Cytomegalovirus Infection Downregulates Vitamin D Receptor in Patients Undergoing Hematopoietic Stem Cell Transplantation.

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative option for patients with hematologic diseases but is associated with high mortality and morbidity. Cytomegalovirus (CMV) infection is common in HSCT patients and modulates vitamin D metabolism in vitro. We aimed at validating CMV-associated vitamin D metabolism in vivo in HSCT.

Methods: Patients treated for significant CMV viremia after HSCT were evaluated for CMV load before, during, and after antiviral treatment. RNA was isolated from whole-blood samples to test for regulation of key components of the vitamin D receptor (VDR) pathway during different phases of CMV viremia.

Results: CMV viremia developed a mean time of 102 (±34) d post-HSCT. Maximum levels of CMV-DNA reached a mean of 5668 (±7257) copies/mL. VDR expression was downregulated to a mean of 64.3% (±42.5%) relative to the VDR expression pre-CMV viremia (P = 0.035) and lagged in recovery following antiviral treatment. Toll-like receptor (TLR) 2 mRNA was upregulated to 225.4% during CMV viremia relative to the expression pre-CMV viremia (P = 0.012) but not TLR6/7/8 and the TLR-adaptor protein MyD88. Levels of 25-OH vitamin D were reduced in all viremic patients (48.0 ± 4.8 versus 25.1 ± 3.7 ng/mL) and were even lower after periods of CMV viremia compared with the control group (48.3 ± 3.5 versus 17.8 ± 1.8 ng/mL; P = 0.008).

Conclusions: CMV viremia is associated with significant dysregulation of vitamin D metabolism in HSCT patients.