Multiple synergizing factors contribute to the strength of the CD8+ T cell response against listeriolysin O

• Published in: International immunology 2006-01, Vol.18 (1), p.89-100
• Main Authors: Bruder, Dunja, Nussbaum, Alexander K., Gakamsky, Dimitry M., Schirle, Markus, Stevanovic, Stefan, Singh-Jasuja, Harpreet, Darji, Ayub, Chakraborty, Trinad, Schild, Hansjörg, Pecht, Israel, Weiss, Siegfried
• Format: Article
• Language: English
• Subjects: aa amino acid; Amino Acid Substitution; Animals; Antigen Presentation - genetics; antigen presentation/processing; APC antigen-presenting cell; Bacterial Toxins - genetics; Bacterial Toxins - immunology; CD8-Positive T-Lymphocytes - immunology; cytotoxic T cells; DC dendritic cell; DNS dansylated; epitopes; Epitopes, T-Lymphocyte - genetics; Epitopes, T-Lymphocyte - immunology; ER endoplasmic reticulum; Female; GM-CSF granulocyte macrophage colony-stimulating factor; Heat-Shock Proteins - genetics; Heat-Shock Proteins - immunology; Hemolysin Proteins; HU hemolytic units; Immunodominant Epitopes - genetics; Immunodominant Epitopes - immunology; LCMV lymphocytic choriomeningitis virus; Listeria monocytogenes - genetics; Listeria monocytogenes - immunology; Listeria monocytogenes - pathogenicity; LLO listeriolysin O; Lymphocyte Activation - genetics; MALDI matrix-associated laser desorption ionization; MHC class I; Mice; Mice, Inbred BALB C; MS mass spectrometry; Mutation; NP nucleoprotein; Protein Transport - genetics; Protein Transport - immunology; TAP Transporter associated with Antigen Processing; TFA trifluoroacetic acid; TOF time of flight
• ISSN: 0953-8178; 1460-2377
• DOI: 10.1093/intimm/dxh352

Immunodominance in CD8+ T cell responses against Listeria monocytogenes is a well-recognized but still not fully understood phenomenon. From listeriolysin, the major virulence factor of L. monocytogenes, only a single epitope, pLLO91-99, is presented by MHC class I molecules in BALB/c mice which dominates the cytotoxic T cell response against this bacterial pathogen. To obtain more insights into the molecular and cellular mechanisms underlying immunodominance of this particular epitope, we compared the various steps involved in the presentation and recognition of pLLO91-99 derived from a wild-type toxin with an equivalent epitope from a mutated toxin. This fully functional variant contains within the pLLO91-99 epitope a conservative isoleucine to alanine replacement at the C-terminal anchor residue which results in loss of antigenicity. The binding properties of the variant peptide to soluble Kd remained unaffected and cytotoxic T cells capable of recognizing the pLLO99A/Kd complex were detectable in BALB/c mice. However, such T cells required higher concentrations of antigen in order to be optimally activated in vitro. A comparison between the TAP translocation efficiency of wild-type and mutant peptide demonstrated that the mutation at the C-terminus leads to a reduced transportation rate. Furthermore, the amino acid substitution changes the in vitro proteasomal cleavage pattern, resulting in a reduced liberation of the correct peptide from a polypeptide precursor. Thus, in all assays employed the immunodominant epitope performs optimally while the variant was found to be inferior. The synergy of all these steps most likely is the decisive factor in the immunodominance of pLLO91-99.