Experimental nickel sensitization in the guinea pig: comparison of different protocols

3 different sensitization protocols were compared for inducing delayed-type nickel contact hypersensitivity in guinea pigs. Open epicutaneous sensitization (OE) induced nickel allergy in 11/22 (50%) guinea pigs. When intradermal injections of Freund's complete adjuvant into the nickel-painted skin was added to the same protocol. 4/13 (31 %) became sensitized. The guinea pig maximization protocol induced nickel allergy in only 7/31 (23%) of the animals. Compared with the 2 other methods, animals sensitized with open epicutaneous applications reacted more rapidly (maximum at 6 h) and strongly (2+ reaction in 12/22 of animals) in previous patch lest sites upon systemic (i p.) nickel challenge. Open epicutaneous sensitization of guinea pigs should he a useful model for studying cellular and immunological mechanisms in nickel contact sensitivity.     

The effect of the guinea pig maximization protocol on the irritant response to deodorized kerosene – the excited skin syndrome *

Deodorized kerosene in a concentration of 50g/100g in pet. did not cause cutaneous inflammation in 10 control guinea pigs. The proportion of 19 guinea pigs exhibiting inflammation following exposure to deodorized kerosene in the guinea pig maximization test increased, but the increase was not significant. The response in a group of 40 animals, half exposed to tetraethyleneglycol diacrylate and half to nonylphenol polyethoxylate-6, increased (z= 3.505, p=0.004). The inflammatory response was related to concentration in both groups of animals which exhibited inflammatory responses to deodorized kerosene. The relevance of this alteration and irritant response of the interpretation of predictive to tests animals for sensitization, routine patch testing and repeated insult contact dermatitis is discussed.     

Experimental contact sensitization with 3,4,5-trichloropyridazine

The potential of 3,4,5-trichloropyridazine to induce contact sensitization was assessed in the guinea pig maximization test of Magnusson and Kligman and also in the closed patch test described by Buehler. The test material was a 1% solution of 3,4,5-trichloropyridazine in a highly refined mineral oil. The test material elicited moderate to severe irritation when diluted in mineral oil to concentrations of 15-25% and minimal irritation at concentrations of 1-3%. Both tests clearly indicated that 3,4,5-trichloropyridazine was a contact sensitizer to guinea pigs, although the response was stronger in the maximization test. Sensitization was distinguished from irritation by the use of concurrent irritation control groups.     

Skin lesions due to okra (Hibiscus esculentus L): proteolytic activity and allergenicity of okra

The present report describes experimental studies on the proteolytic activity of the secretion on the surface of okra pods and the allergenicity of okra components, to clarify the etiology of skin lesions due to okra. Proteolytic activity was detected on the surface of immature okra pods and seemed to be sufficient to cause the skin lesions. Further, in vivo, intradermal injection of the enzyme solution prepared from immature okra pods led to increased capillary permeability in guinea pigs, in contrast to heated preparations. The fraction purified by preparative paper chromatography from an ethyl acetate extract of okra pods showed moderate allergenicity in the guinea pig maximization test. The present experimental evidence supports our suggestions from previous surveys that the proteolytic enzyme of okra may be responsible for development of skin lesions, and that allergic contact dermatitis may also play a part in addition to irritant contact dermatitis.     

Allergic contact dermatitis due to nonylphenol ethoxylate (nonoxynol-6)

The non-ionic emulsifier "nonoxynol-6" found in an industrial waterless hand cleanser induced allergic contact dermatitis on the upper extremities of a uranium mill maintenance worker. The chemical is an irritant for the rabbit. It was not shown to be a cutaneous sensitizer for the albino guinea pit using the guinea pig maximization test.     

Sensitizing potential of acetaldehyde and formaldehyde using a modified cumulative contact enhancement test (CCET)

The contact allergenic activity of acetaldehyde was investigated with a modified cumulative contact enhancement test (CCET) method in guinea pigs. Possible cross-reactivity between acetaldehyde and formaldehyde was also studied. In contrast to the original CCET protocol, we used sham-treated controls and the chemicals were tested with closed epicutaneous application at 1st challenge. The suitability of the method was verified with formaldehyde and the results were comparable with those previously found with the guinea pig maximization test (GPMT). For the 1st time, acetaldehyde was shown to be a contact allergen in predictive tests. No cross-reactivity was observed between acetaldehyde and formaldehyde. Acetaldehyde seems to be a rare sensitizer in man. However, its allergenic activity should be considered, since it might be present as an impurity in ethoxylated surfactants. As the CCET protocol involves topical induction and challenge, we regard the modified version as well suited to evaluation of the contact allergenic potential of chemicals.     

Occupational contact dermatitis due to acrylonitrile

Within DSM Chemicals BV, a producer of acrylonitrile, skin complaints are frequent. The majority of these are of an irritant nature, while a smaller portion is based on acquired allergies. Allergological examination revealed 5 employees with an allergy to acrylonitrile. 1 of these subjects also developed paraesthesiae in the skin sites affected, a finding not previously described for acrylonitrile. In the guinea pig maximization test (GPMT), acrylonitrile showed strong allergenic potential. For prevention and treatment of contact allergologic disorders, close cooperation between occupational health officer, dermatologist and toxicologist in chemical companies is recommended.     

Sensitization studies with mometasone furoate, tixocortol pivalate, and budesonide in the guinea pig

Mometasone furoate is a new corticosteroid, synthesized to have an improved ratio of anti-inflammatory potential to adverse effects. The guinea pig maximization test was used to determine the sensitizing capacity of mometasone furoate, and also to investigate cross-reaction patterns in animals sensitized to tixocortol pivalate and budesonide, respectively. Tixocortol pivalate was shown to be a sensitizer in the guinea pig, but cross-reactions to other tested corticosteroids wore not observed. Furthermore, no sensitizing capacity could be demonstrated for budesonide or mometasone furoate.     

Allergic contact dermatitis from 2-n-octyl-4-isothiazolin-3-one, a paint mildewcide

Severe allergic contact dermatitis from a paint mildewcide, 2-n-octyl-4-isothiazolin-3-one, developed in a worker formulating latex paints within a paint manufacturing company, Guinea pig maximization testing demonstrated this to be a moderate sensitizer. Further cases of allergic contact dermatitis may be encountered as the use of this biocide increases in the market place.     

Experimental study of contact dermatitis due to alstroemeria in guinea pigs

Contact allergy from handling alstroemeria ( Alstroemeria ) has been widely observed in horticulturalists and florists (1–5). α-methylene-γ-butyrolactone (α-MBL) has been shown to be the causative agent (6, 7). In the present study, delayed-type contact dermatitis due to alstroemeria was evaluated using the guinea pig maximization test (GMT) (8), and the intensity of allergic reactions was investigated by quantifying the contents of α-MBL in different parts of alstroemeria by high-performance liquid chromatography (HPLC) (9).     

Identification of contact allergens in C.I. Solvent Red 23 (commercial Sudan III) by chemical analysis and animal testing

C.I. Solvent Red 23, commercial Sudan III, is widely used in cosmetic products. Chemical analyses and guinea pig sensitization tests were carried out to identify its contact allergens. In the Magnusson & Kligman guinea pig maximization test, C.I. Solvent Red 23 showed 20% positive reactions. By conducting chemical analyses with HPLC and GLC, 2-naphthol (82 ppm), azobenzene (48 ppm), Sudan I (570 ppm) and many unknown impurities, as well as the main constituent pigment Sudan III (87%), were found. The chemical structure of one unknown impurity was identified as an isomer of Sudan III. We found that purified Sudan III showed no positive reaction, while the isomer elicited 30% positive reactions, in the same guinea pig test. Furthermore, cross-sensitization with p-phenylenediamine was investigated using the guinea pig test. Animals sensitized with p-phenylenediamine also showed positive elicitation reactions with purified Sudan III. From these results, the contact allergenicity of C.I. Solvent Red 23 is considered to be due to impurities, including the isomer of Sudan III, 1-(o-phenylazophenylazo)-2-naphthol. Positive reactions to Sudan III previously demonstrated in hairdressers are due to cross-sensitivity with p-phenylenediamine.     

Predictive evaluation in animals of the contact allergenic potential of medically important substances I. Comparison of different methods of inducing and measuring cutaneous sensitization

Groups of guinea pigs were sensitized with a 0.1% solution of dinitrochlorobenzene (DNCB) by the Draize intracutaneous method, The course of the induction process, the influence of the vehicles used and the extent to which the reactions are amenable to assessment according to objective criteria were examined. The sensitivity of the standardized Draize test was then compared with that of various other sensitization techniques, including:
The intracutaneous test with adjuvant (optimization test)
The maximization test according to Magnusson & Kligman (1969)
The epidermal sensitization test
The epidermal sensitization lest wish prior irritation of the contact site (by croton oil or sodium lauryl sulphate).
Comparison of these methods revealed that either the additional application of adjuvant or prior irritation of the contact site augmented the degree of sensitization to DNCR just as greatly as the simultaneous use of adjuvant and prior irritation of the skin, (maximization test.). The improved sensitization methods, and in particular the standardised optimization test, may prove to be of particular value for the study of so-called weak allergens.     

Sulphanilic acid: divergent results in the guinea pig maximization test and the local lymph node assay

The guinea pig maximization test (GPMT) has proven to be a valuable tool for the identification of the skin sensitization potential of chemicals. The method identifies a hazard which can lead in the EC to compulsory labelling of that chemical. In the present study, data on sulphanilic acid derived from the GPMT has been compared with results from a second guinea pig assay (the cumulative contact enhancement test) and the murine local lymph node assay, both of which require only topical application of chemical. Except for the GPMT, no test identified any sensitizing activity associated with exposure to sulphanilic acid. These latter results are consistent with the experience gained from substantial human exposure in an occupational setting and from which no cases of allergic contact dermatitis to sulphanilic acid have arisen over a 20-year period. In consequence, it is questioned which test protocol in practice has given the more accurate identification of sensitization hazard relevant to man.     

Dose-response studies of contact allergens using 3 guinea pig models

A multi-dose-response induction protocol for the guinea pig maximization test (GPMT), including a statistical computer program, has earlier been developed to improve the power of predictive tests for identification of contact allergens. This dose-response protocol, with 2 modifications (i.e., increased number of animals in each group and increased number of challenge concentrations) was evaluated in the GPMT, the cumulative contact enhancement test (CCET) and the Freund's complete adjuvant test (FCAT), using potassium dichromate and hydroxycitronellal as model contact allergens. Application of the dose-response protocol on the CCET and the FCAT resulted in either monotone or non-monotone curves with significant dose-response. However, application of the dose-response protocol on the GPMT gave curves with no significant dose-response. The protocol makes it possible to obtain an EC50 value, thus improving the possibility of ranking contact allergens, which is of substantial use for risk assessments. The dose-response protocol could benefit from a few adjustments: a wider span in the induction doses; change to simultaneous increase in intradermal and topical induction doses to obtain a proper dose-response for the GPMT; the addition of further challenge concentrations. In addition the computer program should allow calculation of threshold concentration for sensitization and EC50 value for a non-monotone curve.     

Nickel-sulphate-induced contact dermatitis in the guinea pig maximization test: a dose-response study

Nickel sulphate is a sensitizer in guinea pigs, but the frequency of sensitization varies from study to study. The dose-response relationship for NiSO4.6H2O was evaluated in the guinea pig maximization test in this study. 6 intradermal (0.01%-3.0% aq.) and 6 topical (0.25%-10.0% pet.) concentrations were chosen for induction and NiSO4.6H2O 1% pet. was used for challenge, based on the absence of skin irritation in a pilot study. Blind reading was performed. A logistic dose-response model was applied to the challenge results. At 48 h, a linear relationship was obtained between the intradermal induction dose (but not topical dose) and the response, resulting in a maximum sensitization rate of 40% after 3% i.d. The reactivity disappeared at re-challenge 1 week later. Following a booster closed patch on day 35, using NiSO4 10% pet., the animals were challenged with NiSO4 2% pet. and statistical analyses of 72-h readings revealed a non-linear dose-response relationship, giving a maximum response frequency of 40% after initial induction with NiSO4 3% i.d. and 2% topical.     

Copper hypersensitivity: dermatologic aspects

Reports of immune reactions of both the immediate and delayed types due to cutaneous or systemic exposure to copper have been reviewed, in the endeavor to draw a comprehensive profile of the immunogenic potential of that metal and its compounds. The metal's immunotoxic potential is also briefly reviewed. In principle, as noted for other transition metals, the electropositive copper ion is potentially immunogenic due to its ability to diffuse through biological membranes to form complexes in contact with tissue protein. Based on predictive guinea pig test and the local lymph node assay (LLNA), copper has a low sensitization potential. Reports of immune reactions to copper include immunologic contact urticaria (ICU), allergic contact dermatitis (ACD), systemic allergic reactions (SAR) and contact stomatitis (STO), but considering the widespread use of copper IUDs and the importance of copper in coinage, items of personal adornment and industry, unambiguous reports of sensitization to the metal are extremely rare, and even fewer are the cases, which appear clinically relevant. Reports of immune reactions to copper mainly describe systemic exposure from intrauterine devices and prosthetic materials in dentistry, implicitly excluding induction of the hypersensitivity from contact with the skin as a risk factor. We provide a diagnostic algorithm that might clarify the frequency of copper hypersensitivity.     

How sensitizing is chlorocresol?

Chlorocresol is a biocide with widespread use in industry and pharmaceutical products. It is an occasional human contact sensitizer. The sensitizing potential of chlorocresol was judged strong using the guinea pig maximization test (GPMT) and doubtful in the less sensitive open epicutaneous test (OET). When different induction concentrations were used, the results indicated an optimal sensitizing concentration above which no further increase in the sensitization rate occurred. Rechallenge 2 weeks later showed a marked decrease in sensitivity. Consecutive human patch tests with chlorocresol 2% in pet. showed 11 reactions among 1462 patients tested, but none were explainable and reproducible during re-tests and provocative use tests, indicating that the GPMT overestimated the sensitization potential. The results from guinea pig allergy tests cannot stand alone but have to be validated by other sources of information.     

Predictive evaluation in animals of the contact allergenic potential of medically important substances

Results of the optimization method and of other methods used to assess contact allergy in laboratory animals were compared with known epidemiological data on the occurrence of hypersensitivity reactions in man. Tests were performed with preservatives {formalin, ethylenediamine and sorbic acid), drugs (penicillin G, benzocaine and sulphathiazole) and other contactants belonging to widely different chemical classes (p-phenylenediamine, triclosan, pyrazole derivatives, nickel and chrome salts, eugenol, isoeugenol and mercaptobenzothiazole). The degree of sensitization achieved in guinea pigs by the optimized procedure (intradermal test with adjuvant combination) and the maximization procedure was invariably superior to that produced by the epidermal method using prior irritation of the site of application. Both the optimized procedure and the maximization test seem to be capable of identifying contact allergens that cause hypersensitivity reactions in as few as t in 10,000 of the human population as a whole. The optimization test merits consideration as a standardized and efficiently predictive procedure.     

The sensitizing capacity of atranorin

The allergenic potential of the aromatic lichen substance atranorin has been investigated by means of the guinea pig maximization test of Magnusson & Kligman. Sensitivity was induced in 30% of the animals, which corresponds to a moderate allergenic capacity (grade III). This is in agreement with the clinically-observed frequency of 1.5% among our patients. A modified photoallergy test on the same animals was performed, but irradiation did not increase the number of positive reactions. 4 patients with proven contact sensitivity to atranorin, evernic, usnic or physodic acid, were examined with different dilutions from 0.001 to 0.1%. Irradiation of the test series did not provoke any clear-cut photoallergic reaction.     

Sensitizing potential in mice, guinea pig and man of the preservative Euxyl K 400 and its ingredient methyldibromo glutaronitrile

The allergenicity of the preservative Euxyl K 400 and its principal allergen methyldibromo glutaronitrile (MDBGN) (1,2-dibromo-2,4-dicyanobutane) was investigated using 3 animal models; in mice, the local lymph node assay (LLNA) and in guinea pigs, the guinea pig maximization test (GPMT) and the cumulative contact enhancement test (CCET) with a dose-response protocol included. Previous attempts to define the sensitization capacity of these chemicals have given conflicting results. For comparison, the frequency and causes of positive patch test reactions to Euxyl K 400 and MDBGN were studied in patients referred to an occupational dermatology clinic. This investigation showed that Euxyl K 400 and MDBGN can give rise to contact allergy in man and that the relevant cases found mainly had similar exposure as non-occupational cases. A contact allergenic potential could be detected for MDBGN in 2 animal models, i.e., the CCET and the LLNA, and also for Euxyl K 400 in the LLNA. However, statistical analysis of the results from the GPMT with MDBGN failed to detect the sensitizing potential of this particular allergen. The results indicate that to be able to detect the allergenic potential of Euxyl K 400 and MDBGN, a predictive test method with multiple topical applications at induction is required. It is therefore important that an investigator is aware of the possibility of using various predictive test models for investigation of potential contact allergens.