MAPPING OF MURINE TH1 AND TH2 HELPER T-CELL EPITOPES ON FIMBRIAE FROM PORPHYROMONAS-GINGIVALIS

Th1- and Th2-derived cytokine production in response to synthetic peptides of the fimbrial subunit protein (fimbrilin) from Porphyromonas gingivalis strain 381 was assessed in spleen mononuclear cells (MNC) of BALB/c mice (H-2(d) haplotype) immunised with the fimbrial protein antigen and adjuvant GM-53 in Freund's incomplete adjuvant (FIA). Sixty-seven sequential overlapping 10-mer peptides covering the complete 337 amino-acids (AA) protein of P. gingivalis fimbrilin were synthesised. Stimulation of spleen MNC in vitro with these 10-mer peptides resulted in the production of murine interleukin-2 (IL-2), gamma-interferon (IFN-gamma), IL-4, IL-5 and IL-6. Peptides 13 (AA 61-70), 24 (AA 116-125), 31 (AA 151-160) and 64 (AA 316-325) markedly induced IL-2 production. In particular, peptide 24 (DPLKIKRVHA), which contained I-A(d), I-E(d) and I-A(k) binding motifs, was the most potent stimulator of IL-2, IFN-gamma, IL-4, IL-5 and IL-6 production. Spleen MNC from C3H/HeN mice (H-2(k)) followed by BALB/c mice (H-2(d)) immunised with peptide 24 were high responders to peptide 24 in terms of both IFN-gamma and IL-4 production, whereas A/J mice (H-2(a)) and C57BL/6 mice (H-2(b)) were very low responders, P. gingivalis fimbriae evoked higher delayed-type hypersensitivity (DTH) reactions in B10.D2 (H-2(d)) and B10.BR (H-2(k)) mice followed by C57BL/10 (B10, H-2(b)) and B10.A (H-2(a)) and in guinea-pigs immunised with the fimbriae and GM-53 in FIA. Thus, the Th1 and Th2 helper T cell cytokine-producing responses and the DTH reactions to P. gingivalis fimbriae in mice are restricted by H-2 haplotype and the amino-acid sequence (AA 116-125) within the fimbrial protein molecule acts as a common stimulator of cytokine production in both Th1 and Th2 cells.