Gestational respiratory infections interacting with offspring HLA and CTLA-4 modifies incident β-cell autoantibodies

Abstract

β-cell autoantibodies against insulin (IAA), GAD65 (GADA) and IA-2 (IA-2A) precede onset of childhood type 1 diabetes (T1D). Incidence of the first appearing β-cell autoantibodies peaks at a young age and is patterned by T1D-associated genes, suggesting an early environmental influence. Here, we tested if gestational infections and interactions with child's human leukocyte antigen (HLA) and non-HLA genes affected the appearance of the first β-cell autoantibody. Singletons of mothers without diabetes (n = 7472) with T1D-associated HLA-DR-DQ genotypes were prospectively followed quarterly through the first 4 years of life, then semiannually until age 6 years, using standardized autoantibody analyses. Maternal infections during pregnancy were assessed via questionnaire 3-4.5 months post-delivery. Polymorphisms in twelve non-HLA genes associated with the first appearing β-cell autoantibodies were included in a Cox regression analysis. IAA predominated as the first appearing β-cell autoantibody in younger children (n = 226, median age at seroconversion 1.8 years) and GADA (n = 212; 3.2 years) in children aged ≥2 years. Gestational infections were not associated with the first appearing β-cell autoantibodies overall. However, gestational respiratory infections (G-RI) showed a consistent protective influence on IAA (HR 0.64, 95% CI 0.45-0.91) among CTLA4-(AG, GG) children (G-RI*CTLA4 interaction, p = 0.002). The predominant associations of HLA-DR-DQ 4-8/8-4 with IAA and HLA-DR-DQ 3-2/3-2 with GADA were not observed if a G-RI was reported (G-RI*HLA-DR-DQ interaction, p = 0.03). The role of G-RI may depend on offspring HLA and CTLA-4 alleles and supports a bidirectional trigger for IAA or GADA as a first appearing β-cell autoantibody in early life.

Keywords: Autoimmune diabetes; Autoimmunity; Glutamic acid decarboxylase; HLA; IA-2; Insulin; Type 1 diabetes; β-cell autoantibodies.

Fig 1. Smoothed incidence curve of IAA and GADA as first appearing β-cell autoantibodies from birth to age six years by report of a Gestational Respiratory Infection (G-RI) and offsprings CTLA-4 genotype

A LOWESS curve was plotted through the observed incidences of first appearing β-cell autoantibodies calculated at 3 month intervals during the first 4 years of life and at 6 month intervals thereafter. Incidence curves for IAA-first (panels A and B) and GADA-first (panels C and D) were drawn for children with the CTLA-4 AA (red), AG (black) and GG (blue) genotypes and separately for those offspring of mothers who did (panels B and D) or did not report a G-RI (panels A and C). P-values describing the differences in the risk of the first appearing β-cell autoantibody across the CTLA-4 genotypes were calculated from Proportional Hazard models of CTLA-4 genotypes regressed on the autoantigen-specific hazard of β-cell autoimmunity. The overall Wald test p-value is shown in each panel. In panel (A) IAA-first appeared in 29/1016 with CTLA-4 AA genotype, 61/1576 with CTLA-4 AG and 24/651 with CTLA-4 GG among children with no reported G-RI. In panel (B) IAA-first appeared in 43/955 with CTLA-4 AA, 35/1498 with CTLA-4 AG and 16/561 with CTLA-4 GG among children with a reported G-RI. In panel (C) GADA-first appeared in 33/1016 with CTLA-4 AA, 54/1576 with CTLA-4 AG and 21/651 with CTLA-4 GG among children with no reported G-RI. In panel (D) GADA-first appeared in 19/955 with CTLA-4 AA, 51/1498 with CTLA-4 AG and 26/561 with CTLA-4 GG among children with a reported G-RI.

Fig 2. Country specific assocaiation between CTLA-4 G allele and first appearing β-cell autoantibodies by whether or not a gestational respiratory infection (G-RI) was reported

The association between a child having the CTLA-4 G allele and risk of IAA (panels A and B) or GADA (panels C and D) as the first appearing β-cell autoantibodies are evaluated by Proportional Hazard models. The autoantigen-specific hazard ratios (HR) and 95% CI are provided overall and by country both for offspring of mothers who did (panels B and D) and did not (panels A and C) a reported G-RI. HR<1 indicated children with CTLA-4 G allele had a lower autoantigen-specific risk of the first appearing autoantibody. In panels A and C, CTLA-4 G was shown in relation to IAA-first (A) and GADA-first (C) for 3243 offspring (1273 US, 658 Finland, 155 Germany, 1157 Sweden) of mothers not reporting a G-RI. In panels B and D, CTLA-4 G was shown in relation to IAA-first (B) and GADA-first (D) for 3014 offspring (1307 US, 646 Finland, 198 Germany, 863 Sweden) of mothers who did report a G-RI.

Fig 3. Smoothed incidence curve of IAA and GADA as first appearing β-cell autoantibodies from birth to age six years by report of a gestational respiratory Infection (G-RI) and offsprings HLA-DR-DQ genotype

A LOWESS curve was plotted through the observed incidences of first appearing β-cell autoantibodies calculated at 3 month intervals during the first 4 years of life and at 6 month intervals thereafter. Incidence curves for IAA-first (panels A and B) and GADA-first (panels C and D) were drawn for children with the HLA-DR-DQ3-2/4-8 (red), HLA-DR-DQ4-8/4-8 (black), HLA-DR-DQ4-8/8-4 (blue) and HLA-DR-DQ3-2/3-2 (brown) genotypes and separately for those offspring of mothers who did (panels B and D) or did not report a G-RI (panels A and C). P-values describing the differences in the risk of the first appearing β-cell autoantibody across the HLA genotypes were calculated from Proportional Hazard models that regressed HLA on the autoantigen-specific hazard of β-cell autoimmunity. The overall Wald test p-value is shown in each panel. In panel (A) IAA-first appeared in 47/1415 with HLA-DR-DQ3-2/4-8 genotype, 18/741 with HLA-DR-DQ4-8/4-8, 35/645 with HLA-DR-DQ4-8/8-4 and 11/755 with HLA-DR-DQ3-2/3-2 for children with no reported G-RI. In panel (B) IAA-first appeared in 54/1363 with HLA-DR-DQ3-2/4-8, 18/655 with HLA-DR-DQ4-8/4-8, 14/576 with HLA-DR-DQ4-8/8-4 and 5/735 with HLA-DR-DQ3-2/3-2 for children with a reported G-RI. In panel (C) GADA-first appeared in 52/1415 with HLA-DR-DQ3-2/4-8, 16/741 with HLA-DR-DQ4-8/4-8, 7/645 with HLA-DR-DQ4-8/8-4 and 33/775 with HLA-DR-DQ3-2/3-2 for children with no reported G-RI. In panel (D) GADA-first appeared in 51/1363 with HLA-DR-DQ3-2/4-8, 15/655 with HLA-DR-DQ4-8/4-8, 14/576 with HLA-DR-DQ4-8/8-4 and 17/735 with HLA-DR-DQ3-2/3-2 for children with no reported G-RI.

Fig 4. Country specific association between HLA-DR-DQ4-8/8-4 (DQ8/4) genotype and first appearing β-cell autoantibodies by whether or not a gestational respiratory infection (G-RI) was reported

The association between a child having the HLA-DQ8/4 genotype and risk of IAA (panels A and B) or GADA (panels C and D) as the first appearing β-cell autoantibodies are evaluated by Proportional Hazard models. The autoantigen-specific hazard ratios (HR) and 95% CI are provided overall and by country, both for offspring of mothers who did (panels B and D) and did not (panels A and C) a reported G-RI. HR<1 indicated children with the HLA-DQ8/4 genotype had a lower autoantigen specific risk of the first appearing autoantibody. In panels A and C, HLA-DQ8/4 was shown in relation to IAA-first (A) and GADA-first (C) for 3647 offspring (1491 US, 712 Finland, 188 Germany, 1256 Sweden) of mothers not reporting a G-RI. In panels B and D, HLA-DQ8/4 was shown in relation to IAA-first (B) and GADA-first (D) for 3411 offspring (1563 US, 688 Finland, 235 Germany, 925 Sweden) of mothers who did report a G-RI.