1,25-Dihydroxyvitamin D₃ prolongs graft survival without compromising host resistance to infection or bone mineral density

Background. Recently, we have shown that 1,25-dihydroxyvitamin D₃ prolongs graft survival in mice and rats when the donor and recipient differ at two or more major histocompatability loci. Among the most serious side effects encountered with the currently available transplantation antirejection drugs are an increased susceptibility to infection and decreased bone mineralization. Our results suggest that 1,25-dihydroxyvitamin D₃ prolongs graft survival without these side effects of bone loss and susceptibility to infection. Methods. We compared the ability of 1,25- dihydroxyvitamin D₃-treated, nontreated, or cyclosporine (CsA)-treated mice to resist infection with Candida albicans and herpes simplex virus-1. To determine bone density, femurs were collected from nontreated, 1-25- dihydroxyvitamin D₃-treated (50 ng/mouse/day), or CsA-treated (25 mg/kg/day) mice, and bone ash was determined. Results. Here we show that 1,25- dihydroxyvitamin D₃ treatment does not increase the susceptibility of the host to fungal or viral infection. Furthermore, CsA causes bone loss, whereas 1,25-dihydroxyvitamin D₃ actually increases bone mass. Conclusions. The use of 1,25-dihydroxyvitamin D₃ and its analogs to increase transplant survival will avoid bone loss and opportunistic infection, two important disadvantages of the most widely used transplant antirejection drugs-CsA and the glucocorticoids.