Screening and identification of the mimic epitope of the adhesion protein of Mycoplasma genitalium.

Mycoplasma genitalium adhesion protein (MgPa) is the major adhesion protein of M. genitalium, and its C-terminal domain (amino acid 1075-1444) is the most immunogenic region. However, the exact epitopes of the adhesion protein of M. genitalium are still unclear. We used the purified polyclonal antibody against the recombinant adhesion protein to screen the mimic epitopes of MgPa using a random 12-peptide phage display library. Immunoscreening via the phage display peptide library revealed that 3 motifs (P-S-A-A/V-X-R-F/W-E/S-L-S-P, A-K-I/L-T/Q-X-T-L-X-L, and K-S-L-S-R-X-D-X-I) may represent 3 different mimotopes of MgPa. Results of bioinformatics analysis by MIMOX demonstrated that the key consensus amino acid residues in the aligned mimotopes may be S, A, and F for cluster 1; A, K, I, T, and L for cluster 2; and K, S, L, R, D, and I for cluster 3. Three representative phages could recognize sera from M. genitalium-positive patients to varying degrees, whereas they could not recognize the sera from Mycoplasma pneumoniae -positive patients or the sera from healthy people. These findings will help to clarify the mimic epitopes of MgPa to facilitate diagnosis of the antigen and to understand the antigenic structure of MgPa.