A comparison was made between the number of antigen specific T cells detected using an IFN-γ ELISPOT assay from volunteers receiving 1 × 107 and 1 × 108 (low and high doses) with previously published data from healthy, previously BCG vaccinated adults receiving 5 × 107 PFU (mid dose) MVA85A [9] and [10]. High dose MVA85A induced a significantly greater response to Ag85A peptide at 1 week following immunisation when compared to low and mid doses of MVA85A (p < 0.002 and p < 0.0003; Table 4). At 52 weeks high dose MVA85A induced a greater response than low dose but not mid dose MVA85A (p < 0.002;

Table 4). The total antigen specific T cell response induced by MVA85A was assessed for each dose by calculating the area under the curve (AUC) from 0 to 24 and 0–52 weeks following immunisation with MVA85A. High dose MVA85A (1 × 108 PFU) induced Androgen Receptor Antagonist cost a significantly greater T cell response than either mid or low dose MVA85A over both 0–24 and 0–52 weeks following immunisation MDV3100 ic50 ( Table 5). Finally, we calculated the T cell response to MVA85A relative to the screening response. Using this analysis the dose of vaccine given did not have any significant effect on the peak immune response at 1 week following

immunisation ( Fig. 5). There was however a dose effect at 52 weeks following immunisation with a greater relative response observed in adults receiving the highest dose. We have previously reported that in BCG-vaccinated UK adults, immunisation with 5 × 107 PFU of MVA85A was well-tolerated and induced a strong T cell response that was maintained until at least 24 weeks following immunisation [10] and [13]. The optimal vaccine dose, both for safety and immunogenicity, needs to be determined for the further development of MVA85A. Here, we report the results of a dose finding study where we immunised BCG-vaccinated UK adults with either 1 × 107 over or 1 × 108 PFU of MVA85A. Both doses were well-tolerated and induced a significant increase in the frequency of Ag85A specific T cells detected at peak (one week) and up to one year following immunisation with MVA85A.

When comparing the 2 doses of MVA85A used in this trial with previously published data using an intermediate dose, a clear dose response relationship was observed with a greater frequency of T cells induced both at one and 52 weeks following immunisation in volunteers receiving the higher, 1 × 108 PFU dose. When T cell responses were examined relative to pre-immunisation responses there was no significant effect of dose on the magnitude of response induced at one week following immunisation, however, at one year volunteers who received 1 × 108 PFU of MVA85A had higher numbers of antigen specific T cells detected in peripheral blood. There were no serious vaccine related AEs reported for any volunteer in either the 1 × 107 or 1 × 108 PFU of MVA85A dosing groups.