[Animal dander allergy in children]

Study of Cat Allergy Using Controlled Methodology-A Review of the Literature and a Call to Action

The prevalence of cat allergen-induced AR is increasing worldwide, prompting its study using controlled methodology. Three general categories of allergen exposure models currently exist for the study of cat allergen-induced AR: natural exposure cat rooms, allergen exposure chambers (AEC), and nasal allergen challenges (NAC). We evaluated existing literature surrounding the use of these models to study cat allergen induced AR using online research databases, including OVID Medline, Embase, and Web of Science. We report that natural exposure cat rooms have been important in establishing the foundation for our understanding of cat allergen-induced AR. Major limitations, including variable allergen ranges and differing study designs highlight the need for a more standardized protocol. In comparison, AECs are an exceptional model to mimic real-world allergen exposure and study long-term implications of AR with large sample sizes. Existing AECs are limited by heterogeneous facility designs, differing methods of cat allergen distribution, and issues surrounding cost and accessibility. Conversely, NACs allow for smaller participant cohorts for easier biological sampling and are ideal for phase I, phase 2 or proof-of-concept studies. NACs generally have a standardized protocol and are less expensive compared to AECs. Nevertheless, NACs solely capture acute allergen exposure and have the further limitation of using allergen extracts rather than natural allergen. As the use of combined controlled methodologies is sparse, we recommend concurrent use of AECs and NACs to study short- and long-term effects of AR, thereby providing a more holistic representation of cat allergen-induced AR.

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.

Immunization of Cats against Fel d 1 Results in Reduced Allergic Symptoms of Owners

An innovative approach was tested to treat cat allergy in humans by vaccinating cats with Fel-CuMV (HypoCat^TM), a vaccine against the major cat allergen Fel d 1 based on virus-like particles derived from cucumber mosaic virus (CuMV-VLPs). Upon vaccination, cats develop neutralizing antibodies against the allergen Fel d 1, which reduces the level of reactive allergen, thus lowering the symptoms or even preventing allergic reactions in humans. The combined methodological field study included ten cat-allergic participants who lived together with their cats (n = 13), that were immunized with Fel-CuMV. The aim was to determine methods for measuring a change in allergic symptoms. A home-based provocation test (petting time and organ specific symptom score (OSSS)) and a general weekly (or monthly) symptom score (G(W)SS) were used to assess changes in allergic symptoms. The petting time until a pre-defined level of allergic symptoms was reached increased already early after vaccination of the cats and was apparent over the course of the study. In addition, the OSSS after provocation and G(W)SS recorded a persistent reduction in symptoms over the study period and could serve for long-term assessment. Hence, the immunization of cats with HypoCat^TM (Fel-CuMV) may have a positive impact on the cat allergy of the owner, and changes could be assessed by the provocation test as well as G(W)SS.

Immunization of Cats against Fel d 1 Results in Reduced Allergic Symptoms of Owners

An innovative approach was tested to treat cat allergy in humans by vaccinating cats with Fel-CuMV (HypoCat^TM), a vaccine against the major cat allergen Fel d 1 based on virus-like particles derived from cucumber mosaic virus (CuMV-VLPs). Upon vaccination, cats develop neutralizing antibodies against the allergen Fel d 1, which reduces the level of reactive allergen, thus lowering the symptoms or even preventing allergic reactions in humans. The combined methodological field study included ten cat-allergic participants who lived together with their cats (n = 13), that were immunized with Fel-CuMV. The aim was to determine methods for measuring a change in allergic symptoms. A home-based provocation test (petting time and organ specific symptom score (OSSS)) and a general weekly (or monthly) symptom score (G(W)SS) were used to assess changes in allergic symptoms. The petting time until a pre-defined level of allergic symptoms was reached increased already early after vaccination of the cats and was apparent over the course of the study. In addition, the OSSS after provocation and G(W)SS recorded a persistent reduction in symptoms over the study period and could serve for long-term assessment. Hence, the immunization of cats with HypoCat^TM (Fel-CuMV) may have a positive impact on the cat allergy of the owner, and changes could be assessed by the provocation test as well as G(W)SS.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.

An update on molecular cat allergens: Fel d 1 and what else? Chapter 1: Fel d 1, the major cat allergen

Background

Cats are the major source of indoor inhalant allergens after house dust mites. The global incidence of cat allergies is rising sharply, posing a major public health problem. Ten cat allergens have been identified. The major allergen responsible for symptoms is Fel d 1, a secretoglobin and not a lipocalin, making the cat a special case among mammals.

Main body

Given its clinical predominance, it is essential to have a good knowledge of this allergenic fraction, including its basic structure, to understand the new exciting diagnostic and therapeutic applications currently in development. The recent arrival of the component-resolved diagnosis, which uses molecular allergens, represents a unique opportunity to improve our understanding of the disease. Recombinant Fel d 1 is now available for in vitro diagnosis by the anti-Fel d 1 specific IgE assay. The first part of the review will seek to describe the recent advances related to Fel d 1 in terms of positive diagnosis and assessment of disease severity. In daily practice, anti-Fel d 1 IgE tend to replace those directed against the overall extract but is this attitude justified? We will look at the most recent arguments to try to answer this question. In parallel, a second revolution is taking place thanks to molecular engineering, which has allowed the development of various forms of recombinant Fel d 1 and which seeks to modify the immunomodulatory properties of the molecule and thus the clinical history of the disease via various modalities of anti-Fel d 1-specific immunotherapy. We will endeavor to give a clear and practical overview of all these trends.