CD4+ T Cells Recognizing PE/PPE Antigens Directly or via Cross Reactivity Are Protective against Pulmonary Mycobacterium tuberculosis Infection
Fig 4
Immunogenic features of the Mtb Δppe25-pe19 strain linked to its functional ESX-1 secretion system.
Frequencies of different Th1 cytokine-producing splenic CD4+ T effectors, at 4 weeks p.i., in C57BL/6 mice (n = 5 per group) immunized the Mtb Δppe25-pe19 (A) or the Mtb WT strain (B) and stimulated in vitro with 10 μg/ml of the ESAT-6:1–20 peptide. C) Means ± SD of the frequencies of each Th1 subset, compared between the Mtb Δppe25-pe19- and the Mtb WT-immunized mice. NS = statistically not significant as determined by Mann-Whitney test. The immunized mice were those studied for PE/PPE-specific responses in the Fig 2. D) C57BL/6 mice (n = 2 per group) were immunized s.c. with 1 x 106 CFU/mouse of BCG, Mtb Δppe25-pe19 or Mtb WT strain. At 4 weeks p.i., IFN-γ T-cell responses were studied against ESAT-6, CFP-10 and EspC ESX-1 antigens. EspC:40–54 is an immunodominant I-Ab-restricted epitope that we recently identified by epitope mapping. E) Phagosomal rupture induced in differentiated THP-1 macrophages, infected at MOI of 1, with the Mtb Δppe25-pe19 strain as compared to the Mtb WT and to BCG Pasteur, as determined at day 3 post infection by the CCF-4-based FRET inhibition assay. In parallel, IFN-β (F) and IL-1β (G) were quantified in the culture supernatants of these infected THP-1 cells at 24 h post infection. *, **, *** = statistically significant, as determined by One Way ANOVA test with Tukey’s correction for multiple comparisons, p<0.05, p<0.005 or p<0.001, respectively.