Specificity and Function of Immunogenic Peptides from the 35-Kilodalton Protein ofMycobacterium leprae

Abstract

We identified a T-cell determinant of the 35-kDa antigen ofMycobacterium leprae which is discriminatory against cross-sensitization by its closely related homologue inMycobacterium avium. From synthetic peptides covering the entire sequence, those with the highest affinity and permissive binding to purified HLA-DR molecules were evaluated for the stimulation of proliferation of peripheral blood mononuclear cells (PBMCs) from leprosy patients and healthy sensitized controls. Responses to the peptide pair 206–224, differing by four residues between M. leprae and M. avium, involved both species-specific and cross-reactive T cells. Lymph node cell proliferation in HLA-DRB1*01 transgenic mice was reciprocally species specific, but only the response to the M. leprae peptide in the context of DR1 was immunodominant. Of the cytokines in human PBMC cultures, gamma interferon production was negligible, while interleukin 10 (IL-10) responses in both patients and controls were more pronounced. IL-10 was most frequently induced by the shared 241–255 peptide, indicating that environmental cross-sensitization may skew the response toward a potentially pathogenic cytokine phenotype.

Functional recombinant MHC class II molecules and high-throughput peptide-binding assays

“…Systems that require linking of a given peptide to the β chain limit utility since the stable binding of the linked peptide compromises subsequent binding experiments and/or replacement with any other peptide. Some reported class II expression systems have had low refolding yields [ 21 , 22 ], some associated binding assays have depended upon a low pH incubation to release endogenous peptides [ 6 , 79 - 83 ], and others have had to use high concentrations of reporter peptide to detect interaction thus precluding detection of high-affinity interactions [ 66 , 73 , 80 - 82 , 84 - 87 ].…”

Leprosy: diagnostic and control challenges for a worldwide disease

“…These studies of the human T cell response in leprosy patients have identiWed a number of antigens that induce T cell responses, measured by lymphocyte proliferation or gamma interferon (IFN-) secretion in patients with tuberculoid leprosy. Such antigens include the M. leprae 70-, 65-, 45-, 35-, 18-, and 10-kDa antigens [1,5,31,38,50,84,200,207]. However, due to the high conservation and homology among members of the heat shock family between M. leprae and M. tuberculosis, it is not possible to use such antigens as diagnostic reagents [111].…”

“…However, due to the high conservation and homology among members of the heat shock family between M. leprae and M. tuberculosis, it is not possible to use such antigens as diagnostic reagents [111]. Other antigens, such as the M. leprae 35-kDa antigen, have also been shown to have homology to M. intracellulare and M. avium, containing both speciWc and conserved T cell epitopes [207]. Synthetic peptide antigens (15 amino acids), representing potentially M. leprae-speciWc epitopes have been used to evaluate responses in leprosy patients from the tuberculoid pole, contacts and healthy individuals from nonendemic leprosy areas.…”