited. CD3brightCD56+ T cells rapidly upregulated Tim-3 expression during peg-IFNα treatment, which might explain the observed CD3brightCD56+ T cell dysfunction. Taken together, we provide a possible immunological explanation as to why a majority of CHB patients have a poor therapeutic response to peg-IFNα and present a new clinical outcome indicator that may serve as an auxiliary measurement of the efficacy of peg-IFNα treatment.