IDENTIFICATION OF HEMOLYTIC-ACTIVITY IN SALIVA OF THE LONE STAR TICK (ACARI, IXODIDAE)

Hemolytic activity was identified in the saliva of Amblyomma americanu m (L.) when red blood cells from sheep were incubated with tick saliva in the presence of phosphatidylcholine and sodium deoxycholate. The h emolytic activity was destroyed by boiling or treating with trypsin. T he hemolytic activity in tick saliva was calcium-dependent, and inhibi ted by a phospholipase A(2) inhibitor oleyloxyethyl phosphorylcholine. Phosphatidylserine could replace phosphatidylcholine in the hemolytic assays but phosphatidylethanolamine and phosphatidylinositol were ine ffective. Size exclusion chromatography of tick saliva revealed one pe ak of hemolytic activity, which correlated with the activity of tick s alivary phospholipase A(2), both having a molecular weight approximate to 55,000 daltons. These results suggest that the hemolytic activity in tick saliva results from salivary phospholipase A(2). The hemolytic activity in tick saliva may play a role in lysing host red blood cell s, thus facilitating the lick digestive process.