[Association of the infection of the thymus and bone marrow with the establishment of persistent infection with Junin virus in 2 genera of rodents]

Abstract

Junin virus infection of immune system organs was correlated with persistence establishment in the mouse and rat. Rockland mice under 24 or at 72 and 120 h of age received 10(4) pfu of Junin virus XJ strain by ic route. Separately, two groups of mice under 24 h old were infected with the same dose of XJ or XJCl3 strain by the same route respectively. Results showed that higher thymus virus titer correlated with greater survival. In turn, the former also seemed to correlate with decreasing age at inoculation time, although there was considerable strain dependence. In order to correlate replication levels in thymus with clinical progress in mice, animals under 24 h of age were inoculated with XJ. At 14 days pi apparently healthy mice from this batch were separated from those presenting severe neurologic sings. In the asymptomatic mice, thymus titers ranged from 1.7 to 3.2 log, while no virus was found in thymus harvested from obviously ill animals. However brain virus titers in the two groups proved similar. To confirm these findings, 72 h old Wistar rats were inoculated in with 10(4) pfu of either Junin virus strain: with XJ strain (90% survival) virus could be readily isolated from thymus and bone marrow at day 7 pi, whereas with XJCl3 (5% survival) no virus could be rescued from any organ tested. Therefore, our results strongly suggest a close correlation between productive thymic infection and Junin virus persistence establishment in these rodents, depending on immune response regulation rather than on viral variation.