Recovery of glycosylatedgag virus from mice infected with a glycosylatedgag-negative mutant of moloney murine leukemia virus

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Abstract
Two independent pathways forgag gene expression exist in Moloney murine leukemia virus (M-MuLV). One begins with Pr65 gag that is processed and cleaved into the internal structural proteins of the virion. The other pathway begins with the glycosylatedgag polyprotein, gPr80 gag . gPr80 gag consists of Pr65 gag plus additional N-terminal residues and it is glycosylated. A glycosylated-gag-negative mutant of M-MuLV (Ab-X-MLV) was previously constructed and shown to replicate in tissue culture. To test for the importance of glycosylatedgag in vivo, the Ab-X-MLV mutant was inoculated intraperitoneally into newborn NIH Swiss mice. Mutant-infected mice developed typical lymphoblastic lymphomas at rates comparable to wild-type M-MuLV at either high (2 × 104 XC pfu/animal) or low (2 × 102 XC pfu/animal) doses. However, when viral protein expression was examined in the resultant tumors, six out of six mice showed evidence of virus that had recovered gPr80 gag expression. These results suggest that glycosylatedgag is important for M-MuLV propagation or leukemogenesis in vivo.