Design and characterization of a multistage peptide-based vaccine platform to target Mycobacterium tuberculosis infection

The complex immunopathology\nofMycobacterium tuberculosis(<i>Mtb</i>) is one of the main challenges in developing\na novel vaccine against this pathogen, particularly regarding eliciting\nprotection against both active and latent stages. Multistage vaccines,\nwhich contain antigens expressed in both phases, represent a promising\nstrategy for addressing this issue, as testified by the tuberculosis\nvaccine clinical pipeline. Given this approach, we designed and characterized\na multistage peptide-based vaccine platform containing CD4+ and CD8+\nT cell epitopes previously validated for inducing a relevant T cell\nresponse against <i>Mtb</i>. After preliminary screening,\nCFP10 (32–39), GlfT2 (4–12), HBHA (185–194),\nand PPE15 (1–15) were selected as promising candidates, and\nwe proved that the <b>PM1</b> pool of these peptides triggered\na T cell response in <i>Mtb</i>-sensitized human peripheral\nblood mononuclear cells (PBMCs). Taking advantage of the use of thiol-maleimide\nchemoselective ligation, we synthesized a multiepitope conjugate (<b>Ac-CGHP</b>). Our results showed a structure–activity relationship\nbetween the conjugation and a higher tendency to fold and assume an\nordered secondary structure. Moreover, the palmitoylated conjugate\n(<b>Pal-CGHP</b>) comprising the same peptide antigens was associated\nwith an enhanced cellular uptake in human and murine antigen-presenting\ncells and a better immunogenicity profile. Immunization study, conducted\nin BALB/c mice, showed that <b>Pal-CGHP</b> induced a significantly\nhigher T cell proliferation and production of IFNγ and TNFα\nover <b>PM1</b> formulated in the Sigma Adjuvant System.