Epitope mapping of immunogenic and adhesive structures in repetitive domains of Mycoplasma bovis variable surface lipoproteins

The family of variable surface lipoproteins (Vsps) of the bovine pathogen i l Mycoplasma bovis includes some of the most immunogenic antigens of this m icroorganism. Vsps were shown to undergo high-frequency phase and size vari ations and to possess extensive reiterated coding sequences extending from the N-terminal end to the C-terminal end of the Vsp molecule. In the presen t study, mapping experiments were conducted to detect regions with immunoge nicity and/or adhesion sites in repetitive domains of four Vsp antigens of M. bovis, VspA, VspB, VspE, and VspF, In enzyme-linked immunosorbent assay experiments, sera obtained from naturally infected cattle showed antibodies to different repeating peptide units of the Vsps, particularly to units R( A)1, R(A)2, R(A)4.1, R(B)2,1, R(e)1, and R(F)1, all of which were found to contain immunodominant epitopes of three to seven amino acids, Competitive adherence trials revealed that a number of oligopeptides derived from vario us repeating units of VspA, VspB, VspE, and VspF partially inhibited cytoad hesion of M. bovis PG45 to embryonic bovine lung cells, Consequently, putat ive adherence sites were identified in the same repeating units (R(A)1, R(A )2, R(A)4.1, R(B)2.1, R(E)1, and R(F)1) and in R(F)2, The positions and len gths of the antigenic determinants were mostly identical to those of adhesi on-mediating sites in all short repeating units, whereas in the considerabl y longer R(F)1 unit (84 amino acid residues), there was only one case of id entity among four immunogenic epitopes and six adherence sites. The identif ication of epitopes and adhesive structures in repetitive domains of Vsp mo lecules is consistent with the highly immunogenic nature observed for sever al members of the Vsp family and suggests a possible function for these Vsp molecules as complex adherence-mediating regions in pathogenesis.