LAUSR

Naturally Occurring Murine Leukemia Viruses in Wild Mice: Characterization of a New “Amphotropic” Class Hartley and Rowe (J. W. Hartley and W. P. Rowe, J Virol 19:19 –25, 1976, http:// jvi.asm.org/content/19/1/19.abstract) described a new class of murine leukemia viruses (MLVs) isolated from wild Mus musculus trapped in California, which they designated “amphotropic.” These viruses replicate in mouse, rabbit, mink, human, guinea pig, and rat cells but not in hamster, quail, or duck cells. The amphotropic viruses display N-tropism for mouse cells and do not trigger the XC cell response. Receptor use and envelope (env) sequence variations define three MLV host range subgroups in laboratory mice: ecotropic, polytropic, and xenotropic (E-, P-, and X-MLVs). It was later shown that California wild mice carry a subtype of E-MLVs, termed Cas laboratory mice amphotropic MLV (A-MLV), which uses the phosphate transporter PiT-2 for entry. Bamunusinghe et al. (D. Bamunusinghe et al., J Virol 90:4186 – 4198, 2016, https:// doi.org/10.1128/JVI.03186-15) recently analyzed the genomes of seven MLVs isolated from Eurasian and American wild mice. They found a new MLV host range subgroup isolated from mice from Thailand and California. However, with the exception of the env gene, the Cas genome closely resembles that of A-MLV, a mouse gammaretrovirus with a host range found only in California wild mice, as originally described by Hartley and Rowe.