Animal derived allergenic molecules Christiane Hilger Laboratory of Immunogenetics and Allergology CRP-Santé Luxembourg

Allergens are classified into families

Animal allergen families Tropomyosins Lipocalins PR-1 proteins Trypsin-like serine proteases EF hand domains Caseins Serum albumins Group 2 mite allergens Globins Lipases Phospholipases A

Allergen families: Tropomyosin Biochemical properties –Regulates muscle contraction, also present in non-muscle cells –Alpha-helical protein, MW kDa –Identified as food allergens in crustaceans, molluscs and the fish parasite Anisakis simplex –Identified as inhalant allergens in arthropods (mites, cockroaches) –Highly conserved molecules, frequent cross-sensitisations –Vertebrate tropomyosins seem to be non-allergic Examples –Der p 10, Bla g 7 –Pen a 1 (shrimp), Hel as 1 (snail), Hom a 1 (lobster) Rabbit tropomyosin dimer

Biochemical properties –Transporters for small hydrophobic molecules, such as lipids, steroids, odorants and pheromons –Low sequence identity between lipocalins –Eight-stranded anti-parallel  -barrel –Constitute the vast majority of mammalian dander allergens (inhalant allergen) –  – lactoglobulins of ruminants (food allergen) Examples –  – lactoglobulins: Bos d 5, –Mammalian dander : Can f 1, Can f 2, Fel d 4, Bos d 2, Equ c 1, Mus m 1, Rat n 1 –Group 13 mite allergens, cockroach Bla g 4 –Pigeon tick major allergen Arg r 1 systemic allergen Equ c 1 dimer Allergen families: Lipocalins

Biochemical properties –Ca 2+ binding proteins that share a 12 aa conserved calcium- binding loop, flanked by  -helices on both sides Examples –Parvalbumins: major allergens of fish (Gad c 1, Sal s 1) and amphibians (Ran e 1, Ran e 2) –Troponin C : group 6 allergens in cockroaches (Bla g 6) –Cattle: Bos d 3 (inhalant allergen) Allergen families: EF hand domain Carp parvalbumin Cyp c 1 dimer

Biochemical properties –Main plasma protein, MW 66 kDa –Binds water, cations, fatty acids, hormones, bilirubin, drugs –Regulates colloidal osmotic pressure of blood –Inhalant allergen of animal dander and saliva –Food allergen in meat, egg and milk Examples –Dander: Fel d 2, Can f 3, Equ c 3, Bos d 6, Gal d 5 –Food: Bos d 6, Gal d 5, PSA, SSA Serum albumins are minor allergens, but they are reponsible for large interspecies cross-sensitisations Allergen families: Serum albumins Human serum albumin dimer

Mammalian allergens: Felis domesticus Fel d 1: Tetramer formed by 2 heterodimers consisting each of chain 1 and 2; chains of 70 and 92 aa MW = 38 kDa glycosylated protein present in saliva 96% IgE positive (n=509), marker allergen Fel d 2:Serum albumin, 66 kDa present in saliva, dander, urine 17-35% IgE positive Cross-reactivities with Can f 3, Equ c 3, Sus sPSA, Bos d 6 Fel d 3:Cystatin, cysteine protease inhibitor, 98 aa, 11 kDa isolated from skin cDNA 10 % IgE positive

Mammalian allergens: Felis domesticus Fel d 4:Lipocalin, 171 aa, 19.7 kDa isolated from salivary gland 63 % IgE positive, low IgE values Homologies: Bos d 2, Can f 1, Equ c 1, Mus m1, Rat n 1 Fel d 5: IgA, MW = 400 kDa present in serum 38% IgE positive (n=81) Fel d 6:IgM, MW = 800 kDa present in serum Fel d 7:IgG, MW = 150 kDa present in serum

Mammalian allergens: Canis familiaris Can f 1: Lipocalin, MW = kDa present in dander, saliva % IgE positive Can f 2:Lipocalin, MW = 19 kDa present in dander, saliva % IgE positive Can f 3:Serum albumin, MW = 65 kDa present in dander, saliva, serum % IgE positive Cross-reactivities with Fel d 2, Equ c 3, Sus sPSA, Bos d 6 and other albumins Can f 4:N-terminal sequence known, 18 kDa 60 % IgE positive Can f 1 and 2 are available as recombinant molecules, but the combination of these 2 does not allow to diagnose all patients

Mammalian allergens: Bos domesticus Bos d 2: Lipocalin, MW = 20 kDa (former BDA 20) present in dander, inhalant allergen 100 % IgE positive Bos d 3:S100 calcium binding protein A7, MW = 11 kDa, present in dander, inhalant allergen Bos d 4: Alpha-lactalbumin, MW = 14.2 kDa present in milk, inhalant and food allergen % IgE positive (Europe) Bos d 5:Beta-lactoglobulin, MW = 18.3 kDa present in milk, inhalant and food allergen % IgE positive (Europe) Bos d 6:Serum albumin, MW = 67 kDa present in serum, milk, meat, dander, inhalant and food allergen 48 % IgE positive Cross-reactivities with other albumins

Poultry allergens: Gallus domesticus Gal d 1: Ovomucoid, Trypsin inhibitor, MW = 28 kDa % IgE positive Gal d 2:Ovalbumin, MW = 44 kDa 35 % IgE positive Gal d 3: Ovotransferrin, MW = 78 kDa 53 % IgE positive Gal d 4:Lysozyme, MW = 14 kDa % IgE positive Gal d 5:serum albumin, MW = 69 kDa, formerly alpha-livetin present in serum, meat, dander and egg yolk responsible for bird - egg syndrome Gal d apovitellin: MW = 9 kDa 23 % IgE positive Gal d 1 to Gal d 4 are food allergens of the egg white

Arthropod food and inhalant allergens: Crabs, Shrimps, Lobster Cockroaches, Mites, Midges Tropomyosins are highly cross-reactive molecules found in different arthropod and mollusc species: Food allergens Pen a 1: Penaeus aztecus, brown shrimp Pan s 1:Panulirus stimpsoni, spiny lobster Cha f 1:Charybdis feriatus, crab Inhalant allergens Bla g 7:Blattella germanica, German cockroach Der p 10:Dermatophagoïdes pteronyssinus, Europ house dust mite Chi k 10:Chironomus kiiensis, midge. And many others ….