Prevalence of Circulating Antibodies against a Streptokinase C-Terminal Peptide in Normal Blood Donors

Streptokinase (SK) is a streptococcal protein widely used as a thrombolytic agent. Anti-SK antibodies (Abs) are found in most individuals due to common streptococcal infections. The presence of these Abs increases the possibility of allergic reactions and may reduce the thrombolytic efficacy of SK upon a first therapy. Previous studies report on the immunodominance of the SK C-terminus and the role of this region in plasminogen (Plg) activation. The aim of this study was to assess the prevalence of circulating Abs to the SK C-terminus in normal blood donors. Sera from 1008 subjects aged 30 to 60 years were tested by Ultra-Micro-ELISA using a synthetic peptide resembling the SKC-2 C-terminus. An overall prevalence of 30.4% was found. Prevalence was significantly higher among male than among female donors (RR = 1.70, 1.13 < CI < 2.55). No age effect was observed. This is the first extensive study about Abs directed against a particular region of SK in normal subjects.