Experimental neuroinvasiveness of wild and laboratory Junin virus strains

The neuroinvasiveness of Candid 1 and XJCL3 laboratory strains and CbalV4454 and CbaFHA5069 wild strains of Junin virus was studied in albino mice, guinea pigs, and a South American wild rodent, Calomys musculinus (Cm), of different ages inoculated by a non-neural route. Infectivity in brain, blood and organs, as well as lethality, were determined. The results with the 3 hosts indicate that Junin virus neuroinvasiveness is virus-strain-dependent, host species- and age-dependent, with the Candid 1 strain proving to be the least neuroinvasive of the strains studied. The lethal efficiency index (log PFU/LD50) in 2-day old albino mice and the neuroinvasiveness index (Log PFU/ND50) in 6 +/- 1 day-old Cm of the various strains using the intraperitoneal (ip) route could therefore be useful markers of Junin virus neuroinvasiveness. Moreover, different patterns of infection were established using the results of the presence of infectious virus in brain and viraemia in the 3 hosts. In nearly all cases, virus neuroinvasion was present without detectable viraemia (virus in plasma). Current evidence leads to the assumption that virus might reach the brain associated with the white cells in blood (undetectable by conventional isolation methods) or by another possible mechanism of neuroinvasion which is not haematogenous.