The effect of pregnancy-specific β1-glycoprotein 1 on the transcription factor FOXP3 expression by immunocompetent cells

Recombinant pregnancy-specific glycoprotein-1-Fc reduces functional deficit in a mouse model of permanent brain ischaemia

Background

The well-characterised role of the immune system in acute ischaemic stroke has prompted the search for immunomodulatory therapies. Pregnancy-specific glycoproteins (PSGs) are a group of proteins synthesised by placental trophoblasts which show immunomodulatory properties. The aim of this study was to determine whether a proposed PSG1-based therapeutic enhanced recovery in a mouse model of brain ischaemia and to explore possible immunomodulatory effects.

Methods

Mice underwent permanent electrocoagulation of the left middle cerebral artery (pMCAO). They received saline (n = 20) or recombinant pregnancy-specific glycoprotein-1-alpha “fused” to the Fc domain of IgG1 (rPSG1-Fc) (100 μg) (n = 22) at 1 h post-ischaemia. At 3 and 5 days post-ischaemia, neurobehavioural recovery was assessed by the grid-walking test. At 5 days post-ischaemia, lesion size was determined by NeuN staining. Peripheral T cell populations were quantified via flow cytometry. Immunohistochemistry was used to quantify ICAM-1 expression and FoxP3+ cell infiltration in the ischaemic brain. Immunofluorescence was employed to determine microglial activation status via Iba-1 staining.

Results: rPSG1-Fc significantly enhanced performance in the grid-walking test at 3 and 5 days post-ischaemia. No effect on infarct size was observed. A significant increase in circulating CD4⁺ FoxP3+ cells and brain-infiltrating FoxP3+ cells was noted in rPSG1-Fc-treated mice. Among CD4⁺ cells, rPSG1-Fc enhanced the expression of IL-10 in spleen, blood, draining lymph nodes, and non-draining lymph nodes, while downregulating IFN-γ and IL-17 in spleen and blood. A similar cytokine expression pattern was observed in CD8⁺ cells. rPSG1-Fc reduced activated microglia in the infarct core.

Conclusion

The administration of rPSG1-Fc improved functional recovery in post-ischaemic mice without impacting infarct size. Improved outcome was associated with a modulation of the cytokine-secreting phenotype of CD4⁺ and CD8⁺ T cells towards a more regulatory phenotype, as well as reduced activation of microglia. This establishes proof-of-concept of rPSG1-Fc as a potential stroke immunotherapy.

•

rPSG1-Fc enhances functional recovery in a mouse model of permanent brain ischaemia.

•

rPSG1-Fc increases circulating CD4⁺ FoxP3+ cells and brain-infiltrating FoxP3+ cells.

•

rPSG1-Fc increases the expression of IL-10 among CD4⁺ cells in spleen, blood, and lymph nodes.

The effects of human pregnancy-specific β1-glycoprotein preparation on Th17 polarization of CD4+ cells and their cytokine profile

BACKGROUND

Pregnancy-specific β1-glycoproteins are capable of regulating innate and adaptive immunity, exerting predominantly suppressive effects. In this regard, they are of interest in terms of their pharmacological potential for the treatment of autoimmune diseases and post-transplant complications. The effect of these proteins on the main pro-inflammatory subpopulation of T lymphocytes, IL-17-producing helper T cells (Th17), has not been comprehensively studied. Therefore, the effects of the native pregnancy-specific β1-glycoprotein on the proliferation, Th17 polarization and cytokine profile of human CD4⁺ cells were assessed.

RESULTS

Native human pregnancy-specific β1-glycoprotein (PSG) at а concentration of 100 μg/mL was shown to decrease the frequency of Th17 (RORγτ⁺) in CD4⁺ cell culture and to suppress the proliferation of these cells (RORγτ⁺Ki-67⁺), along with the proliferation of other cells (Ki-67⁺) (n = 11). A PSG concentration of 10 μg/mL showed similar effect, decreasing the frequency of Ki-67⁺ and RORγτ⁺Ki67⁺ cells. Using Luminex xMAP technology, it was shown that PSG decreased IL-4, IL-5, IL-8, IL-12, IL-13, IL-17, MIP-1β, IL-10, IFN-γ, TNF-α, G-CSF, and GM-CSF concentrations in Th17-polarized CD4⁺ cell cultures but did not affect IL-2, IL-7, and MCP-1 output.

CONCLUSIONS

In the experimental model used, PSG had а mainly suppressive effect on the Th17 polarization and cytokine profile of Th17-polarized CD4⁺ cell cultures. As Th17 activity and a pro-inflammatory cytokine background are unfavorable during pregnancy, the observed PSG effects may play a fetoprotective role in vivo.