• Biomedical Science Letters
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• v.20 no.4
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• pp.250-255
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• 2014

Mycobacterium tuberculosis (MTB) resides and replicates inside macrophages. In our previous report, we reported that CD8+ T cell-mediated immune responses specific for the peptide derived from MTB RNA polymerase beta-subunit ($RpoB_{127-135}$) could be induced in TB patients expressing HLA-$A^*0201$ subtype. In order to examine whether $RpoB_{127-135}$ specific CD8+ T cells can recognize MTB infected macrophages in vitro, CD8+ T cell lines specific for $RpoB_{127-135}$ peptide were generated from peripheral blood mononuclear cells (PBMCs) of healthy HLA-$A^*0201$ subjects by in vitro immunization technique. In this study, we observed $RpoB_{127-135}$ specific CD8+ T cells could recognize and destroy macrophages infected with MTB for 2 to 4 days. $RpoB_{127-135}$ specific CD8+ T cell immune response was inducible from PBMC of healthy subjects expressing HLA-$A^*0206$ subtype, one of HLA-A2 supertype members. Next, we investigated the HLA-I processing mechanism of $RpoB_{127-135}$ peptide in MTB infected macrophages. As a result, the presentation of the MTB derived epitope peptide, $RpoB_{127-135}$, to CD8+ T cells was not inhibited by the treatment with brefeldin-A (ER-Golgi transport inhibitor) or lactacystin (proteasome inhibitor), which blocks the classical HLA-I processing pathway. However, $RpoB_{127-135}$ specific CD8+ T cell activity was blocked either by the blocking agent for the endocytosis (cytochalasin D) or by the blocking antibody (W6/32) for HLA-I molecules. Therefore, the $RpoB_{127-135}$ peptide may be processed by accessing the alternate HLA-I processing pathway. Understanding the processing and presentation mechanisms of the MTB derived proteins will help to improve the efficacy of vaccines and the efficiency of therapeutic agents for TB.

• Biomedical Science Letters
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• v.13 no.4
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• pp.325-332
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• 2007

Cell-mediated immune response (CMI) is a major immune protective mechanism against tuberculosis (TB) infection. Among several components involved in CMI, recent studies suggest that CD8+ T cells are important in controlling TB infection. In our previous report, we defined four Mycobacterium tuberculosis (MTB) derived epiotpe peptides specific for HLA-A*0201-restricted CD8+ T cells. These four peptides are $PstAl_{75-83}$, $ThyA_{30-38}$, $RpoB_{127-135}$ and $85B_{15-23}$. In this study, these epitope peptides specific CD8+ T cell responses in tuberculous pleurisy were investigated using ex vivo $IFN-\gamma$ elispot assay and intracellular $IFN-\gamma$ staining method. As a result, we observed these epitope peptide specific CD8+ T cell responses are induced in all three patients with tuberculous pleurisy suggesting that CD8+ T cells are involved in protective immune mechanism against MTB infection in tuberculous pleurisy. However, the CMI to mitogens and MTB antigens from pleural fluids of patients with tuberculous pleurisy does not seem to correlate with that from peripheral blood, although the sample size is too small to make any conclusion. In sum, the MHC I restricted CD8+ T cell responses seem to be induced efficiently in the pleural fluids, at the site of TB infection, in which the CMI is actively induced. In addition, these experiments suggest that MHC I restricted CD8+ T cell mediated immune responses are also involved in protective mechanism against MTB infection in extra-pulmonary TB.

• IMMUNE NETWORK
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• v.3 no.3
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• pp.235-241
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• 2003

Background: The protective immunity against tuberculosis (TB) involves both CD4+ T cells and CD8+ T cells. In our previous study, we defined four Mycobacterium tuberculosis derived peptide epitopes specific for HLA-$A^*0201$ restricted CD8+ T cells ($ThyA_{30-38}$, $RpoB_{127-135}$, $85B_{15-23}$, $PstA1_{75-83}$). In this study, we investigated the immune responses induced by these peptide specific CD8+ T cells in latently and chronically infected people with TB. Methods: We characterized these peptide specific CD8+ T cell population present in PBMC of both TB patients and PPD+healthy people using IFN-${\gamma}$elispot assay, intracellular staining and HLA-A2 dimer staining. Results: The frequency of peptide specific CD8+ T cell was in the range of 1 to 25 in $1.7{\times}10^5$ PBMC based on ex vivo IFN-${\gamma}$ elispot assay, demonstrating that these peptide specific CD8+ T cell responses are induced in both TB patients and PPD+ people. Short term cell lines (STCL) specific for these peptides proliferated in vitro and secreted IFN-${\gamma}$ upon antigenic stimulation in PPD+ donors. Lastly, HLA-$A^*0201$ dimer assays indicated that $PstA1_{75-83}$ specific CD8+ T cell population in PPD+ healthy donors is heterogeneous since approximately 25~33% of $PstA1_{75-83}$ specific CD8+ T cell population in PPD+ healthy donors produced IFN-${\gamma}$ upon peptide stimulation. Conclusion: Our results suggest that MHC class I restricted CD8+ T cell mediated immune responses to M. tuberculosis infection are induced in both TB patients and PPD + people; however, the CD8+ T cell population is functionally heterogeneous.