A 70 kDa MHC class I associated protein (MAP-70) identified as a receptor molecule for Coxsackievirus A9 cell attachment.

One of the major categories of disease-causing micro-organisms are viruses. New studies on many different viruses have shown that virus attachment and cell entry is often a multistep process, requiring many interactions between the virus and cell surface molecules. In this study, we have attempted to identify the cell surface molecules involved in Coxsackievirus A9 (CAV-9), a common human pathogen and a member of the Picornavirus family, infectious process. GMK cells susceptible to virus infection were surfaced labeled with biotin and then solubilized in non-ionic and zwiterionic detergents. Free CAV-9 virions were used as an affinity surface, allowing the virus to bind to the solubilized receptors. The virus-receptor complexes were then immunoprecipitated by an anti CAV-9 serum and protein-A sepharose beads. SDS-PAGE and two-dimensional electrophoresis revealed the presence of integrin alpha v beta 3 molecules and a 70 kDa protein with apparent isoelectric point (pI) 5.5. The identity of the integrin alpha v beta 3 molecules was confirmed by immunoprecipitation and Western blotting; whereas the 70 kDa protein was also found to co-immunoprecipitate with MHC class I molecules in non-stringent conditions. Sequential immunoprecipitation experiments confirmed that the MHC class I associated protein (MAP-70) and the 70 kDa protein utilized by CAV-9 were identical. The role of MAP-70 in CAV-9 infectious process is discussed.