Transcriptome profiling reveals Th2 bias and identifies endogenous itch mediators in poison ivy contact dermatitis.

In the United States, poison ivy exposure is the most common naturally occurring allergen to cause allergic contact dermatitis (ACD). The immune and pruritic mechanisms associated with poison ivy ACD remain largely unexplored. Here, we compared skin whole transcriptomes and itch mediator levels in mouse ACD models induced by the poison ivy allergen, urushiol, and the synthetic allergen, oxazolone. The urushiol model produced a Th2-biased immune response and scratching behavior, resembling findings in poison ivy patients. Urushiol-challenged skin contained elevated levels of the cytokine thymic stromal lymphopoietin (TSLP), a T-cell regulator and itch mediator, and pruritogenic serotonin (5-HT) and endothelin (ET-1), but not substance P (SP) or histamine. The oxazolone model generated a mixed Th1/Th2 response associated with increased levels of substance P, 5-HT, ET-1, but not TSLP or histamine. Injections of a TSLP monoclonal neutralizing antibody, serotonergic or endothelin inhibitors, but not SP inhibitors or antihistamines, reduced scratching behaviors in urushiol-challenged mice. Our findings suggest that the mouse urushiol model may serve as a translational model of human poison ivy ACD study. Inhibiting signaling by TSLP and other cytokines may represent alternatives to the standard steroid/antihistamine regimen for steroid-resistant or -intolerant patients and in exaggerated systemic responses to poison ivy.

Urushiol Patch Test Using the T.R.U.E. TEST System.

BACKGROUND: Poison ivy, poison oak, and poison sumac are the most common causes of allergic contact dermatitis in North America. Although extensive efforts have been made to develop therapies that prevent and treat allergic contact dermatitis to these plants, there lacks an entirely effective method, besides complete avoidance. Efforts to develop a more effective preventive therapy, such as a vaccine, are ongoing. To accurately evaluate the efficacy of these new therapies, an appropriate assessment tool is needed. OBJECTIVE: The aim of this study was to evaluate the safety and appropriate doses of urushiol required for a patch test based on the hydrogel delivery system of the Thin-Layer Rapid Use Epicutaneous Patch Test. METHODS: Nine subjects were patch tested with various doses of urushiol and a negative control on day 0. Patch test sites were inspected for any local reaction on days 2, 4, 7, 14, and 21 after the initial exposure and graded by standard morphology. CONCLUSIONS: All 9 subjects did not have any significant adverse effects. The urushiol patch test using the hydrogel delivery method demonstrated urushiol sensitivity. All doses of urushiol resulted in a local reaction, and severity of reactions was correlated with dosage of urushiol used in the patch test.

Human Metabolome-derived Cofactors Are Required for the Antibacterial Activity of Siderocalin in Urine.

In human urinary tract infections, host cells release the antimicrobial protein siderocalin (SCN; also known as lipocalin-2, neutrophil gelatinase-associated lipocalin, or 24p3) into the urinary tract. By binding to ferric catechol complexes, SCN can sequester iron, a growth-limiting nutrient for most bacterial pathogens. Recent evidence links the antibacterial activity of SCN in human urine to iron sequestration and metabolomic variation between individuals. To determine whether these metabolomic associations correspond to functional Fe(III)-binding SCN ligands, we devised a biophysical protein binding screen to identify SCN ligands through direct analysis of human urine. This screen revealed a series of physiologic unconjugated urinary catechols that were able to function as SCN ligands of which pyrogallol in particular was positively associated with high urinary SCN activity. In a purified, defined culture system, these physiologic SCN ligands were sufficient to activate SCN antibacterial activity against Escherichia coli In the presence of multiple SCN ligands, native mass spectrometry demonstrated that SCN may preferentially combine different ligands to coordinate iron, suggesting that availability of specific ligand combinations affects in vivo SCN antibacterial activity. These results support a mechanistic link between the human urinary metabolome and innate immune function.

Vibriobactin antibodies: a vaccine strategy.

A new target strategy in the development of bacterial vaccines, the induction of antibodies to microbial outer membrane ferrisiderophore complexes, is explored. A vibriobactin (VIB) analogue, with a thiol tether, 1-(2,3-dihydroxybenzoyl)-5,9-bis[[(4S,5R)-2-(2,3-dihydroxyphenyl)-4,5-dihydro-5-methyl-4-oxazolyl]carbonyl]-14-(3-mercaptopropanoyl)-1,5,9,14-tetraazatetradecane, was synthesized and linked to ovalbumin (OVA) and bovine serum albumin (BSA). The antigenicity of the VIB microbial iron chelator conjugates and their iron complexes was evaluated. When mice were immunized with the resulting OVA-VIB conjugate, a selective and unequivocal antigenic response to the VIB hapten was observed; IgG monoclonal antibodies specific to the vibriobactin fragment of the BSA and OVA conjugates were isolated. The results are consistent with the idea that the isolated adducts of siderophores covalently linked to their bacterial outer membrane receptors represent a credible target for vaccine development.

Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2.

Contact with poison ivy (Toxicodendron radicans) is one of the most widely reported ailments at poison centers in the United States, and this plant has been introduced throughout the world, where it occurs with other allergenic members of the cashew family (Anacardiaceae). Approximately 80% of humans develop dermatitis upon exposure to the carbon-based active compound, urushiol. It is not known how poison ivy might respond to increasing concentrations of atmospheric carbon dioxide (CO(2)), but previous work done in controlled growth chambers shows that other vines exhibit large growth enhancement from elevated CO(2). Rising CO(2) is potentially responsible for the increased vine abundance that is inhibiting forest regeneration and increasing tree mortality around the world. In this 6-year study at the Duke University Free-Air CO(2) Enrichment experiment, we show that elevated atmospheric CO(2) in an intact forest ecosystem increases photosynthesis, water use efficiency, growth, and population biomass of poison ivy. The CO(2) growth stimulation exceeds that of most other woody species. Furthermore, high-CO(2) plants produce a more allergenic form of urushiol. Our results indicate that Toxicodendron taxa will become more abundant and more "toxic" in the future, potentially affecting global forest dynamics and human health.

IFN-gamma and TNF-alpha are involved in urushiol-induced contact hypersensitivity in mice.

Contact hypersensitivity (CHS) is a cutaneous T-cell-mediated immunological reaction to applied haptens. Activated antigen-specific T cells release several cytokines and chemokines followed by the recruitment of inflammatory cells and skin damage. CD8+ T cells and CD4+ T cells have been involved in the establishment of previously described CHS. In this study, we investigated the induction of CHS by urushiol in mice. Maximum swelling in mouse ears was elicited 24 h after challenge with urushiol on day 9 of sensitization. IFN-gamma, TNF-alpha and IFN-gamma-inducible protein 10 (IP-10) mRNA were expressed after challenge of the antigen in urushiol-sensitized mice, but not in unsensitized mice. IFN-gamma knockout (KO) mice and TNF-alpha KO mice failed to elicit CHS with urushiol. Contact hypersensitivity and expressions of IFN-gamma, TNF-alpha and IP-10 mRNA were markedly suppressed in CD4+ and CD8+ cell-depleted mice. These results suggest that IFN-gamma, TNF-alpha, and possibly IP-10, play a critical role in CHS induced by urushiol, depending on both CD4+ T cells and CD8+ T cells.

Lipoxygenase-catalyzed polymerization of phenolic lipids suggests a new mechanism for allergic contact dermatitis induced by urushiol and its analogs.

Lipoxygenase was found to catalyze the oxidative polymerization of phenolic lipids containing a (Z,Z)-pentadiene in the side chain, the model compounds of urushiol and its analog, yielding methanol-soluble and insoluble polymers. The structural analysis of the resulted polymers suggested that the polymerization occurred at both the phenol and the unsaturated side chain. The key step of the polymerization was the generation of the hydroperoxide at the unsaturated side chain by lipoxygenase. The decomposition of hydroperoxide and concomitant dehydrogenation of phenol ring catalyzed by lipoxygenase might produce radicals that could be coupled to form cross-linked polymers. This lipoxygenase-mediated reaction implies a new mechanism for contact allergy of urushiol and its analogs.

[Allergic contact dermatitis to common ivy (Hedera helix L.)]. / Allergische Kontaktdermatitis auf Efeu (Hedera helix L.).

Common ivy (Hedera helix L.) is a ubiquitous plant in Europe whose major allergen falcarinol has moderate allergic potential. It is not related to poison ivy (Toxicodendron spp.). There are no cross reactions between the allergens of common ivy (falcarinol) and poison ivy (urushiol). Contact with common ivy or falcarinol may lead to sensitization and then a delayed hypersensitivity reaction. There are only few cases described in the literature. We report on a male hobby gardener with appropriate clinical history and positive patch test. The pathogenic mechanism is a type IV reaction following a sensitization exposure. Gardeners and landscape architects with frequent exposure to common ivy and thus a high risk of sensitization should wear appropriate protective clothing.

Frequency of standard and occupational contact allergens in Tuzla area, Bosnia and Herzegovina: retrospective study.

Allergic contact dermatitis is acute or chronic inflammatory skin disease of allergic etiology, which develops as a result of delayed type of hypersensitivity, i.e. type IV reaction according to the Gell and Coombs classification. In the retrospective study, we reviewed medical records of 495 patients diagnosed with allergic contact dermatitis in the 1988-1998 period. The records were obtained from the Cabinet of Allergology of the Department of Dermatology and Venerology, Tuzla University Hospital Center. There were 312 women and 183 men, aged between 18 and 60 years. The patients were divided into 6 groups according to their occupation. Contact sensitization was established in 295 or 59.6% of them. The type and frequency of causative agent in allergic contact dermatitis depended on working environment. Potassium dichromate, a component part of cement, caused positive reaction in 48% of construction workers tested, which was significantly more than in the "other occupation" group, where 14.6% of patients showed positive reaction to potassium dichromate (p<0.001). Formaldehyde, used in leather processing, was the most frequent among the four leading allergens in the group of shoe workers (13.3%), whereas charcoal tar (used in the metal processing) was the most frequent allergen in the group of metal workers (13.9%). Nickel sulfate, potassium dichromate, cobalt chloride, and urushiol were frequent allergens in the "other occupation" group, housewives, and textile workers. The listed allergens are present at large in everyday life as well as in particular occupations.

Assessment of the ability of the topical skin protectant (TSP) to protect against contact dermatitis to urushiol (Rhus) antigen.

BACKGROUND: Military personnel have a need for effective protection against cutaneous exposure to chemical warfare agents (CWA). Topical Skin Protectant (TSP) is being developed to supplement chemical warfare protective garments. TSP protects against CWA exposure in animals, but does it work for humans? Because humans should not be tested with live CWA, urushiol (poison ivy) extract was used as a surrogate substance in place of CWA for human efficacy testing of TSP. OBJECTIVE: Determine whether TSP protects human skin against experimentally-induced urushiol dermatitis. METHODS: Open urushiol patch testing of 50 rhus-sensitive subjects comparing the 96-hour dermatitis severity scores between TSP protected and TSP unprotected sites. There were 4 paired sites (i.e., protected versus unprotected) per subject. Test sites were scored using a 9-point dermatitis scale of 0.0 to 4.0 (using 0.5 increments). RESULTS: Analysis of variance of the dermatitis scores from 192 paired sites on 48 evaluable subjects showed that TSP protected sites had mean dermatitis scores about 2 points lower than TSP unprotected sites (P <.001). CONCLUSION: Although this study does not provide direct scientific evidence that TSP protects humans against the percutaneous absorption of CWA, it does provide circumstantial evidence that this is the case. The fact that TSP is so highly effective against a lipophilic substance like urushiol and that most common vesicant CWAs are lipophilic and are weaponized in oleaginous vehicles, makes the effectiveness of TSP in preventing absorption and dermatitis from CWA seem likely.

Simultaneous p-tert-butylphenol-formaldehyde resin and p-tert-butylcatechol contact allergies in man and sensitizing capacities of p-tert-butylphenol and p-tert-butylcatechol in guinea pigs.

In patients who are hypersensitive to p-tert-butylphenol-formaldehyde resin (PTBP-F-R), it is necessary, for diagnostic, therapeutic, and preventive reasons, to know the identity of the primary sensitizing substances, their sensitizing capacities, and their crossreaction patterns. The aims of this study were to investigate the presence of a simultaneous p-tert-butylcatechol (PTBC) contact allergy in individuals who were hypersensitive to PTBP-F-R, to investigate the sensitizing capacity of PTBC and p-tert-butylphenol (PTBP) in guinea pigs, and to study any crossreaction patterns. In 294 dermatitis patients tested with PTBP-F-R and PTBC, there was a statistically significant over-representation of simultaneous test reactions. Use of the guinea pig maximization test demonstrated that PTBC is a strong sensitizer giving crossreactions to PTBP. PTBP, however, failed to induce sensitization.

Regulation of the contact sensitivity response to urushiol with anti-urushiol monoclonal antibody ALG 991.

The objective of the studies was to demonstrate that the contact sensitivity (CS) response to poison ivy/oak could be downregulated following treatment with a monoclonal antibody (mAb) reacting with the allergen urushiol. Conjugation of urushiol and its synthetic analogue 3-n-pentadecylcatechol (PDC) to N-acetylcysteine yielded hydrosoluble derivatives which induced humoral immune responses in BALB/c mice. Hybridomas secreting monoclonal antibodies (mAbs) reacting with urushiol and PDC were generated by fusion of B lymphocytes from immunized mice with mouse myeloma P3NS0 cells. The specificity of mAb ALG 991 (IgM isotype) was defined by inhibition of antibody binding by PDC analogues. This demonstrated that mAb ALG 991 reacted with the catechol moiety of urushiol, the region of the allergen being critically important in the induction of contact dermatitis. The CS response to urushiol in BALB/c mice was suppressed by stimulation with mAb ALG 991 and the role of sensitized T cells, including suppressor T cells, has been considered. Suppression of CS was most effective with low doses (1 microg) of mAb incorporated into a vaccine with Freund's adjuvant. This treatment suppressed CS responses in BALB/c mice already sensitized to urushiol.

Induction of hapten-specific tolerance of human CD8+ urushiol (poison ivy)-reactive T lymphocytes.

The interaction of CD28 with B7 molecules (CD80 or CD86) is an essential second signal for both the activation of CD4+ T cells through the T-cell receptor and the prevention of anergy. We studied the requirement of hapten-specific human CD8+ cells for CD28 co-stimulation in recognition of hapten, and anergy induction. Urushiol, the immunogenic hapten of poison ivy (Toxicodendron radicans), elicits a predominantly CD8+ T-cell response. Autologous PBMC were pre-incubated with urushiol prior to fixation by paraformaldehyde. Fixed antigen-presenting cells were unable to present urushiol to human CD8+ urushiol-specific T cells. Addition of anti-CD28, however, overcame this antigen-presenting defect, enabling CD8+ cells to proliferate. Fixation of antigen-presenting cells prevents upregulation of B7, and addition of anti-CD28 substitutes for this signal. Proliferation of CD8+ T cells in response to urushiol was blocked by CTLA4Ig, a recombinant fusion protein that blocks CD28/B7 interactions. Preincubation of urushiol-specific CD8+ cells with fixed PBMC + urushiol for 7 d induced anergy. Anergic CD8+ cells were viable and able to proliferate in response to IL-2, but not in response to urushiol. Induction of anergy required the presence of urushiol, and pre-incubation with irradiated PBMC + urushiol did not have this effect. It is proposed that anergy was induced by presentation of urushiol by fixed PBMC, in the absence of adequate co-stimulation signals. Induction of anergy by blocking of co-stimulation could potentially induce clinical hyposensitization to haptens.

Preservation of allergic contact dermatitis to poison ivy (urushiol) in late HIV disease. The implications and relevance to immunotherapy with contact allergens.

BACKGROUND: Delayed hypersensitivity reactions (DTH) are lost with progression of HIV disease. This loss of DTH commonly occurs before the onset of opportunistic infections and is an independent predictor of disease progression. OBJECTIVE: We wanted to determine whether patients in late HIV disease with a history of allergic contact dermatitis (ACD) to poison ivy continue to react to poison ivy. METHODS: Twelve HIV+ patients with a past history of ACD to poison ivy were tested with an extract prepared from poison ivy leaves. All but 1 patient had CD4+ T cell counts < 200/microliters, and 5 patients had had an opportunistic infection. RESULTS: All 12 patients showed positive reactions ranging from mild erythema and infiltration to marked erythema with bulla formation. CONCLUSIONS: ACD is considered a variant of DTH, and as DTH results in a T helper 1 cytokine pattern. However, the antigen-specific effector cells in ACD may be more diverse than in DTH. This diversity could explain the continued reaction to some contact allergens in late disease and may be important in the use of contact allergens for immunotherapy.

Modulation of fatty acid oxidation alters contact hypersensitivity to urushiols: role of aliphatic chain beta-oxidation in processing and activation of urushiols.

Lithraea caustica, or litre, a tree of the Anacardiaceae family that is endemic to the central region of Chile, induces a severe contact dermatitis in susceptible human beings. The allergen was previously isolated and characterized as a 3-(pentadecyl-10-enyl) catechol, a molecule belonging to the urushiol group of allergens isolated from poison ivy and poison oak plants. Because urushiols are pro-electrophilic haptens, it is believed that the reactive species are generated intracellularly by skin keratinocytes and Langerhans cells. The active species are presumed to modify self proteins which, after proteolytic processing, would generate immunogenic peptides carrying the hapten. The presence of a 15-carbon-length hydrophobic chain should impair antigen presentation of self-modified peptides by class I MHC molecules, either by steric hindrance or by limiting their sorting to the ER lumen. We have proposed that the shortening of the aliphatic chain by beta-oxidation within peroxisomes and/or mitochondria should be a requirement for the antigen presentation process. To test this hypothesis we investigated the effect of drugs that modify the fatty acid metabolism on urushiol-induced contact dermatitis in mice. Clofibrate, a peroxisomal proliferator in mice, increased the immune response to the urushiols from litre by 50%. Conversely, tetradecyl glycidic acid, an inhibitor of the uptake of fatty acids by mitochondria, decreased the hypersensitivity to the hapten. An increase in the level in glutathione by treatment of the animals with 2-oxotiazolidin-4-carboxilic acid lowered the response. Those findings strongly support a role for the fatty acid oxidative metabolism in the processing and activation of urushiols in vivo.

Resorcinols and catechols: a clinical study of cross-sensitivity.

BACKGROUND: All allergic contact dermatitis caused by Philodendron species is common in the Hawaiian islands, and Toxicodendron species are the most common causes of plant-induced allergic contact dermatitis in North America. OBJECTIVE: The purpose of this study was to determine the incidence of cross-sensitivity between these plant species. METHODS: Alkylresorcinols (pentadec[en]yl and heptadec[en]ylresorcinols) were isolated and purified from extracts of Hawaiian-grown Philodendron scandens subspecies scandens and Philodendron lacerum. Alkylcatechols (mixtures of pentadec[en]ylcatechols from an extract of Toxicodendron radicans (poison ivy) were obtained from the Division of Biologics Standards (National Institutes of Health, Bethesda, MD). Seventeen patients from Hawaii and 8 patients from northern California were skin tested with 5 microL (concentrations, 1 to .001 mg/mL) of each allergen applied to the flexor forearm. The test sites remained open and were graded at 72, 96, and 144 hours. All 8 patients from California were naive to Philodendron species, and 8 patients from Hawaii were naive to Toxicodendron species. RESULTS: No cross-reactivity occurred in patients who were Philodendron sensitive and Toxicodendron naive when tested to the homologous Toxicodendron catechols. Conversely, with one exception, no cross-reactivity occurred in patients who were Toxicodendron sensitive and Philodendron naive when tested to homologous Philodendron naive when tested to homologous Philodendron resorcinols. CONCLUSION: Patients who are sensitive to Philodendron species (or other resorcinol-containing plants) may not necessarily be cross-sensitive to Toxicodendron species and vice versa.

Overexpression of vascular permeability factor (VPF/VEGF) and its endothelial cell receptors in delayed hypersensitivity skin reactions.

Delayed hypersensitivity (DH) is a T cell-mediated form of immune response characterized by a predominantly perivascular, mononuclear cell infiltrate. The venules in DH reactions are hyperpermeable to plasma proteins, leading to extravasation of plasma fibrinogen and its extravascular clotting to form a fibrin gel that promotes induration and angiogenesis. The mechanisms responsible for microvascular hyperpermeability in DH are unknown. Recently, a cytokine named vascular permeability factor (VPF, also known as vascular endothelial growth factor or VEGF) has been implicated in the chronic vascular hyperpermeability and angiogenesis of solid and ascites tumors, healing wounds, rheumatoid arthritis, and psoriasis. These findings suggested that VPF/VEGF might also have a role in the pathogenesis of DH. Two model systems were studied: allergic contact dermatitis to poison ivy in human volunteers and classical tuberculin hypersensitivity in rats. In both, in situ hybridization revealed that the mRNAs encoding VPF/VEGF were strikingly overexpressed in keratinocytes of the epidermis; scattered mononuclear cells infiltrating the dermis also overexpressed VPF/VEGF mRNA, to a greater extent in rat tuberculin than in human contact reactions. In contact reactions, mRNAs for two VPF/VEGF vascular endothelial cell receptors, flt-1 and KDR, were also strikingly overexpressed. Abundant fibrin deposition in both models confirmed that dermal microvessels were indeed hyperpermeable to plasma fibrinogen. These results implicate VPF/VEGF as a potentially important mediator in the pathogenesis of cell-mediated immunity and provide further evidence that products of epithelial cells may regulate the inflammatory response.