Screening of different bacterial and viral lysates for reactivity with CLL rAbs by immunoblot. (A) CMV- and mock-infected cells were both harvested at 96 hours p.i. for Western blot analysis with the CLL rAbs CLL69D. Human sera (Se CMV+ and Se CMV−) served as positive and negative controls, respectively. All bacterial and viral lysates were used at the same total protein concentration, and all experiments with virus- and mock-infected cell lysates were done in parallel on the same blot, respectively. (B) Visualization of protein bands on the nitrocellulose membranes after electrophoresis and protein transfer of CMV- and mock-infected cell lysates, respectively, with the use of Ponceau S staining solution. (C) Salmonella Typhimurium (St) was harvested after overnight incubation in Luria broth for Western blot analysis with the CLL rAbs CLL69D and CLL3-21U1. Immune serum (Se St+) served as positive control. (D) Ad2 or mock-infected A549 (Mock) cells were harvested at 48 hours p.i. for Western blot analysis with the CLL rAbs CLL69D and CLL3-21U1. Immune serum (Se Ad+) served as positive control. Experiments with mock- and adenovirus-infected cells were done in parallel on the same blot, respectively. Human sera without reactivity to any of the proteins present in the Salmonella Typhimurium or Ad2 lysates were not available, and all CMV reference sera used showed reactivity with several of the proteins (data not shown) because of extensive cross-reactivity between different serotypes. Actin served as loading control. The culture medium used for propagation of Salmonella Typhimurium was protein- and eukaryotic cell-free; therefore, probing with an actin-specific Ab was not done.