In silico and in vitro analysis of cross-reactivity between Yersinia pseudotuberculosis OmpF porin and thyroid-stimulating hormone receptor

This work is devoted to the ascertainment of serological cross-reactivity between OmpF porin from Yersinia pseudotuberculosis (YpOmpF) and human thyroid-stimulating hormone receptor (hTSHR). Extracts containing hTSHR were isolated from surgical thyroid tissue of patients with clinical and diagnostic signs of diffuse toxic goiter. Monoclonal antibodies to hTSHR (mAbs) were shown to interact both with antigens in thyroid tissue extracts and with YpOmpF. Models of spatial structures of trimer and monomer complexes of YpOmpF with antibodies to hTSHR were also constructed. According to the results of molecular modeling, YpOmpF, being in monomeric form, can, like hTSHR, interact freely with the mAbs. But when the porin trimer is formed the hydrophobic region that comprises in the porin-antibody interaction zone is closed. This circumstance as well as other spatial rearrangement of amino acid residues that determine the efficiency of binding prevents the interaction between YpOmpF trimer and monoclonal antibody to receptor. These in vitro and in silico results confirmed the existence of the phenomenon of molecular mimicry. Thus, an autoimmune disease of the thyroid gland (Graves' disease) that sometimes arises after suffering pseudotuberculosis may be the consequence of the structural and antigenic similarity between YpOmpF and hTSHR.