Background
Fish is one of the most frequent causes of food-induced allergy
alongside cow’s milk, hen’s egg, peanut, tree nut and shellfish, and has
been included in the European mandatory labeling legislation together
with 13 other allergens1. Fish is a valuable source of
healthy nutrients such as omega-3 fatty acids with increasing global
demand. Fish allergy affects 0.1-0.4% of the world’s
population2,3, has an early onset and tends to persist
throughout life4. Allergic reactions are mainly
provoked through ingestion but also by skin contact or by inhalation of
fish steam during fish processing. The allergic reactions triggered by
fish can be life-threatening and even fatal resulting in a heavy
socioeconomic burden and negative impact on quality of
life5,6
β-parvalbumin represents the major fish allergen accounting for up to
90% of sensitization and has been described and characterized in a wide
range of fish species7-10. Parvalbumins are 8-12kDa
calcium-binding muscle proteins with extreme thermal stability and
shared 55-95% amino acid sequence homology among various fish species.
This might account for the cross-reactivity among fish species but case
reports have shown mono-sensitization and clinical allergy to single
fish species11,12. Alongside parvalbumin, collagen,
aldolase, enolase, pyruvate kinase, glucose-6-phosphate isomerase
(G-6-PI), creatine kinase, glyceraldehyde-3-phosphate dehydrogenase
(GAPDH), triosephosphate isomerase (TPI) and tropomyosin are other
registered fish allergens in the World Health Organization and
International Union of Immunological Societies (WHO/IUIS)
database13. Among these allergens, collagen, aldolase
and enolase are more well-characterized. Collagen is another heat stable
protein, with reports showing anaphylaxis provoked by collagen and
illustrating IgE binding to collagen only but not
parvalbumin14,15. Enolase and aldolase, on the other
hand, are identified as major heat-labile fish allergens in cod, salmon
and tuna16.
The current diagnostic workup of fish allergy relies on skin prick test
(SPT), measurement of specific IgE and when indicated, an oral food
challenge17. Although a number of fish extracts are
available on the ImmunoCAP platform, only parvalbumins from cod and
common carp are available for IgE testing and other identified fish
allergens have not been included for diagnosis due to the insufficient
understanding of their allergenic properties and clinical relevance
especially in the Asian populations with high fish consumption. Yet a
considerable number of studies have illustrated the low specificity of
SPT and specific IgE measurement while safety has always been a concern
in oral food challenges18. Together with the reports
of monosensitization to some fish species and parvalbumin-independent
IgE sensitization19, a testing panel inclusive of the
relevant fish allergens for precision component-resolve diagnosis (CRD)
will be of great value.
This study identified fish allergens of salmon (Salmo salar ) and
grass carp (Ctenopharyngodon idella ), which are among the most
commonly farmed and consumed seawater and freshwater fishes in Asia. We
compared the sensitization pattern towards the four major allergens,
β-parvalbumin, enolase, aldolase and collagen, from both salmon and
grass carp in fish allergic subjects from Hong Kong and Japan. Based on
our results, we further characterized the allergen profiles in salmon
meat cooked at the same core temperature by different methods to dissect
the link between dietary preferences and allergen sensitization
profiles.