Cross-reactivity between milk proteins from different animal species

Background Cow's milk allergy is quite frequent in the first years of human life. When breast-feeding is not possible, a cow's milk substitute must be provided for allergic subjects. Different alternatives to cow's milk have been suggested as protein sources (soy, hydrolysed proteins, goat's milk, e tc.), but all these dietetic solutions are not without risks for polyallerg ic or more sensitive subjects. Objective To obtain new information on the suitability of other mammalian m ilks for allergic children, we evaluated the cross-reactivity between milk proteins from different animal species. Methods Milk samples were analysed by sodium dodecyl sulphate polyacrylamid e gel electrophoresis (SDS-PAGE). To detect antibody-antigen complexes, imm unoblotting was performed by using sera from children allergic to cow's and ewe's milk (RAST class greater than or equal to 4) and monoclonal antibodi es (MoAb) specific for bovine proteins (caseins and beta-lactoglobulin). Results IgEs from children allergic to cow's milk are capable of recognizin g most part of milk proteins from mammals bred in European countries (ewe, goat, buffalo), while no serum used in this study contains IgEs reacting wi th camel's milk proteins. Camel's milk was also not recognized from circula ting IgEs from a child specifically allergic to ewe's milk. Specific antibo vine monoclonal antibodies cross-reacted with proteins from other mammalian species, apart from those of camel. Conclusions Homologies in amino acidic composition could justify the cross- reactivity observed between proteins from different animal species. On the other hand, the phylogenetic difference could be responsible for the failed recognition of camel's proteins by circulating IgEs and monoclonal antibod ies.