Lacking the ability to self-replicate, viruses must utilize the replication apparatus of their host cells [9] . Viral infection of a cell begins with attachment of the virus to the cell surface [6, 10, 11] . During attachment to the cell membrane, the viral envelope protein (a structural protein) interacts with the host-cell receptor protein(s) [12] . In non-envelope viruses, the capsid plays this role. The cell receptors that play a major role in viral attachment are predominantly membrane proteins of the immunoglobin superfamily [13] [14] [15] . The identification of virusbinding cellular receptors was rapidly accelerated in the late 1980s owing to developments in the use of monoclonal antibodies and molecular cloning techniques [15] . The various receptors that have been found are surface matrix structures containing carbohydrate, lipid, and protein moieties [1, 16, 17] . In some cases, viral attachment also exploits co-receptors. For example, HIV, which uses the CD4 molecule as its receptor, uses the CXCR4 and CCR5 co-receptors to strengthen the effectiveness of infection [1, 14, 18, 19] . Similarly, hepatitis C virus utilizes CD81 as a receptor and LDLR as a coreceptor [20] .