Vol. 2,1968 Viral Particles from a Rat Neoplasm Induced by Msv

is a passenger virus present in BN rats, and confirmed the notion that MSV (0) belongs to the family of MSV and contains at least part of the genome of the original MSV. Antigenic specificity of MSV (0). Using rat sera prepared against RLV, MLV, Gross leukemia virus (GLV), and MSV (0), the serological specificity of MSV (0) was studied. Based on the neutralization test, MSV (0) was antigenically distinct from MSV (RLV) (Table 4). Anti-RLV serum did not neutralize MSV (0) and anti-MSV (0) serum did not reduce the focus-forming ability of MSV (RLV). It has been reported that anti-GLV (C58 G+ virus) serum, obtained from Lloyd Old, Sloan-Kettering Institute for Cancer Research, neutralized all known pseudotypes of MSV (5), yet did not neutralize MSV (0). This serum is a rat serum prepared against wild-type GLV from C58BL mice and has a very broad spectrum. The same serum has been used by Geering et al. for typing G+ antigens, including those in naturally occurring leukemia viruses (3).