Intracellular inhibition of HIV by hBD2 is mediated by the induction of APOBEC3G. (A) siRNA knockdown of APOBEC3G in CD4⁺ T cells. (B) CD4⁺ T cells transfected with APOBEC3G-specific siRNA or mutant APOBEC3G siRNA were infected with X4 (IIIB) HIV. After virus removal and washing, hBD2 (20 μg/mL) was added to the tissue culture media. Total cellular DNA was isolated at the indicated time points, and the presence of early reverse transcription products was determined by real-time PCR. (C) Triplicate readings were averaged, and inhibition was determined as a percentage of the number of copies of early reverse transcription products in infected treated cells in reference to copies measured in untreated control infections. Shown here are mean percentage of inhibition (± SEMs) of 4 independent experiments that used cells from different donors.