Results
Baseline characteristics
Thirty-eight patients were enrolled, 22 females and 16 males, two patients with previously diagnosed Type 1 diabetes and 3 patients with Autoimmune thyroiditis were exluded at screening. The mean age at study initiation was 37.5 years (+/- 13.31 SD, range: 17-75), the mean time of disease duration 10 years (+/- 7.59, range: 0.25-28). Twelve patients were treated with IVIG and 26 patients with SCIG, the mean dose 300mg/kg/month (+/- 59.6. range: 200-420). The dose of IRT remained unchanged during the duration of the entire study. The mean time of the participation in study was 2 years (+/-0.64, range: 0.25-2). There were no statistically significant differences in baseline characteristics between patient groups with negative and positive values of anti-GAD (>0.9 kU/mL) and anti-TPO (>60 kU/mL) autoantibodies respectively (Table 1).
The prevalence and clinical relevance of autoantibodies in CVID patients
Anti-TPO and anti-GAD autoantibodies markedly prevailed in the spectrum of assessed autoantibodies further including ANA (IgG), anti-dsDNA, anti-EMA (IgG), RF (IgG), ACLA (IgG), anti-F-actin, anti-SLA, anti-LKM1, anti-LC1, anti-AMAM2, anti-MPO, anti-PR3, anti-Sm, anti-RNP, anti-SS-A, anti-SS-B, anti-Scl70, anti-Jo-1, anti-IAA, anti-IA2 and anti-TG. We identified 68.4% (n=26/38) of patients with positive values of anti-TPO and 55.3% (n=21/38) with positive values of anti-GAD autoantibodies in the cohort of CVID patients during the study. Both, anti-TPO and anti-GAD were present in 36.8% of patients (n=14/38) Also, only 1/14 (7%) and 12/20 patietns (60%) with anti-GAD and anti-TPO positivity, respectively, who were followed for ≥1 year (the spectrum of autoantibodies assessed twice at least), remained positive for the entire study.
The mean titer of anti-GAD was 3.22 kU/L (+/- 3.94) in CVID patients, which was significantly lower (p ≤0.0001) compared to the levels of anti-GAD 22.0 kU/L (+/- 26.1) in T1D at the time of the diagnosis (Figure 1). The presence of anti-GAD antibodies in CVID patients was not associated with a disturbed inzulin production or an impaired glucose metablism. The serum levels of C-peptide (891 pmol/L, +/- 601) were comparable to anti-GAD negative CVID patients (924 pmol/L, +/- 781, p= 0.177). On the other hand, significant differences were found when C-peptide serum levels were compared to T1D patients (mean 266.8 pmol/L, +/- 235, p ≤0.0001) (Figure 2). Similar results were also observed with serum levels of glycosylated hemoglobin A1c (g-Hgb), which were comparable between anti-GAD positive CVID patients (32 mmol/mol, +/- 4.04) and negative patients (32 mmol/mol, +/- 5.86, p= 0.65). Conversly, the levels of g-Hgb were significantly higher in newly diagnosed T1D patients (68 mmol/mol, SD 33.06) than in anti-GAD positive CVID patients (p ≤0.0001). The serum concentrations of C-peptide as well as g-Hgb remained unchanged from the baseline to the end-of-study visit.
The mean titer of anti-TPO was 109.7 kU/L (+/- 97.4), which was also significantly lower (p ≤0.0001) in CVID patients compared to the mean levels of anti-TPO 713 kU/L (+/- 520) in AIT patients (Figure 3). The serum concentrations of both TSH and fT4 in anti-TPO positive CVID patients (TSH: 2.08 mIU/L, +/- 1.17, fT4: 14.49 pmol/L, +/- 1.53) did not differ from the anti-TPO negative CVID patients (TSH: 1.67 mIU/L, +/- 0.75, p= 0.218, fT4: 15.17, +/- 3.47, p= 0.518) and the concentration of TSH levels in anti-TPO positive CVID patients did not differ from the AIT patients (1.40 mIU/L, +/- 3.11, p= 0.826). The level of fT4 in anti-TPO positive CVID patients (14.49 pmol/L, +/- 1.53) was even significantly lower than in AIT group (16.71, +/- 2.57, p ≤0.0001). Nevertheless, the values were within normal ranges (11.50 - 22.70 pmol/L). Neither TSH nor fT4 altered during the follow-up period. Moreover, insignificant differences (p = 0.593) were also observed in the proportion of ultrasonographic (USG) evidence of AIT. The USG diagnosis of AIT was considered in only three out of 26 anti-TPO positive CVID patients. On the other hand, one CVID patient probably developed AIT according to USG but no anti-TPO autoantibodies were detected.
The detection of autoantibodies in immunoglobulin therapeutics
The spectrum of autoantibodies including ANA, anti-dsDNA, anti-EMA, RF, ACLA, anti-F-actin, anti-SLA, anti-LKM1, anti-LC1, anti-AMAM2, anti-MPO, anti-PR3, anti-Sm, anti-RNP, anti-SS-A, anti-SS-B, anti-Scl70, anti-Jo-1, anti-IAA, anti-IA2 and anti-TG were not detected or were found to be below the lower limit of reference value (with the exception of anti-TG in SCIG-16.5 solution). In contrast, the anti-GAD and anti-TPO were detected in very high levels in all the teste IRT. The titers of anti-GAD were fluctuating from 3.24 kU/L (+/-1.51, range: 0.9-4.74) in 10% IVIG-I to 24.48 kU/L (+/-13.94, 12.45-40.54) in 10% IVIG-II and anti-TPO from 123.6 kU/L (+/-7.43, 114.30-138.20) in 16.5% SCIG to 156.55 kU/L (+/-19.62, 108.70-165.40) 10% IVIG-I) (Table 2). Only the differences in the content of anti-GAD (p <0.0001) between particular therapeutics were statistically significant (Supplementary Figure 4 and 5).