Abstract
The dermatophyte fungus Trichophyton exhibits unique immunologic properties by its ability to cause both immediate and delayed type hypersensitivity. An 83-kDa Trichophyton tonsurans allergen (Tri t 4) was previously shown to elicit distinct T lymphocyte cytokine profiles in vitro. The homologous protein, Tri r 4, was cloned from a Trichophyton rubrum cDNA library, and the recombinant protein was expressed in Pichia pastoris. This 726-amino acid protein contained an arrangement of catalytic triad residues characteristic of the prolyl oligopeptidase family of serine proteinases (Ser-Asp-His). In addition, a novel Trichophyton allergen, encoding 412 amino acids, was identified by its human IgE antibody-binding activity. Sequence similarity searches showed that this allergen, designated Tri r 2, contained all of the conserved residues characteristic of the class D subtilase subfamily (41-58% overall sequence identity). Forty-two percent of subjects with immediate hypersensitivity skin test reactions to a Trichophyton extract exhibited IgE antibody binding to a recombinant glutathione S-transferase fusion protein containing the carboxyl-terminal 289 amino acids of Tri r 2. Furthermore, this antigen was capable of inducing delayed type hypersensitivity skin test reactions. Our results define two distinct antigens derived from the dermatophyte Trichophyton that serve as targets for diverse immune responses in humans.
Highlights
The dermatophyte fungus Trichophyton exhibits unique immunologic properties by its ability to cause both immediate and delayed type hypersensitivity
Characterization of antigens derived from Trichophyton provides a model system for studying both IgE antibody- and cell-mediated immune responses in humans; elucidation of the amino acid sequences of these antigens is relevant to structural analyses of intrinsic antigenic properties governing diverse immune responses and to the identification of antigenic determinants associated with immediate and delayed type hypersensitivity
Molecular Cloning of Tri r 4 —Screening a T. rubrum cDNA library with a human serum pool obtained from five individuals with high titer IgE Ab to n-Tri t 4 failed to identify positive plaques
Summary
(Received for publication, December 22, 1997, and in revised form, August 26, 1998). Judith A. Forty-two percent of subjects with immediate hypersensitivity skin test reactions to a Trichophyton extract exhibited IgE antibody binding to a recombinant glutathione S-transferase fusion protein containing the carboxyl-terminal 289 amino acids of Tri r 2. This antigen was capable of inducing delayed type hypersensitivity skin test reactions. Characterization of antigens derived from Trichophyton provides a model system for studying both IgE antibody- and cell-mediated immune responses in humans; elucidation of the amino acid sequences of these antigens is relevant to structural analyses of intrinsic antigenic properties governing diverse immune responses and to the identification of antigenic determinants associated with immediate and delayed type hypersensitivity. We characterize a novel T. rubrum allergen (Tri r 2) that has a high degree of sequence identity to the subtilase enzyme family; this protein exhibits delayed type hypersensitivity; Ab, antibody or antibodies; n-Tri t 4, natural Tri t 4; r-Tri r 4, recombinant Tri r 4; bp, base pair(s); PAGE, polyacrylamide gel electrophoresis; GST, glutathione S-transferase
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