Eclipse of coxsackievirus infectivity: the restrictive event for a non-fusing myogenic cell line

Coxsackieviruses A2, A5 and B3 did not replicate in L8CL3-U cells (a non-fusing variant of the rat L8 myogenic cell line) although these cells possessed a common receptor for coxsackieviruses A2 and A5, and a different receptor for coxsackievirus B3. The restriction in replication was identified as a block in viral eclipse, since 6 M-LiCl treatment permitted recovery of the coxsackievirus A2 inoculum from L8CL3-U cells after 2 h at 37 degrees C, and the cells could be transfected by viral RNA. Cellular fusion which was induced in L8CL3-U cultures by herpes simplex virus type 1 (HF strain) facilitated coxsackievirus A2 and A5 replication. Differentiating myogenic L8 cells acquired full susceptibility to infection concurrently with the appearance of acetylcholine receptors, the muscle-specific isoenzyme of creatine phosphokinase, prominent myotube formation and the acquired capacity of the cells to eclipse virus.