Expression of mouse mammary tumor virus envelope protein does not prevent superinfection in vivo or in vitro

Inbred mice expressing endogeneous mouse mammary tumor virus envelope prote ins can be infected with exogenous virus, and the mammary tumors that devel op in these mice usually have many proviruses integrated in their genomes, indicating that this virus is not subject to receptor interference. We show here that transgenic mice expressing an exogenous mouse mammary tumor viru s (C3H) envelope protein can still be infected with this virus. Moreover, c ultured mammary gland cells expressing the mouse mammary tumor virus (C3H) envelope protein can be superinfected with pseudotyped viruses bearing that same protein. Thus cellular expression of the mouse mammary tumor virus en velope protein does not block bearing that same protein. Thus cellular expr ession of the mouse mammary tumor virus envelope protein does not block sup erinfection in vivo or in vitro. (C) 1999 Academic Press.