Structural and functional analysis of the S proteins of two human coronavirus OC43 strains adapted to growth in different cells.

The receptor-binding activity of strain CU (grown in MDCK I cells) and of strain VA (adapted to Vero cells) of human coronavirus OC43 was analyzed and compared with the binding activity of bovine coronavirus (BCV) and of the OC43 strain provided by the American Type Culture Collection (AT). Results obtained with resialylated erythrocytes indicated that the ability of the viruses to recognize 9-O-acetylated sialic acid in an alpha 2,6-linkage decreased in the following order: AT > CU > BCV > VA. Only minor differences were observed with respect to the alpha 2,3-linkage. The amino acid sequence of the S protein of strain CU and VA was derived from the nucleotide sequence of the cloned gene. Strain VA differed from strain CU in 34 positions, 18 in the S1 and 16 in the S2 subunit.