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Maladjusted host immune responses induce experimental cerebral malaria-like pathology in a murine Borrelia and Plasmodium co-infection model.

Normark J, Nelson M, Engström P, Andersson M, Björk R, Moritz T, Fahlgren A, Bergström S - PLoS ONE (2014)

Bottom Line: It indicated diminished bioavailability of NO, which argued for a dysfunctional endothelium.Consistent with this, we observed increased sequestration of CD8+ cells in the brain as well over expression of ICAM-1 and VCAM by brain endothelial cells.In addition we found loss of synchronicity of pro- and anti-inflammatory signals seen in dendritic cells and macrophages, as well as increased numbers of regulatory T-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Umeå University, Umeå, Sweden; Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden; Umeå Center for Microbial Research, Umeå University, Umeå, Sweden; Division of Infectious diseases, Department of Clinical Microbiology, Umeå University, Umeå, Sweden.

ABSTRACT
In the Plasmodium infected host, a balance between pro- and anti-inflammatory responses is required to clear the parasites without inducing major host pathology. Clinical reports suggest that bacterial infection in conjunction with malaria aggravates disease and raises both mortality and morbidity in these patients. In this study, we investigated the immune responses in BALB/c mice, co-infected with Plasmodium berghei NK65 parasites and the relapsing fever bacterium Borrelia duttonii. In contrast to single infections, we identified in the co-infected mice a reduction of L-Arginine levels in the serum. It indicated diminished bioavailability of NO, which argued for a dysfunctional endothelium. Consistent with this, we observed increased sequestration of CD8+ cells in the brain as well over expression of ICAM-1 and VCAM by brain endothelial cells. Co-infected mice further showed an increased inflammatory response through IL-1β and TNF-α, as well as inability to down regulate the same through IL-10. In addition we found loss of synchronicity of pro- and anti-inflammatory signals seen in dendritic cells and macrophages, as well as increased numbers of regulatory T-cells. Our study shows that a situation mimicking experimental cerebral malaria (ECM) is induced in co-infected mice due to loss of timing and control over regulatory mechanisms in antigen presenting cells.

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Co-infection causes conflicting cytokine signaling and persisting nTreg populations.Mice were injected with 1×107P. berghei NK65-infected RBCs and/or 1×105B. duttonii 1120K3 bacteria, and then sacrificed at indicated time points (N = 6 per group). Cytokine level experiments performed in triplicate, nTreg experiment performed in duplicate. Plasma levels of cytokines were measured with multiplex ELISA (A) Plasma IL-10 concentration (pg/mL) (B) Plasma IL-1β concentration (pg/mL) (C) Plasma TNF-α concentration (pg/mL) (D) The percentage fraction of CD4+CD25highFoxP3+ cells, in the total CD4+ cell pool in the spleen determined with flow cytometry. (▪) Represents mice infected with both P. berghei and B. duttonii, (○) indicates animals infected with B. duttonii and (Δ) mice infected with P. berghei.
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pone-0103295-g003: Co-infection causes conflicting cytokine signaling and persisting nTreg populations.Mice were injected with 1×107P. berghei NK65-infected RBCs and/or 1×105B. duttonii 1120K3 bacteria, and then sacrificed at indicated time points (N = 6 per group). Cytokine level experiments performed in triplicate, nTreg experiment performed in duplicate. Plasma levels of cytokines were measured with multiplex ELISA (A) Plasma IL-10 concentration (pg/mL) (B) Plasma IL-1β concentration (pg/mL) (C) Plasma TNF-α concentration (pg/mL) (D) The percentage fraction of CD4+CD25highFoxP3+ cells, in the total CD4+ cell pool in the spleen determined with flow cytometry. (▪) Represents mice infected with both P. berghei and B. duttonii, (○) indicates animals infected with B. duttonii and (Δ) mice infected with P. berghei.

Mentions: The signs of inflammation induced pathology seen in the brain motivated us to analyze the early inhibitory and excitatory mechanisms that control the cellular immune responses to infection. We first analyzed levels of IL-10, an anti-inflammatory cytokine that down-regulates the expression of MHC class II molecules, co-stimulatory, and adhesion molecules. Single infection with P. berghei did not elicit an elevation of IL-10 during the course of the infection (Figure 3A), and pro-inflammatory cytokines (IL-1β, TNF-α and IFN-γ) were not elevated in plasma (Figures 3B, 3C and [35]). In comparison, single infection with B. duttonii caused a peak in IL-10 levels day 3 p.i. In co-infected mice, the IL-10 levels were significantly increased compared to uninfected control early (day 1 p.i.), and late (day 8 p.i.) (Wilcoxon rank sum test, P = 0.026 and 0.004, B. duttonii and P. berghei respectively) (Figure 3A, Table S1). Moreover, this coincided with a burst of the pro-inflammatory cytokines IL-1β and TNF-α in early and late stages of infection (day 8 p.i.). Pro-inflammatory cytokines were induced at higher levels earlier in co-infected mice compared with both single infections (day 1 p.i.) (Figures 3B and 3C, Table S1).


Maladjusted host immune responses induce experimental cerebral malaria-like pathology in a murine Borrelia and Plasmodium co-infection model.

Normark J, Nelson M, Engström P, Andersson M, Björk R, Moritz T, Fahlgren A, Bergström S - PLoS ONE (2014)

Co-infection causes conflicting cytokine signaling and persisting nTreg populations.Mice were injected with 1×107P. berghei NK65-infected RBCs and/or 1×105B. duttonii 1120K3 bacteria, and then sacrificed at indicated time points (N = 6 per group). Cytokine level experiments performed in triplicate, nTreg experiment performed in duplicate. Plasma levels of cytokines were measured with multiplex ELISA (A) Plasma IL-10 concentration (pg/mL) (B) Plasma IL-1β concentration (pg/mL) (C) Plasma TNF-α concentration (pg/mL) (D) The percentage fraction of CD4+CD25highFoxP3+ cells, in the total CD4+ cell pool in the spleen determined with flow cytometry. (▪) Represents mice infected with both P. berghei and B. duttonii, (○) indicates animals infected with B. duttonii and (Δ) mice infected with P. berghei.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4116174&req=5

pone-0103295-g003: Co-infection causes conflicting cytokine signaling and persisting nTreg populations.Mice were injected with 1×107P. berghei NK65-infected RBCs and/or 1×105B. duttonii 1120K3 bacteria, and then sacrificed at indicated time points (N = 6 per group). Cytokine level experiments performed in triplicate, nTreg experiment performed in duplicate. Plasma levels of cytokines were measured with multiplex ELISA (A) Plasma IL-10 concentration (pg/mL) (B) Plasma IL-1β concentration (pg/mL) (C) Plasma TNF-α concentration (pg/mL) (D) The percentage fraction of CD4+CD25highFoxP3+ cells, in the total CD4+ cell pool in the spleen determined with flow cytometry. (▪) Represents mice infected with both P. berghei and B. duttonii, (○) indicates animals infected with B. duttonii and (Δ) mice infected with P. berghei.
Mentions: The signs of inflammation induced pathology seen in the brain motivated us to analyze the early inhibitory and excitatory mechanisms that control the cellular immune responses to infection. We first analyzed levels of IL-10, an anti-inflammatory cytokine that down-regulates the expression of MHC class II molecules, co-stimulatory, and adhesion molecules. Single infection with P. berghei did not elicit an elevation of IL-10 during the course of the infection (Figure 3A), and pro-inflammatory cytokines (IL-1β, TNF-α and IFN-γ) were not elevated in plasma (Figures 3B, 3C and [35]). In comparison, single infection with B. duttonii caused a peak in IL-10 levels day 3 p.i. In co-infected mice, the IL-10 levels were significantly increased compared to uninfected control early (day 1 p.i.), and late (day 8 p.i.) (Wilcoxon rank sum test, P = 0.026 and 0.004, B. duttonii and P. berghei respectively) (Figure 3A, Table S1). Moreover, this coincided with a burst of the pro-inflammatory cytokines IL-1β and TNF-α in early and late stages of infection (day 8 p.i.). Pro-inflammatory cytokines were induced at higher levels earlier in co-infected mice compared with both single infections (day 1 p.i.) (Figures 3B and 3C, Table S1).

Bottom Line: It indicated diminished bioavailability of NO, which argued for a dysfunctional endothelium.Consistent with this, we observed increased sequestration of CD8+ cells in the brain as well over expression of ICAM-1 and VCAM by brain endothelial cells.In addition we found loss of synchronicity of pro- and anti-inflammatory signals seen in dendritic cells and macrophages, as well as increased numbers of regulatory T-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Umeå University, Umeå, Sweden; Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden; Umeå Center for Microbial Research, Umeå University, Umeå, Sweden; Division of Infectious diseases, Department of Clinical Microbiology, Umeå University, Umeå, Sweden.

ABSTRACT
In the Plasmodium infected host, a balance between pro- and anti-inflammatory responses is required to clear the parasites without inducing major host pathology. Clinical reports suggest that bacterial infection in conjunction with malaria aggravates disease and raises both mortality and morbidity in these patients. In this study, we investigated the immune responses in BALB/c mice, co-infected with Plasmodium berghei NK65 parasites and the relapsing fever bacterium Borrelia duttonii. In contrast to single infections, we identified in the co-infected mice a reduction of L-Arginine levels in the serum. It indicated diminished bioavailability of NO, which argued for a dysfunctional endothelium. Consistent with this, we observed increased sequestration of CD8+ cells in the brain as well over expression of ICAM-1 and VCAM by brain endothelial cells. Co-infected mice further showed an increased inflammatory response through IL-1β and TNF-α, as well as inability to down regulate the same through IL-10. In addition we found loss of synchronicity of pro- and anti-inflammatory signals seen in dendritic cells and macrophages, as well as increased numbers of regulatory T-cells. Our study shows that a situation mimicking experimental cerebral malaria (ECM) is induced in co-infected mice due to loss of timing and control over regulatory mechanisms in antigen presenting cells.

Show MeSH
Related in: MedlinePlus