SUMMARYRat C6 glial cells were resistant to infection by several strains of murine coronaviruses. The restriction was not at the adsorption stage, since virus adsorbed to the C6 cells in a similar manner to mouse L cells which supported a lytic infection. The virus could not be internalized by the C6 cells. However, if the virus was introduced into the C6 cells by polyethylene glycol fusion, viral replication occurred and progeny virions were released from the infected cells. These studies indicated that the C6 cells were restrictive to coronavirus replication by preventing the early penetration stage of the viral replicative cycle.

SUMMARYInfection of rat cells, Schwannoma RN2, hepatoma HTC or myoblast L6, with the murine coronavirus JHM strain results in a persistent infection characterized by the release of virus over an extended period of time with a limited cytopathology. Several stages of the viral replication cycle have been examined in these cells in comparison to those in mouse L2 cells, which are totally permissive to JHM infection. Although the rat cells bound as much virus as the mouse cells their ability to internalize it was 40-fold less efficient than the mouse cells. This lower internalization efficiency was not enhanced by pH shock of infected cells, but was by treatment with polyethylene glycol. In all cell types there appeared to be no major differences in the ability of the internalized virus to replicate the viral RNA as determined by slot-blot analysis with a radiolabelled viral cDNA. A similar genetic mechanism appears to be operative in the lines because somatic cell hybrids formed between these lines in various combinations were also deficient in the ability to internalize bound virus. Taken together these results imply that rat cell lines in general share a common deficiency in their inability to internalize murine coronaviruses efficiently. This low efficiency in viral internalization may explain in part the ability of these lines to sustain persistent infections.

Murine coronavirus (MHV) infections of continuous cell lines show a wide spectrum of cell-virus interactions. Cell lines have been identified that can be lytically infected, persistently infected, or non-infectable (1,2,3). At present the mechanisms involved in determining the outcome of the infectious process are not clearly understood. In previous work a cell line, the rat C6 glial line, was identified that was resistant to infection by both the ~1HV3 and JHM strai ns of MHV (l). Studi es have been i niti ated to exami ne the reasons for this restriction in order to understand mechanisms whereby cells can be refractory to coronavirus infections and to understand the replication strategy of these agents.