Fig. 1.

Structure and replication of EcoHIV. (A) Schematic map of EcoHIV. HIV-1 env (1,405 bp) was excised and replaced by the coding region of the MLV ecotropic envelope gp80 with its stop codon in place. All HIV-1 cis-regulatory elements were preserved and expression of the entire construct was driven by the HIV-1 LTR. (B–D) Replication of EcoHIV in murine lymphocytes in culture. Mitogen-stimulated splenic lymphocytes were infected with EcoHIV. (B) Cultures were sampled over time for p24 expression by immunoblot, compared with human CEM cells infected by HIV-1 or EcoHIV. The amount of p24 detected by ELISA in EcoHIV-infected lymphocyte cultures underestimates the protein detected by Western blotting. (C and D) At 7 d after infection, cells were stained for HIV-1 antigens (C Right) and uninfected cells were stained in parallel (C Left) or cocultured with a 9-fold excess of uninfected cells and examined for syncytia after 2 d (D).