Modification of Junin virus neutropism in the guinea pig model.

Virulent and attenuated Junin virus (JV) strains have been employed to study the influence of virus passage history on the neurotropism for guinea pigs. Five i.p. successive passages (P1-P5) of the pathogenic JV-XJ strain and of the attenuated XJO variant were performed in guinea pig spleen. Viral titrations of organ suspensions were made through P1-P5 passages. The XJ strain produced a widespread infection in P1 guinea pigs with viral dissemination to all organs except brain, in P5 animals the brain has been involved as well. XJO-infected P1 guinea pigs showed lower viral titres than XJ-infected P1 animals, and again, the virus reached the CNS in P5 only. The passaging by i.p. route was shown to enhance CNS invasivity of the XJ strain as well as to maintain the XJO neurotropism for guinea pigs. Neurotropism of both strains seemed somewhat affected by the passage history of the virus and the inoculation route appeared critical for its expression. In addition, the neurotropic potential of the attenuated strains has apparently remained unaltered.