During the initial phase of infection paramyxoviruses interact with specific elements on the host cell surface which enable the virions to stably attach to and penetrate the cell membrane. It has been established that these cell surface receptors are sialoglycoconjugates. The proposed research will molecularly identify these receptors. The first phase will elucidate the chemical nature (protein or lipid) of these sialoglycoconjugates. Comparison of the abilities of naturally occurring sialoglycoconjugates and their molecular dissection products to interact with the virus will be used to define the receptor determinant recognized by the virus. The fusion event as well as the adsorption event will be investigated to determine if both events are receptor-specified. The contribution of the virus to early virus-cell interactions will be examined by isolating the minimal subviral unit required for adsorption and fusion. The research will progress from the study of one particular paramyxovirus, Sendai virus, to related viruses such as other paramyxoviruses and myxoviruses. Finally this basic knowledge of virus receptors will be utilized to design receptor analogs that act as antiviral agents.