Experimental allergic encephalomyelitis and vaccination-induced resistance in DA rats

In this report, we show that DA rats (RT1a haplotype) immunized with myelin basic protein (MBP)-CFA develop and recover from an ascending paralysis, with the course and severity of clinical disease similar to the kinetics observed with MBP-CFA-immunized Lewis rats. Experimental allergic encephalomyelitis (EAE) can be adoptively transferred with MBP-stimulated immune spleen cells, with onset of paralysis 4 days following transfer and complete recovery 3-4 days later. To determine if the vaccination-induced resistance response could develop in the DA rat strain, which has previously been shown to occur only in the Lewis rat, we selected a MBP-specific T-cell line by standard methods from DA rats immunized previously with MBP-CFA. The DA T-cell line was encephalitogenic, and DA recipients developed and recovered from T-cell line-mediated paralytic disease. Following recovery from T-cell line-mediated disease, DA recipients were resistant to subsequent disease induction following MBP-CFA challenge, a response consistent with T-cell vaccination, as observed previously in Lewis rats. Analysis of the proliferative response of the DA T-cell line showed that the encephalitogenic fragment was within the 40-67 region of MBP, with no response to the 85-97 fragment. The 85-97 fragment, which is a minor encephalitogenic determinant for the Lewis strain, also appears to be a minor encephalitogenic epitope for DA rats. These results show that the vaccination-induced resistance response occurs in the DA rat strain and that this phenomenon is not unique to the Lewis rat model.