The Fibrinolytic System of the Chacma Baboon (Papio ursinus): Implications for Non-Human Primate Haemostatic Disease Models

Baboon models are useful for investigating haemostatic disorders and potential novel treatments. The fibrinolytic system is an integral component of these models and an important potential therapeutic target. We investigated the fibrinolytic system of the Chacma baboon (Papio ursinus), including the effects of sex and ABO blood group. Tissue-type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), plasminogen, plasmin-α2-antiplasmin (PAP) complexes, thrombin activatable fibrinolysis inhibitor (TAFI), α2-antiplasmin, fibrinogen levels, and clot lysis times of 40 adult Chacma baboons were assessed. Plasminogen activation using escalating concentrations of streptokinase vs. alteplase was determined and compared with normal human plasma. The results were compared between O and non-O ABO blood groups, and between males and females. PAP complexes and fibrinogen were mostly within the human reference interval, while tPA, PAI-1 and α2-antiplasmin tended towards the lower limit. Plasminogen and TAFI were virtually undetectable with the human ELISA kits used. Alteplase was a potent plasminogen activator compared with streptokinase (p < 0.0001), resulting in brisker clot lysis in baboon than in human plasma (10.8 vs. 13.4 min). Blood group O baboons had higher fibrinogen levels (p = 0.0355), while males had lower fibrinogen (p = 0.0134) but higher PAP complex concentrations (p = 0.0188). Except for plasminogen and TAFI, the Chacma baboon fibrinolytic system appears broadly similar to its human counterpart. Streptokinase does not meaningfully activate Chacma baboon fibrinolysis, but alteplase elicits greater plasminogen activation than in humans. These findings, as well as sex- and ABO-blood-group-related differences in fibrinogen, should be considered when designing future pre-clinical drug testing experiments in this species.