[Differentiation among strains of Junín virus by intraperitoneal infection in the rat]

The 2-day-old rat is known to resist intracerebral infection with the XJ prototype strain of Junin virus, but 95-100% mortality results when infected with the attenuated XJC13 strain. When this animal was inoculated by intraperitoneal route, behaviour was diametrically opposite: the XJ strain proved lethal, while de XJC13 led to low mortality. Studies on mortality, virus titer in different organs, and anti-viral humoral response in 2-day-old rats infected with Junin virus strains were carried out in order to use this system as a new attenuation marker. Mortality rates recorded for rats inoculated with either strain, were markedly different, being 84% in the XJ-infected group and barely reaching 17% in the XJC13 group. Brain viral titers were higher in the former group than the latter (10(5.26) PFU/ml vs. 10(3) PFU/ml at day 17 pi). For this reason, viral replication may be used as a virulence marker in this experimental model. Antibody levels were also higher in the XJ group most likely due to greater viral replication. The above findings support the use of the 2-day-old rat as a biologic attenuation marker since susceptibility to infection is strain-dependent.