Involvement of cellular adhesion sequences in the attachment of adenovirus to the HeLa cell surface

Immunofluorescence analysis of HeLa cells incubated with human adenovirus serotype 2 (Ad2) inoculum suggested that Ad2 receptors co-localized with the receptors of fibronectin (FNR) and vitronectin (VNR) at the cell surface. Ad2 adsorption also resulted in the occurrence of intracytoplasmic actin cables with submembranal anchorage. The cell binding of Ad2 virions, pentons and fibres was found to be efficiently inhibited by concanavalin A, laminin, anti-FNR and anti-VNR antibodies. Arginine-glycine-aspartyl tripeptide (RGD) and other related peptides reproducing cellular attachment sequences of adhesion proteins also competed with Ad2 for cell adsorption, and drastically reduced the virus progeny yield at the end of the infectious cycle. Data from binding competition assays with Ad2 virions showed that the apparent affinity constants of RGD motif-containing peptides for Ad2 receptor ranged from 0.75 x 10(8) M-1 to 2.2 x 10(8) M-1, with a number of peptide recognizing sites varying from 1.5 x 10(4) to 9 x 10(4) per cell for the different peptides studied. Polypeptide analysis of labelled plasma membrane fractions isolated after cross-linking to unlabelled Ad2 virions showed three major protein species with apparent M(r) of 130K, 60K and 44K, respectively, reacting with anti-FNR and anti-VNR antibodies. These results suggested that Ad2 and extracellular matrix proteins recognize similar adhesion sequences at the surface of HeLa cells, or alternatively that integrins and Ad2 receptors have overlapping ligand specificity.