Replication of lactate dehydrogenase-elevating virus in various species cell lines infected with dual-, ampho- and xenotropic murine leukaemia viruses in vitro.

Lactate dehydrogenase-elevating virus (LDV) replicates in mouse macrophages in vivo and in vitro. It has been shown that LDV infects and replicates in motorneurons of the spinal cord of old, immunosuppressed C58 mice, which results in an acute poliomyelitis. In spite of extensive study, cells or cell lines other than macrophages which could support LDV infection and replication in vitro have not yet been detected. We have shown that LDV can replicate in mouse or rat cell lines which were previously infected with ecotropic murine leukaemia virus (MuLV). It was examined in this study whether other types of MuLV (dualtropic, amphotropic and xenotropic viruses) can also render the mouse cells or cells of other species susceptible to LDV infection as well as the ecotropic viruses. LDV infection and replication were seen in mouse cells infected with ecotropic, dual-tropic and amphotropic viruses. These were also seen in mink, rabbit and human cell lines infected with dual-, ampho- and xenotropic viruses. These results suggested that virtually all four classes of MuLV have the ability to elicit, in mouse cells or cells from heterologous species, permissiveness to LDV infection. The percent of LDV-infected cells increased up to approximately 80% in concentrated neurovirulent LDV-C-infected ecotropic MuLV-infected-mouse cells. The susceptibility of the cells gradually declined when they were maintained for more than one month. The LDV antigen-positive cells appeared as early as 6-8 h p.i., when a large amount of LDV and MuLV were added simultaneously. The replication of LDV was inhibited in MuLV-infected cells which had been treated previously with actinomycin D and cycloheximide, but not with zidovudine (AZT). A small percent of mouse cells became susceptible to LDV, when the cells were treated with iododeoxyuridine. This suggested that the induction of endogenous MuLV or part(s) of its genome from mouse chromosomes resulted in cells that were permissive to LDV.