Abstract
When rabies virus (ERA strain) was purified by precipitation with zinc acetate, Sephadex filtration, and centrifuging in a sucrose density gradient, usually about half of the virus particles spontaneously lost a portion of their envelope phospholipids. Because of differences in buoyant density, partially delipidized virus particles (about 1.16 g./cm.3) can be separated from intact virus (about 1.14 g./cm.3) by centrifuging in a sucrose density gradient. High egg passage virus (FLURY strain) purified by the same procedure, did not exhibit this type of heterogeneity. The release of phospholipids from ERA strain virus particles did not cause a marked decrease in the infectivity of the virus, but the morphology of the virus envelope changed from bullet- to bag-shaped. The protein (glycoprotein) composition and the RNA contents of intact and partially delipidized virus forms were similar.