The rhinovirus group comprises at least 115 accepted
serotypes and more that are not yet classified. These picornaviruses are small
(20 to 30 nm), naked particles containing sin-gle-stranded, positive-sense RNA.
They are distinguished from enteroviruses by their acid lability and an optimum
temperature of 33 C for in vitro replication. This temperature approximates
that of the nasopharynx in the human host and may be a factor in the
local-ization of pathologic findings at that site. Rhinoviruses are most
consistently isolated in cultures of human diploid fibroblasts. The receptor
for most rhinoviruses (and some cox-sackieviruses) is glycoprotein
intercellular adhesion molecule 1 (ICAM-1), a member of the immunoglobulin
supergene family. ICAM-1 is best known for its role in immunologic cell
adhesion; its ligand is lymphocyte function-associated antigen-1.