Requirements for DI particle prophylaxis against vesicular stomatitis virus infection in vivo

In contrast to biologically active DI particles, neither u.v.-inactivated standard virus nor either of two different homologous u.v.-inactivated DI particles showed any prophylactic effect when injected intracerebrally into mice concomitantly challenged with VSV. Although u.v.-inactivated DI particles did not prevent death when given with the challenge virus, they did significantly lengthen the time until death occurred. Also, both u.v.-inactivated standard virus and DI particles protected mice against late challenge (at 3 or 10 days after treatment). Dosage titrations of preparations of two different active DI particles showed significant prophylaxis against simultaneous challenge with numbers of DI particles 10- to 100-fold lower than those which gave no prophylaxis when u.v.-inactivated. Thus, prophylaxis in this system in this system required biologically active DI particles.