Construction and characterization of expression systems for the env gene of ts1, a mutant of Moloney murine leukemia virus-TB

A temperature-sensitive mutant of the Moloney murine leukemia virus-TB, ts1, causes hindlimb paralysis and immunodeficiency in mice. At the restrictive temperature, the envelope precursor polyprotein, gPr80 env , is inefficiently processed intracellularly, and this is associated with the neurovirulence of ts1. To test the hypothesis that expression of the envelope proteins of ts1 alone without infectious virus production can induce paralysis, it is necessary to use either transmissible retroviral expression vectors or microinjection of eukaryotic gene expression plasmid to introduce the env gene of ts1 into germlines of mice. In this study, we have constructed three retrovirus vectors and three gene expression plasmids, all of which contain the env gene of ts1. By comparing the different expression systems, we found that one construct, p ts1- env(F) can express the envelope proteins at a level comparable to the level expressed in ts1-infected cells. Furthermore, the expressed envelope proteins of p ts1- env(F)-transfected cells possess the phenotypes of the proteins expressed by the env gene of ts1.