Antiviral activity of monoclonal antibodies specific for the internal proteins N and NS of rabies virus.

Monoclonal antibodies (MAbs) specific for the rabies virus nucleoprotein (N protein) and non-structural (NS) protein of the nucleocapsid were introduced into adherent cells (fibroblasts and neuroblastoma) by the scrape-loading technique. After the cells had reattached to the substrate, they were infected with rabies virus. Inhibition of infection was monitored by measuring the intracytoplasmic viral nucleocapsid accumulation with an enzyme immunoassay using anti-N protein rabbit serum and by measuring the release of infectious virus with the plaquing system. Seventeen MAbs defining the three independent antigenic sites on the N protein were able to decrease nucleocapsid accumulation and the release of infectious virus. The MAbs describing the two antigenic sites on NS protein also had an antiviral effect on ERA virus. When an anti-N MAb (0.5 ng per cell) was introduced into CVS-infected cells, virus inhibition was complete if the anti-N MAb was introduced between 0 and 5 h post-infection and ineffective beyond 9 h post-infection. The inhibition was dose-dependent. The MAbs could block virus multiplication either by 'neutralizing' newly translated N and NS proteins or by impairing the initial transcription of the genome.