Calomys musculinus, the natural reservoir of Argentine haemorrhagic fever, is a semipermissive host for a mouse-attenuated mutant of Junin virus.

C167, a mouse-attenuated strain of Junin virus derived from the XJC13 strain, also displayed reduced virulence for the South American cricetid Calomys musculinus, a natural reservoir of this virus in nature. Intracerebral inoculation of C. musculinus with 500 PFU of C167 produced only 25% mortality, whereas the parental XJC13 killed 85% of the animals. The attenuation of C167 for this cricetid was lower than for albino mice. The multiplication of C167 in C. musculinus-derived embryo or kidney fibroblasts was diminished with respect to XJC13, allowing us to define C. musculinus cells as a semipermissive system for C167, whereas murine and Vero cells were restrictive and permissive cultures, respectively. As a consequence, C167 as well as XJC13 were able to establish a persistent infection in C. musculinus embryo fibroblasts and Vero cells, but the mutant could not induce a carrier state in murine cells. Thus, the degree of susceptibility of C. musculinus to C167 was linked to the semipermissiveness of cricetid cells to virus multiplication.