Safety and immunogenicity of a live-attenuated Junin (Argentine hemorrhagic fever) vaccine in rhesus macaques.

The safety and immunogenicity of Candid #1, a live-attenuated Junin virus vaccine, were evaluated in rhesus macaques. Candid #1 was inoculated subcutaneously in graded doses ranging from 16 to 127,200 plaque-forming units (PFU) into four groups of five animals each; four controls received saline. There was no significant effect of the immunization on any physical, hematologic, or biochemical parameter measured. Junin virus was recovered by cocultivation from peripheral blood mononuclear cells (PBMC) of 14 (70%) of 20 animals from 1 to 21 days after immunization; 27 (12%) of 223 PBMC samples that represented animals in all four dose groups were positive. In contrast, virus was recovered from the plasma of only two of 20 macaques (two of 225 samples [0.9%]), and only once (by amplification) from throat swabs. No evidence of reversion was detected in any blood isolate. All animals developed a detectable neutralizing antibody response following vaccination. These results indicate that Candid #1 is safe and immunogenic in nonhuman primates.