Hornet venom allergen antigen 5, Dol m 5: its T-cell epitopes in mice and its antigenic cross-reactivity with a mammalian testis protein.

BACKGROUND: A major venom allergen of white-faced hornet (Dolichovespula maculata) is antigen 5, Dol m 5. It is a 204-residue protein having 23% to 35% sequence identity with several proteins from diverse sources. The biologic function of antigen 5 and its sequence-related proteins is not known.
OBJECTIVE: This study was done to delineate the T-cell epitopes of Dol m 5 and to test their cross-reactivity with a sequence-related mouse testis protein, tpx.
METHODS: T-cell epitope mapping and cross-reactivity were studied with 15- or 20-residue peptides by their stimulation of spleen cells from mice immunized with recombinant Dol m 5 or tpx fragments.
RESULTS: Three of 20 peptides studied were found to represent major T-cell epitopes of Dol m 5, being recognized by five or all of six mouse strains tested. One major epitope peptide, residue 176-195, showed cross-reactivity in BALB/c mice with the homologous antigen 5s from yellow jackets and wasps, as well as with mouse tpx. The cross-reactivity of Dol m 5 and mouse tpx is not reciprocal because spleen cells from tpx-immunized mice were stimulated by the hornet peptide, but cells from Dol m 5-immunized mice were not stimulated by the corresponding tpx peptides.
CONCLUSION: Cross-reactivity of vespid antigen 5 and mouse tpx may be of importance in insect allergy because human and mouse testis proteins are highly homologous.