A persistent and inapparent infection of L cells with the virus of lymphocytic horiomeningitis

L cells infected with the virus of lymphocytic horiomeningitis, train ARMSTRONG, produced infectious progeny; this was unaccompanied by visible signs of cell damage. Serial cultivation of infected cells in a medium free of antibodies was easily accomplished. Initially, retardation of cell multiplication and of first subculture cytopathic effects were observed. Later, a state of equilibrium was attained in which the cells multiplied at a normal rate, while continually producing and releasing virus. Although almost every cell of these carrier cultures could be shown by immuno-fluorescence to be infected, morphologically and functionally pathological alterations were not found. After prolonged cultivation the carried virus was found to be incomplete; its ability to spread from cell to cell was greatly reduced; its ability to kill mice was abolished. These losses were not regained by passages invarious hosts. Otherwise the carried virus resembled the original ARMSTRONG virus in conferring solid immunity to mice, reacting specifically with anti