Cell-specific regulation of APOBEC3F by interferons

Human cytidine deaminase APOBEC3F (A3F) has broad anti-viral activity against hepatitis B virus and retroviruses including human immunodeficiency virus type 1. However, its regulation in viral natural target cells such CD4⁺T lymphocytes, macrophages, and primary liver cells has not been well studied. Here we showed that A3F was up-regulated by interferon (IFN)-α in primary hepatocytes and multiple liver cell lines as well as macrophages. Although the IFN-α signaling pathway was active in T lymphoid cells and induction of other IFN stimulated genes such as PKR was detected, A3F and APOBEC3G (A3G) were not induced by IFN-α in these cells. Thus, additional factors other than known IFN-stimulated genes also regulated IFN-α-induced A3F expression distinctly. A3F and A3G expression levels in primary hepatocytes, especially after IFN-α stimulation, were comparable to those in CD4⁺T lymphocytes in some individuals. Significant variations of A3F and A3G expression in primary hepatocytes from various subjects were observed. Individual variations in A3F and/or A3G regulation and expression might influence the clinical outcomes of hepatitis B infection.