In comparison with binding of the wild-type HKU1 S1A conjugated with nanoparticles to rat erythrocytes, the mutant HKU1 S1A with removal of a glycosylation site at element 2 (N251Q) showed increased binding, and the mutant HKU1 S1A with removal of the glycosylation sites in both elements (N29Q in element 1 + N251Q in element 2) showed greater binding.