Research Accomplishment Reports 2009

Interferon Gamma Regulation in the Foal

D.W. Horohov
Department of Veterinary Sciences

 

Non-Technical Summary

Respiratory diseases remain one of the major impediments to the equine industry. Young foals, in particular, suffer frequently and severely from viral and bacterial infections of the respiratory tract. Rhodococcus equi, in particular, remains the most common cause of subacute or chronic abscessating bronchopneumonia in young foals. Epidemiological and experimental data indicate foals less than 1 month of age are at greatest risk for infection.

The underlying hypothesis of this research project is that the decreased production of interferon-gamma by young foals contributes to their susceptibility to infection with Rhodococcus equi and other intracellular pathogens. We have already demonstrated that young foals are most deficient at interferon-gamma production at the time when R. equi exposure likely occurs. Here we propose to analyze cytokine mRNA expression in a large population of foals from multiple farms that have a high incidence of R. equi infections. We also will investigate possible approaches to enhance interferon-gamma production in the foal and thereby increase resistance to infection.

2009 Project Description

The vulnerability of foals to specific pathogens such as Rhodococcus equi is believed to reflect an innate immunodeficiency, the nature of which remains poorly understood. We have shown that very young foals exhibit a deficit in their ability to produce interferon-gamma (IFN-g), a key cytokine required for resistance to R. equi. This functional deficiency could contribute to the increased susceptibility of foals to R. equi infections.

2009 Impact

Given the central role dendritic cells (DC) play in regulating IFN-g responses, we propose that DC obtained from foals will have phenotypic and functional differences from those derived from adult horses. We have recently reported that monocyte-derived DC (MoDC) from foals differ from MoDC from adults. This functional immaturity of foal MoDC was evidenced by altered surface marker expression and decreased cytokine gene transcription. These functional deficiencies could contribute to the increased susceptibility of foals to R. equi infections.

2009 Publications

Merant, C., C. C. Breathnach, K. Kohler, C. Rashid, P. Van Meter, and D. W. Horohov. 2009. Young foal and adult horse monocyte-derived dendritic cells differ by their degree of phenotypic maturity. Vet Immunol Immunopathol 131:1-8.