Clinical, immunohistochemical, and pathological assessment of a mouse model of experimental autoimmune encephalomyelitis induced by a eukaryotic RpfE-MOG(35-55)-expressing plasmid

Abstract

Background Experimental Autoimmune Encephalomyelitis (EAE) is the most widely used animal model for investigating the pathogenesis of Multiple Sclerosis (MS). However, conventional EAE induction protocols are often labor-intensive and costly. Therefore, developing a simplified and cost-effective method for EAE induction would be valuable for experimental studies. Methods and Results In this study, we established a novel approach for inducing chronic EAE in C57BL/6J mice using a eukaryotic plasmid system. In this method, Resuscitation-promoting factor-E (RpfE), serving as an adjuvant, and Myeline oligodendrocyte glycoprotein (MOG((35-55))), acting as a neuro-antigen, were cloned into pcDNA3.1(+) IRES GFP vector. Mice received two doses of plasmids on the 1st and 7th days of the experiment as follows: group A, 16-16 & micro;g; group B, 32 -16 & micro;g; group C, 32-32 & micro;g; group D, 64-64 & micro;g; and group E served as the control group. Clinical scores were monitored over 9 weeks post-immunization. Significant differences were observed in both severity and timing of peak inflammatory responses among the groups. Histopathological analysis of central nervous system (CNS) tissues demonstrated variable degrees of demyelination and immune cell infiltration, including CD4(+), CD8(+), and CD20(+) cells. The 64-64 & micro;g dose of recombinant plasmid resulted in higher CD4(+) and CD20(+) cell accumulation, reduced demyelination, and delayed disease onset (week 5), whereas the 32-32 & micro;g dose induced greater CD8(+) cell infiltration, more extensive demyelination, and earlier onset (week 4). Conclusions These findings demonstrate that different doses of the RpfE-MOG((35-55)) recombinant plasmid can induce distinct clinical and pathological features of EAE. This plasmid-based approach represents a flexible, reproducible, and cost-effective alternative method for chronic EAE induction in mice.