HIV-1, in contrast to MoMLV, does not spread in primary T-cells from hCD4/hCCR5-transgenic rats. (A) Activated primary T-lymphocytes from a human donor, a hCD4/hCCR5-transgenic, or a hCD4-single-transgenic rat were infected with HIV-1YU-2 (5 ng p24 CA per 2–3 × 106 cells) overnight and washed. Culture supernatants were monitored for the presence of p24 CA. Where indicated, cultures were treated with AZT (10 μM). (B) The same cultures were exposed to replication-competent ecotropic MoMLV-GFP. Percentages of GFP-positive, productively infected cells were determined by flow cytometry. All values are the arithmetic mean ± S.D. of triplicates. Data are representative for two independent experiments.