Background: 25OH-Vit D deficiency is common in hemodialysis (HD) patients despite therapy with 1,25OH-Vit D, and is associated with increased T cell memory. The purpose of this RCT was to test the hypothesis that oral D3 repletion prevents expansion of memory alloimmunity.

Methods: 61 25OH-Vit D deficient (<25ng/mL) HD patients were randomized to receive D3 (n=40) or no repletion (n=21) in a 2:1 ratio. Patients randomized to D3 received 50,000 IU/wk, goal 25OH-Vit D >35ng/mL. Blood was drawn at baseline and 1 yr for IFNΓ ELISPOT panel of reactive T cell assays (responder PBMCs tested against a panel of allogeneic stimulator B cell lines). Univariable analyses (parametric or nonparametric, as appropriate) were used to examine differences between groups, and paired analyses to examine variables over time.

Results: No significant differences in baseline characteristics were observed between patients in the D3 or control groups (Table 1). Baseline 25OH-Vit D levels were low in both groups, and median 25OH-Vit D level significantly increased at 1 yr in the D3 group only (41.3 [IQR 30.7,46.3], p<0.0001 vs baseline; 15.6 [IQR 9.4,19.6] control group). Total IFNΓ ELISPOTs at baseline were similar, but significantly higher in the control group at 1 year (599 [IQR 357,1240], p=0.03 vs baseline; 550 [IQR 301,759] D3 group) (Figure 1). No subjects experienced hypercalcemia or other adverse events with D3 repletion.

Conclusion: This is the first RCT showing an immunologic benefit to 25OH-Vit D repletion. These data are consistent with the idea that environmental stimulants increase alloimmunity in Vit D-deficient patients over time.

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