The use of vesicular stomatitis virus pseudotype production in the study of a temperature-sensitive murine leukemia virus.

A mutant of Moloney murine leukemia virus (MoLV), designated ts₃ was recently shown to have a temperature-sensitive defect associated with the release of mature virus particles budding from the cell membrane Wong, P. K. Y., and McCarter, J. A., Virology58, 396–408 (1974)]. In an attempt to determine whether the defective function resides in an envelope component of the virion, the formation of pseudotypes between VSV and ts₃ was studied under nonpermissive and permissive conditions of ts₃ infection. Whereas similar levels of phenotypic mixing were observed between VSV and wild-type MoLV at both 39 and 34°, the level of pseudotypes formed between VSV and ts₃ was found to be considerably lower at 39° (nonpermissive temperature) than at 34° (permissive temperature). The results of temperature-shift experiments indicate that two separate blocks to VSV ts₃ pseudotype production may occur depending on the length of time ts₃-infected cells are incubated at the nonpermissive temperature. Preincubation of ts₃-infected cells for 24 hr at 39°, prior to superinfection with VSV at 39°, prevents pseudotype formation. In contrast, brief incubation at 39°C, coincident with VSV infection, introduces a reversible block on the release of VSV (ts₃) pseudotypes from the cell membrane. Complementation of ts₃ through ts₃ (VSV) pseudotype production was not detected at the nonpermissive temperature.