Three-dimensional model of the capsid proteins of two biologically different Theiler virus strains: clustering of amino acid difference identifies possible locations of immunogenic sites on the virion.

To explore structural features of the Theiler murine encephalomyelitis virion, we have constructed a three-dimensional model of the capsid proteins (VP1, VP2, and VP3) of the BeAn strain based on the atomic coordinates of the closely related Mengo virus. By superimposition of amino acid differences between BeAn virus and another Theiler virus strain, GDVII, on the three-dimensional model, clusters of differences were found in four distinct sites; the VP1 third corner, the VP2 "puff," and the VP3 first corner and "knob." These clusters, which are found on the surface of the virion, may represent neutralizing immunogenic sites that have come under selective pressure from neutralizing antibodies. Furthermore, the putative viral receptor binding site ("pit") of the two Theiler virus strains was found to be markedly conserved.