[Experimental evaluation of the pathogenicity of Lassa virus variants].

Pathogenicity for guinea pigs and white mice of various Lassa virus variants: native, having had 1 passage in Vero cell culture and 4 passages in newborn white mouse brain; a virus having gone through 10 passages in Vero cells and 8 mouse brain passages (variant No. 10); a small-plaque clone derived from variant No. 10 by the method of plaque-to-plaque cloning (variant No. 11k), was studied. Both the native virus and variant No. 10 were found to be similarly pathogenic for susceptible laboratory animals, while the small-plaque variant of Lassa virus became non-fatal for guinea pigs and white mice. The decline of pathogenic properties in variant No. 11k was shown not to be associated with the presence of temperature-sensitive mutants or defective interfering particles.