Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2008
Publication Date: 2/16/2008
Citation: Karcher, E.L., Beitz, D.C., Stabel, J.R. 2008. Modulation of Cytokine Gene Expression and Secretion During the Periparturient Period in Dairy Cows Naturally Infected with Mycobacterium avium subsp. paratuberculosis. Veterinary Immunology and Immunopathology. 123(3-4):277-288. Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. Clinical signs of disease may be precipitated by stressors such as parturition, heavy lactation, concomitant viral or bacterial infections, and malnutrition. It is well known that parturition causes cows to become immunosuppressed and makes them more susceptible to infections such as mastitis and metritis as well as other viral and bacterial pathogens. The present study was designed to evaluate the effects of the periparturient period on host immunity in healthy cows and naturally infected cows with paratuberculosis. Parturition decreased host immunity in cows regardless of infection status. In addition, paratuberculosis resulted in changes in host immunity compared to healthy noninfected cows. These results suggest that the periparturient period is a highly significant period for the dairy cow and may result in increased susceptibility to infectious diseases.
Technical Abstract: Modulation of cytokine gene expression and secretion during the periparturient period in dairy cows naturally infected with Mycobacterium avium subsp. paratuberculosis Technical 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, typically seen at parturition, may contribute to the transition from the subclinical, or asymptomatic, to the clinical stage of infection. Understanding the effects of stressors 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. Twenty-two multiparous Holstein cows were placed into 3 groups consisting of 5 noninfected healthy cows, 12 subclinical cows, and 5 clinical cows. Blood was collected from the jugular vein for 3 wk pre- to 4 wk post- calving. Peripheral blood mononuclear cells (PBMC) were isolated from the buffy coat fractions of blood and cultured for 24 h with and without concanavalin A (ConA). At 24 h, RNA was extracted from both nonstimulated and ConA-stimulated cells and converted to first-strand cDNA. Real-time PCR was performed on each sample to evaluate the expression of the following genes: IFN-gamma, TNF-alpha, IL-12, IL-10, TGF-beta, IL-4, and beta-actin gene. All reactions were performed in triplicate, and RT-PCR data were analyzed by using 2-ddCt values calibrated to dCt value at +1 d for each animal and Proc Mix procedure of SAS. Analysis of beta-actin within each infection group revealed a day relative to calving effect for clinical cows. Therefore, only control and subclinical cow mRNA cytokine expression was evaluated with RT-PCR. Across the periparturient period, expression of all cytokine mRNA did not differ between nonstimulated and ConA-stimulated PBMCs isolated from subclinical and control cows. Expression of IFN-gamma, TNF-alpha, IL-4, and IL-10 declined at calving compared with prepartum values in both treatment groups. In contrast, IGF-1 mRNA expression increased rapidly at parturition followed by a decline during first 7 d postpartum. PBMC isolated from naturally infected cows secreted higher concentrations of IFN-gamma, IL-10, and TGF-beta in the postpartum period, but minimal effects on cytokine gene expression were noted because of MAP infection. There was no interaction between MAP infection and parturition on serum progesterone or 17beta-estradiol concentrations, but both values rapidly declined for all cows as parturition approached. These data suggest that parturition is a very dynamic time period for host immunity, with great potential for altered immunity to hinder the ability of dairy cows to thwart infectious diseases.