title: Elimination of the listeriolysin O-directed immune response by conservative alteration of the immunodominant listeriolysin O amino acid 91 to 99 epitope.
abstract: A major H2-Kd-presented epitope for antilisterial cytotoxic T lymphocytes (CTLs) is the nanomer peptide which corresponds to the amino acid 91 to 99 (aa91-99) sequence from listeriolysin O (LLO). Although the LLO sequence contains at least five additional nanomer peptides which also satisfy the H2-Kd binding motif, aa91-99 is the only LLO-derived target peptide that is recognized by antilisterial CTLs following infection of BALB/c mice with Listeria monocytogenes. In order to investigate further the immunodominance of the LLO aa91-99 epitope following endogenous processing of LLO, we introduced a point mutation in hly (the gene for LLO) which results in a conservative Y-to-F substitution for the anchor residue at position 2 within the aa91-99 sequence. This "92F" L. monocytogenes mutant produces biologically active LLO and is phenotypically indistinct from wild-type L. monocytogenes in terms of intracellular growth in vitro and virulence in vivo. BALB/c mice actively immunized with the 92F L. monocytogenes mutant are protected against challenge with wild-type L. monocytogenes. Antilisterial CTLs from mice immunized with the 92F mutant lyse targets infected with L. monocytogenes; however, these CTLs do not lyse target cells pulsed with either the LLO aa91-99 peptide, other LLO-derived peptides which satisfy the H2-Kd binding motif, or a peptide corresponding to the LLO aa91-92F-99 sequence. Target cells pulsed with the LLO aa91-92F-99 peptide are, however, lysed by wild-type LLO aa91-99-specific cytotoxic cells. Thus, a conservative amino acid change in the first anchor residue of the immunodominant aa91-99 sequence of LLO eliminates the induction of the cytotoxic cell response to this epitope as well as to any of the other candidate LLO-derived peptides which fit the H2-Kd binding motif. The lack of anti-LLO-specific CTLs following immunization with the 92F mutant does not appear, however, to influence the protective antilisterial immune response.
authors: Veterans Affairs Medical Center, Portland, Oregon 97201, USA.
authors: H G
authors: HG
authors: Bouwer
authors: M
authors: M
authors: Moors
authors: D J
authors: DJ
authors: Hinrichs
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins; D001483:Base Sequence; D003602:Cytotoxicity, Immunologic; D017931:DNA Primers / Q000737:chemistry; D000939:Epitopes; D006183:H-2 Antigens / Q000276:immunology; D006360:Heat-Shock Proteins / Q000276:immunology*; D006460:Hemolysin Proteins; D008089:Listeria monocytogenes / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology; D017354:Point Mutation; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D001427:Bacterial Toxins; D017931:DNA Primers; D000939:Epitopes; D006183:H-2 Antigens; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D010455:Peptides; C038705:hlyA protein, Listeria monocytogenes