Long-term protection against Argentine hemorrhagic fever in Tacaribe virus infected marmosets: virologic and histopathologic findings.

Tacaribe virus may represent a better alternative than attenuated strains of Junin virus (JV) for immunization against Argentine hemorrhagic fever (AHF) because of possible risk of persistent infection of disease associated with live, attenuated strains. Callithrix jacchus marmosets, which suffer 100% mortality if inoculated with the pathogenic XJ strain of JV, were used to evaluate possible Tacaribe virus persistence, subclinical, or long-term disease and the duration of protection against challenge with JV. Histologic studies did not show pathogenic changes due to Tacaribe virus in primates sacrificed from 7 to 480 days postinoculation (pi). No virus was recovered in tissue samples after primary culture or cocultures with sensitive cells. The presence of anti-Tacaribe neutralizing serum antibodies and protection against pathogenic JV were detected up to 480 days after a single dose of Tacaribe virus. However, anti-Junin antibodies were detected only after challenge. In other experiments, protection against JV was evaluated histologically and virologically. Two primates were immunized with Tacaribe virus, challenged with JV, and sacrificed 18 or 21 days later. Subclinical histopathologic findings were associated with recovery of JV only by the sensitive primary culture-coculture techniques. The immunogenicity, degree of protection, and safety of Tacaribe virus indicate its potential as a vaccine against human AHF.