Infection of cultured rat myotubes and neurons from the spinal cord by rabies virus.

Rabies virus multiplication was investigated in cultured primary rat myotubes and neurons. The susceptibility of these two cell types to fixed rabies challenge virus strain (CVS) was monitored by fluorescence and virus titration. Differentiated rat myotubes were susceptible to rabies virus infection, and showed an increasing accumulation of viral material from day one to day four. However, these cells did not release infective viral particles, nor did they accumulate infectious virions in the cytoplasm. In contrast, infected neurons released large amounts of infectious particles. Electron microscopy observation of infected myotubes showed minor alterations and the presence of typical viral inclusions in the cytoplasm without mature virions assembling viral membranes. Competition binding experiments show that alpha-bungarotoxin inhibits rabies virus infection from 10(-5) to 10(-7) M, whereas lower toxin concentrations failed to have any effect. These data do not confirm the hypothesis of a fixed rabies virus amplification step at the site of the viral entry. On the other hand, the high susceptibility of peripheral neurons to rabies virus infection is an argument for the direct uptake of virions by these cells. The restrictive viral multiplication in the myotubes is an alternative explanation for the local persistence of rabies virus at the site of inoculation.