Enterovirus infection, CXC chemokine ligand 10 (CXCL10), and CXCR3 circuit: a mechanism of accelerated beta-cell failure in fulminant type 1 diabetes

Abstract

Objective: Fulminant type 1 diabetes is characterized by the rapid onset of severe hyperglycemia and ketoacidosis, with subsequent poor prognosis of diabetes complications. Causative mechanisms for accelerated beta-cell failure are unclear.

Research design and methods: Subjects comprised three autopsied patients who died from diabetic ketoacidosis within 2-5 days after onset of fulminant type 1 diabetes. We examined islet cell status, including the presence of enterovirus and chemokine/cytokine/major histocompatibility complex (MHC) expressions in the pancreata using immunohistochemical analyses and RT-PCR.

Results: Immunohistochemical analysis revealed the presence of enterovirus-capsid protein in all three affected pancreata. Extensive infiltration of CXCR3 receptor-bearing T-cells and macrophages into islets was observed. Dendritic cells were stained in and around the islets. Specifically, interferon-gamma and CXC chemokine ligand 10 (CXCL10) were strongly coexpressed in all subtypes of islet cells, including beta-cells and alpha-cells. No CXCL10 was expressed in exocrine pancreas. Serum levels of CXCL10 were increased. Expression of MHC class II and hyperexpression of MHC class I was observed in some islet cells.

Conclusions: These results strongly suggest the presence of a circuit for the destruction of beta-cells in fulminant type 1 diabetes. Enterovirus infection of the pancreas initiates coexpression of interferon-gamma and CXCL10 in beta-cells. CXCL10 secreted from beta-cells activates and attracts autoreactive T-cells and macrophages to the islets via CXCR3. These infiltrating autoreactive T-cells and macrophages release inflammatory cytokines including interferon-gamma in the islets, not only damaging beta-cells but also accelerating CXCL10 generation in residual beta-cells and thus further activating cell-mediated autoimmunity until all beta-cells have been destroyed.

FIG. 1.

A: Immunohistochemical demonstration of enterovirus-associated VP1 antigen in pancreatic islets (brown, arrows). Cells with shrunken and dark nuclei (arrows) suggestive of pyknosis, a sign of cell death, were observed (×400, case 1). B: Immunohistochemical staining for glucagon in serial sections of (A) (×400). Comparing (A) and (B) indicates enterovirus VP1 antigen residing on islet cells. C: Homogeneous staining for VP1 was observed in pancreatic acinar cell clusters (brown) with shrunken and darkly staining nuclei suggestive of pyknosis (arrows) (×400). (A high-quality digital representation of this figure is available in the online issue.)

FIG. 2.

Mononuclear cell infiltration into islets with residual β-cells (A) (brown), macrophages (B) (brown), and CD8+ T-cells (C) (brown) (×200, serial sections of case 1). D: Double immunofluorescent staining for CD11c+ dendritic cells (red) and insulin (blue) demonstrates that some dendritic cells surrounded and infiltrated into islets (×400, case 1). E: Double immunofluorescent staining for insulin (blue) and MHC class II antigen (green) demonstrates that some residual β-cells aberrantly express MHC class II molecules (light blue, arrows) (×400, case 1). F: Double immunostaining for CD68+ macrophages (red) and insulin (blue). Insulin was not stained in macrophages (×400, case 1). G: Double immunofluorescent staining for MHC class II molecules (green) and α-cells (blue) demonstrates aberrant expression of MHC class II molecules on vascular endothelium around and within the islets (arrows) (×400, case 1). H: Immunofluorescent staining demonstrates hyperexpression of MHC class I molecules (green) on islet cells (×200, case 1). I: Faint staining of MHC class I molecules (green) were observed on some nondiabetic control islet-cells (×200). J: Double immunostaining of the pancreatic section stained for CXCL10 (purple) and CXCR3 (brown). CXCR3-positive cells have infiltrated islet cells expressing CXCL10 (×200, case 1). (A high-quality digital representation of this figure is available in the online issue.)

FIG. 3.

Triple-immnofluorescent staining for CXCL10 (A), insulin (B), and glucagon (C). A merged image (D) demonstrates expression of CXCL10 on β-cells (light blue) (case 2). A proportion of α-cells (orange, arrowheads) and other types of islet cells (green) also express CXCL10 (×400, case 2). (A high-quality digital representation of this figure is available in the online issue.)

FIG. 4.

Triple-immunofluorescent staining for CXCL10 (A), insulin (B), and interferon-γ (C) in case 3. D: Merged image shows that residual β-cells express both CXCL10 and interferon-γ (arrows) (×400, case 3). (A high-quality digital representation of this figure is available in the online issue.)