The uncoating of paramyxoviruses may not require a low pH mediated step.

The effect of lysosomotropic agents, chloroquine and NH4Cl, on the replication of paramyxoviruses was compared with that on the other enveloped RNA viruses whose uncoating is known to be blocked by the agents. Under the conditions where vesicular stomatitis or influenza virus infection was strongly inhibited at an early step, the agents exhibited little inhibitory effect on the progress of infection by Newcastle disease virus and Sendai virus, allowing viral primary transcription to occur and neither inhibiting the virus production significantly nor reducing the number of infected cells. These results are incompatible with the previous report showing that paramyxovirus and the other enveloped RNA viruses may have in common an intracellular step sensitive to lysosomotropic agents (Miller and Lenard, Proc. Nat. Acad. Sci. USA 78, 3605-3609, 1981) and suggest that paramyxovirus uncoating may not require a low pH mediated lysosomal step.