T-CELL EPITOPE MAPPING OF RAGWEED POLLEN ALLERGEN AMBROSIA-ARTEMISIIFOLIA (AMB-A-5) AND AMBROSIA-TRIFIDA (AMB-T-5) AND THE ROLE OF FREE SULFHYDRYL-GROUPS IN T-CELL RECOGNITION

Ambrosia artemisiifolia (Amb a 5; Ra5S) and Ambrosia trifida (Amb t 5; Ra5G) are homologous allergens purified from short and giant ragweed pollen, respectively. Allergic human sera and hyperimmunized animal an tisera directed against Amb a 5 or Amb t 5 show a high degree of speci es specificity, with little or no cross-reactivity between these two a llergens, suggesting that the major Ab binding epitopes of Amb a 5 and Amb t 5 are distinct. Overlapping synthetic peptides derived from the allergen sequences were used to investigate the specificity of T cell responses in four strains of mice, BALB/c (H-2(d)), CBA (H-2(k)), C57 BL/6 (H-2(b)), and A/J (H-2(a)). All four strains of mice responded to purified Amb a 5 and Amb t 5, Cross-reactivity was found at the T cel l level between Amb a 5 and Amb t 5 in T cells from BALB/c, A/J, and C BA mice, but not in T cells from C57BL/6 mice, A T cell epitope from A mb a 5, residues 27-36 (PWQVVCYESS), was mapped using T cell hybridoma s from BALB/c mice, A T cell epitope in Amb t 5 was mapped in the same strain to residues 24-34 (KYCVCYDSKAI), Disulfide bonds in Amb a 5 an d Amb t 5 were found to be involved in T cell reactivity, Conversion o f disulfide bridges into free sulfhydryl (SH) forms was required for t he response of T cell hybridomas to peptide t5 (residues 27-40) from A mb t5. Reduction of peptide a4 (residues 21-37) from Amb a 5 was essen tial for inducing the cross-reactivity observed with Amb t5-specific T cell hybridomas. It is concluded that free sulfhydryl groups play a m ajor role in the T cell recognition of cross-reactivity T cell epitope s within these related allergens.