Evaluation of the host immune response to Mycobacterium avium subsp. paratuberculosis in naturally infected periparturient dairy cows

Abstract

Johne’s disease (JD) caused by Mycobacterium avium subsp. paratuberculosis (MAP), is estimated to infect more than 22% of US dairy herds. Periods of immunosuppression may contribute to the transition from the subclinical to clinical stage of infection. Understanding the effects of stressors such as parturition on the escalation of disease may provide information that will help manage JD. The objective of this study was to characterize cytokine gene expression and secretion in periparturient dairy cows naturally infected with MAP. Blood was collected from the jugular vein of healthy noninfected, and subclinically and clinically infected dairy cows for 3 wk preto 4 wk post-calving. Real-time PCR was performed to evaluate the expression of the following cytokine genes by peripheral blood mononuclear cells: IFN-γ, TNF-α, IL-12p35, IL-10, TGF-β, and IL-4. To assess the effects of parturient immunosuppression on cytokine gene expression, RT-PCR data were analyzed by using 2 values calibrated to dCt value at +1 d relative to calving for each animal. Department of Animal Science, Iowa State University, Ames, IA 50010. USDA-ARS, National Animal Disease Center, Ames, IA 50010. Primary Researcher and author. Author for correspondence.