Background and purpose: Molecular mimicry was found in the case of Citrobacter braakii O37, which shares epitopes with human erythrocytes. It is believed that erythrocyte-membrane proteins band 3 and glycophorin A (GPA) have common epitopes. Band 3 was recognized by the anti-C. braakii O37 lipopolysaccharide antibodies (LPS-Abs) purified on LPS-affinity columns. This study aimed to investigate the role of GPA in this molecular mimicry.
Methods: Immunochemical methods such as immunoblotting, enzyme-linked immunosorbent assay, inhibition of hemagglutination, and affinity columns were employed.
Results: GPA when immobilized in an affinity column could purify specific GPA antibodies (GPA-Abs) from whole anti-C. braakii O37 serum. The purified antibodies, in turn, recognized GPA in immunoblotting tests. Treatment of human erythrocytes with sialidase significantly improved the hemagglutination titer by GPA-Abs. Furthermore, hemagglutination was inhibited to a greater extent by asialo-GPA than by the native form. GPA from blood groups M and N could similarly inhibit hemagglutination, and the most significant inhibition was recorded by GPA from the blood group MN. GPA-Abs could not recognize the LPS from C. braakii O37.
Conclusions: Results confirmed that an antibody population in the anti-C. braakii O37 serum recognized GPA. However, there was no reactivity with LPS of C. braakii O37, indicating that the antibodies may be produced against the outer membrane protein of the bacteria.