CYP27A1 and viral infectious disease: Viral infection can induce immediate early NF-κB activation and triggers the rapid transcription of the BA transporter SLCO1B2 (solute carrier organic anion transporter family member 1B2) and BA-synthesis-rate-limiting enzymes, including CYP7A1 (cholesterol 7α-hydroxylase), CYP7B1 (cytochrome P450 family member 7B1), and CYP27A1 (cytochrome P450 family member 27A).