However, in animals of susceptible MHC haplotypes (H-2 s,q,r,v,f,p ), the virus is cleared from neurons in the brain but persists in glial cells (Brahic et al., 1981; Rodriguez et al., 1983) and macrophages (Dal Canto and Lipton, 1982; Levy et al., 1992; Rossi et al., 1997) of the spinal cord white matter and brainstem (Fig. 6 ).