CYP27B1 and infection: The lack of positive correlation between CAMP and CYP27B1/VDR expression was not totally unexpected, as hMPV infection not only downregulated CAMP expression induced by inactive vitamin D (VD3 and 25(OH)D3), but also basal CAMP expression (VDR- and CYP27B1-independent) as well as 1,25(OH)2D3 induced CAMP expression (CYP27B1-independent) (Figures 1A,B).