Abstract Number: PB1816
Meeting: ISTH 2020 Congress
Background: Physical interactions between platelets and many bacteria is a key feature of innate immunity. Platelets are known to bind strains of Staphylococcus aureus via fibrinogen bridging with bacterial clumping factors. Platelet binding to bacteria assists in recruitment of additional immune factors via physical immobilization, chemokine signaling, and leukocyte recruitment. Such binding frequently results in platelet activation and aggregation, and thrombocytopenia is common with sepsis.
Aims: To determine whether lyophilized human platelets (LHPs), a platelet derived hemostatic agent currently under clinical development (Thrombosomes®), are capable of physical interactions with bacteria in a manner like fresh platelets.
Methods: LHPs or fresh drawn platelets were incubated with chemically fixed S. aureus (Cowan I strain) with or without supplementation of 1 mg/mL fibrinogen, 1 mM Ca2+ and Mg2+ and assessed by light transmission aggregometry. Platelets were biotinylated and streptavidin stained and S. aureuswas labeled with BODIPY-FL to facilitate detection by flow cytometry and fluorescence microscopy.
Results: Fresh platelets activated and aggregated with chemically fixed S. aureus with a 5-minute lag time. LHPs agglutinated with S. aureus to a lesser magnitude than did fresh platelets (Figure 1). The interaction of S. aureus with LHPs was greater in the presence of fibrinogen and cations. Physical association of LHPs with S. aureus was confirmed by flow cytometry and fluorescence microscopy using orthogonal fluorescence staining methods (Figure 2).
Conclusions: Lyophilized human platelets participate in physical interactions with the Cowan I strain of S. aureus in vitro in a fibrinogen-dependent manner, though to a lesser extent than fresh platelets. Additional investigation is necessary to determine implications for in vivo immune responses and interactions with other pathogenic species upon LHP transfusion, and to determine whether LHP transfusion is suitable in sepsis treatments.
To cite this abstract in AMA style:Lee A, Moskowitz KA. Lyophilized Human Platelets Exhibit Adhesive Interactions with Staphylococcus aureus [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/lyophilized-human-platelets-exhibit-adhesive-interactions-with-staphylococcus-aureus/. Accessed January 27, 2022.
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