Cat Allergen Research Articles

Targeting immunodominant Bet v 1 epitopes with monoclonal antibodies prevents the birch allergic response

Blocking the major cat allergen, Fel d 1, with mAbs was effective in preventing an acute cat allergic response. This study sought to extend the allergen-specific antibody approach and demonstrate that a combination of mAbs targeting Bet v 1, the immunodominant and most abundant allergenic protein in birch pollen, can prevent the birch allergic response. Bet v 1-specific mAbs, REGN5713, REGN5714, and REGN5715, were isolated using the VelocImmune platform. Surface plasmon resonance, x-ray crystallography, and cryo-electron microscopy determined binding kinetics and structural data. Inhibition of IgE-binding, basophil activation, and mast cell degranulation were assessed via blocking ELISA, flow cytometry, and the passive cutaneous anaphylaxis mouse model. REGN5713, REGN5714, and REGN5715 bind with high affinity and noncompetitively to Bet v 1. Acocktail of all 3 antibodies, REGN5713/14/15, blocks IgE binding to Bet v 1 and inhibits Bet v 1- and birch pollen extract-induced basophil activation exvivo and mast cell degranulation invivo. Crystal structures of the complex of Bet v 1 with immunoglobulin antigen-binding fragments of REGN5713 or REGN5715 show distinct interaction sites on Bet v 1. Cryo-electron microscopy reveals a planar and roughly symmetrical complex formed by REGN5713/14/15 bound to Bet v 1. These data confirm the immunodominance of Bet v 1 in birch allergy and demonstrate blockade of the birch allergic response with REGN5713/14/15. Structural analyses show simultaneous binding of REGN5713, REGN5714, and REGN5715 with substantial areas of Bet v 1 exposed, suggesting that targeting specific epitopes is sufficient to block the allergic response.

Low-affinity but high-avidity interactions may offer an explanation for IgE-mediated allergen cross-reactivity.

BackgroundAllergy is a global disease with overall frequencies of >20%. Symptoms vary from irritating local itching to life‐threatening systemic anaphylaxis. Even though allergies are allergen‐specific, there is a wide range of cross‐reactivities (eg apple and latex) that remain largely unexplained. Given the abilities of low‐affinity IgG antibodies to inhibit mast cells activation, here we elucidate the minimal affinity of IgE antibodies to induce type I hypersensitivity.MethodsThree mature (high‐affinity) IgE antibodies recognizing three distinct epitopes on Fel d 1, the major cat allergen, were back‐mutated to germline conformation, resulting in binding to Fel d 1 with low affinity. The ability of these IgE antibodies to activate mast cells in vitro and in vivo was tested.ResultsWe demonstrate that affinities as low as 10−7 M are sufficient to activate mast cells in vitro and drive allergic reactions in vivo. Low‐affinity IgE antibodies are able to do so, since they bind allergens bivalently on the surface of mast cells, leading to high‐avidity interactions.ConclusionsThese results suggest that the underlying mechanism of allergen cross‐reactivity may be low‐affinity but high‐avidity binding between IgE antibodies and cross‐reactive allergen.

Deposition Rates of Asthma Triggers on Conventional and Enclosed Window Treatments

Environmental interventions are an important element of managing allergies and asthma. Health professionals often recommend that draperies be replaced with window blinds however no data exist on accumulation of inhalant allergens or inflammatory bioaerosols on window treatments. Installing blinds that accumulate less dust may reduce breathing zone exposures when blinds are adjusted if hazardous amounts of bioaerosols are deposited. We sought to determine the rate of accumulation of dust, allergens, bacterial endotoxin and fungal glucan on window blinds of two distinct types mounted on the two types of windows most commonly installed in U.S. homes. The blinds tested were conventional horizontal slat blinds hanging on the inside of the window (roomside blinds) and similar blinds placed between the exterior window glass and an extra pane of glass on the interior side (between-glass blinds). The study was conducted in six households as a paired, repeated measures study. Households were identified for participation, having met the study criteria of children and cats living inside a carpeted home. Standard window blinds accumulated cat allergen, endotoxin and fungal glucan at rates of 5940ng/m², 1910EU/m², and 11,360ng/m² per month. Between-glass blinds reduced the loading of asthma triggers by 25- to 185-fold. Comparison with clinical thresholds associated with asthma morbidity indicates that room-side blinds accumulate potentially hazardous quantities of asthma triggers.

Differential Correlations among Allergy Tests According to Indoor Allergens in Allergic Rhinitis

Several allergy tests are used for the diagnosis of allergic rhinitis; however, few studies have reported a direct comparison of the skin prick test (SPT), multiple allergen simultaneous test (MAST), and ImmunoCAP according to specific allergens. This study aimed to evaluate the correlations between each test and allergic rhinitis symptoms and to evaluate the correlations of the MAST and ImmunoCAP with the SPT for representative indoor allergens in Korea. Electronic medical charts were retrospectively reviewed, and 698 patients with allergic rhinitis who had performed SPT, MAST, and ImmunoCAP were enrolled. Correlations between each allergy test for 4 representative indoor allergens and the symptoms of allergic rhinitis were analyzed. Agreements of the MAST and ImmunoCAP with the SPT were compared according to each allergen. The SPT showed higher correlations with allergic rhinitis symptoms for 4 indoor allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae, cat, and dog allergens) than the MAST or ImmunoCAP. In comparison between the MAST and SPT, the least correlation was observed for the dog allergen, whereas between the ImmunoCAP and SPT, the least correlation was observed for the cat allergen. The correlation between the ImmunoCAP and SPT was higher than that between the MAST and SPT for the dog allergen, whereas no significant differences were noted for other allergens. Overall, the SPT showed a higher correlation with allergic rhinitis symptoms than the MAST or ImmunoCAP for 4 indoor allergens. ImmunoCAP showed similar reactivity to MAST; however, it showed better positivity with dog allergen in patients who were reactive to the allergen in the SPT. Care should be taken while evaluating dog allergen sensitization using the MAST.

РАСПРОСТРАНЕННОСТЬ АЛЛЕРГИЧЕСКОГО РИНИТА И БРОНХИАЛЬНОЙ АСТМЫ СРЕДИ ГОРОДСКИХ ДЕТЕЙ ДОШКОЛЬНОГО ВОЗРАСТА: РЕЗУЛЬТАТЫ ОДНОМОМЕНТНОГО ИССЛЕДОВАНИЯ

The aim of the trial was to study the prevalence and clinical and allergic characteristics of allergic rhinitis (AR) and bronchial asthma (BA) in urban preschool children. Materials and methods of research: a one-minute study was carried out on an urban sample of 3–6 year olds (n=3205), consisting of 2 stages – screening and clinical. The study of the prevalence of AR and BA symptoms at the screening stage was carried out by questioning parents using the ISAAC questionnaire. At the clinical stage, the diagnosis of AR and BA was verified based on the diagnostic criteria of the ARIA (2008 revision) and GINA (updated 2017) documents. At the clinical stage, skin prick testing with extracts of inhalation and food allergens from Allergopharma Joachim Ganzer KG (Germany) was carried out. Results: the prevalence of AR and BA among urban children 3–6 years of age was 10,6 and 5,7%, respectively. 80 (52,0%) children with AR and 42 (32,8%) children with BA have not previously been diagnosed in practical healthcare institutions. 107 (69,5%) children with AR and 76 (59,4%) children with BA had a mild severity of the disease, 4 (2,6%) children with AR and 2 (1,6%) children with BA had major severity. 80 (62,5%) of children with BA are diagnosed with a controlled course of the disease and 48 (37,5%) have a partially controlled/uncontrolled course of the disease. Most often, in children with AR and BA, sensitization to the D. pteronyssinus mite was recorded – 95 (61,%) and 68 (53,1%), birch pollen – 63 (40,9%) and 42 (32,8%) and cat allergens – 30 (19,5%) and 20 (15,6%), respectively. Conclusion: the prevalence of AR and BA among preschool children was 10,6 and 5,7%, respectively. More than half of children with AR and 1/3 of children with BA do not have a diagnosis established in practical health care institutions. Most often, in 3–6 years old children with AR and BA, sensitization to the D. pteronyssinus mite, birch pollen and cat allergens is recorded.

Sensitization pattern of cat and dog dander allergen in 16 426 patients with allergic diseases

Objective:To explore the sensitization feature of cat and dog dander and time trend in northern region. Methods:During year 2017 to year 2019, subjects with self-reported allergic diseases received skin prick test for cat and dog dander allergen. Skin index（SI） ≥2+ was considered as positive SPT. SI2+ was defined as mild sensitization, SI3+ was defined as moderate sensitization while SI4+ was defined as severe sensitization. The age and gender difference of sensitization rate between cat and dog dander allergen was analyzed. Meanwhile, the trend of cat and dog dander sensitization rate was analyzed. Results:Overall, 16 426 subjects were enrolled in this study. ① The sensitization rate of cat dander was significantly higher than dog dander（11.8% vs 6.0%, P<0.001）. Severe sensitization rate of cat dander was significantly higher than dog dander（5.9% vs 1.7%, P<0.001） while there was no significant difference of mild sensitization rate. ②Sensitization age of cat dander was younger than dog dander（P<0.001）. Sensitization rate of cat and dog dander was higher in subjects ≤18y compared with those >18y（20.2% vs 10.9%, P<0.001; 8.1% vs 5.7%, P<0, 001）. The highest sensitization rate was presented in 13-18y age group（27.3% vs 9.9%, P<0.001）, following by 7-12y age group（26.0% vs 9.2%, P<0.001）. Sensitization rate of cat dander was higher in male than in female（13.7% vs 10.7%, P<0.001） while no gender difference was observed in dog dander sensitization（6.2% vs 5.8%, P=0.411）. ③595 subjects（3.6%） were both sensitized to cat and dog dander while 1733 subjects（10.6%） were sensitized either to cat or dog dander. Single sensitization rate of cat dander was higher than single sensitization rate of dog dander（8.2% vs 2.3%, P<0.001）. There was a positive correlation between the cat and dog dander sensitization rate（r=0.386, P<0.001）. ④During 2017-2019, the sensitization rate of cat dander increased but without significantly statistic difference while dog dander sensitization rate was descending from 7.4% to 4.6% significantly（χ²=38.298, P<0.001）. Conclusion:Cat dander sensitization rate was higher than dog dander with a peak age in adolescence. A trend of rising for cat dander allergy and descending for dog dander allergy was observed during the past three years.

Severe Anaphylactic Shock Following a Slow Loris Bite in a Patient with Cat Allergy.

The slow loris monkey is one of the few venomous mammals. Its venom repels predators and can cause anaphylactic shock and even death in humans. The venom protein has been evaluated and has high sequence similarity to cat allergen; however, no studies involving subjects with cat allergy and who have been exposed to slow loris venom have been reported. We herein report the first case of severe anaphylactic shock following a slow loris bite in a patient with cat allergy.

Associations between Environmental dust composition and Atopic Dermatitis in urban and rural settings.

Environmental exposures are involved in the pathogenesis of the allergic phenotype and in determining which individual triggers a person becomes sensitized to. Atopic dermatitis (AD) may modulate these effects through increased penetration through the skin modifying the immune system and AD may be triggered or intensified by environmental exposures. These exposures and immune-modulating factors may differ in urban and rural environments. To compare house dust composition in urban and rural settings and correlate them with AD outcomes. Dust samples were collected from the beds of 156 children aged 6months to 3years. 42% of participants had atopic dermatitis. Samples were analyzed for bacterial endotoxin, fungal (β-1,3-glucan) levels, and house dust mite, cockroach, dog, cat, mouse, and peanut allergen. Exposures were compared in urban and rural environments and in participants with and without AD. Endotoxin but not fungal β-glucan exposure is higher in the environment of healthy controls than children with AD in both urban and rural settings. House dust mite allergen exposure is high in urban and rural settings with Dermatophagoides detected in 100% of samples. Cat and dog allergen exposure mirrors pet ownership patterns which differ slightly between groups and environments. Mouse allergen exposure is higher in urban homes. Environmental endotoxin may be protective against AD in both urban and rural settings. There are marked differences in allergen exposure in urban and rural settings, but these are unlikely to be important protective or risk factors.

Passive Prophylactic Administration with a Single Dose of Anti-Fel d 1 Monoclonal Antibodies REGN1908-1909 in Cat Allergen-induced Allergic Rhinitis: A Randomized, Double-Blind, Placebo-controlled Clinical Trial.

Rationale: Sensitization to Fel d 1 (Felis domesticus allergen 1) contributes to persistent allergic rhinitis and asthma. Existing treatment options for cat allergy, including allergen immunotherapy, are only moderately effective, and allergen immunotherapy has limited use because of safety concerns.Objectives: To explore the relationship among the pharmacokinetic, clinical, and immunological effects of anti–Fel d 1 monoclonal antibodies (REGN1908–1909) in patients after treatment.Methods: Patients received REGN1908–1909 (n = 36) or a placebo (n = 37) in a phase 1b study. Fel d 1–induced basophil and IgE-facilitated allergen binding responses were evaluated at baseline and Days 8, 29, and 85. Cytokine and chemokine concentrations in nasal fluids were measured, and REGN1908–1909 inhibition of allergen–IgE binding in patient serum was evaluated.Measurements and Main Results: Peak serum drug concentrations were concordant with maximal observed clinical response. The anti–Fel d 1 IgE/cat dander IgE ratio in pretreatment serum correlated with Total Nasal Symptom Score improvement. The allergen-neutralizing capacity of REGN1908–1909 was observed in serum and nasal fluid and was detected in an inhibition assay. Type 2 cytokines (IL-4, IL-5, and IL-13) and chemokines (CCL17/TARC, CCL5/RANTES [regulated upon activation, normal T-cell expressed and secreted]) in nasal fluid were inhibited in REGN1908–1909–treated patients compared with placebo (P < 0.05 for all); IL-13 and IL-5 concentrations correlated with Total Nasal Symptom Score improvement. Ex vivo assays demonstrated that REGN1908 and REGN1909 combined were more potent than each alone for inhibiting FcεRI- and FcεRII (CD23)–mediated allergic responses and subsequent T-cell activation.Conclusions: A single, passive-dose administration of Fel d 1–neutralizing IgG antibodies improved nasal symptoms in cat-allergic patients and was underscored by suppression of FcεRI-, FcεRII-, and T-helper cell type 2–mediated allergic responses.Clinical trial registered with www.clinicaltrials.gov (NCT02127801)

Sensitization to Common Allergens Among Children with Asthma and Allergic Rhinitis in Qatar.

BackgroundChildhood asthma (A) and allergic rhinitis (AR) are common in Qatar. Aeroallergens sensitization is integral in disease pathogenesis and clinical presentation. Determining sensitization patterns assists clinicians in tailoring an efficient medical management.ObjectiveTo determine the aeroallergen sensitization pattern and relationship to clinical parameters.MethodsA retrospective review of children (2–14-years) files with i) Pediatric Allergist/or Pulmonologist confirmed-diagnosis of A, and AR, and ii) positive skin prick test (SPT).ResultsAmong 473 patients (69.1% males; 30.9% females), aged 7.6 years, family history was positive in 66.3%: 59.4% in A, 64.2% AR, and 78.2% A-AR. The number of allergens/patients was 2.1±1.7. Median eosinophil count was 400 cells/ul and IgE 287 KU/L. Rates of A, AR, and A-AR varied significantly in children ≤5 years compared to >10 years: A was 43.2% vs 17.8%, and AR 34.5% vs 16.4%. Two hundred and four children (43.1%) were mono-sensitized, 215 (45.5%) oligosensitized (2–3 allergens), and 54 (11.4%) polysensitized (≥4 allergens). A-AR ranked the top number of positive allergens. The commonest aeroallergen was Der p1 (38.1%), followed by Der f (29.0%), cat (22.6%), alternaria (18.8%), American cockroach (18.4%), and dog (14.0%). House dust mite (HDM) and American cockroach were commoner in ≤5 years than older >10-year children (52.5%, 24.1%), while cat and dog allergens were commoner in older ones (37.1%, 21.6%).ConclusionFamily history is quite positive in patients with A and AR. Common aeroallergens include HDM, cats, and alternaria in the young children, while animal allergens were commoner in the older children.

Incidence and remission of aeroallergen sensitization in adults in Northern Finland: 15\xa0years longitudinal study

Studies on the longitudinal changes in sensitization to aeroallergens in adult populations are sparse. The aim was to evaluate changes in sensitization to aeroallergens [birch, timothy, cat and house dust mite (HDM)] in an unselected adult population aged from 31 to 46 years. Data were gathered from a cohort of adults (Northern Finland Birth Cohort 1966) who had been skin prick tested (SPT) with birch, timothy, cat and HDM allergens at the age of 31 years and at age 46 (n = 5484 and 5373 respectively). Data from both time points were available for 3409 participants, who made up the cohort of the longitudinal study. The overall prevalence of sensitization to any of the selected allergens was 30.3% (n = 1661) in 31-year-olds and 30.7% (n = 1649) in 46-year-olds. In general, men were more sensitized (P < 0.001) and also had more polysensitization (P < 0.001) compared to women. In longitudinal sub-population incidence of sensitization was 7.1%. Birch was the most prevalent new sensitizer, however, the difference was not statistically significant when compared to cat. We conclude that new sensitization, demonstrated by positive findings in SPT, can still occur in middle age and this should be taken into account when managing allergic manifestations in adults as sensitization can be considered the first step in developing clinical allergy.

Array-based measurements of aero-allergen-specific IgE correlate with skin-prick test reactivity in asthma regardless of specific IgG4 or total IgE measurements

Skin prick testing (SPT) and measurement of serum allergen-specific IgE (sIgE) are used to investigate asthma and other allergic conditions. Measurement of serum total IgE (tIgE) and allergen-specific IgG4 (sIgG4) may also be useful. The aim was to ascertain the correlation between these serological parameters and SPT. Sera from 60 suspected asthmatic patients and 18 healthy controls were assayed for sIgE and sIgG4 reactivity against a panel of 70 SPT allergen preparations, and for tIgE. The patients were also assessed by skin prick tests for reactivity to cat, dog, house dust mite and grass allergens. Over 50% of the patients had tIgE levels above the 75th percentile of the controls. 58% of patients and 39% of controls showed sIgE reactivity to ≥1 allergen. The mean number of allergens detected by sIgE was 3.1 in suspected asthma patients and 0.9 in controls. 58% of patients and 50% of controls showed sIgG4 reactivity to ≥1 allergen. The mean number of allergens detected by sIgG4 was 2.5 in patients and 1.7 in controls. For the patients, a strong correlation was observed between clinical SPT reactivity and serum sIgE levels to cat, dog, house dust mite (HDM) and grass allergens. SPT correlations using sIgE/sIgG4 or sIgE/tIgE ratios were not markedly higher. The measurement of serum sIgE by microarray using SPT allergen preparations showed good correlation with clinical SPT reactivity to cat, dog, HDM and grass allergens. This concordance was not improved by measuring tIgE or sIgG4.

Farm Environment During Pregnancy and Childhood and Polysensitization at the Age of 31: Prospective Birth Cohort Study in Finland.

The farm environment, especially contact with farm animals in early childhood, may prevent allergic sensitization during adulthood. However, prospective associations between exposure to the farm environment and polysensitization have not been studied. Polysensitization is a risk factor for asthma and asthma-related morbidity. Objective: To investigate whether exposure to a farming environment in early childhood, especially exposure to animals, is associated with sensitization to specific allergens and polysensitization at the age of 31. In a prospective birth cohort study, 5509 individuals born in northern Finland in 1966 underwent skin prick testing against birch, timothy, cat, and house dust mite at the age of 31. Prenatal exposure to the farming environment was documented at birth, whereas information on childhood exposure to pets was only collected retrospectively at the age of 31. Data were analyzed using logistic regression. Being born to a family with farm animals was associated with a reduced risk of sensitization to birch, timothy, and cat (adjusted odds ratio [aOR], 0.55 [95%CI, 0.43-0.70]; aOR, 0.62 [95%CI, 0.48-0.79]; aOR, 0.60 [95%CI, 0.47-0.75]) and polysensitization at the age of 31 (aOR, 0.62 [95%CI, 0.48-0.80]). The number of animal species present during childhood was dose-dependently associated with a reduced risk of sensitization to birch, timothy, and cat, as well as of polysensitization. No association was found with sensitization to house dust mite. Growing up on a farm and contact with higher numbers of animal species in childhood are associated with less frequent sensitization to birch, timothy, and cat allergens and polysensitization in adulthood, but not with sensitization to house dust mite.

The Major Cat Allergen, Fel d 1, Is a Viable Target for CRISPR Gene Editing.

Allergy to domestic cat (Felis domesticus) affects >10% of the population. Fel d 1, the major cat allergen, causes IgE sensitization in >90% of cat allergic subjects and accounts for 60-90% of anti-cat IgE. Our goal was to identify and target conserved regions of Fel d 1 using CRISPR gene editing, as an approach for ultimately generating allergen-free cats.

Commissioning of a Larger Naturalistic Exposure Chamber for Cat Dander

We previously developed a 2-person capacity (14.4 m3) Naturalistic Exposure Chamber (NEC) providing naturalistic and controlled exposure to cat allergen. We scaled this model to a larger 8-person capacity room (36.7 m3). Fel-d-1 was measured throughout the room and over time for 2-hour aerosolization tests. Target Fel-d-1 was 40-100 ng/m3 to mimic home environments.

A Single-Dose of REGN1908-1909 Reduced Bronchoconstriction in Cat-Allergic Subjects with Mild Asthma for up to 3 months following a controlled cat allergen challenge: A Phase 2, Randomized, Double-Blind, Placebo-Controlled Study

To evaluate the efficacy of a novel anti-Fel d 1 monoclonal antibody cocktail (REGN1908-1909) in reducing acute bronchoconstriction, defined as early asthmatic response (EAR), in cat-allergic subjects with mild asthma (NCT03838731).

RISK FACTORS FOR INNER CITY ASTHMA PATIENTS

Asthma patients in inner cities have the highest prevalence of asthma and the highest death rates in America. The purpose of this study was to evaluate sensitization and exposure to common indoor allergens seen for asthma treatment at Grady Memorial Hospital, Atlanta, Ga. Eighty asthma patients were enrolled in the emergency department and 64 in hospital clinics in this study. Neither sensitization nor visibility In this population, cat allergens are prevalent. The findings show that black asthma patients are exposed to high levels of mite and cockroach allergens in downtown Atlanta and that a high percentage of patients with asthma are sensitized to these allergens; a significant risk factor for asthma in this population is the combination of sensitization and exposure.&#x0D; Keywords: asthma; mechanical ventilation, status asthmaticus , Pathophysiology epidemiology mechanisms.

Comprehensive mapping of immune tolerance yields a regulatory TNF receptor 2 signature in a murine model of successful Fel d 1-specific immunotherapy using high-dose CpG adjuvant.

BackgroundThe prevalence of allergy to cat is expanding worldwide. Allergen‐specific immunotherapy (AIT) has advantages over symptomatic pharmacotherapy and promises long‐lasting disease control in allergic patients. However, there is still a need to improve cat AIT regarding efficacy, safety, and adherence to the treatment. Here, we aim to boost immune tolerance to the major cat allergen Fel d 1 by increasing the anti‐inflammatory activity of AIT with the established immunomodulatory adjuvant CpG, but at a higher dose than previously used in AIT.MethodsTogether with CpG, we used endotoxin‐free Fel d 1 as therapeutic allergen throughout the study in a BALB/c model of allergy to Fel d 1, thus mimicking the conditions of human AIT trials. Multidimensional immune phenotyping including mass cytometry (CyTOF) was applied to analyze AIT‐specific immune signatures.ResultsWe show that AIT with high‐dose CpG in combination with endotoxin‐free Fel d 1 reverts all major hallmarks of allergy. High‐dimensional CyTOF analysis of the immune cell signatures initiating and sustaining the AIT effect indicates the simultaneous engagement of both, the pDC‐Treg and B‐cell axis, with the emergence of a systemic GATA3+ FoxP3hi biTreg population. The regulatory immune signature also suggests the involvement of the anti‐inflammatory TNF/TNFR2 signaling cascade in NK and B cells at an early stage and in Tregs later during AIT.ConclusionOur results highlight the potential of CpG adjuvant in a novel formulation to be further exploited for inducing allergen‐specific tolerance in patients with cat allergy or other allergic diseases.

Sensitization to cat and dog components and prediction of symptoms in cat-sensitized children.

Sensitization to cat and/or dog allergens during childhood represents a risk factor for the development of allergic diseases later in life. The study investigated the association of patterns of sensitization to cat and dog allergen components with clinical symptoms of allergy to these furry animals among cat-sensitized children. The children were evaluated for the presence of bronchial asthma, atopic dermatitis and allergic rhinitis. Their mothers completed a questionnaire on pet exposure at home. Levels of serum IgE cat epitopes Fel d (1, 2, 4), as well as dog components Can f (1, 2, 3, 5) were measured in all the studied children. Respiratory symptoms following exposure to the cat allergen were most common in children with Fel d 2 epitope (p = 0.041). After contact with a dog, respiratory symptoms were most common in children with Can f 1 epitope (p = 0.042), atopic dermatitis in children with sensitization to both Can f 1 (p = 0.009) and Can f 2 (p = 0.002), whereas eye symptoms occurred mostly in children with Can f 3 (p = 0.039). Molecular diagnosis in patients with pet allergy may help clinicians to predict clinical symptoms and their severity.

Cat-NPC2, a Newly Identified Allergen, With High Cross-Reactivity to Can f 7.

PurposePet-derived allergens are the common indoor inhalant allergens. Among them, cat and dog allergens constitute more than 80% of animal allergic patients, which greatly affect the quality-of-life of patients and increase the burden of social health care. The aim of this study was to identify Cat-Niemann pick type C2 (NPC2) protein, a homologue of Can f 7, as a new allergen.MethodsCat-NPC2 complementary DNA (cDNA) was cloned and optimized for amplification and expression in Escherichia coli. Then, recombinant Cat-NPC2 (rCat-NPC2) was purified by Ni2+ affinity chromatography. The allergenicity was assessed by enzyme-linked immunosorbent assay (ELISA), western blot and basophil activation test (BAT). Based on the sequence similarity, the cross-reactivity between Cat-NPC2 and Can f 7 was investigated by inhibition ELISA. Circular dichroism spectroscopy and homology modeling were used to characterize the structure of Cat-NPC2.ResultsThe cDNA sequence of Cat-NPC2 was cloned with a 450-bp open reading frame coding for 149 amino acids (GenBank MN_737596). The condon-optimized NPC2 gene was subcloned and expressed in E. coli with a molecular weight of 18.9 kDa. The native Cat-NPC2 was detected in cat dander extracts. The allergenicity determined by ELISA, western blot and BAT suggested at least 14.5% cat-allergic patients displayed high specific immunoglobulin E (IgE) recognition of Cat-NPC2. The predicted structure of Cat-NPC2 was found to consist of 7 β-strands arranged in 2 β-sheets. An ELISA based assay showed that rCat-NPC2 bound to cholesterol in a dose dependent manner. Based on the structure and sequence similarities, IgE cross-reactivity was demonstrated between Cat-NPC2 and Can f 7/Der f 2.ConclusionsIn the study, a novel cat allergen, belonging to the NPC2 protein family, was identified and characterized at both molecular and immunological levels. The study will offer a deeper understanding of cat allergens and improve a component-resolved diagnosis in pet allergy.