Selective clearance of a benign clone of Venezuelan equine encephalitis virus from hamster plasma by hepatic reticuloendothelial cells.

A benign small-plaque clone of Venezuelan equine encephalitis virus was efficiently removed from the blood of inoculated hamsters by adsorption to cells of the hepatic reticuloendothelial system. More than 99% of infectious small-plaque virus, intrinsically labeled with 32P, was cleared from the blood within 30 min of inoculation; 47.6% of the 32P-labeled small-plaque virus inoculum was concentrated in the liver. In contrast, only 0.8% of a virulent large-plaque clone of the virus was cleared from the blood. The affinity of small-plaque virus for liver tissue was confirmed by electron microscopy, since inoculated small-plaque virions were readily visualized in phagocytic vacuoles of hepatic endothelial and Kupffer cells, where they appeared to be undergoing degradation. In contrast, large-plaque virus was not visualized in the liver. A critical determinant of virulence for viruses that do not replicate in hepatic reticuloendothelial cells may be the efficiency with which they are removed from the blood by adsorption to such cells.