Fig. 2

The histograms report the prevalence of a immune-associated escape mutations, b NA-induced immune-escape mutations, c stop-codons. The prevalence was calculated in the group of 255 patients infected with HBV genotype-A (yellow bars) and in the group of 573 patients infected with HBV genotype-D (green bars). Statistically significant differences were assessed by Chi Squared Test for independence based on a 2 × 2 contingency table. * P < 0.05; ** P < 0.01; *** P < 0.001. In A) a schematic representation of HBsAg functional domains is also reported: N-terminus HBsAg (encompassing amino acids [aa] 1–7), transmembrane domain 1 (TM1, aa: 8–22), loop protruding inside the virion (23-79aa), transmembrane domain 2 (TM2, aa: 80–98), major hydrophilic region (MHR, aa: 99–169) and transmembrane domain 3 and 4 (TM3/4, aa: 170–226). The MHR contains B cell-epitopes including the a-determinant (aa: 124–147)