Viral evolution toward change in receptor usage: Adaptation of a major group human rhinovirus to grow in ICAM-1-negative cells

Major receptor group common cold virus HRV89 was adapted to grow in HEp-2 c ells, which are permissive for minor group human rhinoviruses (HRVS) but wh ich only marginally support growth of major-group viruses. After 32 blind p assages in these cells, each alternating with boosts of the recovered virus in HeLa cells, HRV89 acquired the capacity to effectively replicate in HEp -2 cells, attaining virus titers comparable to those in HeLa cells although no cytopathic effect was observed. Several clones were isolated and shown to replicate in HeLa cells whose ICAM-1 was blocked with monoclonal antibod y R6.5 and in COS-7 cells, which are devoid of ICAM-1. Blocking experiments with recombinant very-low-density lipoprotein receptor fragments and enzym e-linked immunosorbent assays indicated that the mutants bound a receptor d ifferent from that used by minor-group viruses. Determination of the genomi c RNA sequence encoding the capsid protein region revealed no changes in am ino acid residues at positions equivalent to those involved in the interact ion of HRV14 or HRV16 with ICAM-1. One mutation was within the footprint of a very-low-density lipoprotein receptor fragment bound to minor-group viru s HRV2. Since ICAM-1 not only functions as a vehicle for cell entry but has also a "catalytic" function in uncoating, the use of other receptors must have important consequences for the entry pathway and demonstrates the plas ticity of these viruses.