EAE models of neuropathic pain in multiple sclerosis do not require pertussis toxin

Experimental autoimmune encephalomyelitis (EAE) is a preclinical model of multiple sclerosis (MS), typically induced with two inoculations of myelin oligodendrocyte glycoprotein (MOG_35-55) emulsified in complete Freund's adjuvant (CFA), and supplemented with pertussis toxin (PTX). Although PTX has been considered essential, recent studies suggest that EAE pathology can develop without it.

Indices of clinical disease and neuropathic pain were evaluated in a conventional model of EAE that included PTX (EAE-PTX) and one that lacked PTX (EAE-nPTX), as well as in multiple control groups that lacked MOG_35-55 (CFA-PTX and CFA-nPTX).

A battery of behavioral tests were used to evaluate motor dysfunction and hypersensitivity to mechanical, cold, and heat stimuli with a repeated-measures design in male and female C57BL/6 mice. One month after the first EAE inoculation, fluoromyelin staining was used to evaluate demyelination in spinal cord, cortex, and peripheral nerve, while ATF3 was used as a marker of injury in sensory neurons of lumbar L4-L5 dorsal root ganglia (DRG).

Compared to CFA-PTX and CFA-nPTX controls, both EAE-PTX and EAE-nPTX groups developed motor dysfunction, behavioral hypersensitivity, and demyelination in ventral spinal cord but not cortex. Spinal demyelination was greater in EAE-nPTX than in EAE-PTX. ATF3 was detected in lumbar DRG of all EAE and CFA control groups, suggesting that systemic inflammation, rather than MOG_35-55-driven neuropathology, contributes to neuron damage.

PTX is not required for the manifestation of motor dysfunction and neuropathic pain in MOG_35-55-based EAE models. Newer EAE-nPTX models have the distinct advantage of mimicking MS disease while avoiding confounding effects of pertussis toxin.