PBMC were obtained from a cohort of patients with eAg-negative CHB before, during and after PegIFN¦Á 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 PegIFN¦Á 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, PegIFN¦Á was able to potently and cumulatively drive the proliferation and expansion in absolute numbers of CD56bright NK cell numbers (p <0.001), with induction of the pro-proliferative cytokine IL-15. Expanded CD56bright NK cells showed enhanced expression of activation markers and the activating receptor NKp46, accompanied by augmentation of TRAIL and IFN-¦Ã 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 CD56bright NK cells.
IFN-¦Á mediates divergent effects on the innate and adaptive arms of the immune system in vivo. The efficacy of PegIFN¦Á may be limited by its depleting effect on CD8 T cells; conversely, it can cumulatively drive proliferation, activation and antiviral potential of CD56bright NK cells.