Experimental infection of suckling mice with a host range mutant of Junin virus

Pathogenesis of arenavirus hemorrhagic fevers

Viral hemorrhagic fevers (VHFs) caused by arenaviruses belong to the most devastating emerging human diseases and represent serious public health problems. Arenavirus VHFs in humans are acute diseases characterized by fever and, in severe cases, different degrees of hemorrhages associated with a shock syndrome in the terminal stage. Over the past years, much has been learned about the pathogenesis of arenaviruses at the cellular level, in particular their ability to subvert the host cell's innate antiviral defenses. Clinical studies and novel animal models have provided important new information about the interaction of hemorrhagic arenaviruses with the host's adaptive immune system, in particular virus-induced immunosuppression, and have provided the first hints towards an understanding of the terminal hemorrhagic shock syndrome. The scope of this article is to review our current knowledge on arenavirus VHF pathogenesis with an emphasis on recent developments.

Glycoprotein-mediated biological properties of a host range mutant of Junin virus

The biological properties mediated by the main envelope glycoprotein (GP1) of a mouse-attenuated mutant of Junin virus, named Cl67, were investigated in comparison with its parental strain XJCl3. In contrast to the parental strain, this mutant was unable to multiply in primary cultures of mouse embryo fibroblasts (MEFs). Impairment of Cl67 multiplication was associated with a lack of virus binding to MEF, probably due to an altered interaction between GP1 and cellular receptors. Antigenic and immunogenic characterization of GP1, performed by neutralization assays, demonstrated that, under certain conditions, polyclonal and monoclonal antibodies exhibited differential affinity and specificity for each virus. Cl67-infected Vero cells showed a marked pH-dependent fusion capability, suggesting more efficient low pH triggering of fusion by mutant virus GP1 in comparison with the parental strain.

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.