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MicroRNA-155 enhances T cell trafficking and antiviral effector function in a model of coronavirus-induced neurologic disease

View Article: PubMed Central - PubMed

ABSTRACT

Background: MicroRNAs (miRNAs) are noncoding RNAs that modulate cellular gene expression, primarily at the post-transcriptional level. We sought to examine the functional role of miR-155 in a model of viral-induced neuroinflammation.

Methods: Acute encephalomyelitis and immune-mediated demyelination were induced by intracranial injection with the neurotropic JHM strain of mouse hepatitis virus (JHMV) into C57BL/6 miR-155+/+ wildtype (WT) mice or miR-155−/− mice. Morbidity and mortality, viral load and immune cell accumulation in the CNS, and spinal cord demyelination were assessed at defined points post-infection. T cells harvested from infected mice were used to examine cytolytic activity, cytokine activity, and expression of certain chemokine receptors. To determine the impact of miR-155 on trafficking, T cells from infected WT or miR-155−/− mice were adoptively transferred into RAG1−/− mice, and T cell accumulation into the CNS was assessed using flow cytometry. Statistical significance was determined using the Mantel-Cox log-rank test or Student’s T tests.

Results: Compared to WT mice, JHMV-infected miR-155−/− mice developed exacerbated disease concomitant with increased morbidity/mortality and an inability to control viral replication within the CNS. In corroboration with increased susceptibility to disease, miR-155−/− mice had diminished CD8+ T cell responses in terms of numbers, cytolytic activity, IFN-γ secretion, and homing to the CNS that corresponded with reduced expression of the chemokine receptor CXCR3. Both IFN-γ secretion and trafficking were impaired in miR-155−/−, virus-specific CD4+ T cells; however, expression of the chemokine homing receptors analyzed on CD4+ cells was not affected. Except for very early during infection, there were not significant differences in macrophage infiltration into the CNS between WT and miR-155−/− JHMV-infected mice, and the severity of demyelination was similar at 14 days p.i. between WT and miR-155−/− JHMV-infected mice.

Conclusions: These findings support a novel role for miR-155 in host defense in a model of viral-induced encephalomyelitis. Specifically, miR-155 enhances antiviral T cell responses including cytokine secretion, cytolytic activity, and homing to the CNS in response to viral infection. Further, miR-155 can play either a host-protective or host-damaging role during neuroinflammation depending on the disease trigger.

No MeSH data available.


Chemokine receptor expression on virus-specific WT and miR-155−/− mice. WT and miR-155−/− mice were infected i.p. with DM-MHV and spleens were isolated at day 8 p.i.. Flow cytometric analysis revealed similar levels of CXCR3 on virus-specific CD4+ T cells isolated from WT and miR-155−/− mice (a, b). However, expression of CXCR3 was decreased (p < 0.05) on virus-specific CD8+ T cells isolated from miR-155−/− mice compared to WT mice (c, d). Flow cytometric analysis revealed similar levels of CCR5 on both virus-specific CD4+ T cells (e, f) and virus-specific CD8+ T cells (g, h) isolated from WT and miR-155−/− mice. Plots represent average ± SEM; statistical significance was measured using unpaired, one-tailed Student’s T tests. Data are representative of two independent experiments, with a minimum of four mice per group per experiment. *p < 0.05; **p < 0.01
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Fig5: Chemokine receptor expression on virus-specific WT and miR-155−/− mice. WT and miR-155−/− mice were infected i.p. with DM-MHV and spleens were isolated at day 8 p.i.. Flow cytometric analysis revealed similar levels of CXCR3 on virus-specific CD4+ T cells isolated from WT and miR-155−/− mice (a, b). However, expression of CXCR3 was decreased (p < 0.05) on virus-specific CD8+ T cells isolated from miR-155−/− mice compared to WT mice (c, d). Flow cytometric analysis revealed similar levels of CCR5 on both virus-specific CD4+ T cells (e, f) and virus-specific CD8+ T cells (g, h) isolated from WT and miR-155−/− mice. Plots represent average ± SEM; statistical significance was measured using unpaired, one-tailed Student’s T tests. Data are representative of two independent experiments, with a minimum of four mice per group per experiment. *p < 0.05; **p < 0.01

Mentions: Our findings indicate that in the absence of miR-155, antiviral T cell responses are dampened following JHMV infection of the CNS. In addition, the inability to control viral replication within the CNS was associated with fewer numbers of T cells within the CNS of JHMV-infected miR-155−/− mice compared to infected WT mice, raising the possibility of a deficiency in T cell homing in the absence of miR-155. We have previously shown that T cell expression of the chemokine receptor CXCR3, the signaling receptor for the chemokine CXCL10, is important in enhancing the ability of these cells to migrate and accumulate within the CNS of JHMV-infected mice [44, 45, 63–65]. We therefore tested whether expression of CXCR3 was decreased on T cells from JHMV-infected miR-155−/− mice. There were no differences in expression of CXCR3 on M133-147-specific CD4+ T cells (Fig. 5a, b). In contrast, there was an overall reduction (p < 0.05) in the frequency of CXCR3-positive S510-518-positive CD8+ T cells (Fig. 5c), as well as a reduction (p < 0.01) of CXCR3 on a per-cell level (Fig. 5d). These findings indicate that miR-155 regulates expression of CXCR3 on CD8+ T cells, and this corresponds with impaired trafficking of these cells to the CNS following JHMV infection. The paucity in CD4+ T cell trafficking to the CNS of JHMV-infected miR-155−/− mice suggests the possibility that other T cell homing receptors such as CCR5 may be affected by miR-155 deficiency and account for impaired CNS migration [66]; however, analysis of CCR5 on virus-specific CD4+ (Fig. 5e, f) and CD8+ T cells (Fig. 5g, h) indicated no differences in surface expression of this homing receptor between WT and miR-155−/− T cells.Fig. 5


MicroRNA-155 enhances T cell trafficking and antiviral effector function in a model of coronavirus-induced neurologic disease
Chemokine receptor expression on virus-specific WT and miR-155−/− mice. WT and miR-155−/− mice were infected i.p. with DM-MHV and spleens were isolated at day 8 p.i.. Flow cytometric analysis revealed similar levels of CXCR3 on virus-specific CD4+ T cells isolated from WT and miR-155−/− mice (a, b). However, expression of CXCR3 was decreased (p < 0.05) on virus-specific CD8+ T cells isolated from miR-155−/− mice compared to WT mice (c, d). Flow cytometric analysis revealed similar levels of CCR5 on both virus-specific CD4+ T cells (e, f) and virus-specific CD8+ T cells (g, h) isolated from WT and miR-155−/− mice. Plots represent average ± SEM; statistical significance was measured using unpaired, one-tailed Student’s T tests. Data are representative of two independent experiments, with a minimum of four mice per group per experiment. *p < 0.05; **p < 0.01
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Fig5: Chemokine receptor expression on virus-specific WT and miR-155−/− mice. WT and miR-155−/− mice were infected i.p. with DM-MHV and spleens were isolated at day 8 p.i.. Flow cytometric analysis revealed similar levels of CXCR3 on virus-specific CD4+ T cells isolated from WT and miR-155−/− mice (a, b). However, expression of CXCR3 was decreased (p < 0.05) on virus-specific CD8+ T cells isolated from miR-155−/− mice compared to WT mice (c, d). Flow cytometric analysis revealed similar levels of CCR5 on both virus-specific CD4+ T cells (e, f) and virus-specific CD8+ T cells (g, h) isolated from WT and miR-155−/− mice. Plots represent average ± SEM; statistical significance was measured using unpaired, one-tailed Student’s T tests. Data are representative of two independent experiments, with a minimum of four mice per group per experiment. *p < 0.05; **p < 0.01
Mentions: Our findings indicate that in the absence of miR-155, antiviral T cell responses are dampened following JHMV infection of the CNS. In addition, the inability to control viral replication within the CNS was associated with fewer numbers of T cells within the CNS of JHMV-infected miR-155−/− mice compared to infected WT mice, raising the possibility of a deficiency in T cell homing in the absence of miR-155. We have previously shown that T cell expression of the chemokine receptor CXCR3, the signaling receptor for the chemokine CXCL10, is important in enhancing the ability of these cells to migrate and accumulate within the CNS of JHMV-infected mice [44, 45, 63–65]. We therefore tested whether expression of CXCR3 was decreased on T cells from JHMV-infected miR-155−/− mice. There were no differences in expression of CXCR3 on M133-147-specific CD4+ T cells (Fig. 5a, b). In contrast, there was an overall reduction (p < 0.05) in the frequency of CXCR3-positive S510-518-positive CD8+ T cells (Fig. 5c), as well as a reduction (p < 0.01) of CXCR3 on a per-cell level (Fig. 5d). These findings indicate that miR-155 regulates expression of CXCR3 on CD8+ T cells, and this corresponds with impaired trafficking of these cells to the CNS following JHMV infection. The paucity in CD4+ T cell trafficking to the CNS of JHMV-infected miR-155−/− mice suggests the possibility that other T cell homing receptors such as CCR5 may be affected by miR-155 deficiency and account for impaired CNS migration [66]; however, analysis of CCR5 on virus-specific CD4+ (Fig. 5e, f) and CD8+ T cells (Fig. 5g, h) indicated no differences in surface expression of this homing receptor between WT and miR-155−/− T cells.Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

Background: MicroRNAs (miRNAs) are noncoding RNAs that modulate cellular gene expression, primarily at the post-transcriptional level. We sought to examine the functional role of miR-155 in a model of viral-induced neuroinflammation.

Methods: Acute encephalomyelitis and immune-mediated demyelination were induced by intracranial injection with the neurotropic JHM strain of mouse hepatitis virus (JHMV) into C57BL/6 miR-155+/+ wildtype (WT) mice or miR-155&minus;/&minus; mice. Morbidity and mortality, viral load and immune cell accumulation in the CNS, and spinal cord demyelination were assessed at defined points post-infection. T cells harvested from infected mice were used to examine cytolytic activity, cytokine activity, and expression of certain chemokine receptors. To determine the impact of miR-155 on trafficking, T cells from infected WT or miR-155&minus;/&minus; mice were adoptively transferred into RAG1&minus;/&minus; mice, and T cell accumulation into the CNS was assessed using flow cytometry. Statistical significance was determined using the Mantel-Cox log-rank test or Student&rsquo;s T tests.

Results: Compared to WT mice, JHMV-infected miR-155&minus;/&minus; mice developed exacerbated disease concomitant with increased morbidity/mortality and an inability to control viral replication within the CNS. In corroboration with increased susceptibility to disease, miR-155&minus;/&minus; mice had diminished CD8+ T cell responses in terms of numbers, cytolytic activity, IFN-&gamma; secretion, and homing to the CNS that corresponded with reduced expression of the chemokine receptor CXCR3. Both IFN-&gamma; secretion and trafficking were impaired in miR-155&minus;/&minus;, virus-specific CD4+ T cells; however, expression of the chemokine homing receptors analyzed on CD4+ cells was not affected. Except for very early during infection, there were not significant differences in macrophage infiltration into the CNS between WT and miR-155&minus;/&minus; JHMV-infected mice, and the severity of demyelination was similar at 14&nbsp;days p.i. between WT and miR-155&minus;/&minus; JHMV-infected mice.

Conclusions: These findings support a novel role for miR-155 in host defense in a model of viral-induced encephalomyelitis. Specifically, miR-155 enhances antiviral T cell responses including cytokine secretion, cytolytic activity, and homing to the CNS in response to viral infection. Further, miR-155 can play either a host-protective or host-damaging role during neuroinflammation depending on the disease trigger.

No MeSH data available.