|KOO, HYE CHEONG|
|PARK, YONG HO|
|KWON, NAM HOON|
|HAMILTON, MARY JO|
Submitted to: Veterinary Immunology International Symposium
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2004
Publication Date: 7/26/2004
Citation: Koo, H., Davis, W.C., Park, Y., Kwon, N., Hamilton, M., Barrington, G.M., Dahl, J.N., Waters, W.R. 2004. Analysis of the immune response to m. avium subsp. paratuberculosis in experimentally infected calves and naturally infected cows with clinical symptoms [abstract]. Veterinary Immunology International Symposium. Paper No. WK.11.6.6:368.
Technical Abstract: Johne's disease of cattle is widespread and causes significant economic loss to producers due to increased food consumption, a decrease in milk production and poor health of affected animals. Control of the disease has been hindered by the lack of an effective vaccine and sensitive specific diagnostic assays that identify infected animals before they begin to shed bacteria. The present study was conducted to gain further insight into factors affecting the immune response to the causative agent, M. paratuberculosis (Map) and to determine if multicolor flow cytometry (FC) can be used to monitor the appearance of an immune response to Map. Neonatal calves (N = 5) were infected by the oral route and followed for 18 months using in vitro culture of antigen stimulated PBMC with FC, commercial IFN-g and serum ELISAs, and fecal culture. Uninfected calves (N = 3) were used as controls. A persistent proliferative response to PPD and soluble Map antigens was detected by 6 months by FC. CD4+ T cells with a memory phenotype (CD45R0+) expressing CD25 and CD26 were the predominant cell type responding to antigens. Few CD8+ proliferated in response to antigens at 6 or 12 months. However, a response was evident in some animals by 18 months. Although gd T cells comprised a large proportion of cells in cultures, especially in unstimulated cultures, they did not appear to be responding to antigen at 6 or 12 months. By 18 months, gd T cells exhibited and increase in expression of activation molecules ACT2 and CD26 in response to antigen or cytokines secreted by CD4+ T cells. The IFN-g assay yielded inconsistent results over time, with IFN-g detected in some cultures. The commercial ELISAs for Map have remained negative to 18 months. Fecal cultures have also remained negative. The studies presented here clearly show multicolor FC can be used to study the immune response to Map and also used as to detect animals infected with Map before they begin shedding bacteria.