α-Defensin-1 inhibited HIV-1 infection following reverse transcription and integration. Activated CD4+ T cells infected with HIV-1HxB2–pseudotyped replication-defective luciferase virus were treated with α-defensin-1 at 5 μg/ml, or with AZT at 5 μM (A) or L-731,988 at 10 μM (B), at different time points after infection. Infected cells were collected at 48 hours after infection, and luciferase activity was measured. P < 0.05, α-defensin-1–treated cells vs. nontreated controls at different time points, α-defensin-1–treated vs. AZT-treated cells at 9 and 16 hours after infection, α-defensin-1–treated vs. L-731,988–treated cells at 24 hours after infection. Data are mean ± SD of triplicate samples and represent 3 independent experiments.