Date of Award


Degree Type


Degree Name

Master of Science (MS)




Dr. L. A. Prevec


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 and McCarter, 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 non-permissive and permissive conditions of ts₃ infection. Whereas similar levels of phenotypic mixing were observed between VSV and wild type MoLV at both 39ºC and 34ºC, the level of pseudotypes formed between VSV and ts₃ was found to be considerably lower at 39ºC (non-permissive temperature) than at 34ºC (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 non-permissive temperature. Pre-incubation of ts₃-infected cells for 24 hours at 39ºC, prior to super-infection with VSV at 39ºC, introduces an irreversible block at VSV (ts₃) pseudotype production. In contrast, brief incubation at 39ºC, coincident with VSV infection, introduces a reversible block which prevents the release of VSV (ts₃) pseudotypes from the cell membrane. Complementation of ts₃ through ts₃ (VSV) pseudotype production was not detected at the non-permissive temperature.

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