Lawsonia intracellularis-specific interferon γ gene expression by peripheral blood mononuclear cells in vaccinated and naturally infected foals.

This research focuses on the immune responses to Lawsonia intracellularis, a bacterium which causes equine proliferative enteropathy (EPE), in vaccinated and naturally infected foals. The study found that vaccinated foals have a higher expression of the interferon (IFN)-γ gene, which is critical to immune responses, compared to non-vaccinated foals.

Study Aim and Methodology

• The objective of this study was to understand the cell-mediated immune response of foals to Lawsonia intracellularis —a bacterium that causes EPE— after vaccination or natural infection.
• The researchers assessed gene expression of IFN-γ, a type of interferon protein that plays a critical role in inducing and modulating an array of immune responses, in peripheral blood mononuclear cells of foals.
• Cell samples were collected from both vaccinated (6 in total) and control (non-vaccinated) foals (6 in total) every 30 days over a 180-day period after the first vaccination.
• In addition, cell samples were also taken from clinically affected foals (16 in total) within 7 to 10 days of EPE diagnosis.

Results and Findings

• Absence of disease in vaccinated foals and presence of antibodies against the pathogen (seroconversion) was observed in 5 out of the 6 vaccinated foals between 60 and 90 days after the first vaccine administration.
• The seroconverted foals remained seropositive (presence of antibodies) for the remaining study period.
• It was observed that all vaccinated foals had a significantly higher (P<0.05) IFN-γ gene expression on days 60-180 after the first vaccine administration compared to IFN-γ gene expression in control (unvaccinated) foals.
• However, when comparing IFN-γ gene transcription between foals suffering from natural infection and vaccinated ones, a significant difference (P<0.05) was only noticed on the first day of the study (day zero).

Interpretation of Findings

• The results suggest that vaccination against Lawsonia intracellularis triggers an immune response in foals that is characterized by high IFN-γ gene expression.
• This elevated IFN-γ level plays a protective role and may therefore contribute to the foals’ resistance against EPE.
• The fact that no significant difference was found in gene expression between naturally infected foals and vaccinated ones after the first day suggests that both groups initiate a similar immune response after initial exposure to the bacterium.
• Though more research is needed to understand the natural progression of the disease and design optimal vaccination strategies.