Distinct human T cell repertoires mediate immediate and delayed-type hypersensitivity to the Trichophyton antigen, Tri r 2

The fungal secretory peptide micasin induces itch by activating MRGPRX1/C11/A1 on peripheral neurons

Pruritus is the leading symptom of dermatophytosis. Microsporium canis is one of the predominant dermatophytes causing dermatophytosis. However, the pruritogenic agents and the related molecular mechanisms of the dermatophyte M. canis remain poorly understood. Here, the secretion of the dermatophyte M. canis was found to dose-dependently evoke itch in mice. The fungal peptide micasin secreted from M. canis was then identified to elicit mouse significant scratching and itching responses. The peptide micasin was further revealed to directly activate mouse dorsal root ganglia (DRG) neurons to mediate the non-histaminergic itch. Knockout and antagonistic experiments demonstrated that MRGPRX1/C11/A1 rather than MRGPRX2/b2 activated by micasin contributed to pruritus. The chimera and mutation of MRGPRX1 showed that three domains (ECL3, TMH3 and TMH6) and four hydrophobic residues (Y99, F237, L240 and W241) of MRGPRX1 played the key role in micasin-triggered MRGPRX1 activation. Our study sheds light on the dermatophytosis-associated pruritus and may provide potential therapeutic targets and strategies against pruritus caused by dermatophytes.

Pathogenesis, Immunology and Management of Dermatophytosis

Dermatophytic infections of the skin and appendages are a common occurrence. The pathogenesis involves complex interplay of agent (dermatophytes), host (inherent host defense and host immune response) and the environment. Infection management has become an important public health issue, due to increased incidence of recurrent, recalcitrant or extensive infections. Recent years have seen a significant rise in incidence of chronic infections which have been difficult to treat. In this review, we review the literature on management of dermatophytoses and bridge the gap in therapeutic recommendations.

Immunopathogenesis of Dermatophytoses and Factors Leading to Recalcitrant Infections

The pathogenesis of dermatophytic infections involves the interplay of three major factors: the dermatophyte, the inherent host defense, and the adaptive host immune response. The fungal virulence factors determine the adhesion and invasion of the skin while the immune response depends on an interaction of the pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMP) with pattern recognition receptors (PRRs) of the host, which lead to a differential Th (T helper) 1, Th2, Th17, and Treg response. While anthropophilic dermatophytes Trichophyton rubrum and now increasingly by T. interdigitale subvert the immune response via mannans, zoophilic species are eliminated due to a brisk immune response. Notably, delayed-type hypersensitivity (Th1) response of T lymphocytes causes the elimination of fungal infection, while chronic disease caused by anthropophilic species corresponds to toll-like receptor 2 mediated IL (interleukin)-10 release and generation of T-regulatory cells with immunosuppressive potential. Major steps that determine the ultimate clinical course and chronicity include genetic susceptibility factors, impaired epidermal and immunological barriers, variations in the composition of sebum and sweat, carbon dioxide tension, skin pH, and topical steroid abuse. It is important to understand these multifarious aspects to surmount the problem of recalcitrant dermatophytosis when the disorder fails conventional therapeutic agents.

The effect of cytoplasmic crude extracts of Trichophyton verrucosum on cell mediated immunity

OBJECTIVE

Trichophyton verrucosum is a slow growing dermatophyte responsible for a number of skin diseases such as ringworm, and is characterized by patches of hair loss and thick crusts on the host skin in domestic animals. In this study, we examined the immunomodulatory effects of crude extract of Trichophyton verrucosum (TV)cytoplasm in a mouse model.

METHODS

The TV variate was cultured on Sabouraud dextrose agar and the mycelium was grinded by mechanical force. The purified protein was obtained from crude extract of the fungus, and protein concentration was measured by BradFord assay. Six to eight week-female BALB/c mice were divided into three groups: test group, receiving cytoplasmic crude extract plus defibrinated sheep blood; control group, receiving defibrinated sheep blood; and normal group, receiving normal saline. Injections were performed on days 0, 3, 5, 7 and 9 and the mice were sacrificed four days after the last injection. T lymphocyte metabolic activity was examined by methyl thiazol tetrazolium (MTT) assay, and also interleukin-4 (IL-4) and interferon-γ (IFNγ) levels were evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

MTT assay showed that the TV extract stimulated lymphocyte metabolic activity. ELISA results showed that despite increase in the level of IFNγ, no changes were observed in IL-4 level.

CONCLUSIONS

Results indicated that crude extract of TV cytoplasm may probably act as an immune modulator, which affects Th₁ responses. The TV crude extract may be an appropriate agent to induce cellular immunity for combating dermatophytosis infection in animals; and therefore, TV extract may have some potential applications in vaccine/adjuvant technology.

Environment and Host-Genetic Determinants in Early Development of Allergic Asthma: Contribution of Fungi

Asthma is a chronic debilitating airway disease affecting millions of people worldwide. Although largely thought to be a disease of the first world, it is now clear that it is on the rise in many middle- and lower-income countries. The disease is complex, and its etiology is poorly understood, which explains failure of most treatment strategies. We know that in children, asthma is closely linked to poor lung function in the first 3-years of life, when the lung is still undergoing post-natal alveolarization phase. Epidemiological studies also suggest that environmental factors around that age do play a critical part in the establishment of early wheezing which persists until adulthood. Some of the factors that contribute to early development of asthma in children in Western world are clear, however, in low- to middle-income countries this is likely to differ significantly. The contribution of fungal species in the development of allergic diseases is known in adults and in experimental models. However, it is unclear whether early exposure during perinatal or post-natal lung development influences a protective or promotes allergic asthma. Host immune cells and responses will play a crucial part in early development of allergic asthma. How immune cells and their receptors may recognize fungi and promote allergic asthma or protect by tolerance among other immune mechanisms is not fully understood in this early lung development stage. The aim of this review is to discuss what fungal species are present during early exposure as well as their contribution to the development of allergic responses. We also discuss how the host has evolved to promote tolerance to limit hyper-responsiveness to innocuous fungi, and how host evasion by fungi during early development consequentially results in allergic diseases.

Global Analysis of Cell Wall Genes Revealed Putative Virulence Factors in the Dermatophyte Trichophyton rubrum

The fungal cell wall is a structure in constant contact with the external environment. It confers shape to the cell and protects it from external threats. During host adaptation, the cell wall structure of fungal pathogens is continuously reshaped by the orchestrated action of numerous genes. These genes respond to environmental stresses and challenging growth conditions, influencing the infective potential of the fungus. Here, we aimed to identify cell wall biosynthesis-related genes that putatively encode virulence factors in Trichophyton rubrum. We used RNA-seq to examine the impact of two drugs, namely undecanoic acid, and acriflavine as well as the effects of the carbon source switching from glucose to keratin on T. rubrum cell wall metabolism. By using functional annotation based on Gene Ontology terms, we identified significantly differentially expressed cell wall-related genes in all stress conditions. We also exposed T. rubrum to osmotic and other cell wall stressors and evaluated the susceptibility and gene modulation in response to stress. The changes in the ambient environment caused continuous cell wall remodeling, forcing the fungus to undergo modulatory restructuring. The influence of the external challenges indicated a highly complex response pattern. The genes that were modulated simultaneously in the three stress conditions highlight potential targets for antifungal development.

Keratin hydrolysis by dermatophytes

Dermatophytes are the most common cause of superficial fungal infections (tinea infections) and are a specialized group of filamentous fungi capable of infecting and degrading keratinised tissues, including skin, hair, and nail. Essential to their pathogenicity and virulence is the production of a broad spectrum of proteolytic enzymes and other key proteins involved in keratin biodegradation and utilization of its breakdown products. The initial stage of biodegradation of native keratin is considered to be sulfitolysis, in which the extensive disulfide bridges present in keratin are hydrolyzed, although some secreted subtilisins can degrade dye-impregnated keratin azure without prior reduction (Sub3 and Sub4). Sulfitolysis facilitates the extracellular biodegradation of keratin by the dermatophytes' extensive array of endo- and exoproteases. The importance of dermatophyte proteases in infection is widely recognized, and these enzymes have also been identified as important virulence determinants and allergens. Finally, the short peptide and amino acid breakdown products are taken up by the dermatophytes, using as yet poorly characterised transporters, and utilized for metabolism. In this review, we describe the process of keratin biodegradation by dermatophytes, with an especial focus on recent developments in cutting edge molecular biology and '-omic' studies that are helping to dissect the complex process of keratin breakdown and utilization.

New insights in dermatophyte research

Dermatophyte research has renewed interest because of changing human floras with changing socioeconomic conditions, and because of severe chronic infections in patients with congenital immune disorders. Main taxonomic traits at the generic level have changed considerably, and now fine-tuning at the species level with state-of-the-art technology has become urgent. Research on virulence factors focuses on secreted proteases now has support in genome data. It is speculated that most protease families are used for degrading hard keratin during nitrogen recycling in the environment, while others, such as Sub6 may have emerged as a result of ancestral gene duplication, and are likely to have specific roles during infection. Virulence may differ between mating partners of the same species and concepts of zoo- and anthropophily may require revision in some recently redefined species. Many of these questions benefit from international cooperation and exchange of materials. The aim of the ISHAM Working Group Dermatophytes aims to stimulate and coordinate international networking on these fungi.

Predicting HLA CD4 Immunogenicity in Human Populations

Background

Prediction of T cell immunogenicity is a topic of considerable interest, both in terms of basic understanding of the mechanisms of T cells responses and in terms of practical applications. HLA binding affinity is often used to predict T cell epitopes, since HLA binding affinity is a key requisite for human T cell immunogenicity. However, immunogenicity at the population it is complicated by the high level of variability of HLA molecules, potential other factors beyond HLA as well as the frequent lack of HLA typing data. To overcome those issues, we explored an alternative approach to identify the common characteristics able to distinguish immunogenic peptides from non-recognized peptides.

Methods

Sets of dominant epitopes derived from peer-reviewed published papers were used in conjunction with negative peptides from the same experiments/donors to train neural networks and generate an “immunogenicity score.” We also compared the performance of the immunogenicity score with previously described method for immunogenicity prediction based on HLA class II binding at the population level.

Results

The immunogenicity score was validated on a series of independent datasets derived from the published literature, representing 57 independent studies where immunogenicity in human populations was assessed by testing overlapping peptides spanning different antigens. Overall, these testing datasets corresponded to over 2,000 peptides and tested in over 1,600 different human donors. The 7-allele method prediction and the immunogenicity score were associated with similar performance [average area under the ROC curve (AUC) values of 0.703 and 0.702, respectively] while the combined methods reached an average AUC of 0.725. This increase in average AUC value is significant compared with the immunogenicity score (p = 0.0135) and a strong trend toward significance is observed when compared to the 7-allele method (p = 0.0938). The new immunogenicity score method is now freely available using CD4 T cell immunogenicity prediction tool on the Immune Epitope Database website (http://tools.iedb.org/CD4episcore).

Conclusion

The new immunogenicity score predicts CD4 T cell immunogenicity at the population level starting from protein sequences and with no need for HLA typing. Its efficacy has been validated in the context of different antigen sources, ethnicities, and disparate techniques for epitope identification.

Circulating Memory CD4+ T Cells Target Conserved Epitopes of Rhinovirus Capsid Proteins and Respond Rapidly to Experimental Infection in Humans

Rhinovirus (RV) is a major cause of common cold and an important trigger of acute episodes of chronic lung diseases. Antigenic variation across the numerous RV strains results in frequent infections and a lack of durable cross-protection. Because the nature of human CD4⁺ T cells that target RV is largely unknown, T cell epitopes of RV capsid proteins were analyzed, and cognate T cells were characterized in healthy subjects and those infected by intranasal challenge. Peptide epitopes of the RV-A16 capsid proteins VP1 and VP2 were identified by peptide/MHC class II tetramer-guided epitope mapping, validated by direct ex vivo enumeration, and interrogated using a variety of in silico methods. Among noninfected subjects, those circulating RV-A16-specific CD4⁺ T cells detected at the highest frequencies targeted 10 unique epitopes that bound to diverse HLA-DR molecules. T cell epitopes localized to conserved molecular regions of biological significance to the virus were enriched for HLA class I and II binding motifs, and constituted both species-specific (RV-A) and pan-species (RV-A, -B, and -C) varieties. Circulating epitope-specific T cells comprised both memory Th1 and T follicular helper cells, and were rapidly expanded and activated after intranasal challenge with RV-A16. Cross-reactivity was evidenced by identification of a common *0401-restricted epitope for RV-A16 and RV-A39 by tetramer-guided epitope mapping and the ability for RV-A16-specific Th1 cells to proliferate in response to their RV-A39 peptide counterpart. The preferential persistence of high-frequency RV-specific memory Th1 cells that recognize a limited set of conserved epitopes likely arises from iterative priming by previous exposures to different RV strains.

Sensitization to fungal allergens: Resolved and unresolved issues

Exposure and sensitization to fungal allergens can promote the development and worsening of allergic diseases. Although numerous species of fungi have been associated with allergic diseases in the literature, the significance of fungi from the genera Alternaria, Cladosporium, Penicillium, Aspergillus, and Malassezia has been well documented. However, it should be emphasized that the contribution of different fungal allergens to allergic diseases is not identical, but species-specific. Alternaria and Cladosporium species are considered to be important outdoor allergens, and sensitization and exposure to species of these genera is related to the development of asthma and rhinitis, as well as epidemics of asthma exacerbation, including life-threatening asthma exacerbation. In contrast, xerophilic species of Penicillium and Aspergillus, excluding Aspergillus fumigatus, are implicated in allergic diseases as indoor allergens. A. fumigatus has a high capacity to colonize the bronchial tract of asthmatic patients, causing severe persistent asthma and low lung function, and sometimes leading to allergic bronchopulmonary aspergillosis. Malassezia are common commensals of healthy skin, although they are also associated with atopic dermatitis, especially on the head and neck, but not with respiratory allergies. Despite its importance in the management of allergic diseases, precise recognition of species-specific IgE sensitization to fungal allergens is often challenging because the majority of fungal extracts exhibit broad cross-reactivity with taxonomically unrelated fungi. Recent progress in gene technology has contributed to the identification of specific and cross-reactive allergen components from different fungal sources. However, data demonstrating the clinical relevance of IgE reactivity to these allergen components are still insufficient.

Allergens and their role in the allergic immune response

Allergens are recognized as the proteins that induce immunoglobulin E (IgE) responses in humans. The proteins come from a range of sources and, not surprisingly, have many different biological functions. However, the delivery of allergens to the nose is exclusively on particles, which carry a range of molecules in addition to the protein allergens. These molecules include pathogen-associated molecular patterns (PAMPs) that can alter the response. Although the response to allergens is characterized by IgE antibodies, it also includes other isotypes (IgG, IgA, and IgG4), as well as T cells. The challenge is to identify the characteristics of these exposures that favor the production of this form of response. The primary features of the exposure appear to be the delivery in particles, such as pollen grains or mite feces, containing both proteins and PAMPs, but with overall low dose. Within this model, there is a simple direct relationship between the dose of exposure to mite or grass pollen and the prevalence of IgE responses. By contrast, the highest levels of exposure to cat allergen are associated with a lower prevalence of IgE responses. Although the detailed mechanisms for this phenomenon are not clear, it appears that enhanced production of interleukin-10 in response to specific Fel d 1 peptides could influence the response. However, it is striking that the animal sources that are most clearly associated with decreased responses at high allergen dose are derived from animals from which humans evolved more recently (∼65 million years ago). Although the nose is still recognized as the primary route for sensitization to inhalant allergens, there is increasing evidence that the skin is also an important site for the generation of IgE antibody responses. By contrast, it is now evident that delivery of foreign proteins by the oral route or sublingually will favor the generation of tolerance.

Pathogenesis of tinea

Dermatophytes are hyphomycetes that can degrade keratin. This puts them in a position to cause infections of the keratin-containing superficial skin. The resulting clinical picture is called tinea. The pathogenesis and course of tinea is decisively determined by pathogen-related factors and by the defense mechanisms of the host. An infection starts with an adherence of fungal propagules, followed by the formation of hyphae that can spread within the tissue. This process is accompanied by a release of fungal enzymes and other pathogenic factors. Next keratinocytes are activated, the epidermal barrier is destroyed, epidermal proliferation is enhanced and defensins are expressed within the epidermis. In addition, innate and specific immune responses are initiated, involving neutrophilic granulocytes, macrophages, antibodies and T cells. The cellular mechanisms are thought to be crucial for healing. Special conditions apply to nail infections, because within nail plates the fungi are not accessible to effective defense mechanisms, as well as to infections of hair follicles that contain specific concentrations of steroid hormones. Dermatophytes that penetrate into the dermis can cause granulomatous inflammatory reactions and systemic immune reactions are supposed to be a trigger of so-called id reactions.

Epitope-specific T-cell responses and allergic phenotypes: implications for T-cell peptide therapy

In the 1990s, elucidation of the primary amino acid sequence of several major allergens using molecular cloning techniques opened the door to T-cell epitope mapping studies. Such analyses underscored the complexity of the allergen-specific T-cell repertoire and the challenges to using allergen-derived peptides to identify epitope-specific differences associated with allergic and nonallergic responses. This review highlights important factors that may influence the nature of epitope-specific T-cell responses observed in vitro. These include the properties of the allergen, genetics of the host and selection of patients with defined allergic phenotypes based on serum antibody profiles and skin test reactivity. By taking these factors into account, T-cell epitope-specific differences associated with distinct allergic phenotypes can be identified. Observations at the T-cell epitope level undermine the Th1/Th2 paradigm as a model for the development of allergic versus nonallergic responses. Instead, they support the mounting data that point to a network of interactions between T helper cells and regulatory T cells, which controls the allergic response. The ability of peptides that localize to polypeptide chain 2 of the major cat allergen, Fel d 1, to preferentially induce interleukin-10 and interferon-gamma is discussed. Mechanisms whereby specific allergen-derived peptides may modify the T-cell repertoire and influence the immune outcome are also outlined. Further investigation of allergen-derived T-cell epitopes is warranted in order to optimize the design of peptide vaccines for the treatment of allergic disease.

Comparative analysis of secreted enzymes between the anthropophilic-zoophilic sister species Trichophyton tonsurans and Trichophyton equinum

Trichophyton tonsurans (TT) and Trichophyton equinum (TE) are two closely related dermatophytes with very different host preferences. This study was designed to examine the genetic and transcript level variations of secreted enzymes between TT and TE. Thirty-one genes representing 10 gene families were selected for comparison and complete genomic and cDNA sequences were elucidated. Sequence analyses of the selected genes identified 104 polymorphisms between the two dermatophytes, 37 of which are expected to encode changes in their polypeptide sequence. Quantitative RT-PCR was used to examine the differences in levels of transcript between TT and TE grown over 14d in aqueous keratin medium. Differences in transcript expression between TT and TE were gene specific and ranged from 1.1-fold to 33-fold. Intra-specific variability across all genes ranged from 41% to 250%. Despite their overall genetic similarity, TT and TE exhibit a moderate degree of variability in the genomic make-up of their secreted enzymes and the extent to which they are transcribed when grown in an aqueous keratin medium. Such differences may contribute to how these genetically similar organisms have adapted to infect divergent host organisms.

Use of western blot to study Microsporum canis antigenic proteins in canine dermatophytosis

Western blotting was used to describe the Microsporum canis proteins with antigenic activity in dogs with dermatophytosis. Electrophoretic separation of whole fungal strain extract cultured from a cat was performed under denaturing conditions. The proteins were blotted onto nitrocellulose and probed with sera collected from 22 dogs with dermatophytosis (18 M. canis, 3 M. gypseum, 1 Trichophyton mentagrophytes; group A), 20 dogs with skin diseases other than dermatophytosis, and 22 dogs with no clinical cutaneous signs (group B, n = 42). Nine principal IgG-binding proteins with apparent molecular weights of 180, 144, 130, 120, 102, 96, 80, 68, and 48 kD were visualised on group A blots. For these proteins, serological cross-reactivity with different strains of M. canis may be indirectly confirmed, whereas additional proteins were found to react with sera from individual dogs. The proteins visualised in this study may represent diagnostic markers of dermatophyte infection. The proteins should be further evaluated for their role in the cellular immune response of dogs with dermatophytosis.

Immunization and dermatophytes

PURPOSE OF REVIEW

Despite the availability of effective vaccines for certain animal species, vaccination against dermatophytosis requires improvement and further development in both animals and humans. This review provides an update on the current situation and focuses on recent advances in host-dermatophyte relationships that could have implications for future vaccination against the most prevalent of the fungal diseases.

RECENT FINDINGS

Numerous dermatophytic virulence factors have recently been isolated and characterized at the molecular level, notably secreted proteases involved in the invasion of the keratin network. Their precise roles in the different steps of the infectious process and in immunopathogenesis are being studied, while all aspects of the host immune response against dermatophytes, including the innate response, are becoming increasingly documented. In addition, new molecular tools are now available for studying dermatophytes, which will accelerate research on this topic.

SUMMARY

The growth of knowledge concerning all aspects of the host-dermatophyte relationship should contribute towards sound strategies for the development of effective and safe vaccines against dermatophytosis.

Pathogenesis of dermatophytosis

Despite the superficial localization of most dermatophytosis, host-fungus relationship in these infections is complex and still poorly elucidated. Though many efforts have been accomplished to characterize secreted dermatophytic proteases at the molecular level, only punctual insights have been afforded into other aspects of the pathogenesis of dermatophytosis, such as fungal adhesion, regulation of gene expression during the infection process, and immunomodulation by fungal factors. However, new genetic tools were recently developed, allowing a more rapid and high-throughput functional investigation of dermatophyte genes and the identification of new putative virulence factors. In addition, sophisticated in vitro infection models are now used and will open the way to a more comprehensive view of the interactions between these fungi and host epidermal cells, especially keratinocytes.

Immunoprophylaxis of dermatophytosis in animals

Dermatophytosis is a relatively common disease in many countries occurring endemically both in companion and food animals. Fungi belonging to the genera Trichophyton and Microsporum are most often isolated from clinical cases. Measures to control and prevent dermatophytosis include sanitation, hygienic measures and treatment. In some countries, successful control and eradication have been achieved by mass vaccination of cattle and fur-bearing animals. Vaccines containing live attenuated cells of the fungus stimulate a cell-mediated immune response conferring long-lasting protection against subsequent challenge by the homologous fungus. A delayed type hypersensitivity (DTH) skin test using appropriate dermatophyte antigens is suitable to assess the response. Inactivated dermatophyte vaccines are available for use in cattle, horse, dog, and cat in some countries. However, the scientific literature is scarce making it difficult to conclude on efficacy and appropriate use. Current vaccines are all first generation vaccines. Attempts have been made to prepare subunit vaccines based on new knowledge about virulence factors like the keratinases, so far with limited success. Candidate antigens must be able to stimulate a strong T helper 1 cell response and future research should focus on identification of major T-cell epitopes that specifically elicit a DTH reaction. Dermatophytosis is a zoonotic disease. In Norway and a few other countries, systematic vaccination against cattle ringworm has almost eliminated the disease, and ringworm in man caused by T. verrucosum is almost nonexistent. A similar benefit could be expected if a safe and efficacious vaccine was available for Microsporum canis infection in cats and dogs.

Comprehensive analysis of proteins secreted by Trichophyton rubrum and Trichophyton violaceum under in vitro conditions

Dermatophytes cause most superficial mycoses in humans and animals. Their pathogenicity is probably linked with the secretion of proteins degrading keratinised structures. Using 2D-PAGE and a shotgun mass spectrometry approach, we identified 80 proteins from Trichophyton rubrum and Trichophyton violaceum secretomes, under conditions mimicking those in the host. Identified proteins included endo- and exoproteases, other hydrolases, and oxidoreductases. Our findings can contribute to a better understanding of the virulence mechanisms of the two species and the different types of infection they cause.

T-cell responses to allergens

The allergic response in human beings is engineered by CD4(+) T lymphocytes, which secrete T(H)2 cytokines in response to activation by allergen-derived peptides. Although T(H)2 cells have been well characterized, defining the properties of allergen-specific T cells has proved challenging in human beings because of their low frequency within the T-cell repertoire. However, recent studies have provided insight into the molecular signature of long-lived human memory T(H)2 cells, which are allergen-specific. T-cell responses directed against allergens develop in early life and are heavily influenced by the type and dose of allergen, and possibly coexposure to microbial products. These responses are susceptible to suppression by regulatory T cells. This article highlights recent advances in the characterization of allergen-specific memory T(H)2 cells and discusses the heterogeneous nature of regulatory T cells and possible mechanisms of action. The relevance of T-cell epitope mapping studies to understanding the unique nature of T-cell responses to different allergens, as well as to peptide vaccine development, is reviewed. Experimental techniques and approaches for analyzing allergen-specific T cells and identifying novel T-cell epitopes are described that may lead to new T-cell-based therapies.

Mechanisms of allergen specific immunotherapy--T-cell tolerance and more

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific T-regulatory (Treg) cells and T helper 2 cells appears to be decisive in the development of allergic and healthy immune response against allergens. Treg cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific T helper 2 cells in allergic individuals. A decrease in interleukin (IL)-4, IL-5 and IL-13 production by allergen-specific CD4+ T cells due to the induction of peripheral T cell tolerance is the most essential step in allergen-specific immunotherapy (SIT). Suppressed proliferative and cytokine responses against the major allergens are induced by multiple suppressor factors, such as cytokines like IL-10 and transforming growth factor (TGF)-beta and cell surface molecules like cytotoxic T lymphocyte antigen-4, programmed death-1 and histamine receptor 2. There is considerable rationale for targeting T cells to increase efficacy of SIT. Such novel approaches include the use of modified allergens produced using recombinant DNA technology and adjuvants or additional drugs, which may increase the generation of allergen-specific peripheral tolerance. By the application of the recent knowledge in Treg cells and related mechanisms of peripheral tolerance, more rational and safer approaches are awaiting for the future of prevention and cure of allergic diseases.

Prevention of allergy by a recombinant multi-allergen vaccine with reduced IgE binding and preserved T cell epitopes

Novel approaches for the prevention of allergy are required, because of the inevitably increasing prevalence of allergic diseases during the last 30 years. Here, a recombinant chimeric protein, which comprises the whole amino acid sequences of three bee venom major allergens has been engineered and used in prevention of bee venom sensitization in mice. Phospholipase A2 (Api m 1), hyaluronidase (Api m 2) and melittin (Api m 3) fragments with overlapping amino acids were assembled in a different order in the Api m (1/2/3) chimeric protein, which preserved entire T cell epitopes, whereas B cell epitopes of all three allergens were abrogated. Accordingly, IgE cross-linking leading to mast cell and basophil mediator release was profoundly reduced in humans. Supporting these findings, the Api m (1/2/3) induced 100 to 1000 times less type-1 skin test reactivity in allergic patients. Treatment of mice with Api m (1/2/3) led to a significant reduction of specific IgE development towards native allergen, representing a protective vaccine effect in vivo. These results demonstrate a novel prototype of a preventive allergy vaccine, which preserves the entire T cell epitope repertoire, but bypasses induction of IgE against native allergen, and side effects related to mast cell/basophil IgE FcepsilonRI cross-linking in sensitized individuals.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

HLA-DQ8 is a predisposing molecule for detergent enzyme subtilisin BPN'-induced hypersensitivity

Several million individuals are exposed to agents in the workplace associated with atopy and asthma. Detergent enzymes have been implicated in occupationally induced hypersensitivity. However, the genetic susceptibility and T cell responses to detergent enzymes are undefined. We generated and used HLA-DQ6, -DQ8, -DR2, -DR3, and -DR4 transgenic mice to examine the immune and inflammatory components involved in the response to the detergent enzyme subtilisin BPN'. Based on in vitro and in vivo studies, for the first time, we present evidence that DQ8 is a strong susceptibility marker for BPN'-induced hypersensitivity. Only DQ8 mice showed consistent T cell responses to five immunodominant regions of BPN' comprising peptides #14 to 16, 36-37, 42-43, 62-63, and 80-81. The DQ8 mice also developed allergic eosinophilic inflammatory reactions in the airways following intranasal instillations of this enzyme. The DQ8 mice also responded to BPN' with a significant IgG1 and IgE production. We propose that the HLA Class II tg mice are useful for understanding allergenic responses to enzymes in humans, screening of allergenic and immunogenic properties of detergent enzymes, and for the development of modified enzymes to maintain efficient detergent qualities without allergic properties.

Allergy and dermatophytes

Tinea pedis (athlete's foot) and onychomycosis (infection of the toenails) caused by the dermatophyte fungus Trichophyton are highly prevalent in adults. Several Trichophyton allergens have been identified based on elicitation of immunoglobulin E antibody-mediated immediate-hypersensitivity (IH) responses. Evidence of an etiologic role for Trichophyton in asthma in some subjects with IH and chronic dermatophytosis is provided by bronchial reactivity to Trichophyton. Improvement of asthma after systemic antifungal treatment corroborates this link. A unique feature of Trichophyton allergens is the ability of the same antigen to elicit delayed-type hypersensitivity (DTH) in individuals who lack IH reactivity. Delayed responses appear to confer protection, while IH responses do not, based on the association with acute versus chronic skin infection. The amino acid sequence identity of Trichophyton allergens with diverse enzyme families supports a dual role for these proteins in fungal pathogenesis and allergic disease. Characterizing the immunologic properties of Trichophyton allergens and defining immune mechanisms which drive dichotomous responses are pivotal to understanding the dermatophyte-allergy relationship. Recent studies have identified DTH-associated major T-cell epitopes which could facilitate the development of peptide vaccines. Characterization of additional molecular targets by using new techniques may aid not only in the eradication of infection but also in the resolution of allergic symptoms.

Effect of chemical adjuvants on DNA vaccination

DNA vaccination is useful for generating immune responses, particularly the cell-mediated immune response, in a wide variety of species. However, DNA vaccination generally induces only relatively weak responses; hence, various approaches have been developed recently in order to improve its efficacy or immunopotency. The use of a chemical adjuvant is one of them. Previously we have shown that Bupivacaine or Marcaine can modulate immune responses induced by DNA vaccines [Proc. Natl. Acad. Sci. 90 (1993) 4156]. Following that lead, we have recently tested several additional chemicals for their usefulness as adjuvants in DNA inoculation. Of a total of five chemicals tested, levamisole exhibited strongest Th1 stimulatory activity whereas Tween 80 showed weakest Th1 activity, as determined by IgG2a production, and saline formulation induced weak T cell proliferation and DTH, in animals inoculated with a DNA construct expressing the foot-mouth disease viral capsule protein VP1. Furthermore, co-inoculation of levamisole increased the production of IFN-gamma by more than 100-fold as compared to that by DNA inoculation formulated in saline. In contrast, a previously reported chemical adjuvant, bupivacaine, stimulated only modest levels of overall antibody production, with relatively low level of Ig2a. These results demonstrate the usefulness of various chemicals, particularly levamisole, for modulating the outcome of DNA vaccination, in both the intensity of the immune response and the polarity of such response (toward Th1).

Genes of tolerance

Activation-induced cell death, anergy and/or immune response modulation by T-regulatory cells (T(Reg)) are essential mechanisms of peripheral T-cell tolerance. There is growing evidence that anergy, tolerance and active suppression are not entirely distinct, but rather, represent linked mechanisms possibly involving the same cells and multiple suppressor mechanisms. Skewing of allergen-specific effector T cells to T(Reg) cells appears as a crucial event in the control of healthy immune response to allergens and successful allergen-specific immunotherapy. The T(Reg) cell response is characterized by abolished allergen-induced specific T-cell proliferation and suppressed T helper 1 (Th1)- and Th2-type cytokine secretion. In addition, mediators of allergic inflammation that trigger cAMP-associated G-protein coupled receptors, such as histamine receptor 2 may contribute to peripheral tolerance mechanisms. The increased levels of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) that are produced by T(Reg) cells potently suppress immunoglobulin E (IgE) production, while simultaneously increasing production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation such as mast cells, basophils and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms. It is associated with regulation of antibody isotypes and effector cells to the direction of a healthy immune response and opens a window for novel therapies of allergic diseases.

T cell epitope-specific defects in the immune response to cat allergen in patients with atopic dermatitis

Atopic dermatitis (AD) is often associated with high titer IgE antibodies (ab) to allergens, and IL-10-mediated regulation of IFN-gamma has been proposed to contribute to this IgE ab production. However, the relevance of IL-10 and IFN-gamma to IgE associated with AD has not been examined in the context of an allergen-specific system. Analysis of PBMC responses in vitro showed deficient T cell proliferation to overlapping IL-10- (peptide (P) 2:1) and IFN-gamma- (P2:2) inducing chain 2 major epitopes of cat allergen (Fel d 1) in cultures from sensitized AD patients (mean IgE to cat=20.9 IU/ml). Diminished IFN-gamma induction by Fel d 1 and P2:2, along with elevated peptide-induced IL-10 (except for P2:1) was observed in PBMC cultures from AD subjects compared with non-AD (sensitized and non-sensitized) subjects. Neither T cell proliferation nor IFN-gamma production to chain 2 epitopes could be restored by anti-IL-10 mAb in cultures from sensitized AD subjects. Moreover, allergen avoidance was associated with a paradoxical decrease in both IL-10 and IFN-gamma in peptide-stimulated PBMC from these subjects. Control of IFN-gamma production to chain 2 epitopes by IL-10 may be relevant to sensitization status. Development of high titer IgE ab in AD could reflect a failure of this mechanism.

A Role for IL-10-Mediated HLA-DR7-Restricted T Cell-Dependent Events in Development of the Modified Th2 Response to Cat Allergen

Although high dose exposure to inhaled cat allergen (Fel d 1) can cause a form of tolerance (modified Th2 response), the T cell mechanism for this phenomenon has not been studied. T cell responses to Fel d 1 were characterized in both allergic (IgE(pos)) and modified Th2 (IgE(neg)IgG(pos)) responders as well as serum Ab-negative controls (IgE(neg)IgG(neg)). Fel d 1 stimulated high levels of IL-10 in PBMC cultures from all individuals, with evidence of Th2 and Th1 cytokine skewing in allergic and control subjects, respectively. Using overlapping peptides, epitopes at the N terminus of Fel d 1 chain 2 were shown to stimulate strong T cell proliferation and to preferentially induce IL-10 (peptide 2:1 (P2:1)) or IFN-gamma (P2:2) regardless of the allergic status of the donor. Injection of cat extract during conventional immunotherapy stimulated expansion of IL-10- and IFN-gamma-producing chain 2 epitope-specific T cells along with increased Fel d 1-specific serum IgG and IgG4 Ab. Six of 12 modified responders expressed the major HLA-DRB1 allele, *0701, and both P2:1 and P2:2 were predicted ligands for this allele. Cultures from DR7-positive modified responders produced the highest levels of IL-10 to P2:1 in addition to other major and minor epitopes within chains 1 and 2. In the presence of anti-IL-10 mAb, both T cell proliferation and IFN-gamma production were enhanced in a Fel d 1- and epitope-specific manner. We conclude that IL-10-producing T cells specific for chain 2 epitopes are relevant to tolerance induction, and that DR7-restricted recognition of these epitopes favors a modified Th2 response.

Recombinant expression and antigenic properties of a 31.5-kDa keratinolytic subtilisin-like serine protease from Microsporum canis

A secreted 31.5-kDa keratinolytic subtilase (SUB3; AJ431180) is thought to be a Microsporum canis virulence factor and represents a candidate for vaccination trials. In this study, the recombinant keratinase (r-SUB3) was produced by the Pichia pastoris expression system and purified to homogeneity. Recombinant SUB3 displayed identical biochemical properties with the native protease. Experimentally cutaneously infected guinea pigs showed specific lymphoproliferative response towards r-SUB3, while no specific humoral immune response was induced except for one animal. The heterologous expression of SUB3 provides a valuable tool for addressing further investigations on the role of this keratinase in the specific cellular immune response and on its use in vaccination trials in the cat.

Immunity and hypersensitivity to gp43 antigen in susceptible and resistant mice infected withParacoccidioides brasiliensis

Pathogenic mechanisms underlying paracoccidioidomycosis are still poorly understood. A well-established murine model of resistance (mouse lineage A/Sn) and susceptibility (lineage B10.A) to P. brasiliensis pulmonary infection was here employed to compare immune response to gp43, the major antigenic component of the fungus. Mice were infected and their cellular and humoral immunity to gp43 were investigated for up to 16 weeks. In both mouse strains, challenge with gp43 indistinguishably evoked a typical immediate-hypersensitivity response, followed by a 24-h late-phase reaction consistent with the same type of immunological activation. IL-4 was detected in cultures of gp43-stimulated lymph node cells only in susceptible animals 2 weeks post-infection, while IL-5 was found throughout the study in both mouse strains. IL-10 appeared in the supernatants of stimulated cells from resistant and susceptible animals in increasing amounts as infection advanced. Conversely, interferon (IFN)-gamma was produced under gp43 stimulation only by cells from A/Sn animals. The humoral response was characterized by low levels of anti-gp43. Titration of IgG isotypes, however, revealed a predominance of IgG1. IgG2a levels were highest in resistant animals, whereas IgG2b levels were highest in susceptible mice. In conclusion, immunity induced by gp43 exhibits common features in A/Sn and B10.A phenotypes, such as immediate hypersensitivity, late phase reaction and high levels of IL-10, but some differences between the strains are also seen.

Allergy immunotherapy and inhibition of Th2 immune responses: a sufficient strategy?

Th2 immune responses mediated by the secretion of IL-4, IL-5 and IL-13 are key in the pathogenesis of atopic disorders, including allergen-induced asthma, rhinoconjunctivitis and anaphylaxis. Although such responses are downregulated to some degree by conventional specific immunotherapy, this approach is only partially effective and has a substantial risk of adverse effects. Many strategies for immunotherapeutic prophylaxis and for treatment of atopic diseases have been devised on the basis of mouse allergy and autoimmune models, including the downregulation of Th2 responses by the induction of regulatory T cell activity, Th2 to Th1 immune deviation, Th1 crossregulation of Th2 immune responses, anergy and immunosuppressive cytokines. The blockade of events that are not allergen-specific, such as T cell costimulation and downstream events dependent on IgE, cytokines and chemokines, has also been pursued. With the exception of monoclonal antibody therapy for the blockade of IgE effector function, the application of most of these strategies to humans is at an early stage. Whether the inhibition of Th2 responses without concurrent downregulation of Th1 responses will be sufficient for allergic immunotherapy, particularly for atopic dermatitis and asthma, is an important but unresolved issue.

The skin fungus-induced Th1- and Th2-related cytokine, chemokine and prostaglandin E2 production in peripheral blood mononuclear cells from patients with atopic dermatitis and psoriasis vulgaris

BACKGROUND

It is suggested that skin fungi may be involved in the development of atopic dermatitis (AD) and psoriasis vulgaris (PV).

OBJECTIVE

We studied skin fungus-induced Th1- or Th2-related cytokine, chemokine and prostaglandin E2 (PGE2) secretion in peripheral blood mononuclear cells (PBMC) from patients with AD and PV and normal subjects.

METHODS

PBMC were cultured with the extracts of Malassezia furfur (MF), Candida albicans (CA) and Trichophyton rubrum (TR). The cytokine, chemokine and PGE2 amounts in the supernatants were measured by enzyme-linked immunosorbent assays.

RESULTS

MF induced IL-4 and macrophage-derived chemokine (MDC) secretion in AD patients, while induced IFN-gamma and interferon-inducible protein of 10 kDa (IP-10) secretion in PV patients, however, did not induce either secretion in normal subjects. CA induced IL-4, MDC, IFN-gamma and IP-10 secretion in AD and PV patients and normal subjects. In AD patients, the magnitude of IL-4 and MDC responses to CA was higher than that to MF. Compared with PV patients and normal subjects, the magnitude of IL-4 and MDC responses to CA was higher while that of IFN-gamma and IP-10 responses to CA was lower in AD patients. TR induced moderate IL-4 and MDC secretion only in AD patients. The three fungi induced higher levels of PGE2 secretion in AD patients than in PV patients and normal subjects. Cyclooxygenase-2 inhibitor NS-398 suppressed PGE2 responses to MF, CA and TR, and partially suppressed IL-4 and MDC responses to MF, CA and TR, while enhanced IFN-gamma and IP-10 responses to CA in AD patients, and these effects of NS-398 were reversed by cyclic AMP analogue.

CONCLUSION

AD patients manifest Th2-skewed responses to MF, CA and TR, which may be partially attributable to the enhanced PGE2 responses to these fungi. PV patients manifest Th1-skewed responses to MF.

Human leukocyte antigen Class II amino acid epitopes: susceptibility and progression markers for beryllium hypersensitivity

Chronic beryllium disease (CBD) is a hypersensitivity granulomatosis characterized by beryllium hypersensitivity (BH) and mediated by CD4+ T cells. However, all individuals with BH may not develop CBD. To examine the role of the three different human leukocyte antigen (HLA) Class II isotypes in BH with (CBD) and without clinical disease (BHWCD), we performed DNA-based typing of HLA-DPB1, HLA-DQB1, and HLA-DRB1 loci on 55 subjects with BH (25 with established CBD and 30 with BHWCD), and compared this with the results for 82 beryllium-exposed workers with no evidence of BH. The allele distribution was utilized to identify candidate amino acid epitopes that differed between the study groups. HLA-DPB1-E69 was the most important marker for BH, and did not differentiate BHWCD from CBD. A significant association with CBD was observed with HLA-DQB1-G86 (p(corr) < 0.04), and HLA-DRB1-S11 was significantly increased in CBD as compared with BHWCD (p < 0.03). These observations suggest that HLA-DPB1-E69 is a marker for susceptibility to BH and not just a progression marker for CBD. In addition, HLA amino acid epitopes on HLA-DRB1 and -DQB1, in concert with or independently of HLA-DPB1-E69, may be associated with progression to CBD.

The role of allergens in the induction of asthma

Despite the strong and consistent association between immediate hypersensitivity and asthma, there is still controversy about the role inhaled allergens play and about the timing of events related to sensitization. Recent studies have provided further evidence on the nature of the immune response to allergens, the timing of this response, and, in particular, whether any response to allergens occurs in utero. Some of the studies also provide a better explanation for why there is not a simple dose response relationship between allergens and asthma. The new studies also raise major issues about the nature of the immune response in nonallergic individuals. Taken together, the findings do not support a simple view about the balance between TH1 and TH2 responses, but strongly support the relevance of IgE to the risk of asthma.

Chronic soluble antigen sensitization primes a unique memory/effector T cell repertoire associated with th2 phenotype acquisition in vivo

Although much progress has been made in characterization of the signaling pathways that control Th cell commitment, little is known about the early events that govern differentiation of IL-4-producing T lymphocytes in vivo. We have previously shown that chronic administration of low dose, soluble hen egg white lysozyme (HEL) induced the selective development of Ag-specific Th2 in genetically predisposed BALB/c mice. Here, we show that these memory/effector Th2 cells express a unique TCR Vbeta repertoire, different from the TCR Vbeta profile of primary effector cells from HEL-adjuvant-primed mice. This Th2-associated repertoire contains a highly frequent public clonotype characterized by preferred TCR AV and BV gene segment usage along with conserved sequences in the third hypervariable regions of both TCR chains. This Th2 clonotype, which is not recruited in primary effector T cells from HEL-adjuvant-immunized mice, recognized an IA(d)-restricted HEL determinant, preferentially processed by dendritic cells, but not by B cells. Thus, IL-4-producing CD4 T cells that expand following chronic Ag sensitization emerge from a distinct pool of precursors, supporting the hypothesis that ligand-TCR interactions play a crucial role in the regulation of Ag-specific Th2 cell development 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

Distinct immune responses in humans to the Trichophyton rubrum Ag, Tri r 2, are associated with different patterns of T cell epitope recognition based on in vitro proliferation to peptides derived from this 29-kDa protein. Specifically, the amino-terminal immunodominant epitope, peptide 5 (P5), stimulates strong T cell proliferative responses in subjects with delayed (DTH), but not immediate (IH) hypersensitivity skin tests. Evidence of a role for cytokines or changes in epitope recognition over time was examined in responses to Trichophyton using primary PBMC cultures established from seven IH and seven DTH subjects. Responses stimulated by Tri r 2 were dominated by the Th1 cytokine IFN-gamma (IFN-gamma:IL-5 > or = 4:1) in five DTH subjects, even in the presence of Th2-dominated responses (IFN-gamma:IL-5 < or = 3:1) to a subset of major epitopes. Paradoxically, P5 induced IL-5 and IL-10 production in DTH, but not IH subjects (p = 0.003 (IL-5), p = 0.024 (IL-10)), with no significant difference in IFN-gamma levels between the two groups. In cultures from IH responders, no IL-5 was measurable after stimulation with P6 and P7 (as well as P5); this region of the molecule was shown previously to stimulate markedly reduced T cell proliferation in these individuals. Repeat proliferation assays confirmed no change in the pattern of peptide recognition after > or =20 mo in IH or DTH subjects. We conclude that T cell repertoires associated with distinct immune responses to Tri r 2 can be distinguished based on Th2 cytokine induction by DTH-associated major epitopes localizing to the amino-terminal region of the molecule.

The role of immunoglobulin E in allergy and asthma

It has been nearly a century since the first suggestion that a soluble factor in plasma or serum might be responsible for the symptoms of allergic disease and asthma, and more than 30 yr since immunoglobulin E (IgE) was identified as the key molecule in mediating what are now described as type 1 hypersensitivity reactions (allergic asthma, allergic rhinitis, food allergy, atopic dermatitis, some forms of drug allergy, and insect sting allergy). Since that time, many of the details of the inflammatory cascade underlying allergy and asthma have been elucidated, and IgE is now known to play a key upstream role. The goals of this report are to review the cellular and molecular events set in motion by IgE and to examine the evidence for its participation in both the immediate allergic response and the late-phase or chronic inflammatory response in the skin and lungs.

Independent genetic control of B- and T-cell tolerance in strains of mouse selected for extreme phenotypes of oral tolerance

Two strains of mice were genetically selected for susceptibility (TS-Ab/HetS strain) or resistance (TR-Ab/HetS strain) to oral tolerance of the humoral response by using ovalbumin (OVA). The progressive interstrain divergence produced by bi-directional selective breeding during 15 generations demonstrated the polygenic nature of oral tolerance. This paper shows the humoral and delayed-type hypersensitivity (DTH) responses, after intragastric administration of OVA and subsequent immunization with that immunogen in complete Freund adjuvant (CFA). Only the TS-Ab/HetS mice were tolerant for immunoglobulin (Ig)G production with its tolerance degree being the same as that obtained when Al ((OH)(3)) was employed. The DTH reactivity was not correlated to the antibody responsiveness, because both the TS-Ab/HetS and TR-Ab/HetS strains had their DTH reactions suppressed. The cyclophosphamide (Cy) pretreatment prevented DTH suppression on TR-Ab/HetS but do not in TS-Ab/HetS mice. Interstrain difference was also observed for the splenic index in the Cy-treated groups, although the number of splenocytes was the same. Flux cytometry cell analysis showed the recovery of CD3(+) cell numbers in both strains, but only the TR-Ab/HetS mice had their CD4/CD8 pattern restored. These results suggest: firstly, the independent control of DTH and humoral tolerance responsiveness; secondly no support for the clonal anergy concept; and thirdly the matrix proteins neo-synthesis after Cy treatment may facilitate the tolerance abrogation.

Rapid determination of HLA B*07 ligands from the West Nile virus NY99 genome

Defined T cell epitopes for West Nile (WN) virus may be useful for developing subunit vaccines against WN virus infection and diagnostic reagents to detect WN virus-specific immune response. We applied a bioinformatics (EpiMatrix) approach to search the WN virus NY99 genome for HLA B*07 restricted cytotoxic T cell (CTL) epitopes. Ninety-five of 3,433 WN virus peptides scored above a predetermined cutoff, suggesting that these would be likely to bind to HLA B*07 and would also be likely candidate CTL epitopes. Compared with other methods for genome mapping, derivation of these ligands was rapid and inexpensive. Major histocompatibility complex ligands identified by this method may be used to screen T cells from WN virus-exposed persons for cell-mediated response to WN virus or to develop diagnostic reagents for immunopathogenesis studies and epidemiologic surveillance.