Experimental Autoimmune Encephalomyelitis (EAE), also called Experimental Allergic Encephalomyelitis, is an animal model of Multiple Sclerosis. Animal models of human diseases are diseases of non-human species (often rodents) which closely resemble their human counterparts and are be studied with a view to better understanding and treating the human form. EAE is not multiple sclerosis, nor is it a single disease in a single species, but its different forms resemble the various forms and stages of MS very closely in a large number of ways.
EAE is an acute or chronic-relapsing, acquired, inflammatory and demyelinating autoimmune disease. The animals are injected with the whole or parts of various proteins that make up myelin, the insulating sheath that surrounds nerve cells (neurons). These proteins induce an autoimmune response in the animals – that is the animal’s immune system mounts an attack on its own myelin as a result of exposure to the injection. The animals develop a disease process that closely resembles MS in humans.
EAE has been induced in a number of different animal species including mice, rats, guinea pigs, rabbits, macaques, rhesus monkeys and marmosets. For various reasons including the number of immunological tools, the availability, lifespan and fecundity of the animals and the resemblance of the induced disease to MS, mice and rats are the most commonly used species.
The animals are in-bred to reliably produce susceptibility to EAE in the animals. As with humans and MS, not all mice or rats will have a natural propensity to acquire EAE. Moreover, different breeds will develop different forms of EAE, some of which act as good models for the different human forms of MS. Different EAE forms are also used as models for the different stages of MS.
Several proteins or parts of proteins (antigens) are used to induce EAE including: Myelin Basic Protein (MBP), Proteolipid Protein (PLP), and Myelin Oligodendrocyte Glycoprotein (MOG).
Researching EAE has a number of benefits:
Because EAE is an animal disease, it enables researchers (especially immunologists) to study demyelination (the process underlying the symptoms of MS) in ways that would not be morally acceptable in studies of MS in humans.
It allows researchers to test potential treatments for MS for their efficacy and safety without putting the lives of people at risk.
It allows researchers to experiment with different ways of inducing EAE to attempt to find potential causes of MS.
Because the generations times of most of the EAE species are short, and because they breed very fast, large populations of such animals can be turned over in short periods of time.
Researching EAE has a number of disadvantages:
EAE is not multiple sclerosis and a number of significant assumptions are made when proposing EAE as an animal model for MS.
It is undeniable that the animals involved suffer considerably – at the very least they are given the animal equivalent of MS – and questions about the ethics of EAE are inescapable.