CD8A and chronic hepatitis B virus infection: Based on this background, the aim of our study was to characterise in better detail the functional heterogeneity of HBV-specific and total CD8 T cells in chronic hepatitis B (CHB) patients, to assess whether this can affect individual responses to immune modulatory strategies and to identify CD8 T cell functional and phenotypic parameters to quantify HBV-specific T cell impairment in individual patients in the perspective of novel diagnostic tools based on T cell analysis.