The enzyme-linked immunosorbent assay (ELISA) was performed essentially as described previously [28] . In order to determine if the MPER peptide was surface exposed on the Ad virion whole virus ELISA was performed. Briefly, different amounts of viruses ranging from 4610 6 to 9610 9 VPs were immobilized on 96-well plate (Nunc Maxisorp, Rochester, NY) by overnight incubation in 100 ml of 100 mM carbonate buffer (pH 9.5) per well at 4uC. After washing with 0.05% Tween 20 in Phosphate-buffered saline (PBS) and blocking with blocking solution (2% bovine serum albumin and 0.05% Tween 20 in PBS), the immobilized viruses were incubated with anti-HIV 2F5 monoclonal antibody (cat# 1475) for 2 hr at room temperature (RT) followed by incubation with an AP-conjugated goat antihuman antibody. Colormetric reaction was performed with pnitrophenyl phosphate (Sigma-Aldrich, St. Louis, MO) as recommended by the manufacturer, and optical density at 405 nm (OD 405nm ) was determined with a microplate reader (Molecular Devices).