Characterization of the interferon gamma response to Lawsonia intracellularis using an equine proliferative enteropathy challenge (EPE) model.

The research examines the interferon gamma response to Lawsonia intracellularis, a bacterium that causes proliferative enteropathy (an intestinal disease) in horses, using an infection model. The study identifies interferon gamma as likely playing a key role in protecting horses from this disease.

Lawsonia intracellularis and Equine Proliferative Enteropathy (EPE)

• The study focuses on Lawsonia intracellularis, a bacterium that causes a group of clinical diseases collectively known as proliferative enteropathy. These conditions are characterized by excessive growth of the intestinal lining and can include ailments such as ileitis and intestinal adenomatosis.
• Initially, Lawsonia intracellularis was recognized as a cause for proliferative enteropathy in pigs, but the research notes this bacterium as an emerging cause of the disease in other mammalian species, including horses.
• Equine proliferative enteropathy (EPE) has been reported globally. However, its definitive diagnosis is challenging and its epidemiology is not well understood. Notably, weanlings (young horses typically under a year old) seem to be the most susceptible to the infection, although the reasons for their particular vulnerability are not clear.

EPE Clinical Forms and IFN-γ Response

• Using an infection model for EPE, researchers found that the disease, similar to the porcine version, can manifest in three clinical forms: classical, subclinical, and acute.
• In a group of six weanlings, one showed signs of classic EPE, one developed acute EPE, and two developed subclinical EPE. No noticeable effect was observed when the weanlings were subjected to pharmacological stress using dexamethasone, a potent corticosteroid.
• Crucially, the study found that peripheral blood cells from the weanlings exhibiting clinical EPE showed a decreased expression of interferon-gamma (IFN-γ) following in vitro (in the lab) stimulation with Lawsonia intracellularis. In contrast, the weanlings not showing clinical disease symptoms generated a robust IFN-γ response.
• These findings suggest that IFN-γ, a cytokine crucial in host defense against viral and other infections, likely performs a significant role in protecting horses from diseases caused by Lawsonia intracellularis.