CD8A and viral infectious disease: Except for defective proliferation, the enhanced expression of some inhibitory receptors may contribute to the CD8+ T-cell exhaustion in chronic HBV-infected patients.31 Significant finding in CHB patients showed that circulating HBV-specific CD8+ T cells were mainly PD-1 positive;11 in line with those observations in other different viral infections, the exhausted T cells affected by high viral loads would upregulate their expression of PD-1.9, 32, 33