Human rhinoviruses (HRVs) comprise over 100 different serotypes and are the predominant cause of the common cold. Although HRV infections are generally mild and self-limiting, they can also be associated with more serious illnesses, specifically, exacerbation of disease in individuals with underlying respiratory disorders. HRVs are a group of small single-stranded positive-sense RNA viruses that translate their genetic information into a polyprotein precursor that is mainly processed by a virally encoded 3C protease (3Cpro; EC 18.104.22.168) to generate functional viral proteins and enzymes. The enzymatic activity of HRV 3Cpro is essential to viral replication, and is distinguished from most other proteases by the fact that it has a cysteine nucleophile but with a chymotrypsin-like serine protease folding. This unique protein structure together with its essential role in viral replication made the 3Cpro an excellent target for antiviral intervention.
 Q.M. Wanga et al. Human rhinovirus 3C protease as a potential target for the development of antiviral agents. Curr Protein Pept. Sci. 2007, 8, 19-27.