Trichophyton Antigens Associated with IgE Antibodies and Delayed Type Hypersensitivity

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.Dermatophyte fungi of the genus Trichophyton colonize keratinized tissues in humans including nails, hair shafts, and the stratum corneum of the skin. Trichophyton tonsurans, Trichophyton mentagrophytes, and Trichophyton rubrum are common causes worldwide of tinea capitis, athlete's foot, and onychomycosis (infection of the nail beds) (1). An estimated 30 -70% of adults are asymptomatic carriers of these pathogens, and the incidence of symptomatic disease increases with age (2). The immune response to antigens derived from Trichophyton is unique in that both immediate hypersensitivity (IH) 1 and delayed type hypersensitivity (DTH) skin test reactions are induced. Studies suggest that the nature of the underlying immune response to Trichophyton antigens is related to the severity of dermatophytosis; IH skin tests are associated with chronic recurrent infections characterized by low-grade inflammatory lesions and the presence of IgE antibodies (Ab) (4 -7). In contrast, DTH reactions are associated with highly inflamed lesions that resolve spontaneously and a resistance to re-infection (4, 8 -13). The implication of these findings is that cellmediated immune responses to Trichophyton are more effective at eradicating infection and may confer protection. Chronic dermatophytosis has been associated with allergic disease in the respiratory tract in individuals with immediate hypersensitivity (14 -17). Furthermore, exposure to Trichophyton proteins may result in bronchial sensitization and symptomatic asthma that can be controlled with systemic antifungal therapy (7,18,19).Experimental mouse models support a role...

Differential gene expression in the pathogenic dermatophyte Arthroderma benhamiae in vitro versus during infection

“…Recombinantly expressed Tri r2 cannot be attributed enzymic activity on various protein substrates, but this antigen induced delayed type hypersensitivity (DTH) reactions and was the first known recombinant protein triggering both IgE antibody-and cell-mediated immune responses in humans (Woodfolk et al, 1998). Interestingly, DTH reactions are assumed to be associated with highly inflammatory skin lesions in dermatophytosis (for review see Woodfolk, 2005).…”

“…In contrast, we found that the gene encoding the serine protease subtilisin Sub6, which was not detectably activated during in vitro growth on keratin, was the most upregulated host-specific A. benhamiae sequence. Interestingly, Sub6 has been previously identified as the major allergen Tri r2 in T. rubrum (Woodfolk et al, 1998). Besides SUB6, the closely related SUB7 as well as SUB1 and SUB2 were specifically upregulated in vivo.…”

Diversity of the Human Allergen-Specific T Cell Repertoire Associated with Distinct Skin Test Reactions: Delayed-Type Hypersensitivity-Associated Major Epitopes Induce Th1- and Th2-Dominated Responses

“…However, studying cytokine production induced by whole Ag in T cell clones or lines does not provide insight into the diversity of T cell populations that constitute allergen-specific T cell repertoires. Cloning of Ags derived from Trichophyton rubrum has provided molecular tools for examining the T cell repertoire associated with distinct immune responses to Trichophyton (21). We recently reported major differences between IH and DTH responders in T cell repertoires specific for a 29-kDa allergen derived from T. rubrum, Tri r 2, which is a serine proteinase homologue (22).…”

“…r-Tri r 2 (29 kDa) was produced in Escherichia coli strain BL21 as a GST fusion protein using the pGEX-4T-3 expression vector (21). rGST produced by the same method was used as a negative control in skin test and in vitro lymphocyte cultures.…”

Multiplication of an ancestral gene encoding secreted fungalysin preceded species differentiation in the dermatophytes Trichophyton and Microsporum

“…In M. canis, a three-member metalloprotease (fungalysin) gene family (Brouta et al, 2002) including the previously characterized 43?5 kDa protease (Brouta et al, 2001), as well as a subtilisin gene family (Descamps et al, 2002) including a previously characterized 31?5 kDa protease (Mignon et al, 1998), were identified. In T. rubrum, a single serine protease has been characterized at gene level (Woodfolk et al, 1998).…”