Detection of enterovirus in the islet cells of patients with type 1 diabetes: what do we learn from immunohistochemistry?

Immunohistochemical detection of enteroviruses in pancreatic tissues of patients with type 1 diabetes using a polyclonal antibody against 2A protease of Coxsackievirus

AIMS/INTRODUCTION

The need for antiserum for immunohistochemical (IHC) detection of enterovirus (EV) in formaldehyde-fixed and paraffin-embedded samples is increasing. The gold standard monoclonal antibody (clone 5D8/1) against EV-envelope protein (VP1) was proven to cross-react with other proteins. Another candidate marker of EV proteins is 2A protease (2Apro ), which is encoded by the EV gene and translated by the host cells during EV replication, and participates processing proproteins to viral capsid proteins.

MATERIALS AND METHODS

We raised polyclonal antiserum by immunizing a rabbit with an 18-mer peptide of Coxsackievirus B1 (CVB1)-2Apro , and examined the specificity and sensitivity for EV on formaldehyde-fixed and paraffin-embedded tissue samples.

RESULTS

Enzyme-linked immunosorbent assay study showed a high titer of antibody for 18-mer peptide of CVB1-2Apro , cross-reacting with CVB3-2Apro peptide. IHC showed that antiserum against 2Apro reacted with CVB1-infected and VP1-positive Vero cells. Confocal laser scanning microscopy showed that antigen stained by the 2Apro antibody located in the same cell with VP1 stained by 5D8/1. IHC using 2Apro antiserum showed dense staining in the islets of EV-associated fulminant type 1 diabetes pancreas and that located in the same cell stained positive for VP1 (5D8/1). Specificity of 2Apro antiserum by IHC staining was confirmed by negative 2Apro in 14 VP1-negative non-diabetes control pancreases.

CONCLUSIONS

Our study provides a new polyclonal antiserum against CVB1-2Apro , which might be useful for IHC of EV-infected human tissues stored as archive of formaldehyde-fixed and paraffin-embedded tissue samples.

An ancestral retroviral protein identified as a therapeutic target in type-1 diabetes

Human endogenous retroviruses (HERVs), remnants of ancestral viral genomic insertions, are known to represent 8% of the human genome and are associated with several pathologies. In particular, the envelope protein of HERV-W family (HERV-W-Env) has been involved in multiple sclerosis pathogenesis. Investigations to detect HERV-W-Env in a few other autoimmune diseases were negative, except in type-1 diabetes (T1D). In patients suffering from T1D, HERV-W-Env protein was detected in 70% of sera, and its corresponding RNA was detected in 57% of peripheral blood mononuclear cells. While studies on human Langerhans islets evidenced the inhibition of insulin secretion by HERV-W-Env, this endogenous protein was found to be expressed by acinar cells in 75% of human T1D pancreata. An extensive immunohistological analysis further revealed a significant correlation between HERV-W-Env expression and macrophage infiltrates in the exocrine part of human pancreata. Such findings were corroborated by in vivo studies on transgenic mice expressing HERV-W-env gene, which displayed hyperglycemia and decreased levels of insulin, along with immune cell infiltrates in their pancreas. Altogether, these results strongly suggest an involvement of HERV-W-Env in T1D pathogenesis. They also provide potentially novel therapeutic perspectives, since unveiling a pathogenic target in T1D.

Application of bioinformatics in probe design enables detection of enteroviruses on different taxonomic levels by advanced in situ hybridization technology

BACKGROUND

Enteroviral infections are common, affecting humans across all age groups. RT-PCR is widely used to detect these viruses in clinical samples. However, there is a need for sensitive and specific in situ detection methods for formalin-fixed tissues, allowing for the anatomical localization of the virus and identification of its serotype.

OBJECTIVES

The aim was to design novel enterovirus probes, assess the impact of probe design for the detection and optimize the new single molecule in situ hybridization technology for the detection of enteroviruses in formalin-fixed paraffin-embedded samples.

STUDY DESIGN

Four enterovirus RNA-targeted oligonucleotide RNA probes - two probes for wide range enterovirus detection and two for serotype-targeted detection of Coxsackievirus B1 (CVB1) - were designed and validated for the commercially available QuantiGene ViewRNA in situ hybridization method. The probe specificities were tested using a panel of cell lines infected with different enterovirus serotypes and CVB infected mouse pancreata.

RESULTS

The two widely reactive probe sets recognized 19 and 20 of the 20 enterovirus serotypes tested, as well as 27 and 31 of the 31 CVB1 strains tested. The two CVB1 specific probe sets detected 30 and 14 of the 31 CVB1 strains, with only minor cross-reactivity to other serotypes. Similar results were observed in stained tissues from CVB -infected mice.

CONCLUSIONS

These novel in-house designed probe sets enable the detection of enteroviruses from formalin-fixed tissue samples. Optimization of probe sequences makes it possible to tailor the assay for the detection of enteroviruses on the serotype or species level.