CROSS-ANTIGENICITY OF HORSE SERUM-ALBUMIN WITH DOG AND CAT ALBUMINS -STUDY OF 3 SHORT PEPTIDES WITH SIGNIFICANT INHIBITORY ACTIVITY TOWARDS SPECIFIC HUMAN IGE AND TGG ANTIBODIES

Horse serum albumin is present in the near vicinity of the animal, whi le dog and cat serum albumins are very common allergens present in hou se dust. Human patients clinically defined as allergic to horse could react with horse serum albumin by means of IgE or IgG antibodies. Stud ies regarding the specificities of these antibodies by inhibition enzy me-linked immunosorbent assay (ELISA) and depletion experiments have d emonstrated that they are directed against dog serum albumin and cross -react not only with horse serum albumin but with other serum albumins from different origins. To investigate these observations further, we isolated and characterized three tryptic peptides(P1, P2 and P3) from horse serum albumin. The peptide pi contains loops 1 and 2 of the fir st domain, P2 is derived from loop 4 of the second domain, and P3 cont ains the disulphide loop 9 of the third domain. These were able to inh ibit the binding of the patients' IgE and IgG antibodies to horst albu min as well as to dog and cat serum albumins. This indicates that thes e peptides are involved in the observed cross-reactions, They also sha red common epitopes, as revealed by human IgE antibodies. After reduct ion and alkylation, they totally lost their inhibitory capacity, sugge sting that the intra-chain disulphide bridges, essential for the prese rvation of the loop structure, probably maintain their allergenic/anti genic reactivity.