Mus cervicolor murine leukemia virus isolate M813 belongs to a unique receptor interference group

Murine leukemia virus (MuLV) M813 was originally isolated from the Southeas t Asian rodent Mus cervi-color. As,vith the ecotropic MuLVs derived from Mu s musculus, its host range is limited to rodent cells. Earlier studies have mapped its receptor to chromosome 2, but it has not been established wheth er M813 shares a common receptor with any other MuLVs. In this study, we ha ve performed interference assays with M813 and viruses from four interferen ce groups of MuLV. The infection efficiency of M813 was not compromised in cells expressing any one of the other MuLVs, demonstrating that M813 must u se a distinct receptor for cell entry. The entire M813 env coding region wa s molecularly cloned. Sequence analysis revealed high similarity with other MuLVs but with a unique receptor-binding domain. Substitution of M813 env sequences in Moloney MuLV resulted in a replication-competent virus with a host range and interference profile similar to those of the biological clon e M813. M813 thus defines a novel receptor interference group of type C MuL Vs.