MURINE LEUKEMIA-VIRUS ENVELOPE PROTEIN IN TRANSGENIC-MOUSE SERUM BLOCKS INFECTION IN-VITRO

Transgenic mice bearing a murine retroviral envelope transgene (Fv4) h ave Fv4 gp70(env) (SU) in their serum in amounts sufficient to block i nfection by ecotropic virus in vitro. Fv4 Env in serum is derived larg ely but not exclusively from hematopoietic cells. Tail cells from Fv4 mice and cell lines transduced with the Fv4 env transgene synthesize b oth components of the envelope protein (gp70 SU and p15E TM) but secre te the gp70 moiety, in the absence of retroviral particles. Blocking o f the ecotropic viral receptor by secreted gp70 SU may contribute to r esistance to retroviral infection in these mice.