RABIES VIRUS ANTINUCLEOPROTEIN ANTIBODY PROTECTS AGAINST RABIES VIRUSCHALLENGE IN-VIVO AND INHIBITS RABIES VIRUS-REPLICATION IN-VITRO

We previously reported that A/WySnJ mice vaccinated via a tail scratch with a recombinant raccoon poxvirus (RCN) expressing the rabies virus internal structural nucleoprotein (N) (RCN-N) were protected against a street rabies virus (D. L. Lodmell, J. W. Sumner, J. J. Esposito, W. J. Bellini, and L. C. Ewalt, J. Virol. 65:3400-3405, 1991). To improv e our understanding of the mechanism(s) of this protection, we investi gated whether sera of A/WySnj mice that had been vaccinated with RCN-N but not challenged with street rabies virus had anti-rabies virus act ivity. In vivo studies illustrated that mice inoculated in the footpad with preincubated mixtures of anti-N sera and virus were protected. I n addition, anti-N sera inoculated into the site of virus challenge pr otected mice. The antiviral activity of anti-N sera was also demonstra ted in vitro. Infectious virus was not detected in cultures 24 h follo wing infection with virus that had been preincubated with anti-N sera. At later time points, infectious virus was detected, but inhibition o f viral production was consistently greater-than-or-equal-to 99% compa red with control cultures. The protective and antiviral inhibitory act ivity of the anti-N sera was identified as anti-N antibody by several methods. First, absorption of anti-N sera with goat anti-mouse immunog lobulin serum, but not normal goat serum, removed the activity. Second , radioimmuno-precipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of sucrose density gradient-fractionated anti-N sera showed that antiviral activity was present only in the fra ction containing anti-N antibody. Finally, absorption of anti-N sera w ith insect cells infected with a baculovirus expressing the N protein removed the protective activity. These data indicate that anti-N antib ody is a component of the resistance to rabies virus infections.