Division of Infection and Immunity, UCL, London, U.K.; Department of Clinical Medicine, University of Bologna, Semeiotica Medica, S.Orsola-Malpighi Hospital, Bologna, Italy.
BACKGROUND AND AIMS:
A better understanding of the immunomodulatory effects of Peg-IFN-γ therapy could allow more rational optimisation of future therapeutic approaches in CHB. In this study we evaluated the dynamic changes in the innate and adaptive arms of the immune system induced by Peg-IFN-γ.
PBMC were obtained from a cohort of patients with eAg-negative CHB before, during and after Peg-IFN-γ treatment. The number, phenotype and function of global and virus-specific T cells and NK cells were analyzed by flow cytometry and serum cytokines by ELISA or CBA.
The absolute number of CD8 T cells was strikingly reduced on Peg-IFN-γ therapy (p<0.001), with a predominant loss of end-stage effectors including CMV-specific CD8 T cells. There was no significant recovery of the exhausted HBV-specific CD8 T cell response. By contrast, Peg-IFN-γ was able to potently and cumulatively drive the proliferation and expansion in absolute numbers of CD56(bright)NK cell numbers (p<0.001), with induction of the pro-proliferative cytokine IL-15. Expanded CD56(bright)NK cells showed enhanced expression of activation markers and the activating receptor NKp46, accompanied by augmentation in TRAIL and IFN-γ expression (p<0.001). Peak virological response (temporal within individual patients and cross-sectional within the cohort) correlated with the degree of expansion of functional CD56(bright)NK cells.
IFN-γ mediates divergent effects on the innate and adaptive arms of the immune system in vivo. The efficacy of Peg-IFN-γ may be limited by its depleting effect on CD8 T cells; conversely, it can cumulatively drive proliferation, activation and antiviral potential of CD56(bright)NK cells.