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 antisera directed against Amb a 5 or Amb t 5 show a high degree of species specificity, with little or no cross-reactivity between these two allergens, 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-2d), CBA (H-2k), C57BL/6 (H-2b), and A/J (H-2a). All four strains of mice responded to purified Amb a 5 and Amb t 5. Cross-reactivity was found at the T cell level between Amb a 5 and Amb t 5 in T cells from BALB/c, A/J, and CBA mice, but not in T cells from C57BL/6 mice. A T cell epitope from Amb a 5, residues 27-36 (PWQVVCYESS), was mapped using T cell hybridomas 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 and Amb t 5 were found to be involved in T cell reactivity. Conversion of disulfide bridges into free sulfhydryl (SH) forms was required for the response of T cell hybridomas to peptide t5 (residues 27-40) from Amb t 5. Reduction of peptide a4 (residues 21-37) from Amb a 5 was essential for inducing the cross-reactivity observed with Amb t 5-specific T cell hybridomas. It is concluded that free sulfhydryl groups play a major role in the T cell recognition of cross-reactivity T cell epitopes within these related allergens.
Zhu
X
X
ImmuLogic Pharmaceutical Corporation, Waltham, MA 02154, USA.
Greenstein
J L
JL
Rogers
B L
BL
Kuo
M C
MC
D000485:Allergens; D000595:Amino Acid Sequence; D000818:Animals; D052179:Antigens, Plant; D018604:Epitope Mapping; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000276:immunology*; D011058:Pollen; D013438:Sulfhydryl Compounds / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; D013438:Sulfhydryl Compounds; C069543:group 5 allergens, Ambrosia