Goat milk with different α S2-casein content: analysis of allergenic potency by REAST-inhibition assay

Abstract

In goat at CSN1S2 locus, seven alleles have been observed, characterized by different levels of expression, and, in particular, a null allele CSN1S2 O that significantly influences protein composition of milk. In a local goat breed reared in the North East of Sicily, “Argentata dell’Etna”, the combined use of electrophoretic milk analysis (SDS-PAGE) and 11th exon genomic analysis (PCR-RFLP) made it possible to identify three genotypes respectively normal (CSN1S2 NN), heterozygote for the null allele (CSN1S2 NO) and homozygote for the null allele (CSN1S2 OO). In 214 “Argentata dell’Etna” goats, CSN1S2 O allele has shown a frequency of 0.033. An immunological test, REAST-inhibition assay (REAST, reverse enzyme allergo sorbent test), was carried out on three lyophilized milk samples (casein and seroprotein fractions) produced by goats with different genotypes at CSN1S2 locus, in order to assess their allergenic potency. By comparing the C 50, the casein fraction CSN1S2 NN turned out to be the most allergenic, followed by the fraction CSN1S2 OO with 60% potency compared to the first one, while the fraction CSN1S2 NO presented 54% potency compared to the first one.