CHARACTERIZATION OF CHIMERAS BETWEEN THE ECOTROPIC MOLONEY MURINE LEUKEMIA-VIRUS AND THE AMPHOTROPIC 4070A ENVELOPE PROTEINS

A series of 22 chimeric envelope (env) genes were generated between th e ecotropic Moloney murine leukemia virus and the amphotropic 4070A is olate. The chimeric envelopes were expressed within the complete, repl ication competent provirus and tested for virus viability by transient expression assays. Eleven of the 22 viruses were viable. Five of thes e chimeric viruses showed an ecotropic host range, and six exhibited a n amphotropic host range and viral interference. The host range determ inants map to the first half of the surface (SU) protein. The N-termin al 72 amino acids of 4070A (42 of processed SU) are not required for a mphotropic receptor usage. Ecotropic and amphotropic viruses differ in their ability to form large, multinucleated syncytia when cocultured with the rat XC cell line. Ecotropic murine leukemia virus forms large syncytia with XC cells, whereas no syncytia are reported for amphotro pic virus. All chimeras which contained the N-terminal half of the eco tropic SU protein, encoding the receptor binding domain, formed the la rge multinucleated syncytia with XC cells.