Type-C RNA Virus Isolated From SJL/J Mice

Summary

Type-C RNA viruses from spleen extracts of apparently normal SJL/J mice of various ages were isolated by tissue culture methods. The infectious virus was first detected in 20% of animals 1–2 months old. At 4 months, 60% were positive, at 8 months, 45%, and at 12 months, 20% were positive. The infectivity titers were mostly low. The virus could act as a helper in the rescue of murine sarcoma virus (MSV) genome from nonproducer cells. The virus is designated D1-MuLV and was N-tropic. SJL/J mouse embryo cells were N-type in their susceptibility to murine leukemia viruses. Dl-MuLV was antigenically related to AKR leukemia virus, as shown by complement fixation tests, neutralization tests, and immunoelectron microscopy. The Dl-MuLV envelope antigen was unique in that no antisera against other type-C viruses reacted with it in immungelectron microscopy. The virus inoculated into newborn SJL/J and AL/N mice induced lymphocytic leukemia, but no acceleration or induction of development ot reticulum cell neoplasm, type-B, was observed in these and C57BL/6 mice. MSV(D1-MuLV) injection in newborn SJL/J mice subsequently treated with antilymphocyte serum induced reticulum cell neoplasm type-A at the injection site.