Molecular and biological characteristics of echovirus 22, a representative of a new picornavirus group

Recent sequence analysis revealed that the human pathogen echovirus 22 (EV22) is genetically distant from all the other picornaviruses studied to date (T. Hyypiä, C. Horsnell, M. Maaronen, M. Khan, N. Kalkkinen, P. Auvinen, L. Kinnunen, and G. Stanway, Proc. Natl. Acad. Sci. USA 89:8847-8851, 1992). We have further characterized the biological properties of the virus and show here that the virion has properties similar to those of other picornaviruses. However, the protein composition is unique, in that most copies of one of the three major capsid proteins, VP0, do not undergo the further processing to VP2 and VP4 observed during the maturation of the virus in previously studied picornaviruses. Alignment of the capsid protein sequences with those of other picornaviruses revealed, furthermore, that the VP3 polypeptide contains an apparent insertion of approximately 25 amino acids at its amino terminus. An arginine-glycine-aspartic acid (RGD) motif is found in VP1, and by using synthetic peptides, it was shown that this sequence plays a role in cell surface receptor recognition. Finally, EV23 was shown to share remarkable identity with EV22 in certain parts of the genome and also belongs to this previously unrecognized picornavirus group.