Bites of the European pigeon tick (Argas reflexus): Risk of IgE-mediated sensitizations and anaphylactic reactions

BACKGROUND: Local and systemic reactions can occur after bites of Argas reflexus (Argas), a soft tick parasitizing pigeons. OBJECTIVE: Risk assessment of IgE-mediated sensitizations and systemic reactions after Argas bites. METHODS: Case histories, skin prick tests (SPTs) with a whole-body extract of Argas containing major allergen Arg r 1, and common inhalants and specific IgE measurements were obtained from 148 subjects who had had Argas bites and 20 volunteers as a control group. RESULTS: Systemic reactions (urticaria, angioedema, dyspnea, cardiovascular dysregulation, unconsciousness) were reported in 12 of 148 (8%); 146 of 148 (99%) had local reactions. Atopy was found in 37 of 146 (25%) with local reactions and 3 of 12 (25%) with systemic reactions. SPT to Argas was positive in 24 of 148 (16%) with a high proportion of atopics 10 of 24 (42%); specific IgE to Argas was detectable in 12 of 135 (8% of 148) with moderate concordance to systemic reactions. No positive SPT or specific IgE results to Argas were obtained in the control group. Immunoblotting of 23 sera revealed an IgE-binding protein in 19 of 23 sera (82%) at 22 kd, indicating a major allergen of Argas. CONCLUSION: Severe anaphylactic reactions were infrequently (approximately 8%) found after bites of the soft tick Argas reflexus. Atopy is a risk factor for skin sensitizations to Argas, but not for systemic reactions after bites by Argas. Using a whole-body extract of Argas, diagnosis through SPT and specific IgE is hampered by false-negative and irrelevant positive results, particularly in atopy.     

Allergy to pigeon tick (Argas reflexus): demonstration of specific IgE-binding components

BACKGROUND: The European tick, Argas reflexus, is an urban pest parasitizing urban pigeons and may cause a wide range of allergic reactions. METHODS: Specific IgE to A. reflexus, SDS-PAGE and IgE immunoblotting, performed with tick extract, were carried out in the sera of 6 patients who reported allergic reactions after tick bite. RESULTS: Specific IgE to A. reflexus (RAST class ranging from 1 to 3) were detected in the sera of 6 patients who reported allergic reactions (urticaria and angioedema in 2 and anaphylaxis in the other 4 patients) after tick bite. IgE reactivity to two bands of 22 and 40 kDa were identified in the patient sera. CONCLUSIONS: Allergy to A. reflexus has to be considered in allergic patients living in buildings where pigeons have their nests. The powerful sensitizing property of tick allergen is underlined by the observation that none of our patients was atopic.     

Pigeon tick bite: A neglected cause of idiopathic nocturnal anaphylaxis

Anaphylaxis is a serious systemic allergic reaction with rapid onset and potentially life‐threatening. We report in detail a case of severe nocturnal anaphylaxis due to pigeon tick bite showing the diagnostic value of the extract and the recombinant allergen in the diagnostic procedures (basophil activation test, IgE immunoblot, and experimental ImmunoCAP). Apart from the presented case, we describe that during the last 10 years, we have collected 28 cases of allergy to Argas reflexus from several European countries. We suspect that this allergy is underdiagnosed because of the lack of diagnostic reagents. Because of the growing number of pigeons in Middle and Southern Europe cities, some cases of idiopathic anaphylaxis could potentially be caused by A. reflexus in those countries. The identification of pigeon ticks as a trigger of anaphylaxis would greatly improve medical care and advice for these patients as the parasite can be exterminated by eradication measures to avoid further incidents.     

Fel d 4, a cat lipocalin allergen

BACKGROUND: Cat allergy is unique among allergy to mammals in that the major allergen Fel d 1 is a uteroglobin-like protein and not a lipocalin. The biochemical spectrum of the cat allergens is thus uncertain, particularly with regard to the role that a cat lipocalin protein may play in sensitization to cats in allergic individuals. OBJECTIVE: To analyse cDNA encoding a lipocalin allergen and the corresponding recombinant allergen at both the molecular and immunological levels. METHODS: A submandibular salivary gland cDNA expression library was constructed and screened for clones producing IgE-binding polypeptides. cDNA encoding a lipocalin allergen and its corresponding recombinant allergen were analysed. RESULTS: An IgE binding molecule with high sequence identity to the boar salivary lipocalin and the horse lipocalin Equ c 1 allergen was isolated and designated, Fel d 4. Serum from 62.96% of cat-allergic subjects examined had measurable IgE antibody to Fel d 4 but typically at low levels. Despite this in 47% of sera the anti-Fel d 4 IgE titres were higher than the anti-Fel d 1 titres. IgE binding to the lipocalin allergen could be blocked by an allergen extract from cow and to a lesser degree by extracts from horse and dog. CONCLUSION: Fel d 4 is a lipocalin allergen produced by the cat, which binds IgE at relatively high frequency in cat-sensitive individuals. The allergen provides not only a means for investigating differences in the immune response to lipocalin allergens from that found for other mammalian species but also an important reagent for the diagnosis of cat allergy.     

Delayed Anaphylaxis to Red Meat Associated With Specific IgE Antibodies to Galactose

A novel delayed anaphylactic reaction to red meat, associated with tick bites and IgE antibodies against galactose-α-1, 3-galactose (α-gal), was reported in 2009 in the US, Australia and Europe. In this case, serum specific IgE to galactose-α-1, 3-galactose (>100 kU/L) and IgE to multiple non-primate mammalian proteins were positive. However, the pathogenesis of this disease remains unclear. We report the first case in Asia of delayed anaphylactic reaction to red meat, which was induced by bites from the hard tick, Hematophagous ixodidae. We confirmed the increased concentration of IgE reactive epitopes in non-primate mammalian organs, which may be rich in α-gal proteins in lymphatic and endothelial tissues. All confirmed ticks associated with this disorder in the literature and in our case belonged to the hard tick family. We hypothesize that hard tick saliva is enriched with blood-type substances, such as oligosaccharides, from the non-primate mammal victim''s blood after days to weeks of blood sucking, which sensitizes humans through the injection route while blood sucking.     

Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite.

BACKGROUND: It is unclear whether antimicrobial treatment after an Ixodes scapularis tick bite will prevent Lyme disease. METHODS: In an area of New York where Lyme disease is hyperendemic we conducted a randomized, double-blind, placebo-controlled trial of treatment with a single 200-mg dose of doxycycline in 482 subjects who had removed attached I. scapularis ticks from their bodies within the previous 72 hours. At base line, three weeks, and six weeks, subjects were interviewed and examined, and serum antibody tests were performed, along with blood cultures for Borrelia burgdorferi. Entomologists confirmed the species of the ticks and classified them according to sex, stage, and degree of engorgement. RESULTS: Erythema migrans developed at the site of the tick bite in a significantly smaller proportion of the subjects in the doxycycline group than of those in the placebo group (1 of 235 subjects [0.4 percent] vs. 8 of 247 subjects [3.2 percent], P<0.04). The efficacy of treatment was 87 percent (95 percent confidence interval, 25 to 98 percent). Objective extracutaneous signs of Lyme disease did not develop in any subject, and there were no asymptomatic seroconversions. Treatment with doxycycline was associated with more frequent adverse effects (in 30.1 percent of subjects, as compared with 11.1 percent of those assigned to placebo; P<0.001), primarily nausea (15.4 percent vs. 2.6 percent) and vomiting (5.8 percent vs. 1.3 percent). Erythema migrans developed more frequently after untreated bites from nymphal ticks than after bites from adult female ticks (8 of 142 bites [5.6 percent] vs. 0 of 97 bites [0 percent], P=0.02) and particularly after bites from nymphal ticks that were at least partially engorged with blood (8 of 81 bites [9.9 percent], as compared with 0 of 59 bites from unfed, or flat, nymphal ticks [0 percent]; P=0.02). CONCLUSIONS: A single 200-mg dose of doxycycline given within 72 hours after an I. scapularis tick bite can prevent the development of Lyme disease.     

Determination of the T cell epitopes of the lipocalin allergen, Rat n 1

BACKGROUND: Laboratory animal allergy (LAA) is an important cause of occupational sensitization and asthma. Rats are a frequent cause of LAA and the major rat allergen, Rat n 1, is a member of the lipocalin protein family, which includes several other animal allergens such as the cow allergen, Bos d 2. To date, Bos d 2 is the only mammalian lipocalin allergen to have been studied in detail. OBJECTIVE: We undertook a cross-sectional study of a large population of individuals exposed to laboratory rats to determine the proliferative responses of peripheral blood mononuclear cells (PBMCs) to the major rat allergen, Rat n 1. METHODS: Eighty-three cases (defined by a positive skin prick test (SPT) > or =3 mm and/or a positive RAST > or =2% binding) and 274 referents without specific IgE to rats were tested for their proliferative responses of PBMCs to rat allergen. Cytokine release to rat urinary protein was examined in 28 sensitized and 42 non-sensitized exposed individuals. RESULTS: Proliferation to rat urinary protein was weak in all individuals. Four regions within Rat n 1 were identified as containing potential immunodominant T cell epitopes and three of these co-localized within the conserved regions of the lipocalin molecule. All four regions within Rat n 1 overlapped considerably with the characterized epitopes of the lipocalin allergen, Bos d 2. IL-5 and ratios of IL-5/IFN-gamma were significantly increased in cases. CONCLUSION: The response to Rat n 1 is remarkably similar to the cow lipocalin allergen Bos d 2. T cell epitopes within lipocalins appear to co-localize with the conserved regions of the molecule. LAA is characterized by an increased production of IL-5. Investigation of other lipocalin allergens will provide further information about the allergenicity of this group of proteins.     

IgE antibodies to omega-5 gliadin in children with wheat-induced anaphylaxis

BACKGROUND: Wheat can cause severe immunoglobulin E (IgE)-mediated systemic reactions including anaphylaxis but knowledge on relevant wheat allergens at the molecular level is scanty. METHODS: Seven children (aged from 6 months to 13 years) experiencing from 2 to 10 anaphylactic reactions in a year after eating food-containing wheat were examined. Purified omega-5 gliadin was used as an allergen in IgE enzyme-linked immunosorbent assay (ELISA) and in skin prick testing (SPT). Wheat CAP radioallergosorbent test (RAST) and SPT were also examined. RESULTS: All seven anaphylactic children, but none of 15 control subjects had IgE antibodies to omega-5 gliadin in ELISA. Five of the six tested anaphylactic children showed positive SPT to omega-5 and crude gliadin, and all seven had positive wheat CAP RAST and SPT. One child was challenged with wheat, which caused anaphylaxis. After adherence to a wheat-free diet four children remained symptomless and three experienced one to two anaphylactic reactions. CONCLUSION: The present results show that wheat omega-5 gliadin is a major sensitizing allergen in children with wheat-induced anaphylaxis. They also suggest that omega-5 gliadin IgE ELISA could be used as a diagnostic test for this severe allergy.     

The tick fauna of eastern Germany]

The occurrence of several tick species in selected areas of Eastern Germany is described. From May 1987 till December 1989 8,472 ticks from 430 places were examined. Ixodidae of the genus Ixodes, Dermacentor and Haemaphysalis as well as Argasidae of the genus Argas were identified. The most common species was Ixodes ricinus. Furthermore, an endemic area of Dermacentor reticulatus was detected in the Düben-Dahlen and Annaburg health. Two other species of ticks, which were found frequently and sometimes with a high intensity on the host were Ixodes hexagonus and Ixodes canisuga. On the other side the species Haemaphysalis concinna and Argas vespertilionis were present at only one respectively two places and with a low population density.     

Advances in mosquito allergy

PURPOSE OF REVIEW: Allergic reactions, including severe local and systemic reactions to mosquito bites, are immunological in nature, and involve immunoglobulin E, immunoglobulin G, and T-lymphocyte-mediated hypersensitivities in response to allergens in mosquito saliva. Naturally acquired desensitization to mosquito saliva may occur during childhood or during long-term exposure to mosquitoes. Due to the lack of availability of mosquito salivary preparations for use in skin tests and in-vitro tests, allergic reactions to mosquito bites are under diagnosed and under treated. RECENT FINDINGS: Recombinant saliva allergens with biological activity are being developed. Recombinant Aedes aegypti salivary allergen rAed a 2 has been expressed, purified, characterized and used in in-vitro diagnosis of mosquito allergy. Mosquito saliva-induced non-immunoglobulin E-mediated skin mast cell degranulation was found to induce macrophage-inflammatory protein 2 in the skin and interleukin-10 in draining lymph nodes. SUMMARY: In this review, we discuss the allergic reactions to mosquito salivary allergens, the immune mechanisms involved, natural desensitization and immunotherapy with mosquito extracts, characteristics of salivary allergens and their recombinant forms, and prevention and treatment of allergic reactions to mosquito bites. Eventually, recombinant salivary allergens will significantly improve the diagnosis of mosquito allergy, and will also improve specific immunotherapy for patients with systemic reactions to mosquito bites.     

Invasion: exotic ticks (Acari: Argasidae, Ixodidae) imported into the United States. A review and new records.

A review of the literature and unpublished records from the U.S. National Tick Collection on the importation of ticks from foreign lands reveals that at least 99 exotic tick species assignable to 11 genera have been either detected and destroyed at ports of entry or inadvertently imported into the United States in the past half century. This number includes four argasid and 95 ixodid species, some of which are important vectors of agents that cause disease to both man and animals. If one includes Aponomma sp. and Hyalomma sp. and the subspecies of Rhipicephalus, the total exceeds 100 taxa. It is notable that the number of imported tick species recorded herein exceeds the total number of tick species native to the United States. It appears that the soft tick genera Argas, Antricola and Nothoaspis have not been imported, although at some point in time Argas persicus (Oken) was introduced because it is resident although not often collected. The hard tick genera Anomalohimalaya, Cosmiomma, Margaropus, Nosomma and Rhipicentor, and the nuttalliellid genus Nuttalliella have also not been imported.     

Molecular cloning and characterization of full-length cDNAs encoding a novel high-molecular-weight Dermatophagoides pteronyssinus mite allergen, Der p 11

BACKGROUND: Dermatophagoides pteronyssinus (Dp) and D. farinae (Df) mites are the most important source of indoor aeroallergens. Most Dp mite allergens identified to date have relatively low molecular weights (MWs). Identification of high-MW mite allergens is a crucial step in characterizing the complete spectrum of mite allergens and to provide appropriate tools for diagnostic and therapeutic application. METHODS: The full-length Der p 11 cDNA clone was isolated using cDNA library immunoscreening, the 5'-3' rapid amplification of cDNA ends (RACE) system and polymerase chain reactions (PCR). The whole cDNA insert and its PCR-derived DNA fragments (p1 to p4) were generated and expressed in the Escherichia coli expression system. The allergenicity of the recombinant protein and its peptide fragments was examined by IgE immunodot assays. The IgE-binding reactivity of rDer p 11 was analyzed in the serum of 50 asthmatic children with positive reactivity to Dp mite extract. Its recombinant peptide fragments were also examined by immunodot assays in 30 mite-allergic children. RESULTS: Der p 11 cDNA consists of a 2625-bp open reading frame encoding a 103-kDa protein with 875 amino acids. It exhibits significant homology with the paramyosin of other invertebrates. The protein sequence alignment of this newly identified Dp mite allergen (denominated as Der p 11) revealed over 89% identity with Der f 11 and Blo t 1. Among 50 Dp-sensitive asthmatic children, rDer p 11 showed positive IgE-binding reactivity to 39 patients (78%). Using immunodot assays, multiple human IgE-binding activities were demonstrated in all four fragments of Der p 11. Using immunoblot assays, the dominant IgG-binding epitope for monoclonal antibody (mAb642) was located in fragment p3 only. In immunoblot assays, cross-inhibition between rDer p 11 and rDer f 11 was up to 73-80% at concentrations of 100 microg/ml. CONCLUSIONS: This study confirms that the newly identified recombinant Der p 11 is a novel and important high-MW Dp mite allergen for asthmatic children. Our data also indicates that human IgE-binding major epitopes are scattered over the entire molecule of Der p 11.     

Identification of galactose‐α‐1,3‐galactose in the gastrointestinal tract of the tick Ixodes ricinus; possible relationship with red meat allergy

Patients with IgE antibodies against the carbohydrate epitope galactose‐α‐1,3‐galactose (α‐Gal) have reported severe allergic reactions after consumption of red meat. Investigations have revealed associations between IgE to α‐Gal and tick bites. We provide the first direct evidence that α‐Gal is present within ticks thus potentially explaining the relationship between tick exposure and sensitization to α‐Gal, with development of red meat allergy as a secondary phenomena. Serum from Swedish patients with delayed severe reactions to red meat was included in the study. A dose‐dependent inhibition of IgE responses to α‐Gal by the tick Ixodes ricinus is demonstrated. Furthermore, using cryostat‐cut sections of I. ricinus, we show that both a monoclonal and a polyclonal antibody against α‐Gal stains the gastrointestinal tract of the tick. The same pattern is seen when staining with patient sera IgE positive to α‐Gal. These results confirm that the α‐Gal epitope is present in I. ricinus and imply host exposure to α‐Gal during a tick bite. This provides further evidence that tick bites are associated with IgE responses to α‐Gal and red meat allergy.     

Comparative identification of protein profiles and major allergens of saliva, salivary gland and whole body extracts of mosquito species in Thailand

Allergic reactions to mosquito bites, such as generalized urticaria or severe local reactions are common problems worldwide. The diverse sources of allergen prepared from different mosquito body parts usage are a major obstacle to obtaining safe and effective tests and immunotherapy for mosquito bite allergy. Thus, the reactions are often not recognized and allergen immunotherapy is seldom used for severe reaction to mosquito bites. In a search for appropriate allergen sources, the protein profiles of saliva, salivary glands and whole body extracts were comparatively analyzed from 4 common mosquito species of Thailand and/or South East Asia; viz. Culex quinquefasciatus, Aedes aegypti, Aedes albopictus and a zoophilic strain, Anopheles minimus. The major allergens in the extracts which elicited specific IgE responses in the pooled sera of subjects allergic to mosquito bites were identified. It was concluded that mosquito saliva was the best source of allergens. Additionally, both species-specific and species-shared allergens of the 4 mosquito species were identified. The major saliva allergens having MWs of 36, 32 and 22 kDa were identified. The identificstion of major allergens should facilitate the production of specific recombinant allergens and contribute to improvement in the diagnosis and specific immunotherapy of Thai mosquito bite allergy patients.     

美洲蟑螂重组BCG-Arg变应原致BALB/C小鼠的免疫原性评估

对表达美洲蟑螂Arg变应原的BCG进行免疫原性评估,为BCG脱敏疫苗的研制奠定基础。106CFU重组BCG-Arg皮下注射免疫BALB/C小鼠,分别于免疫0、2、4、6、8周收集血清。使用纯化的重组Arg包被ELISA板,ELISA检测Arg特异性IgG及IgG1I、gG2a亚类。重组BCG-Arg皮下注射免疫BALB/C小鼠2周后,血清Arg特异性IgG显著高于对照组（P〈0.05）,实验组IgG1及IgG2a也显著高于对照组（P〈0.05）,IgG2a升高更明显。重组美洲大蠊BCG-Arg具免疫原性,并且诱导Th1优势免疫应答。     

Cloning, expression, and characterization of recombinant Hev b 3, a Hevea brasiliensis protein associated with latex allergy in patients with spina bifida.

BACKGROUND: Two natural rubber latex proteins, Hev b 1 and Hev b 3, have been described in spina bifida (SB)-associated latex allergy. OBJECTIVE: The aim of this study was to clone and express Hev b 3 and to obtain the immunologic active and soluble recombinant allergen for diagnosis of SB-associated latex allergy. METHODS: A complementary DNA (cDNA) coding for Hev b 3 was amplified from RNA of fresh latex collected from Malaysian rubber trees (Hevea brasiliensis). PCR primers were designed according to sequences of internal peptide fragments of natural (n) Hev b 3. The 5'-end sequence was obtained by specific amplification of cDNA ends. The recombinant (r) Hev b 3 was produced in Escherichia coli as a 6xHis tagged protein. Immunoblotting and inhibition assays were performed to characterize the recombinant allergen. RESULTS: An Hev b 3 cDNA clone of 922 bp encoding a protein of 204 amino acid residues corresponding to a molecular weight of 22.3 kd was obtained. In immunoblots 29/35, latex-allergic patients with SB revealed IgE binding to rHev b 3, as did 4 of 15 of the latex-sensitized group. The presence of all IgE epitopes on rHev b 3 was shown by its ability to abolish all IgE binding to nHev b 3. Hev b 3 is related to Hev b 1 by a sequence identity of 47%. Cross-reactivity between these 2 latex allergens was illustrated by the large extent of inhibition of IgE binding to nHev b 1 by rHev b 3. CONCLUSION: rHev b 3 constitutes a suitable in vitro reagent for the diagnosis of latex allergy in patients with SB. The determination of the full sequence of Hev b 3 and the production of the recombinant allergen will allow the epitope mapping and improve diagnostic reagents for latex allergy.     

Molecular characterization of a Haemaphysalis longicornis tick salivary gland-associated 29-kilodalton protein and its effect as a vaccine against tick infestation in rabbits

The use of tick vaccines in mammalian hosts has been shown to be the most promising alternative tick control method to current use of acaricides, which suffers from a number of limitations. However, the success of this method is dependent on the identification, cloning, and in vitro expression of tick molecules involved in the mediation of key physiological roles with respect to the biological success of a tick as a vector and pest. We have sequenced and characterized a Haemaphysalis longicornis tick salivary gland-associated cDNA coding for a 29-kDa extracellular matrix-like protein. This protein is expressed in both unfed and fed immature and mature H. longicornis ticks. The predicted amino acid sequence of p29 shows high homology to sequences of some known extracellular matrix like-proteins with the structural conservation similar to all known collagen proteins. Immunization with the recombinant p29 conferred a significant protective immunity in rabbits, resulting in reduced engorgement weight for adult ticks and up to 40 and 56% mortality in larvae and nymphs that fed on the immunized rabbits. We speculate that this protein is associated with formation of tick cement, a chemical compound that enables the tick to remain attached to the host, and suggest a role for p29 as a candidate tick vaccine molecule for the control of ticks. We have discussed our findings with respect to the search of tick molecules for vaccine candidates.     

Tick bites in a Lyme borreliosis highly endemic area in Switzerland

The duration of tick feeding is an important indicator to evaluate the risk of Borrelia burgdorferi sensu lato transmission, which increases considerably with the blood meal duration. This blood meal duration may be estimated from scutal index, the ratio between body length (idiosoma) and scutum width. For the estimation of blood meal duration in Ixodes ricinus, nymphal and adult female ticks were detached at predetermined intervals (24, 48, 72, and 96h) from laboratory mice and rabbits and their scutal index calculated. From this, non-linear regression equations were developed to determine the duration of attachment for nymphal and adult female I. ricinus ticks. As part of an epidemiological study addressing the risk of subclinical (seroconversion) and clinical infections after a tick bite in the Neuchatel area (Switzerland) over 3 years (2003-2005), duration of tick attachment and anatomical site of bites collected on participants as well as seasonal distribution of tick bites were studied. Tick attachment duration was estimated in all ticks collected during this study (n=261). Nymphs were attached for a mean (+/- standard error, SE) of 31.6h (+/-2.6) and females for a mean (+/-SE) of 29.6h (+/-3.2). Most nymphs were removed after 24h of blood meal whereas most females were removed before 24h. Legs were the major anatomical sites of bites for women (40.7%), men (44.4%), and almost all age classes. Only children <10 years old were bitten more frequently on the head (41.2%) and on the neck (38.5%) than participants >10 years. The majority of tick bites were recorded from May to July during the 3 years. Attachment sites can influence the discovery of ticks, hence the duration of the tick bite. A detailed body examination after each outing in forest and an early withdrawal of an attached tick is an effective way to prevent Lyme borreliosis.     

Complementary DNA cloning and immunologic characterization of a new Penicillium citrinum allergen (Pen c 3)

BACKGROUND: Penicillium citrinum has been identified as the most prevalent airborne Penicillium species in the Taipei area. It is important to understand the allergenic composition of this ubiquitous fungal species. OBJECTIVE: The complementary DNA (cDNA) clone of an allergen from P citrinum was isolated and expressed in Escherichia coli as a fusion protein. mAbs were prepared with the recombinant protein as antigen. The corresponding natural allergen in the fungal extracts was identified with the mAbs. METHODS: A Uni-Zap XR P citrinum cDNA library was screened with sera from asthmatic patients. An IgE-binding cDNA clone was isolated and expressed as a glutathione-S-transferase fusion protein. The frequency of IgE binding to the expressed protein was analyzed by immunoblotting. Spleen cells from BALB/c mice immunized with the recombinant protein were fused with NS-1 cells for mAb generation. RESULTS: A P citrinum cDNA library was screened with a mixture of serum samples from 4 asthmatic patients. An IgE-binding cDNA clone was obtained and designated as PCE2. PCE2 has a 694-bp insert that contains a 167 amino acids open reading frame. The deduced amino acid sequence of the encoded protein has 82.6% (138 amino acids) identity with an Aspergillus fumigatus peroxisomal membrane protein allergen (Asp f 3). PCE2 was expressed in E coli as a fusion protein and designated as Pen c 3. Sera from 13 (46%) of the 28 Penicillium-sensitized asthmatic patients demonstrated IgE binding to Pen c 3. In addition, 11 of the 13 Pen c 3-positive serum samples have IgE immunoblot reactivity to recombinant Asp f 3. The presence of IgE cross-reactivity between Pen c 3 and Asp f 3 was also detected by immunoblot inhibition. Four of the 6 mAbs generated against Pen c 3 cross-react with Asp f 3. The presence of the corresponding 18-k natural allergens in the crude extracts of P citrinum and A fumigatus were detected by immunoblot with use of the mAbs and sera from asthmatic patients. CONCLUSION: Results obtained suggest that the peroxisomal membrane protein (Pen c 3) is an important allergen of P citrinum. PCE2 is a full-length cDNA clone encoding this allergen. In addition, the mAbs generated may be useful in standardizing the diagnostic allergenic extracts.