8 Entry of Minor Group Human Rhinoviruses into the Cell

Abstract

So far, there are 102 immunologically characterized serotypes of human rhinoviruses (HRVs), the main pathogens of the common cold (Uncapher et al. 1991). HRVs belong to the large family of picornaviridae, characterized by an icosahedral protein shell assembled of 60 protomers which in turn contain one copy of the viral capsid proteins VP1 through VP4 (for review, see Stanway 1990). The RNA genome is of positive polarity and about 7500 nucleotides in length. Following entry into the cytoplasm, it is translated into a polyprotein, which is cotranslationally cleaved into the structural and nonstructural proteins by two virus-encoded proteinases (see, e.g., Kuechler et al. 1993). Concomitantly with RNA encapsidation, a maturation cleavage of VP0 to VP2 and VP4 takes place. This is carried out by a proteinase which has not yet been identified.

The majority (91 serotypes) of the HRVs gain access to the cell via the intercellular adhesion molecule 1 (ICAM-1). How this protein manages the rapid delivery of the virus into the cell is not clear, since it is devoid of an internalization signal in its cytoplasmic carboxy-terminal region (Greve et al. 1989; Staunton et al. 1989; Tomassini et al. 1989). Only one serotype (HRV-87) attaches to a sialylated membrane protein of unknown function. However, the remainder of 10 serotypes, the minor receptor group, is internalized via membrane proteins which for a long time escaped identification. Whereas major group viruses exclusively bind to cells of human or primate origin, minor group viruses attach to cells of a large variety...