Figure 1. ICAM-1 incorporation into HIV-1 pseudoviruses does not diminish specific infectivity.

(A) Western blotting analysis of purified HXB2 pseudoviruses lacking and containing ICAM-1 (ICAM⁻ and ICAM⁺, respectively). Equal amounts of p24 were analyzed for ICAM-1 and Env incorporation and proteolytic cleavage of Env. (B) Immunostaining of ICAM⁻ or ICAM⁺ HXB2 pseudotypes labeled with Gag-GFP (green). Viruses were immobilized onto a coverslip and incubated with anti-ICAM-1 antibody followed by anti-mouse Cy5-conjugated antibody (red). Colocalization of GFP and ICAM-1 staining (yellow) shows incorporation of ICAM-1 into virions. (C) Production of HXB2 pseudoviruses lacking or containing ICAM-1 by transfected 293T cells. The concentration of p24 in extracellular medium was determined by ELISA. (D) Viral titer for ICAM⁻ and ICAM⁺ viruses was determined on TZM-bl cells (negative for LFA-1) using β-Gal assay. Specific infectivity was calculated by dividing the viral titer (infectious units/ml) to the p24 content (pg/ml). Data points are means and SEM for three independent experiments performed in triplicate.