Relapsing-remitting experimental allergic encephalomyelitis (R-EAE) is an animal model for multiple sclerosis (MS). Many potential immunomodulatory strategies for MS have been used first in EAE to assess their effectiveness. Recently, the injection of plasmid DNA has been shown to induce potent humoral and cellular immune responses. The primary aim of our experiments reported here was to determine if vaccination with cDNAs encoding myelin proteolipid protein (PLP) could prime for a PLP-specific immune response and affect subsequent R-EAE. We constructed cDNAs encoding whole PLP (pPLP_all) or encephalitogenic epitopes PLP_139–151 (pPLP_139–151) and PLP_178–191 (pPLP_178–191). Following DNA injection, we induced R-EAE in SJL/J mice using PLP_139–151 or PLP_178–191 peptides in adjuvant. All 3 plasmid constructs enhanced R-EAE induced with PLP_139–151 and injection of mice with pPLP_all increased R-EAE induced with PLP_139–151. DNA immunization induced higher PLP peptide-specific lymphoproliferative responses than did vector alone following R-EAE induction with IgGl or IgG2b antibody responses. These data suggest that DNA immunization of PLP can modulate immune responses, leading to enhancement of R-EAE.