151. The Minor Receptor Group of Human Rhinovirus (HRV) Includes HRV23 and HRV25, but the Presence of a Lysine in the VP1 HI Loop Is Not Sufficient for Receptor Binding
- Author
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Dieter Blaas, Tapani Hovi, Luc Snyers, Pia Laine, Irene Goesler, Manuela Reithmayer, Merja Roivainen, and Marketa Vlasak
- Subjects
Rhinovirus ,Picornavirus ,Molecular Sequence Data ,Immunology ,Receptors, Cytoplasmic and Nuclear ,Virus Replication ,medicine.disease_cause ,Microbiology ,Maltose-Binding Proteins ,Viral Proteins ,Maltose-binding protein ,Virology ,Chlorocebus aethiops ,medicine ,Animals ,Humans ,Amino Acid Sequence ,Serotyping ,Binding site ,Receptor ,Binding Sites ,biology ,Lysine ,Ligand (biochemistry) ,biology.organism_classification ,Molecular biology ,Fusion protein ,Virus-Cell Interactions ,Receptors, LDL ,Insect Science ,COS Cells ,LDL receptor ,biology.protein ,Enterovirus ,Carrier Proteins ,Sequence Alignment ,HeLa Cells ,Transcription Factors - Abstract
Human rhinoviruses (HRVs), the main causative agents of common cold, were originally classified as acid-sensitive picornaviruses (34). Later, based on competition for cellular binding sites, two different groups of viruses using nonidentical receptors for cell attachment were defined within the genus Rhinovirus (18). Subsequently, 24 (1) and finally 100 serotypes (counting the subtypes HRV1A and HRV1B as one strain) were assigned to the two receptor groups by using cross-competition and inhibition of cell binding by a monoclonal antibody recognizing intercellular adhesion molecule 1 (ICAM-1), the receptor of the major group of HRVs (32, 33, 35). According to these reports, 90 serotypes bind ICAM-1, whereas both subtypes of HRV1 (HRV1A and HRV1B) and 8 other serotypes were categorized as belonging to the minor group; they were later shown to use members of the low-density-lipoprotein receptor (LDLR) family for cell entry (12, 20, 36). HRV87 was noted to be an exception in that it binds a sialylated membrane protein. Based on comparison of nucleotide sequences in several genomic regions, HRV87 was subsequently classified as an acid-sensitive enterovirus and found to be a prime strain of enterovirus 68 that uses decay-accelerating factor as a receptor (2, 27). By phylogenetic analysis of capsid protein VP4/VP2 coding sequences of all HRV prototype strains, 74 HRV serotypes, including all the minor receptor group ones, were classified as HRV species A, while the 25 remaining serotypes form HRV species B (27). In a paper from the Colonno group, primary data on the competition with an ICAM-1-blocking antibody were not explicitly presented for all serotypes, in particular not for HRV23 and HRV25, and the presumed allocation of all HRVs to either group was depicted only in the form of a summarizing figure (35). Despite this, it was generally accepted that 90 serotypes, including HRV23 and HRV25, were major group viruses. Later, Crump and colleagues reported that recombinant soluble ICAM-1 and a chimeric ICAM-1/immunoglobulin A molecule failed to neutralize these two serotypes and concluded that they most probably use a receptor different from the major and minor group receptors (4, 5). This finding remained largely unnoticed by the picornavirus community. As soon as the capsid protein VP1 sequences of all human rhinoviruses were determined (15, 16), we became aware of genetic clustering of HRV23 and HRV25 close to certain minor receptor group serotypes and of the presence of a lysine in the HI loop. This residue is strictly conserved in all minor group viruses and is believed to be essential but not sufficient for attachment to members of the LDLR family (37). A lysine is also present at the equivalent position in HRV8, -18, -24, -40, -54, -56, -58, -85, -95, and -98. However, these latter serotypes had been explicitly shown to be neutralized by soluble recombinant ICAM-1 (5). Therefore, we wondered whether at least HRV23 and HRV25 might use members of the LDLR family as receptors. We also wondered whether the other HRVs containing the conserved lysine might eventually possess dual receptor specificity and attach to ICAM-1 as well as to LDLR. The ligand binding domain at the N terminus of LDLR that is implicated in binding minor group HRVs is composed of seven imperfect direct repeats of roughly 40 amino acid residues in length. Three disulfide bridges and a Ca2+ ion within an octagonal cage formed by the carboxylates of three aspartates and one glutamate, together with two backbone oxygens, stabilize this structure (7). The very-low-density lipoprotein receptor (VLDLR) and LDLR-related protein (LRP) possess 8 and 31 such modules, respectively (30). In LRP the modules are not contiguous but are arranged in clusters of 2, 8, 10, and 11. We have previously shown that a soluble recombinant fusion protein composed of the maltose binding protein (MBP) and an artificial concatemer of five copies of repeat 3 (V3) of VLDLR arranged in tandem (MBP-V33333) exhibits strong virus neutralization capacity toward the 10 minor group HRVs (36). Therefore, by using cell protection assays with this protein, ligand blots, and replication in COS-7 cells that do not express ICAM-1, we investigated the nature of the strains containing a lysine residue in the HI loop and found that HRV23 and HRV25 possess all characteristics of minor group viruses. Examination of the major group serotypes with the lysine in the HI loop as mentioned above showed that none was able to use both ICAM-1 and LDLR for cell binding. Therefore, out of the numbered 99 HRV serotypes, altogether, 12 serotypes (if we count HRV1A and -B separately) belong to the minor receptor group.
- Published
- 2005