Characterisation of allergens in pilchard, responsible for the development of occupational allergy in the seafood processing industry in the Western Cape

Abstract

The increase in popularity of fish, coupled with technological advances in the fishing industry and changes in the control and management of fishing resources, has led to a significant increase of fish processing workers from 13 million in 1970 to 38 million in 2002. Whereas allergic reactions to fish proteins were previously only documented in consumers, increasing reports of occupational fish allergies of fish processing workers has become evident. In South Africa, the reported prevalence of occupational asthma associated with fish processing workers is 2 - 8%, and the prevalence of occupational protein contact dermatitis 3 - 11%. Pilchard is one of the most consumed fish species in South Africa and the immunological analysis of this species will therefore contribute to the provision of occupational health services in the pilchard processing industry. Proteins extracted from fresh, frozen and canned pilchard (Sardinops sagax), as well as fresh samples of six other processed and consumed South African fish were characterised by denaturing protein electrophoresis and immunoblotted with different monoclonal and polyclonal antibodies. Sera from sensitised workers were subsequently used to characterise the membrane-bound pilchard proteins and analysed for human Immunoglobulin G (lgG) and Immunoglobulin E (IgE) antibodies to determine antigen recognition. A protein of 12 kDa molecular weight was found to be present in all fish protein extracts, however, at various concentrations. With the aid of the monoclonal and polyclonal antibodies, the 12 kDa protein was postulated to be parvalbumin, a known allergen in some fish species. Immunoblotting experiments for the identification of workers' IgG- and IgE-reactivities to fresh, frozen and canned pilchard showed a 12 kDa protein as an immunolgically reactive fish protein. This protein was also found to occur in dimeric, trimeric and tetrameric forms, which may have significant implications in the diagnosis and management of occupational sensitisation to pilchard.