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

Abstract

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.

Keywords: Fel d 1; allergens; anti-Fel d1 IgY; blocking antibodies; cat allergies.

Figure 1

Multi‐disciplinary approach as proposed by AIRWAYS ICPs

Figure 2

Fel d 1 crystalline (A) and three‐dimensional (B) structures, showing four subunits composed of two covalently linked heterodimers containing two distinct chains. From https://www.rcsb.org/structure/2EJN, open source image

Figure 3

Beta‐hexosaminidase assay results from eggs from blocking experiments using eggs from chickens immunized to Fel d 1 to produce anti‐Fel d 1 IgY (immune) and eggs from the same chickens prior to Fel d 1 exposure (pre‐immune). β‐hexosaminidase levels are expressed as percentages of baseline levels from control samples incubated without antibodies

Figure 4

Reduction in salivary active Fel d 1 levels (µg/mL) in response to a diet with an egg product ingredient containing anti‐Fel d 1 IgY. The line with circle data points depicts data from the control diet group and the line with triangle data points depicts data from the test diet group. Asterisks denote statistical significance (P < .05) compared with baseline based on linear mixed model analysis (Source: CC‐BY‐NC Satyaraj et al, 2019136)

Figure 5

Active Fel d 1 levels (µg/g hair) means and SE across weeks. Means were significantly reduced from baseline at week 1 (P < .05) and weeks 3 through 10 (P < .001) using linear mixed effect models and P‐value adjustments using the single‐step method Columns with the lighter color denote values that were statistically different from baseline (Source: CC BY 3.0, Satyaraj et al, 2019137)

Figure 6

Change in active Fel d 1 (µg/g hair) means over time based on initial concentrations. Cats were divided into quartiles based on their baseline aFel d 1 levels and linear regression was used to estimate the initial level (intercept) and the change in aFel d 1 over time (slope). The graph represents a total of 1470 samples obtained during the 12‐week study. The slope of decline in aFel d 1 levels was significantly steeper for those cats in the highest quartile (P < .001) but did not differ among the three lower quartiles (P > .1) based on ANOVA with Tukey Post hoc Tests. Cats with the highest Fel d 1 production showed the greatest response to the intervention (Source: CC BY 3.0, Satyaraj et al, 2019137)