Isolation of a hemagglutinating, immunizing, and non-infectious subunit of the rabies virion

Summary

Purified rabies virus treated with saponin (1 mg/ml) at 37° C for 20 minutes showed a loss in infectivity to 0.01 per cent and a significant increase in hemagglutinating activity. After CsCl density gradient centrifugation the hemagglutinating activity of saponin-treated virus showed a density of 1.29 g/ml whereas virus-bound hemagglutinin banded at 1.20 and 1.22 g/ml. In electron micrographs saponin-treated virus showed coiled and looped filaments possibly originating from the virus surface; gradient fractions associated with hemagglutinating activity appeared as polydisperse but otherwise homogeneous network of loops and coils. Deoxycholate treatment destroyed these structures as well as the hemagglutinating activity of the preparation. Potency testing of gradient purified virus and virus subunits showed that the hemagglutinin preparation contained the total immunizing capacity of the rabies virus particle, whereas the complement fixing, non-hemagglutinating material (density 1.32 g/ml) had only little protective activity. In serum-neutralization tests antibody titers of 1∶5000 were achieved after application of 2 μg protein of each, virion- and hemagglutinin vaccine; the same amount of complement fixing antigen resulted in a titer of 1∶12 only. The significance of these results for the production of a non-dangerous, antirabies split-virus vaccine is discussed.