As shown in Table 2, the 9-O-Ac-Sia receptor-binding function of homodimeric HE proteins, comprised of a receptor-binding (lectin) domain and receptor-destroying domain, of HCoV-OC43 and HCoV-HKU1 was reported to be lost, and its loss was reported to be associated with an accumulation of mutations in the OC43-HE lectin domain or massive deletions found in the HKU1-HE lectin domain during evolution in humans [94].