The molecular basis for demyelination induced by the neurotropic murine coronavirus JHM (JHMV or MHV4) is unknown. We have attempted to explore this issue by using neutralizing monoclonal antibodies specific for the major JHMV glycoprotein (E2) to select sets of neutralization resistant (NR) antigenic variant viruses. Monoclonal antibodies J.7.2 and J.2.2 bind to topographically distinct sites on E2. NR variants selected with J.7.2, like parental JHMV, predominantly cause a fatal encephalitis when given intracerebrally to mice, while J.2.2-selected NR variants cause a subacute disease characterized by paralysis and severe demyelination. We report here that consecutive selection with both J.2.2 and J.7.2 monoclonal antibodies results in NR variants which are markedly attenuated in both encephalitic potential and ability to induce demyelination. Analysis of the different variants suggests that the subregion of E2 bound by monoclonal antibody J.7.2 may be a critical viral determinant of paralysis and demyelination in this model system.