Characterization of HLA-DR- and TCR-binding residues of an immunodominant and genetically permissive peptide of the 16-kDa protein of Mycobacterium tuberculosis.
The 16-kDa protein of Mycobacterium tuberculosis represents an important antigenic target during bacillary latency and, consequently, should be considered as candidate subunit vaccine component. In this study, we have used CD4 T cell clones that recognize the peptide p91-110, an immunodominant and genetically permissive epitope, in the context of five different HLA-DR molecules and truncated and substituted variants of this peptide, to identify the minimal binding sequence (HLA-DR-binding core) and the minimal stimulatory sequence (TCR-binding core), as well as the residues that contact HLA-DR molecules and the TCR. We have found a common 9-mer sequence, spanning amino acids 93-101, as the binding core for HLA-DR1, -DR11, -DR13 and -DR7, but a longer (13-mer) sequence spanning amino acids 92-104 was required for binding to the HLA-DR15 molecules. F(93) was required for binding to all the tested HLA-DR molecules, hence allowing us to identify it as the N-terminal primary anchor residue (P1). Additionally, the binding requirements for other residues varied considerably between the tested alleles: A(94) for HLA-DR15, V(99) for HLA-DR1, -DR15, -DR11 and -DR7, R(100) for HLA-DR11 and -DR13, and L(104) for HLA-DR15. Concerning the residues of p91-110 peptide required for binding to the TCR, the pepscan analysis results would support the contention that P(-1) E(92), P6 F(98) would be important TCR contact sites because their substitutions led to full loss of T cell activation. Moreover, P8 R(100) is found to be critical residue in binding to HLA-DR11- and -DR13-restricted T cell clones, without influencing binding to the relevant HLA-DR molecule. Our results could be useful to design peptides with altered HLA anchor residues or TCR interaction sites to achieve remarkable increase in activity and to study their vaccine potential.
Caccamo
Nadia
N
Department of Biopathology, University of Palermo, Corso Tukory 211, I-90134 Palermo, Italy.
Meraviglia
Serena
S
La Mendola
Carmela
C
Bosze
Szylvia
S
Hudecz
Ferencz
F
Ivanyi
Juraj
J
Dieli
Francesco
F
Salerno
Alfredo
A
D001426:Bacterial Proteins / Q000276:immunology*; D006684:HLA-DR Antigens / Q000276:immunology*; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D010455:Peptides / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
D001426:Bacterial Proteins; D006684:HLA-DR Antigens; D010455:Peptides; D011948:Receptors, Antigen, T-Cell