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Published on: July 11, 2015
Evidence for a novel gene expression program in peripheral blood mononuclear cells from Mycobacterium avium subsp.
Paul M Coussens1, Christopher J Colvin, Guilherme J M Rosa
1Department of Animal Science and Center for Animal Functional Genomics, Michigan State University, East Lansing, Michigan 48824, USA. coussens@msu.edu
Insights
Johne's disease alters gene expression in cow immune cells. Peripheral blood mononuclear cells (PBMCs) from infected cows show distinct gene expression profiles compared to healthy controls, even without stimulation.
Area of Science:
- Immunology
- Genomics
- Veterinary Medicine
Background:
- Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis, is a chronic infectious disease in ruminants.
- Understanding host immune responses at the gene expression level is crucial for developing diagnostic and therapeutic strategies.
Purpose of the Study:
- To compare gene expression profiles in peripheral blood mononuclear cells (PBMCs) of Johne's disease-positive and control cattle.
- To identify specific genes and pathways affected by Mycobacterium avium subsp. paratuberculosis infection and in vitro stimulation.
Main Methods:
- Utilized a bovine-specific cDNA microarray to analyze gene expression in PBMCs from infected and control Holstein cows.
- Compared gene expression following in vitro stimulation with Mycobacterium avium subsp. paratuberculosis versus phosphate-buffered saline (nil-stimulation).
- Employed mixed-model analysis for gene expression patterns and quantitative real-time reverse transcriptase PCR for validation.
Main Results:
- Mycobacterium avium subsp. paratuberculosis stimulation significantly altered the expression of 16 genes in infected cow PBMCs, including gamma interferon.
- Gene expression patterns differed significantly between infected and control cows, irrespective of in vitro stimulation.
- 86 genes were differentially expressed in stimulated PBMCs from infected cows compared to controls; 110 genes were differentially expressed in nil-stimulated cells.
Conclusions:
- Johne's disease infection fundamentally alters the gene expression program of bovine PBMCs.
- Significant differences in gene expression exist between infected and uninfected cows, even in unstimulated cells.
- These findings provide insights into the host's molecular response to Mycobacterium avium subsp. paratuberculosis infection.
Abstract:
A bovine-specific cDNA microarray system was used to compare gene expression profiles of peripheral blood mononuclear cells (PBMCs) from control uninfected (n = 4) and Johne's disease-positive (n = 6) Holstein cows. Microarray experiments were designed so that for each animal, a direct comparison was made between PBMCs stimulated in vitro with Mycobacterium avium subsp. paratuberculosis and PBMCs stimulated with phosphate-buffered saline (nil-stimulated PBMCs). As expected, M. avium subsp. paratuberculosis stimulation of infected cow PBMCs enhanced expression of gamma interferon transcripts. In addition, expression of 15 other genes was significantly affected (>1.25-fold change; P < 0.05) by in vitro stimulation with M. avium subsp. paratuberculosis. Similar treatment of control cow PBMCs with M. avium subsp. paratuberculosis resulted in significant changes in expression of 13 genes, only 2 of which were also affected in PBMCs from the infected cow PBMCs. To compare gene expression patterns in the two cow infection groups (infected cows and uninfected cows), a mixed-model analysis was performed with the microarray data. This analysis indicated that there were major differences in the gene expression patterns between cells isolated from the two groups of cows, regardless of in vitro stimulation. A total of 86 genes were significantly differentially expressed (P < 0.01) in M. avium subsp. paratuberculosis-stimulated PBMCs from infected cows compared to expression in similarly treated PBMCs from control cows. Surprisingly, a larger number of genes (110 genes) were also found to be significantly differentially expressed (P < 0.01) in nil-stimulated cells from the two infection groups. The expression patterns of selected genes were substantiated by quantitative real-time reverse transcriptase PCR. Flow cytometric analysis indicated that there were no gross differences in the relative populations of major immune cell types in PBMCs from infected and control cows. Thus, data presented in this report indicate that the gene expression program of PBMCs from M. avium subsp. paratuberculosis-infected cows is inherently different from that of cells from control uninfected cows.
