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Virus adsorption and uptake of human rhinovirus 14 (HRV14) were studied with HeLa cells and baby hamster kidney (BHK) cells which were transfected with the HRV14 receptor intercellular adhesion molecule-1 (ICAM-1). Transmission electron microscopy of HeLa cells revealed that HRV14 was internalized via clathrin-coated pits and -coated vesicles. A minority of virus particles also used uncoated vesicles for entry. The internalization showed the characteristics of receptor-mediated endocytosis. Presence of the carboxylic ionophore monensin inhibited viral uncoating, indicating a pH-dependent entry mechanism. The expression of ICAM-1 on the surface of the ICAM-1 transfected baby hamster kidney cells (BHK-ICAM cells) allowed extensive virus adsorption and internalization through membrane channels. Virus particles were lined up in these channels like pearls on a string, but did not induce a productive infection. Although ICAM-1 was expressed to the same degree on BHK-ICAM and HeLa cells, HRV14 induced neither viral protein and RNA syntheses nor infectious virus progeny in BHK-ICAM cells. ICAM-1 on the transfected BHK cells was a functional active receptor as it rendered these cells permissive to coxsackievirus A21. These results suggest that HRV14 uptake into BHK-ICAM cells is blocked directly in or shortly after its final step of internalization, the uncoating. Our findings underline that the receptor ICAM-1 determines virus uptake into cells, however, is not sufficient to confer susceptibility of BHK cells to HRV14 infection.

Pseudorabies virus (PrV), an alphaherpesvirus of swine, uses cellular heparan sulfate residues as a receptor for attachment. Interaction of the virus with its receptor is mediated by the envelope glycoprotein C (PrV-gC), a protein with heparin-binding properties. We have previously shown that a region of this protein shows structural similarities to the high-affinity heparin-binding site of the serum protease-inhibitor antithrombin III (ATII). In this publication, we describe the effect of ATIII on interaction of PrV with its cellular receptor. ATIII bound specifically to heparan sulfate residues on the surface of herpesvirus-permissive RK13 cells. Binding of ATIII to RK13 cells interfered with adsorption of radioactively labelled PrV to these cells. Enzymatic treatment using heparinase I (E.C. 4.2.2.7) removed the receptor for PrV as well as the receptor for ATIII. Since amino acids 130-137 of the high affinity heparin-binding site of ATIII show structural similarities to amino acids 134-141 of PrV-gC, both sequences were synthesized as synthetic peptides. Although interaction of the peptide derived from ATIII with heparin was significantly stronger, both peptides interacted specifically with heparin in assays in vitro. These results suggest that PrV and ATIII interact with the same structure on the cellular surface.

The pseudorabies virus glycoprotein III (PrV-gIII) has been identified previously as the major viral component binding to a heparin-like receptor on the surface of target cells. The amino acid sequence of gIII contains three regions corresponding to consensus sequences for heparin binding. A synthetic peptide corresponding to amino acids 134 to 141 of PrV-gIII bound heparin in a dot blot assay. In contrast, a synthetic peptide derived from amino acids 290-299 of PrV-gIII did not bind heparin. We therefore conclude that the region containing amino acid 134-141 is involved in binding to the heparin-like cellular receptor.