Gene Expression Profiling Reveals New Pathways and Genes Associated with Visna/Maedi Viral Disease

Abstract

Visna/Maedi virus (VMV) is a lentivirus that infects the cells of the monocyte/macrophage lineage in sheep, goats and wild ruminants. Infection with VMV causes a multisystemic inflammatory disorder, which includes pneumonia, encephalitis, mastitis or arthritis. The immune response to VMV infection is complex, and the infection and pathogenesis of this virus are not totally characterized yet. In this work, a gene expression microarray was used to identify the differentially expressed genes in VMV infection and disease development by comparing sheep with different serologic status and with presence of VM-characteristic clinical lesions. The expression profile analysis has revealed many interesting genes that may be associated with the viral infection process. Among them, the OXT gene appeared significantly up-regulated, so the oxytocin-secreting system could play an essential role in VM disease. Moreover, some of the most significantly enriched functions in up-regulated genes appeared the complement pathway, which (in combination with the Toll-like receptor signaling network) could compose a mechanism in the VMV pathogenesis. Identifying the host genetic factors associated with VMV infection can be applied to develop strategies for preventing infection and develop effective vaccines that lead to therapeutic treatments.

Keywords: Visna/Maedi; expression profiling; infection; microarray; pathogenesis; sheep.

Figure 1

Heat-map of the most significant up- and down-regulated genes in the Lesions group relative to the Seronegative or Asymptomatic group. A blue color indicates genes’ down-regulation while a yellow color indicates genes’ up-regulation. The color intensity from blue to yellow indicates the gene expression levels.

Figure 2

Expression of the selected 26 genes in a. Lesions group relative to Seronegative group b. Lesions group relative to Asymptomatic group measured by microarray and RT-qPCR. Bars represent the difference in Fold Change between groups of animals compared. Fifteen animals were included in the expression microarray and 18 animals in the RT-qPCR analysis. Statistically significant differences in the expression measured by RT-qPCR of the indicated genes are showed with an asterisk (p < 0.05).

Figure 3

The Top 10 significant enriched GO terms in the Lesions group relative to the Seronegative group. (a) Up-regulated genes (b) Down-regulated genes.

Figure 4

The Top 10 significant enriched GO terms in the Lesions group relative to the Asymptomatic group. (a) Up-regulated genes (b) Down-regulated genes.

Figure 5

Enriched functional GO terms groups obtained with FatiGO (Babelomics 4.3) in the significant up-regulated (red) and down-regulated (blue) genes when comparing the Lesions group with the Seronegative group. p value is the highest adjusted p value of its groups GO terms: Mitotic cell cycle (p = 3.91 × 10⁻¹⁹), Meiotic cell cycle (p = 1.77 × 10⁻³), Immune response (p = 4.14 × 10⁻¹¹), Positive regulation of ubiquitin-protein ligase activity (p = 9.14 × 10⁻³), Development and cell/tissue/organ differentiation (p = 1.11 × 10⁻¹⁰), Regulation of transcription (p = 7.97 × 10⁻⁵), Response to hormone and corticoids (p = 1.35 × 10⁻⁷), More responses (p = 1.16 × 10⁻⁶).

Figure 6

Enriched functional GO terms groups obtained with FatiGO (Babelomics 4.3) in the significant up-regulated (red) and down-regulated (blue) genes when comparing the Lesions group with the Asymptomatic group. p value is the highest adjusted p value of its groups GO terms: Mitotic cell cycle (p = 3.30 × 10⁻⁹), Immune response (p = 4.35 × 10⁻⁷), Response to cAMP (p = 6.02 × 10⁻³), Development and cell/tissue/organ differentiation (p = 2.33 × 10⁻⁸), Regulation of transcription (p = 6.51 × 10⁻⁶), Response to hormone and corticoids (p = 2.54 × 10⁻⁶), Regulation of apoptosis or programmed cell death (p = 1.34 × 10⁻³).