Ljungan virus (LV) has been implemented as a risk factor for either islet autoimmunity, clinical onset of diabetes in islet autoantibody positive children, or both. LV antibodies (LVA) were associated with insulin autoantibodies (IAA) in young age at onset DQ8-positive type 1 diabetes (T1D) children from Southern Sweden. The specificity of LVA, determined in a radiobinding assay (RBA) with LV cDNA has been questioned as cross-reactivity with human parechovirus could not be excluded. The aim of the present study was to validate and confirm LVA in T1D patients and controls from Northern Sweden using both RBA and an indirect antibody (IgG) capture immunoassay (ACI).
A total of 69 T1D patients newly diagnosed at 1-18 years of age and 294 healthy controls (all 14 years of age) were ascertained in 2005-2011 in the county of Jämtland. LVA were analyzed by RBA and antibodies to a total of 4 LV VP1 (lj), 10 human parechovirus 3 (hpa) and some other hpa peptides analyzed by ACI. A/H1N1 antibodies were also analyzed. Islet autoantibodies (IAA, GADA, IA-2A and ZnT8R,W and QA) were analyzed by IASP harmonized RBA.
Also in Northern Swedish subjects, LVA was associated with IAA (p<0.01) and HLA-DQ (p<0.01). Antibodies against the hpa 3 peptides showed significant inter-peptide antibody correlation (p<0.003-0.001) as did the LV peptide (p<0.001) ACI antibodies. ACI antibodies against LV peptide VP1 31-60 correlated to LVA (p<0.009) as did the polyprotein LV peptide 2193-2222 (p<0.001). VP1 31-60 (p<0.007) but not 2193-2222 (p=0.153) correlated to IAA. Among 10 hpa peptides, only VP1 1-30 (p<0.001) and VP1 95-124 (p<0.009) also correlated to LVA. None of these peptide sequences are represented in the LV.
In conclusion, the association between LVA and IAA was confirmed in subjects from Northern Sweden also extended to CIA antibodies against the LV VP1 31-60 peptide.