RICKETTSIA-RICKETTSII HAS PROTEINS WITH CROSS-REACTING EPITOPES TO EUKARYOTIC PHOSPHOLIPASE A(2) AND PHOSPHOLIPASE-C

The entry, and possibly the exit, of rickettsiae from eukaryotic cells , as well as erythrocyte lysis by some members of this group of organi sms, is thought to be mediated by a phospholipase A activity even thou gh the enzyme has not been isolated from these organisms. Evidence for phospholipase C, on the other hand, has not been reported for the gen us Rickettsia. In this study, in a preliminary attempt to demonstrate the presence of phospholipase A(2) and phospholipase C in the virulent Sheila Smith strain of Rickettsia rickettsii, we performed immunoblot ting and immune-gold electron microscopy using anti-phospholipase A(2) and antiphospholipase C IgG antibodies (raised against mammalian enzy mes). We provide evidence for cross-reactivity of the antibodies with proteins present in R. rickettsii. Western blots showed a higher stain ing intensity with anti-phospholipase C antibody than with anti-phosph olipase A(2). According to the results obtained with the immune-gold l abeling of phospholipase A(2) and phospholipase C reactive epitopes, m ost of the phospholipase A(2) cross-reactive material appears to be as sociated with the membrane of the organism while the phospholipase C c ross-reactive material appears to be randomly distributed throughout t he cell.