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Our vaccine is designed to treat and prevent infection by Mycobacterium avium subspecies paratuberculosis (MAP) which is known to cause the systemic infection and the chronic inflammation of the gut seen in many farm animals such as cattle (where it is known as Johne’s disease; JD), sheep and deer and in many wild animals such as foxes and badgers. It is our belief that MAP is also responsible for the chronic and gross inflammation of the gut and dysregulation of the immune system seen in patients with Crohn’s disease (CD).


MAP does not directly cause the gross inflammation seen in Crohn’s disease by taking the immune system on head-to-head. In fact, it minimises its own recognition by hiding inside human cells that it has infected and surrounding itself with a protective coating. That is, MAP has its own “stealth” system that makes it difficult for the immune system to see and destroy it.

Nevertheless, it initiates a cascade of events with disastrous consequences. Firstly, it damages the delicate but very important nerves in the gut. Secondly, the dysregulation of the immune system that it brings about destabilises the gut wall, rendering it leaky. This allows the gut wall to be penetrated by other gut organisms such as bacteria, yeasts and viruses from the gut lumen, together with irritant or allergic food residues. It is the disorganised response to these secondary invaders and irritants that causes the various segments of the massive inflammatory response characteristic of the pathologies seen in CD in humans.

MAP is an extremely difficult organism to isolate and culture – which is part of the reason why the idea of MAP being implicated in CD has taken so long to be seriously considered by gastroenterologists. In recent years, MAP has been shown to be present by testing for its DNA using PCR (polymerase chain reaction) technology. This work has indicated that MAP is present in up to 92% of patients with CD (Bull et al; 2003). A simple yet elegant test that allows MAP to be seen in situ in tissue has now been developed by Prof Hermon-Taylor and is currently undergoing final testing. To date, this test shows that all CD patients are infected with MAP.

The main reservoir of MAP infection in humans is farm animals, especially dairy cows, where it can live in the animal for many years without causing clinical disease; a state known as “subclinical infection”. Conventional vaccines against MAP used to treat JD in cattle can reduce but do not stop the shedding of MAP from livestock onto the ground where MAP can enter the water table. MAP is also present in the milk we drink as it is able to withstand the normal pasteurisation processes used to kill other forms of mycobacteria.