The highest frequency of IFN-γ ELISpot responders occurred in the highest dose group: 9/20 (45%) subjects in the 10 YU group,

7/20 (35%) subjects in the 40 YU group, and 14/19 (74%) subjects in the 80 YU PF-01367338 in vivo group (Table 3). The frequency of responders was similar between immunization cohorts across all dose groups, including the two highest dose groups. A total of 14/29 (48%) subjects responded in Cohort A (weekly dosing) and 16/30 (53%) subjects in Cohort B (monthly) (Table 3). At the lowest dose, however, the monthly immunization regimen generated a 2-fold higher frequency of ELISpot responders than the weekly regimen. The kinetics of the emergence of the IFN-γ ELISpot response was dependent on dose and immunization regimen. While responses were seen as early as day 15, generally the highest responses occurred at later time-points

(Fig. 2). For 80 YU, 7/14 (50%) of eventual responders exhibited IFN-γ responses by day 15 whereas for 10 and 40 YU there ISRIB was a slower kinetics with only 1/9 (11%) and 1/7 (14%), respectively, eventual responders exhibiting responses at this early timepoint. On day 15, there were also almost twice as many responders in Cohort B than in Cohort A across dose groups: 3/14 (21%) eventual responders in Cohort A versus 6/16 (38%) in Cohort B. The majority of ELISpot responders (18/30 [60%]) demonstrated responsiveness by the end of the study, 28 days following the final immunization. crotamiton In the 10 YU group, ELISpot

responses were preferentially seen when PBMCs were stimulated with HBV recombinant antigens. In contrast, in the 40 and 80 YU groups, there was a 2-fold higher frequency of ELISpot responders to peptide pools. The production of IFN-γ in response to stimulation with HBV recombinant antigens was mainly directed to HBsAg and HBcAg (43% to HBsAg or HBcAg versus 20% to HBx). Across dose groups, the majority of ELISpot responses after stimulation of PBMCs with peptide pools were directed to overlapping pools of 15-residue peptides representing the HBV insert sequence. Lymphocyte proliferation in response to HBV recombinant antigens was observed in most (90%) subjects. The number of LPA responders was slightly higher in the two highest dose groups (40 and 80 YU: 100% and 90%, respectively) compared with the lowest dose group (10 YU: 77%) (Table 3). The frequency and magnitude of LPA responses were similar regardless of the immunization regimen (Cohort A: 92%; Cohort B: 88%) (Fig. 3). In contrast to the ELISpot results, approximately 50% of subjects across dose groups displayed responses by day 15 (Fig. 3). However, the number of LPA responders was lowest at this time-point compared with later times. All three HBV antigens were able to stimulate lymphocyte proliferation; HBcAg elicited the highest number of LPA responders across dose groups and HBx the lowest.