N-Tropic variants obtained after co-infection with N- and B-tropic murine leukemia viruses

Sc-1 cells co-infected with small XC plaque-forming N-tropic and large XC plaque-forming B-tropic murine leukemia viruses produced, in addition to parental types, progeny with the phenotype, large XC plaque morphology, and N-tropism. This phenotype remained stable through end point titration and plaque purification on NIH/3T3 cells and growth on BALB/3T3 cells. These N-tropic viruses (XLP-N virus) grow to unusually high titer and make very large XC plaques.