This was recently shown with a non-protective, cryptic CD8+ T-cell epitope in ESAT-6 16. TB10.4 is a promising vaccine candidate against infection with M.tb, and as a vaccine Ag it is part of a fusion protein
subunit vaccine HyVac4 based on TB10.4 and Ag85B that RG7204 datasheet is currently in clinical trials 15. TB10.4 is expressed by both M.tb and the currently available vaccine, BCG 15. In this paper, we examined in detail the T-cell epitope pattern induced against TB10.4, by comparing the epitopes induced by the recombinant protein with that induced by a live vector such as BCG or M.tb. We furthermore examined the differences in the in vivo and in vitro cellular uptake and ingestion of the two vaccines to compare the uptake of a vaccine based on a recombinant protein (TB10.4) in the adjuvant CAF01 and a vaccine based on a
live vector (BCG). We first analyzed T-cell epitope-specificity against TB10.4 in mice immunized with (i) TB10.4 formulated in the Th1-promoting adjuvant CAF01 (consisting of dimethyl dioctadecyl ammonium bromide (DDA) and the synthetic cord factor of M.tb, TDB (trehalose 6,6′-dibehenate)17), (ii) BCG or (iii) an aerosol exposure to virulent M.tb Erdman. An F1 cross of C57BL/6×BALB/c mice (hereafter named CB6F1 mice) were immunized once with BCG or three times with recombinant TB10.4, or challenged by the aerosol route learn more with virulent M.tb Erdman. Splenocytes were isolated from mice at approximately week 4 post immunizations with TB10.4/CAF01 or BCG or week 4 post infection. Galactosylceramidase Lymphocytes were stimulated in vitro with overlapping peptides covering the TB10.4 sequence (Fig. 1A, left panel). T-cell specificity against
the different peptides P1–P9 used for stimulation was assessed by ELISA on supernatants from stimulated-lymphocyte cultures after 72 h. Surprisingly, the results showed that all three groups induced unique epitope recognition patterns. Mice immunized with TB10.4 generated IFN-γ-producing T cells that were specific for peptide 3 (P3) and to a lesser extent P7 in the spleen (and blood, data not shown), resulting in secretion of 1600±237 and 934±217 pg/mL IFN-γ. T cells from the BCG-immunized group mainly recognized the peptide P8 (2635±25 pg/mL IFN-γ) and P9 (658±302 pg/mL IFN-γ). Furthermore, a third distinct epitope recognition pattern was seen in the group challenged with virulent M.tb, where especially peptides P1 and P8 were strongly recognized, inducing IFN-γ release between 6500 and 11 000 pg/mL IFN-γ. Twenty-four weeks after infection, or 16 wk post BCG or TB10.4 vaccination, the epitope patterns had not changed significantly (Fig. 1B). Taken together, clear differences in the epitopes recognized on the same Ag, TB10.4, were observed between the groups that were immunized with TB10.4 in CAF01 or TB10.4 expressed by BCG or M.tb, and these differences were not only transient, since epitope recognition was highly comparable at an early and late time point.