Heparan sulfate glycosaminoglycans are receptors sufficient to mediate theinitial binding of adenovirus types 2 and 5

Cell infection by adenovirus serotypes 2 and 5 (Ad2/5) initiates with the a ttachment of Ad fiber to the coxsackievirus and Ad receptor (CAR) followed by alpha (v) integrin-mediated entry. We recently demonstrated that heparan sulfate glycosaminoglycans (HS GAGs) expressed on cell surfaces are involv ed in the binding and infection of Ad2/5 (M. C. Dechecchi, A. Tamanini, A. Bonizzato, and G. Cabrini, Virology 268:382-390, 2000). The role of HS GAGs was investigated using extracellular soluble domain 1 of CAR (sCAR-D1) and heparin as soluble receptor analogues of CAR and HS GAGs in A549 and recom binant CHO cell lines with differential levels of expression of the two rec eptors and cultured to various densities. Complete inhibition of binding an d infection was obtained by preincubating Ad2/5 with both heparin (10 mug/m l) and sCAR-D1 (200 mug/ml) in A549 cells. Partial inhibition was observed when heparin and sCAR-D1 were preincubated separately with Ad. The level of heparin-sensitive [H-3]Ad2/5 binding doubled in sparse A549 cells (50 to 7 0,000 cells/cm(2)) with respect to that of cells grown to confluence (200 t o 300,000 cells/cm2), in parallel with increased expression of HS GAGs. [H- 3]Ad2 bound to sparse CAR-negative CHO cells expressing HS GAGs (CHO K1). N o [H-3]Ad2 binding was observed in CHO KI cells upon competitive inhibition with heparin and in HS GAG-defective CHO A745, D677, and E606 clones. HS-s ensitive Ad2 infection was obtained in CAR-negative sparse CHO K1 cells but not in CHO A745 cells, which were permissive to infection only upon transf ection with CAR. These results demonstrate that HS GAGs are sufficient to m ediate the initial binding of Ad2/5.