Intracellular stability of nonreplicating paramyxovirus nucleocapsids.

Using Northern blot analysis, we have demonstrated the ability of infectious measles and Sendai virus particles to rescue the intracellular replication of their homologous defective interfering (DI) nucleocapsids up to 3 days and 1 day, respectively, after initial DI infection. The half-life of the paramyxovirus DI nucleocapsids was therefore judged to be similar to that of rhabdoviruses, and to significantly differ from that of orthomyxoviruses. Moreover, we conclude that the intracellular half-life of measles virus DI nucleocapsids makes possible DI replication in the human body after vaccination with a DI-contaminated attenuated live virus, even when this vaccination represents a low multiplicity of infection.