Diabetologia: Detection of enterovirus RNA in peripheral blood mononuclear cells is associated with the presence of a susceptibility allele of the type 1 diabetes risk gene IFIH1 and disease stage

Background: Type 1 diabetes is caused by the progressive loss of insulin-producing beta cells in pancreatic islets
.
Genetic factors are important in susceptibility to disease development
.
However, the coincidence rate for identical twins is only about 50%, and the incidence has steadily increased, especially in those individuals with lower genetic susceptibility, suggesting that environmental factors also play a key role
.
A prominent candidate environmental factor is viral infection, particularly infection with coxsackieviruses, a subgroup of enteroviruses (EVs) that have been extensively studied and associated with type 1 diabetes
.
EVs were detected more frequently in stool samples, pancreatic biopsies, and peripheral blood of patients with type 1 diabetes than those without type 1 diabetes, and the presence of anti-coxsackievirus neutralizing antibodies was associated with beta-cell autoimmunity
.
Studies have shown that EVs are more common in both serum/plasma and peripheral blood mononuclear cells (PBMCs) in patients with type 1 diabetes and islet autoimmunity
.
Similarly, EV infection was detected in pancreatic tissue in approximately 70% of postmortem donors with recent onset type 1 diabetes, compared with less than 10% of postmortem donors with non-type 1 diabetes of similar age
.

Mechanistically, there is an interaction between EV infection and genetic variants that predispose to type 1 diabetes
.
Several risk-determining variants have been identified in the interferon gene IFIH1 (interferon induced with helicase C domain 1) encoding the cytoplasmic viral pattern recognition receptor melanoma differentiation-associated protein 5 (MDA5)
.
MDA5 is essential for the detection of members of the PicorNaviridae family, and its activation leads to the production of type I interferons and proinflammatory cytokines
.
Most informatively, there are four rare SNPs that reduce or eliminate the function of MDA5, and that these variants all confer protection against type 1 diabetes
.
For the common SNP rs1990760 (Thr946Ala) in IFIH1, 946Thr is the susceptible allele
.
In PBMCs, a disease-protective allele (946Ala) was associated with reduced expression of IFIH1 under basal conditions or after stimulation with interferon beta or polyinosinic acid
.
Functionally, however, a greater degree of divergence has been reported, with one study finding protection associated with reduced type I interferon responses, which was not seen in other studies
.
Another study observed a reduction in type III, but not type I, interferon responses in virus-infected islets in donors homozygous for the IFIH1 susceptible allele
.

OBJECTIVE: Enterovirus infection has long been recognized as a key environmental factor associated with the emergence of autoimmunity and/or overt type 1 diabetes, in which insulin-producing pancreatic beta cells are destroyed by an autoimmune response
.
Genetic susceptibility of the type 1 diabetes risk gene IFIH1 (interferon induced with helicase C domain 1), encoding the viral pattern recognition receptor melanoma differentiation-associated protein 5 (MDA5), supports the link between enterovirus infection and type 1 diabetes potential connection between
.

METHODS: Molecular biology techniques were used to detect enterovirus RNA in peripheral blood samples of 79 children and 72 adults, of which patients with type 1 diabetes and those without type 1 diabetes had multiple autoantibodies
.
We also detected the expression of enterovirus protein VP1 in pancreatic islet tissue from 43 postmortem patients with type 1 diabetes by immunohistochemistry
.

Results The detection sensitivity of peripheral blood cell compartment specimens was higher than that of non-cell compartment specimens (OR21.
69; 95%CI3.
64,229.
20; P<0.
0001)
.
In addition, we showed that children with autoimmunity were more likely than children without autoimmunity to test positive for enterovirus RNA (OR 11.
60; 95% CI 1.
89, 126.
90; P=0.
0065)
.
In addition, we found that individuals carrying the susceptible allele (946Thr) of a common variant of IFIH1 (rs1990760, Thr946Ala) were more likely to be positive for enteroviruses in peripheral blood (OR 3.
07; 95% CI 1.
02, 8.
58; p=0.
045)
.
In contrast, using immunohistochemistry, no correlation was detected between the enterovirus VP1 protein and variants commonly found in IFIH1 in pancreatic islets from donors with type 1 diabetes
.

Figure 1 Detection of EV-RNA in peripheral blood
.
In the pediatric cohort, specific subgroups (D) were assessed for the presence of EV-RNA in plasma and PBMC (A) and PBMC (D)
.
In an adult cohort, the presence of EV-RNA was assessed in defined peripheral blood cell subsets (B) and in individuals with and without type 1 diabetes (C)
.
Red shading indicates EV-RNA positivity; white indicates EV-RNA negativity
.
The difference between the two groups was statistically significant: *p<0.
001; **p<0.
01; *p<0.
05
.
T1D, type 1 diabetes

Table 1 Detection of EV-RNA and IFIH1 genes in children and adults

Table 2 Detection of EV-RNA ORs according to IFIH1 variants

Figure 2 Detection of EV capsid protein VP1 in islet slices
.
The expression of EV capsid protein VP1 in the tissues of 43 patients with type 1 diabetes was detected by immunohistochemistry, and IFIH1 gene mutation (rs1990760, Thr946Ala) was found
.
Red shading indicates EV-RNA positivity; white indicates EV-RNA negativity
.
The difference between the two groups was not statistically significant (Fisher's exact test, two-sided)

Conclusions: Our data suggest that in peripheral blood, antigen-presenting cells are the major source of enterovirus infection, and infection is associated with disease stage and genetic susceptibility, supporting a role for enterovirus infection prior to disease onset
.

Original source: Sioofy-Khojine AB, Richardson SJ, Locke JM, et al.
Detection of enterovirus RNA in peripheral blood mononuclear cells correlates with the presence of the predisposing allele of the type 1 diabetes risk gene IFIH1 and with disease stage.
Diabetologia 2022 Jul twenty two