Abstract
Identification of HLA-restricted peptides derived from mycobacterial antigens that are endowed with high affinity and strong antigenicity is not only of interest in tuberculosis (TB) diagnostics and treatment efficacy evaluation, but might also provide potential candidates for the development of therapeutic vaccines against drug-resistant TB. Our previous work demonstrated that lipoprotein Z (LppZ) displayed high immunogenicity and antigenicity in active TB patients. In the present study, ten HLA-A2-restricted LppZ peptides (LppZp1-10) were predicted by bioinformatics, among which LppZp7 and LppZp10 were verified to possess high affinity to HLA-A2 molecules using T2 cell-based affinity binding assay. Moreover, results from ELISpot assay showed that both LppZp7 and LppZp10 peptides were able to induce more IFN-γ producing cells upon ex vivo stimulation of PBMC from HLA-A2+ active TB (ATB) patients as compared to those from healthy controls (HCs). Also, the numbers of LppZp7 and LppZp10-specific IFN-γ producing cells exhibited positive correlations with those of ESAT-6 peptide (E6p) or CFP-10 peptide (C10p) in ATB. Interestingly, stimulation with LppZp7/p10 mixture was able to induce higher intracellular expression of IFN-γ and IL-2 cytokines in CD8+ and CD4+ T cells from ATB as compared to HC, associated with lower expression of TNF-α in both CD8+ and CD4+ T cells. Taken together, HLA-A2-restricted LppZp7 and LppZp10 peptides display high immunoreactivity in HLA-matched ATB patients demonstrated by high responsiveness in both CD8+ and CD4+ T cells. With the ability to induce strong antigen-specific cellular responses, LppZp7 and LppZp10 are of potential value for the future applications in the prevention and control of TB.
Highlights
Tuberculosis (TB) is the leading cause of death from the single infectious agent, Mycobacterium tuberculosis (M.tb)
HLA-A2-restricted peptides were predicted on the website http: //www-bimas.cit.nih.gov/molbio/hla_bind
Our results showed that the immune responses to ESAT-6 peptide (E6p) and culture filtrate protein 10 (CFP-10) peptide (C10p) in active TB (ATB) patients (102 ± 16.35 and 89.87 ± 18.77 spot-forming units (SFUs)/2.5 × 105 Peripheral blood mononuclear cells (PBMCs), respectively) were significantly higher than those in healthy controls (HCs) group (2.556 ± 0.669 and 2.556 ± 0.747 SFUs/2.5 × 105 PBMCs, respectively) (p = 0.001) (Figure 5A)
Summary
Tuberculosis (TB) is the leading cause of death from the single infectious agent, Mycobacterium tuberculosis (M.tb). It is still one of the most severe global health problems. The rapid increase of multiple drug-resistant (MDR) and extensively drug-resistant (XDR) TB in clinic leads to the longer duration of the treatment and the use of more expensive drugs whereas less efficacy, increasing the economic burden as well as the morbidity of global TB (Basak et al, 2016). Bacille Calmette-Guérin (BCG) is the only vaccine available for the prevention of TB, which is widely used in high-incidence regions. To develop new vaccines either for the prevention of TB or the immunotherapy of drug-resistant TB in the future is worthy of exploration
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