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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 Interferon-γ Signaling Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the Interferon-γ signaling 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). The enrichment score is calculated by walking down a list of genes ranked by their correlation with the LFM phenotype (green line), increasing a running-sum statistic when a gene in that gene set is encountered (each black vertical line underneath the enrichment plot) and decreasing it when a gene that isn’t in the gene set is encountered. The enrichment score is the maximum deviation from zero encountered in the walk. Magnitude and direction of correlation between expression of individual genes with LFM group is indicated on the color scale below the black lines with red indicating positive correlation and blue indicating negative correlation. Interferon-γ signaling gene expression was positively correlated with LFM (enriched in LFM) at D0 and D6 and negatively correlated with LFM on D2 (enriched in HFM).
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pone.0153615.g004: Temporal Expression Profile of Interferon-γ Signaling Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the Interferon-γ signaling 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). The enrichment score is calculated by walking down a list of genes ranked by their correlation with the LFM phenotype (green line), increasing a running-sum statistic when a gene in that gene set is encountered (each black vertical line underneath the enrichment plot) and decreasing it when a gene that isn’t in the gene set is encountered. The enrichment score is the maximum deviation from zero encountered in the walk. Magnitude and direction of correlation between expression of individual genes with LFM group is indicated on the color scale below the black lines with red indicating positive correlation and blue indicating negative correlation. Interferon-γ signaling gene expression was positively correlated with LFM (enriched in LFM) at D0 and D6 and negatively correlated with LFM on D2 (enriched in HFM).

Mentions: Gene set enrichment analyses found that the expression of many of the significant gene sets oscillated between being positively or negatively correlated with the low fetal mortality across the three time-points. Interferon and pro-inflammatory signaling gene sets were among the most significant gene sets. Their expression was positively correlated with LFM phenotype at D0, negatively correlated at D2, and again positively correlated at D6 (Fig 4). These gene sets included ‘Interferon Alpha Response’, ‘Interferon Gamma Response’, ‘TNF-alpha signaling via NFKB’, and ‘Inflammatory Response’. Functional categories under these broader terms include interferon-inducible genes with antiviral function (IFIT3, ISG15, ISG20, MX1, RSAD2), cytokines and cytokine receptors (CCL4, CXCL10, IL1A, IL10, S100A9, S100A12, TNFSF10), PRRs (NOD1, TLR2, TLR4), NF-κB signaling genes (CD14, MYD88, IL1A, NFKBIE, RELA, RELB), and hemostasis (GP1BA, ITGB3, PF4, SERPINB2, SERPINE1). The discovery of elevated levels of these genes in LFM gilts prior to inoculation is particularly interesting, and this could contribute to the low fetal mortality phenotype. One interpretation of this result is that the LFM gilts were primed to respond more quickly and effectively to the initial stage of infection in the uterine vasculature and tissue. If this was the case, it offers the exciting prospect of identifying blood biomarkers that could be developed into a screening test to predict the extent of fetal pathology in gilts/sows prior to PRRSV infection. A similar discovery of innate immune gene expression prior to infection was recently made for a model of Salmonella infection in pigs [53]. In that study, the expression profiles of networks containing genes that had previously been implicated in resistance to Salmonella were positively correlated with a low shedding phenotype. Further research is warranted using larger numbers of biological replicates to confirm these findings, and to investigate the underlying reason for the elevated expression of these genes.


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 Interferon-γ Signaling Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the Interferon-γ signaling 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). The enrichment score is calculated by walking down a list of genes ranked by their correlation with the LFM phenotype (green line), increasing a running-sum statistic when a gene in that gene set is encountered (each black vertical line underneath the enrichment plot) and decreasing it when a gene that isn’t in the gene set is encountered. The enrichment score is the maximum deviation from zero encountered in the walk. Magnitude and direction of correlation between expression of individual genes with LFM group is indicated on the color scale below the black lines with red indicating positive correlation and blue indicating negative correlation. Interferon-γ signaling gene expression was positively correlated with LFM (enriched in LFM) at D0 and D6 and negatively correlated with LFM on D2 (enriched in HFM).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0153615.g004: Temporal Expression Profile of Interferon-γ Signaling Gene Set in Gilts Exhibiting Low Fetal Mortality.Enrichment plots for the Interferon-γ signaling 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). The enrichment score is calculated by walking down a list of genes ranked by their correlation with the LFM phenotype (green line), increasing a running-sum statistic when a gene in that gene set is encountered (each black vertical line underneath the enrichment plot) and decreasing it when a gene that isn’t in the gene set is encountered. The enrichment score is the maximum deviation from zero encountered in the walk. Magnitude and direction of correlation between expression of individual genes with LFM group is indicated on the color scale below the black lines with red indicating positive correlation and blue indicating negative correlation. Interferon-γ signaling gene expression was positively correlated with LFM (enriched in LFM) at D0 and D6 and negatively correlated with LFM on D2 (enriched in HFM).
Mentions: Gene set enrichment analyses found that the expression of many of the significant gene sets oscillated between being positively or negatively correlated with the low fetal mortality across the three time-points. Interferon and pro-inflammatory signaling gene sets were among the most significant gene sets. Their expression was positively correlated with LFM phenotype at D0, negatively correlated at D2, and again positively correlated at D6 (Fig 4). These gene sets included ‘Interferon Alpha Response’, ‘Interferon Gamma Response’, ‘TNF-alpha signaling via NFKB’, and ‘Inflammatory Response’. Functional categories under these broader terms include interferon-inducible genes with antiviral function (IFIT3, ISG15, ISG20, MX1, RSAD2), cytokines and cytokine receptors (CCL4, CXCL10, IL1A, IL10, S100A9, S100A12, TNFSF10), PRRs (NOD1, TLR2, TLR4), NF-κB signaling genes (CD14, MYD88, IL1A, NFKBIE, RELA, RELB), and hemostasis (GP1BA, ITGB3, PF4, SERPINB2, SERPINE1). The discovery of elevated levels of these genes in LFM gilts prior to inoculation is particularly interesting, and this could contribute to the low fetal mortality phenotype. One interpretation of this result is that the LFM gilts were primed to respond more quickly and effectively to the initial stage of infection in the uterine vasculature and tissue. If this was the case, it offers the exciting prospect of identifying blood biomarkers that could be developed into a screening test to predict the extent of fetal pathology in gilts/sows prior to PRRSV infection. A similar discovery of innate immune gene expression prior to infection was recently made for a model of Salmonella infection in pigs [53]. In that study, the expression profiles of networks containing genes that had previously been implicated in resistance to Salmonella were positively correlated with a low shedding phenotype. Further research is warranted using larger numbers of biological replicates to confirm these findings, and to investigate the underlying reason for the elevated expression of these genes.

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