Experimental infection of suckling mice with a host range mutant of Junin virus.

Experimental infection of three mouse strains with a non-pathogenic mutant of Junin virus named Cl67 was compared with respect to the parental XJCl3 strain. After intracerebral (ic) or intraperitoneal inoculation, XJCl3 was highly virulent for 2 day-old C3H/HeJ, OF1, and BALB/cJ mouse strains, whereas its derivative Cl67 was attenuated. Survival of the Cl67-infected mouse was associated with a restricted replication at the site of inoculation which would impair spread of virus. Thus, the reduced virulence of Cl67 for suckling mice is independent of the mouse strain and the route of viral entry. When Cl67 was preinoculated ic 10 days before the challenge inoculation with XJCl3 by the same route, mice were partially protected from lethal infection. Since neutralizing antibodies were first detected at 30 days post-infection, an interference mechanism is postulated as a mechanism of protection of the mice.