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Differences in Whole Blood Gene Expression Associated with Infection Time-Course and Extent of Fetal Mortality in a Reproductive Model of Type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Infection.

Wilkinson JM, Ladinig A, Bao H, Kommadath A, Stothard P, Lunney JK, Harding JC, Plastow GS - PLoS ONE (2016)

Bottom Line: A concomitant decrease in expression of protein synthesis and T lymphocyte markers was observed.Differentially expressed genes (DEGs) associated with extremes of litter mortality rate were identified at all three time-points.This study has increased our knowledge of the early response to PRRSV in the blood of pregnant gilts, and could ultimately lead to the development of a biomarker panel that can be used to predict PRRSV-associated reproductive pathology.

View Article: PubMed Central - PubMed

Affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada.

ABSTRACT
Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection of pregnant females causes fetal death and increased piglet mortality, but there is substantial variation in the extent of reproductive pathology between individual dams. This study used RNA-sequencing to characterize the whole blood transcriptional response to type 2 PRRSV in pregnant gilts during the first week of infection (at 0, 2, and 6 days post-inoculation), and attempted to identify gene expression signatures associated with a low or high level of fetal mortality rates (LFM and HFM; n = 8/group) at necropsy, 21 days post-inoculation. The initial response to infection measured at 2 days post-inoculation saw an upregulation of genes involved in innate immunity, such as interferon-stimulated antiviral genes and inflammatory markers, and apoptosis. A concomitant decrease in expression of protein synthesis and T lymphocyte markers was observed. By day 6 the pattern had reversed, with a drop in innate immune signaling and an increase in the expression of genes involved in cell division and T cell signaling. Differentially expressed genes (DEGs) associated with extremes of litter mortality rate were identified at all three time-points. Among the 15 DEGs upregulated in LFM gilts on all three days were several genes involved in platelet function, including integrins ITGA2B and ITGB3, and the chemokine PF4 (CXCL4). LFM gilts exhibited a higher baseline expression of interferon-stimulated and pro-inflammatory genes prior to infection, and of T cell markers two days post-infection, indicative of a more rapid progression of the immune response to PRRSV. This study has increased our knowledge of the early response to PRRSV in the blood of pregnant gilts, and could ultimately lead to the development of a biomarker panel that can be used to predict PRRSV-associated reproductive pathology.

No MeSH data available.


Related in: MedlinePlus

Temporal Expression Profile of E2F Target Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the ‘E2F target’ gene set produced by Gene Set Enrichment Analysis of transcriptional data from the blood of low and high fetal mortality (LFM and HFM) groups at three time-points during PRRSV-infection: D0 (A), D2 (B), and D6 (C). E2F target gene expression is negatively correlated with LFM (enriched in HFM) at D0 and D6 and positively correlated with LFM on D2 (enriched in LFM).
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pone.0153615.g005: Temporal Expression Profile of E2F Target Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the ‘E2F target’ gene set produced by Gene Set Enrichment Analysis of transcriptional data from the blood of low and high fetal mortality (LFM and HFM) groups at three time-points during PRRSV-infection: D0 (A), D2 (B), and D6 (C). E2F target gene expression is negatively correlated with LFM (enriched in HFM) at D0 and D6 and positively correlated with LFM on D2 (enriched in LFM).

Mentions: Two other significant gene sets show the opposite oscillating pattern of gene expression to the interferon and inflammatory gene sets. Expression of the ‘MYC Targets v1’ and ‘E2F Targets’ gene sets are negatively correlated with LFM at D0 and D6, but positively correlated at D2 (Fig 5). Specific genes among these sets function in cell cycle signaling (CCNB2, CCNE1, CDC25B, MYC), DNA replication and recombination (CDC45, PCNA, POLD2, RAD51AP1), and cytokinesis (AURKB, BUB3, CENPE, KIF22). The negative relationship between interferon and cell cycle signaling at D0 and D6 may be attributable to the cellular effects of interferon signaling, while the positive correlation between MYC and E2F signaling at D2 and the LFM phenotype could relate to T cell activation. Among the 105 genes that were upregulated in LFM gilts at D2 were a number of genes associated with T lymphocytes and T cell receptor signaling. These genes include plasma membrane proteins (CD3D, CD8B, CD27, CD28, CTLA4, ICOS, LCK, TRBV19), cytolytic enzymes (GZMA, GZMB, GZMK), and intracellular signal transduction components (LAT, LEF1, SH2D1A). As discussed previously, there is a general decline in lymphocyte numbers in all gilts at D2 compared to D0. T cell numbers were numerically greater in LFM than HFM gilts at D2, but not statistically different. However, the expression profile of LFM gilts does indicate a greater extent of T cell activation at D2. Many of the most upregulated genes are known to be specifically upregulated following T cell activation. This includes three members of the CD28 family of T cell membrane proteins: CD28, CTLA4, and ICOS. These proteins bind to B7 family proteins on antigen presenting cells and transmit co-stimulatory signals to the T cell. Transcription of all three molecules is upregulated following initial TCR engagement with the MHC complex, particularly CTLA4 and ICOS, which are not found on the surface of resting CTL or T helper cells [55, 56]. Likewise, expression of the cytolytic granzyme genes is controlled by TCR activation [57]. Again, these results fit with the hypothesis that LFM gilts are capable of initiating faster immune responses to infection, with a more rapid innate response succeeded by an earlier T cell response. Specific T cell responses are considered weak in PRRSV infections compared to many other viral pathogens, but they likely contribute to the eventual clearance of the virus and are an essential component of vaccines that are at least moderately effective at preventing infection.


Differences in Whole Blood Gene Expression Associated with Infection Time-Course and Extent of Fetal Mortality in a Reproductive Model of Type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Infection.

Wilkinson JM, Ladinig A, Bao H, Kommadath A, Stothard P, Lunney JK, Harding JC, Plastow GS - PLoS ONE (2016)

Temporal Expression Profile of E2F Target Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the ‘E2F target’ gene set produced by Gene Set Enrichment Analysis of transcriptional data from the blood of low and high fetal mortality (LFM and HFM) groups at three time-points during PRRSV-infection: D0 (A), D2 (B), and D6 (C). E2F target gene expression is negatively correlated with LFM (enriched in HFM) at D0 and D6 and positively correlated with LFM on D2 (enriched in LFM).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4836665&req=5

pone.0153615.g005: Temporal Expression Profile of E2F Target Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the ‘E2F target’ gene set produced by Gene Set Enrichment Analysis of transcriptional data from the blood of low and high fetal mortality (LFM and HFM) groups at three time-points during PRRSV-infection: D0 (A), D2 (B), and D6 (C). E2F target gene expression is negatively correlated with LFM (enriched in HFM) at D0 and D6 and positively correlated with LFM on D2 (enriched in LFM).
Mentions: Two other significant gene sets show the opposite oscillating pattern of gene expression to the interferon and inflammatory gene sets. Expression of the ‘MYC Targets v1’ and ‘E2F Targets’ gene sets are negatively correlated with LFM at D0 and D6, but positively correlated at D2 (Fig 5). Specific genes among these sets function in cell cycle signaling (CCNB2, CCNE1, CDC25B, MYC), DNA replication and recombination (CDC45, PCNA, POLD2, RAD51AP1), and cytokinesis (AURKB, BUB3, CENPE, KIF22). The negative relationship between interferon and cell cycle signaling at D0 and D6 may be attributable to the cellular effects of interferon signaling, while the positive correlation between MYC and E2F signaling at D2 and the LFM phenotype could relate to T cell activation. Among the 105 genes that were upregulated in LFM gilts at D2 were a number of genes associated with T lymphocytes and T cell receptor signaling. These genes include plasma membrane proteins (CD3D, CD8B, CD27, CD28, CTLA4, ICOS, LCK, TRBV19), cytolytic enzymes (GZMA, GZMB, GZMK), and intracellular signal transduction components (LAT, LEF1, SH2D1A). As discussed previously, there is a general decline in lymphocyte numbers in all gilts at D2 compared to D0. T cell numbers were numerically greater in LFM than HFM gilts at D2, but not statistically different. However, the expression profile of LFM gilts does indicate a greater extent of T cell activation at D2. Many of the most upregulated genes are known to be specifically upregulated following T cell activation. This includes three members of the CD28 family of T cell membrane proteins: CD28, CTLA4, and ICOS. These proteins bind to B7 family proteins on antigen presenting cells and transmit co-stimulatory signals to the T cell. Transcription of all three molecules is upregulated following initial TCR engagement with the MHC complex, particularly CTLA4 and ICOS, which are not found on the surface of resting CTL or T helper cells [55, 56]. Likewise, expression of the cytolytic granzyme genes is controlled by TCR activation [57]. Again, these results fit with the hypothesis that LFM gilts are capable of initiating faster immune responses to infection, with a more rapid innate response succeeded by an earlier T cell response. Specific T cell responses are considered weak in PRRSV infections compared to many other viral pathogens, but they likely contribute to the eventual clearance of the virus and are an essential component of vaccines that are at least moderately effective at preventing infection.

Bottom Line: A concomitant decrease in expression of protein synthesis and T lymphocyte markers was observed.Differentially expressed genes (DEGs) associated with extremes of litter mortality rate were identified at all three time-points.This study has increased our knowledge of the early response to PRRSV in the blood of pregnant gilts, and could ultimately lead to the development of a biomarker panel that can be used to predict PRRSV-associated reproductive pathology.

View Article: PubMed Central - PubMed

Affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada.

ABSTRACT
Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection of pregnant females causes fetal death and increased piglet mortality, but there is substantial variation in the extent of reproductive pathology between individual dams. This study used RNA-sequencing to characterize the whole blood transcriptional response to type 2 PRRSV in pregnant gilts during the first week of infection (at 0, 2, and 6 days post-inoculation), and attempted to identify gene expression signatures associated with a low or high level of fetal mortality rates (LFM and HFM; n = 8/group) at necropsy, 21 days post-inoculation. The initial response to infection measured at 2 days post-inoculation saw an upregulation of genes involved in innate immunity, such as interferon-stimulated antiviral genes and inflammatory markers, and apoptosis. A concomitant decrease in expression of protein synthesis and T lymphocyte markers was observed. By day 6 the pattern had reversed, with a drop in innate immune signaling and an increase in the expression of genes involved in cell division and T cell signaling. Differentially expressed genes (DEGs) associated with extremes of litter mortality rate were identified at all three time-points. Among the 15 DEGs upregulated in LFM gilts on all three days were several genes involved in platelet function, including integrins ITGA2B and ITGB3, and the chemokine PF4 (CXCL4). LFM gilts exhibited a higher baseline expression of interferon-stimulated and pro-inflammatory genes prior to infection, and of T cell markers two days post-infection, indicative of a more rapid progression of the immune response to PRRSV. This study has increased our knowledge of the early response to PRRSV in the blood of pregnant gilts, and could ultimately lead to the development of a biomarker panel that can be used to predict PRRSV-associated reproductive pathology.

No MeSH data available.


Related in: MedlinePlus