Neurovirulence of wild and laboratory Junin virus strains in animal hosts.

The neurovirulence 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, of different ages inoculated by the intracerebral route. Infectivity in brain and organs, lethality, and neuropathological lesions were determined. The laboratory and wild strains showed similar neurovirulence only in 2-day-old mice. The neurovirulence of laboratory strains decreased with the age of the animal, and the Candid #1 strain affected only 2-day-old mice. In guinea pigs, the 2 wild strains and XJCL3 laboratory strain were neurovirulent for 11-day-old and adult animals giving moderate lymphocytic infiltration in the brain and mild lesions in the spinal cord. Virus titres from the brain and the spinal cord were lower with the XJCL3 and CbalV4454 strains than with the CbaFHA5069 strain; with the latter, virus was recovered only from the lymph nodes, the lung, kidney, liver, and spleen. The Candid #1 strain was not neurovirulent even for 11-day-old animals. In contrast, the laboratory strains were neurovirulent for Calomys musculinus, depending on the age of the animal. Virus was recovered from the brains showing lymphocyte infiltration but not from other organs. The CbaFHA5069 strain was not neurovirulent, although virus was recovered from the brain, spleen, liver, lymph nodes, and salivary glands. These results with the 3 hosts indicate that Junin virus neurovirulence is virus strain-dependent, and host species and age-dependent, with the Candid #1 strain proving the least neurovirulent of the strains studied.