Monoclonal antibodies that recognize DIII alone are considered DIII specific. Monoclonal antibodies that recognized the E ectodomain but not DIII alone may contact residues that map to domain I or II or both, although cooperative contacts with DIII cannot be ruled out. Most of our 46 monoclonal antibodies recognized yeast that displayed the entire ectodomain of E ( Fig. 1a and Supplementary Table 1 online) . Sixteen antibodies recognized yeast that displayed DIII alone, and 10 of 12 strongly neutralizing antibodies localized to DIII. Only two neutralizing antibodies (E53 and E60) recognized the E ectodomain but not DIII alone.