Permeability changes of plasma and lysosomal membranes in HeLa cells infected with rabbit poxvirus

Infection of HeLa-cell monolayer cultures with rabbit poxvirus induces a marked decrease in cell-associated protein and in the activities of lactate dehydrogenase, acid phosphatase, and beta-glucuronidase. This effect begins to occur around 10 hours post-infection (p.i.) and is accompanied by a concomitant rise of these enzyme activities in the culture medium. Only few cells detach from infected monolayers and these cannot account for protein release. Virion release can be inhibited at 4 degrees C, whereas protein release cannot and it seems therefore that these events do not happen by a common mechanism. Moreover, penetration studies with [14C]-sucrose indicate that protein release reflects a true increase in plasma membrane permeability. Using the Gomori stain for acid phosphatase, a release of the enzyme into the cytoplasm around 8 hours p.i. can be confirmed rendering a causative role of lysosomal hydrolases in the pathogenesis of the observed plasma membrane permeability changes possible but not proving it.