The effect of reducing levels of cat allergen (Fel d 1) on clinical symptoms in patients with cat allergy

KAAACI Guidelines for Allergen Immunotherapy

Allergen immunotherapy (AIT) is a causative treatment for various allergic diseases such as allergic rhinitis, allergic asthma, and bee venom allergy that induces tolerance to offending allergens. The need for uniform practice guidelines in AIT is continuously growing because of the increasing discovery of potential candidates for AIT and evolving interest in new therapeutic approaches. This guideline is an updated version of the Korean Academy of Asthma Allergy and Clinical Immunology recommendations for AIT published in 2010. This updated guideline proposes an expert opinion by allergy, pediatrics, and otorhinolaryngology specialists with an extensive literature review. The guideline deals with basic knowledge and methodological aspects of AIT, including mechanisms, clinical efficacy, patient selection, allergens extract selection, schedule and doses, management of adverse reactions, efficacy measurements, and special consideration in pediatrics. The guidelines for sublingual immunotherapy will be covered in detail in a separate article.

KAAACI Allergic Rhinitis Guidelines: Part 2. Update in Non-pharmacological Management

Allergic rhinitis is the most common chronic disease worldwide. Various upper airway symptoms lower quality of life, and due to the recurrent symptoms, multiple treatments are usually attempted rather than one definitive treatment. There are alternatives to medical (medication-based) and non-medical treatments. A guideline is needed to understand allergic rhinitis and develop an appropriate treatment plan. We have developed guidelines for medical treatment based on previous reports. The current guidelines herein are associated with the "KAAACI Evidence-Based Guidelines for Allergic Rhinitis in Korea, Part 1: Update in pharmacotherapy" in which we aimed to provide evidence-based recommendations for the medical treatment of allergic rhinitis. Part 2 focuses on non-pharmacological management, including allergen-specific immunotherapy, subcutaneous or sublingual immunotherapy, nasal saline irrigation, environmental management strategies, companion animal management, and nasal turbinate surgery. The evidence to support the treatment efficacy, safety, and selection has been systematically reviewed. However, larger controlled studies are needed to elevate the level of evidence to select rational non-medical therapeutic options for patients with allergic rhinitis.

Effects of mechanical washing and drying on the removal of pet allergens

Background: In Korea, the number of households with indoor pets is rapidly increasing in parallel with changes in cultural lifestyles. The sensitization rate of pet allergens is also increasing in Korea. Objective: We evaluated the effectiveness of washing machines to remove dog and cat hair and their allergens. In addition, this study aimed to investigate whether only a mechanical dryer without mechanical washing could be used for pet allergen removal. Method: We brushed cats and dogs, and thereafter collected their hair and used a residential vacuum cleaner to obtain dust and other particulate matter from a household. The contents of the vacuum bag were sifted through a 300-μm sieve filter. Some of the contents were placed in phosphate-buffered saline solution with 0.5% Tween 20 to make a liquid extract. Hair, dust, and liquid extract-contaminated fabric samples after mechanical washing or after drying without mechanical washing were analyzed for pet allergens (Fel d l [cat], Can f 1 [dog]) by using a two-site enzyme-linked immunosorbent assay. We assessed the remaining allergens in the contaminated fabrics after mechanical drying and washing. Results: The mean Fel d l and mean Can f 1 removal ratios after mechanical washing with detergent were > 99.99% for the dust, hair, and liquid extract. The removal ratios after mechanical washing without a detergent were lower for both Fel d 1 and Can f 1, for hair, dust, and their respective liquid extracts (p < 0.05). Mechanical drying was just as effective as mechanical washing with detergent for removing Can f 1 but was less effective for Fel d 1 (p < 0.05). Conclusion: Mechanical washing with detergent is important to remove pet allergens from contaminated fabrics. If washing is difficult, then using just a dryer without washing can be an alternative method to remove allergens from contaminated bedding or clothing.

Human allergy to cats: A review for veterinarians on prevalence, causes, symptoms and control

PRACTICAL RELEVANCE

Human allergy to cats affects a substantial and growing proportion of the global population, and cat allergy is regarded as the third most common cause of human respiratory allergies, and the second most common indoor cause. Veterinarians will frequently encounter owners who are cat-allergic, and having an understanding of this disease and the methods available to help control the allergy will assist them in giving appropriate advice, alongside human healthcare professionals.

AIM

The aim of this review is to summarise currently available data on the prevalence, causes, symptoms and control of human allergy to cats. In terms of managing cat allergy, the emphasis is on reviewing current and emerging modalities to reduce environmental exposure to cat allergens rather than on pharmacotherapy or immunotherapy, as it is in these areas in particular that the veterinarian may be able to offer help and advice to complement that of human healthcare professionals.

EVIDENCE BASE

The information in this review is drawn from the current and historical literature on human allergy to cats, and approaches to reduce exposure to cat allergens and manage symptoms of cat allergy.

The nanotopography of SiO2 particles impacts the selectivity and 3D fold of bound allergens

A detailed description of the changes that occur during the formation of protein corona represents a fundamental question in nanoscience, given that it not only impacts the behaviour of nanoparticles but also affects the bound proteins. Relevant questions include whether proteins selectively bind particles, whether a specific orientation is preferred for binding, and whether particle binding leads to a modulation of their 3D fold. For allergens, it is important to answer these questions given that all these effects can modify the allergenic response of atopic individuals. These potential impacts on the bound allergen are closely related to the specific properties of the involved nanoparticles. One important property influencing the formation of protein corona is the nanotopography of the particles. Herein, we studied the effect of nanoparticle porosity on allergen binding using mesoporous and non-porous SiO₂ NPs. We investigated (i) the selectivity of allergen binding from a mixture such as crude pollen extract, (ii) whether allergen binding results in a preferred orientation, (iii) the influence of binding on the conformation of the allergen, and (iv) how the binding affects the allergenic response. Nanotopography was found to play a major role in the formation of protein corona, impacting the physicochemical and biological properties of the NP-bound allergen. The porosity of the surface of the SiO₂ nanoparticles resulted in a higher binding capacity with pronounced selectivity for (preferentially) binding the major birch pollen allergen Bet v 1. Furthermore, the binding of Bet v 1 to the mesoporous rather than the non-porous SiO₂ nanoparticles influenced the 3D fold of the protein, resulting in at least partial unfolding. Consequently, this conformational change influenced the allergenic response, as observed by mediator release assays employing the sera of patients and immune effector cells. For an in-depth understanding of the bio-nano interactions, the properties of the particles need to be considered not only regarding the identity and morphology of the material, but also their nanotopography, given that porosity may greatly influence the structure, and hence the biological behaviour of the bound proteins. Thus, thorough structural investigations upon the formation of protein corona are important when considering immunological outcomes, as particle binding can influence the allergenic response elicited by the bound allergen.

Human allergy to cats: A review of the impact on cat ownership and relinquishment

Practical relevance:

Cats have become increasingly common as companion animals, and in many countries their popularity now exceeds that of dogs. At the same time, human allergies (including allergy to cats) have been increasing and it has been estimated that globally up to 10-20% of human adults are sensitised to cats.

Aim:

This review summarises the available published data on how human allergy to cats affects cat ownership and considers the implications of the findings on the wider human-cat bond and how adverse effects can be minimised.

Evidence base:

Online databases were searched for all original studies up to December 2020 that had quantified the impact of human allergy to cats on ownership or relinquishment. Objective quantifiable data appeared to fall into three broad outcomes - (1) choosing to avoid cat ownership; (2) relinquishment of owned cats; and (3) return of cats after acquisition from a rehoming centre. The data retrieved on these topics are the focus of this review. In some studies, data from cats and dogs were combined and these have also been included in the review.

Keep the cat, change the care pathway: A transformational approach to managing Fel d 1, the major cat allergen

Background

Allergies to cats are the most common animal‐origin allergy, and affect approximately 1 in 5 adults worldwide. The prevalence of allergy to furry animals has been increasing, and allergy to cats is a major risk factor for the development of asthma and rhinitis. The diagnosis of cat allergy is now well established. The exact significance of component‐resolved diagnosis in the diagnosis of cat allergy remains to be fully understood. Allergen avoidance is effective but often has a psychologic impact. Allergen immunotherapy is not well demonstrated. There is a need for innovative approaches to better manage cat allergens. Next‐generation care pathways for asthma and rhinitis will define the place of cat allergen avoidance.

Methods and Results

This manuscript, based on content presented at the European Academy of Allergy and Clinical Immunology Congress 2019, provides information on the prevalence and impact of cat allergies and the molecular biology of Fel d 1, the major cat allergen.

Discussion

The authors present the scientific basis of a novel care pathway that utilizes anti‐Fel d 1 IgY antibodies to safely and effectively neutralize Fel d 1 after its production by the cat but before human exposure.

Conclusion

Efficacy of a feline diet with an egg product ingredient containing anti‐Fel d 1 IgY antibodies was demonstrated in vitro, ex vivo, and in vivo, and further validated by a pilot exposure study involving cat‐allergic human participants.

Reduction of active Fel d1 from cats using an antiFel d1 egg IgY antibody

BACKGROUND

Fel d1 is the most important allergen from cats. Fel d1 is produced primarily in saliva and spread to the haircoat during grooming and then transferred to the environment via hair and dander.

OBJECTIVES

A novel approach to reducing allergenic Fel d1 exposure was evaluated, involving binding the Fel d1 with an anti-Fel d1 polyclonal egg IgY antibody. The hypothesis was that hair from cats who had been fed foods containing anti-Fel d1 IgY would show a significant reduction in active Fel d1 (aFel d1).

METHODS

Hair collected from 105 cats completing a 12-week study was evaluated for aFel d1 via ELISA. Hair was collected four times over a 2-week baseline period, then weekly during the 10 week treatment period during which cats consumed a food containing the anti-Fel d1 IgY.

RESULTS

Baseline aFel d1 (μg/g hair) varied greatly among the cats in this study. From week 3, there was a significant reduction in mean aFel d1 with an overall average decrease of 47% by week 10, ranging from a 33-71% decrease vs baseline. Cats with the highest baseline aFel d1 showed the greatest decrease in aFel d1.

CONCLUSIONS & CLINICAL IMPLICATIONS

Feeding anti-Fel d1 IgY to cats successfully reduced aFel d1 on their haircoat with the greatest decreases observed in cats with initially high levels. Feeding a diet with anti Fel d1 IgY significantly reduced the active Fel d1 on the hair of cats.

Influence of time and phenotype on salivary Fel d1 in domestic shorthair cats

Objectives

Fel d1 is a major allergen that may affect humans sensitive to cat allergens, and it can be detected in the saliva and on the hair of cats. We studied the variability of salivary Fel d1 in typical house cats (ie, neutered domestic shorthair cats) and the factors that could be associated with that variability.

Methods

Saliva samples were collected from 64 cats, twice daily, every other day, for a year, at two locations (Missouri, USA, and Ontario, Canada). Salivary Fel d1 levels were measured using an immunoassay. Correlations and linear mixed-effects model analyses were run to assess which factors significantly affected the Fel d1 levels.

Results

Salivary Fel d1 levels varied significantly both within and among cats. Cat averages over the year ranged from 0.4–35 µg/ml, and a higher average correlated with a higher SD (P <0.001). The first collection of the day tended to be higher than the afternoon collection (P <0.001). Sex, coat color or body size did not relate to cats’ average Fel d1 production, but older cats tended to have lower salivary Fel d1 levels (P <0.001). Fel d1 levels from four samples were reliable in identifying cats producing stable low levels of Fel d1.

Conclusions and relevance

We observed a wide and continuous range of salivary Fel d1 production in domestic shorthair cats. In particular, a subset of cats had stable low levels throughout the course of the year, and they can be identified by analyzing a few saliva samples rather than their physical appearance.

BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis (Revised Edition 2017; First edition 2007)

This is an updated guideline for the diagnosis and management of allergic and non-allergic rhinitis, first published in 2007. It was produced by the Standards of Care Committee of the British Society of Allergy and Clinical Immunology, using accredited methods. Allergic rhinitis is common and affects 10-15% of children and 26% of adults in the UK, it affects quality of life, school and work attendance, and is a risk factor for development of asthma. Allergic rhinitis is diagnosed by history and examination, supported by specific allergy tests. Topical nasal corticosteroids are the treatment of choice for moderate to severe disease. Combination therapy with intranasal corticosteroid plus intranasal antihistamine is more effective than either alone and provides second line treatment for those with rhinitis poorly controlled on monotherapy. Immunotherapy is highly effective when the specific allergen is the responsible driver for the symptoms. Treatment of rhinitis is associated with benefits for asthma. Non-allergic rhinitis also is a risk factor for the development of asthma and may be eosinophilic and steroid-responsive or neurogenic and non- inflammatory. Non-allergic rhinitis may be a presenting complaint for systemic disorders such as granulomatous or eosinophilic polyangiitis, and sarcoidoisis. Infective rhinitis can be caused by viruses, and less commonly by bacteria, fungi and protozoa.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Pediatric allergic rhinitis and asthma: can the march be halted?

The strong epidemiologic and pathophysiologic link between allergic rhinitis (AR) and asthma has led to the concept of 'united airways disease' or 'respiratory allergy', implying that allergy, in its widest sense, underlies this clinical syndrome. Progression from AR to asthma is frequent and part of the 'atopic march'. Since pediatric immune responses are more adaptable and therefore may be more amenable to treatment, interventions at early childhood are characterized by a higher chance to affect the natural history of respiratory allergy. Although current treatments are quite effective in alleviating respiratory allergy symptoms, it has proven much more difficult to confirm any influence on the progression of the disease. Much more promising is the field of specific allergen immunotherapy, where current evidence, although not yet of ideal robustness, points towards a disease-modifying effect. In addition, newer or emerging, possibly more effective or more targeted interventions are promising in the preventive sense.

Allergic rhinitis and quality of life in children

Allergic rhinitis is a respiratory disease caused by an inflammatory process related to IgE mediated reaction versus allergens to which the subject is sensitized. Allergic rhinitis is not an isolated disease because the nasal mucosa inflammation involves paranasal sinuses and lower airways, thus worsening the asthmatic symptoms. Recently, a new classification of allergic rhinitis based on the duration and severity of clinical symptoms has been proposed. This classification takes into consideration both the quality of life and the possible impact of the symptoms on school, work and free-time activities. Children&#x0027;s quality of life is severely compromised by frequent night awakenings, easy fatigue, defects of language and irritability, which can have a negative influence on learning abilities. Allergic rhinitis has a negative impact on the quality of life of the whole family because it can cause interference on social life, and financial costs.

Efficacy of a novel air filtration pillow for avoidance of perennial allergens in symptomatic adults

BACKGROUND

Nighttime allergen exposures are a primary contributor to the development of allergic and asthmatic morbidities. Disease management guidelines recommend the use of environmental control measures to reduce these exposures, but clinically relevant reductions are difficult to achieve because most measures control only 1 allergen source among many in the bedroom environment.

OBJECTIVE

To determine whether a novel localized approach to nighttime allergen avoidance provides effective exposure reductions and clinical benefits.

METHODS

Thirty-five adults with perennial allergic rhinoconjunctivitis (dog, cat, or dust mite sensitivity) were randomized to receive PureZone, a combination therapy involving localized air filtration and pillow encasement, or placebo in a crossover trial with two 2-week treatment periods separated by a 1-week washout. Nasal and ocular allergy symptoms, quality of life, and breathing zone particulate exposure were assessed. Bedroom allergen dust samples were collected in the sleeping environment.

RESULTS

Reductions (>99.99%) in allergen-sized particulate (> or = 0.3 microm) in the breathing zone led to significant improvements in nocturnal nasal and ocular allergy symptoms (P < .001) and quality of life (P = .02) for the active vs placebo device. Significant nocturnal symptom reductions vs placebo occurred the second night of use and were maintained for the duration of treatment; these reductions improved sleep problems in particular (P = .02). Allergens were detected in 100% of bedrooms, of which 44% had levels that exceeded sensitizing thresholds.

CONCLUSIONS

The combination therapy of pillow encasement and localized air filtration provided effective nighttime allergen exposure reductions and clinical benefits without the use of adjunctive therapy.

Human allergy to environmental pet danders: a public health perspective

The prevalence of human allergy to pet danders has increased rapidly over the past six decades, as a consequence of lifestyle changes that have enhanced ambient exposure to pet allergens. This is a problem of global public health importance, as the morbidity associated with allergic diseases disproportionately affects socio-economically disadvantaged populations, particularly children. Although the public often seeks advice from veterinary health-care professionals regarding healthy pet ownership practices, including strategies for reducing residential pet dander exposure, many misconceptions persist in the public domain regarding pet dander allergy, such as the belief that certain dog and cat breeds are 'hypoallergenic' due to their hair/coat type. This review considers the epidemiology of human exposure to the major cat and dog dander allergens, Fel d 1 and Can f 1 respectively, and the sensitization mechanisms to them, including the hygiene hypothesis and the putative role of bacterial endotoxin. The literature regarding primary and secondary exposures in different ambient environments is explored including threshold effects that influence allergen sensitization and elicitation of symptoms, and environmental intervention strategies that seek to reduce allergen exposure. Pet-specific factors, including the aetiopathogenesis of the several cat and dog allergens that have been characterized to the molecular level, individual animal characteristics that influence Fel d 1 and Can f 1 shedding, and pet-directed interventions intended to reduce allergen dispersal, are discussed.

Asthma counselling targeted to removal of domestic animals

OBJECTIVES

To create and evaluate the efficacy of a short individualized educational intervention program, based on Prochaska's transtheoretical model, for a six-month period in a population of adult asthma patients living with domestic animals but sensitized to these pets.

METHODS

A randomized, controlled study using a pretested questionnaire was conducted at three different times (pretest, and at three and six months postintervention).

RESULTS

Eleven members (29%) of the intervention group and eight members (21%) of the control group removed their pets within six months (X(2)=3.23; P>0.35). The two groups showed similar improvements in their perception of the benefits of pet removal and in their level of belief that they could do it. The experimental group showed a greater improvement in knowledge acquisition about asthma and allergies than the control group (P<0.05). Both experimental and standard educational interventions were effective in facilitating progression through the stages of behavioural change.

CONCLUSION

Overall, the results do not support the utility of behavioural change educational intervention, tailored to the transtheoretical model stage of the individual, in the context of convincing patients to remove their pets from their homes. However, the decision-making aid appears to be helpful in raising awareness of the problem of asthma and allergy in the patient, and in developing appropriate knowledge.

Montelukast in the management of allergic rhinitis

Allergic rhinitis is the most common atopic disorder seen in the outpatient clinic setting diagnosed by history, physical exam and objective testing. According to the Allergic Rhinitis and its Impact on Asthma (ARIA) document, it is classified by chronicity (intermittent or persistent), and severity which is based on symptoms and quality of life (mild, or moderate/severe). It has enormous socioeconomic costs and significant reduction in quality of life. Allergen avoidance should be implemented, particularly in children, to reduce level of exposure; unfortunately efforts are often inadequate. Montelukast, a novel medication, is an antagonist to the leukotriene receptor. It is nonsedating, dosed once daily, and has a safety profile similar in adults and children with approval down to 6 months of age. A review of the literature undoubtedly establishes montelukast as a viable alternative for the treatment of seasonal allergic rhinitis. Its benefits are equivalent to antihistamines, when used as monotherapy, but less than intranasal corticosteroids. The addition of an antihistamine to montelukast does appear to have added benefits and at times is reported to be equivalent to intranasal corticosteroids.

Latest developments in the management of allergic rhinitis

Allergic rhinitis (AR) is the most common chronic atopic disease, and it is associated with considerable costs and comorbidities. The management of AR includes environmental control measures, pharmacotherapy, and immunotherapy. This article discusses several developments and findings that have recently emerged in these three areas. The effectiveness of traditional methods of mitigating allergen exposure, such as the use of impermeable dust mite-proof bedding covers, has been rendered debatable. Exposure to environmental factors, such as household pets, is known to provoke exacerbation of allergic disease but now is proposed to have protective effects in certain settings. Changes in the choices of pharmacotherapy continue to occur as antileukotrienes and derivatives of certain antihistamines are added to the armamentarium against AR. However, a critical review of the clinical trials involving these drugs suggests that the changes are not necessarily incremental. Innovative methods of immunomodulation are currently being developed, with the objective of optimizing efficacy and safety. These include alternative routes or forms of delivering immunotherapy and other novel approaches in altering the pathobiology of AR.

Allergen avoidance and prevention of atopy

PURPOSE OF REVIEW

Recent increases in the prevalence of atopic disease argue strongly that environmental factors operating primarily in early life play a significant role. Exposure to food and inhalant allergens early in life may constitute a risk factor amenable to manipulation.

RECENT FINDINGS

Recent observational and interventional studies have produced conflicting data regarding the effectiveness of allergen avoidance in primary and secondary prevention of atopic diseases.

SUMMARY

Exclusive breast feeding for 4-6 months may protect against the development of allergic diseases in early childhood and remains good advice. Convincing proof for the preventive effects of the delayed introduction of solid foods and hydrolyzed formula in formula-fed infants is lacking. There is some evidence to support a preventive effect of house dust mite allergen avoidance before sensitization occurs. The effect of exposure to animal allergen is uncertain, with some studies showing an increase in sensitization while others suggest a protective effect. Therefore, no evidence-based advice can be given at this stage regarding allergen avoidance measures to be adopted by families with infants at high risk of atopy, except perhaps to breast feed exclusively for at least 4 months. Data regarding the secondary prevention of allergic disease by allergen avoidance were more secure until the publication this year of two randomized controlled trials which suggest that mattress impermeable covers, the main dust mite allergen avoidance measure, may not work. Allergen avoidance, however, should remain an essential part of the management of allergic diseases, even if the benefit of mattress covers is in doubt.

Pet allergen control measures for allergic asthma in children and adults

BACKGROUND

Although pet removal has been recommended in guidelines on the management of allergic asthma, pet ownership remains high in families where one or more members have an allergy to pet dander. Allergen control measures such as air filtration units placed in the homes of pet-allergic asthmatics have been used as a means of reducing allergen exposure.

OBJECTIVES

To determine the clinical efficacy of pet allergen control measures in the homes of people with pet-allergic asthma.

SEARCH STRATEGY

An electronic search of the Cochrane Controlled Trials Register was carried out. No restriction was placed on language of publication.

SELECTION CRITERIA

Randomised controlled trials comparing an active allergen reduction measure with control were considered for analysis. Participants had stable pet-allergic asthma.

DATA COLLECTION AND ANALYSIS

34 references were identified by electronic searching, but only three appeared suitable for potential inclusion in the review. Two met the inclusion criteria for the analysis. Both examined the effectiveness of air filtration units. Two reviewers extracted data independently. A limited amount of data were usable for a meta-analysis.

MAIN RESULTS

Both trials were small (n=22 and n=35). No significant differences were detected between active intervention and control on the primary and secondary outcome measures reported in the studies. Data on absence from school or work were not reported in either study. No meta-analysis could be performed due to lack of common outcomes.

REVIEWER'S CONCLUSIONS

The available trials are too small to provide evidence for or against the use of airfiltration units to reduce allergen levels in the management of pet-allergic asthma. Adequately powered trials are needed. There are no trials of other allergen reduction measures, such as pet washing or possibly pet removal.